The Journal of Prosthodontics and Dental Materials

THE JOURNAL OF

PROSTHODONTICS AND DENTAL MATERIALS

Official e-publication of Indian Prosthodontic Society

MUMBAI - NAVI MUMBAI BRANCH

Volume 1 Issue 1 & 2 January – June & July – December 2020

Editorial Team

President: Dr. Sharat Shetty Immediate Past President: Dr. Omkar Shetty President Elect: Dr. R. D. Das Secretary: Dr. Saloni Mistry Treasurer: Dr. Parmeet Banga Editor: Dr. Naisargi Shah E.C. Members: Dr. Gaurang Mistry Dr. Anuradha Nemane Dr. Praveen Badwaik Dr. Sankalp Bhandarkar Dr. Sumit Bedia Dr. Anita Gala- Doshi

INDIAN PROSTHODONTIC SOCIETY MUMBAI-NAVI MUMBAI BRANCH EXECUTIVE COUNCIL

Editor: Dr Naisargi Shah Professor and Head, Dept of Prosthodontics, Terna Dental College, Nerul, Navi Mumbai. +91 9819238483 +91 8976876779

: [email protected] Associate Editors: Dr. Praveen Badwaik Dr. Anita Gala Doshi Advisors to Editor: Dr. Suhasini Nagda Dr. Sabita M. Ram Dr. Suresh Meshram Dr. Jyoti Karani Research Editor: Dr. Omkar Shetty Guest Editors: Dr. B. Srinivasan Dr. Nisha Patel Peer Review Board Dr. Milind Karmarkar Dr. Arti Wadkar Dr. Jyoti Tembhurne Dr. Jyoti Nadgere Dr. Sharat Shetty Dr. Ali Tunkiwala Dr. Rathin Das Dr. Saloni Mistry Dr. Gaurang Mistry Dr. Sandeep Gurav Student Editor: Dr. Sayali Raut

THE JOURNAL OF


The Journal of Prosthodontics and Dental Materials is an comprehensive e-journal that will acknowledge latest research and clinical expertise in the field of Prosthodontics, Implantology and Dental Materials. This bi-annual journal is an attempt to impart information and enlighten the practioners, academicians and students all over.

INFORMATION FOR THE AUTHORS The manuscript will be reviewed for possible publication with the understanding

that it is being submitted to JPDM alone at that point in time and has not been published anywhere, simultaneously submitted or already accepted or publication elsewhere. The journal expects that the 'corresponding author' authorised by all the contributors will communicate with the journal for all matters related to the manuscript. The order of naming contributors should be based on the relative contribution of the contributor towards the study and writing the manuscript. Once submitted the order cannot be changed without written consent of all the contributors. Conflicts of interest/competing interests, if any, must be disclosed.

All manuscripts received will be duly acknowledged by e-mail. Submitted manuscripts will initially be reviewed by the Editors. Manuscripts with insufficient originality, serious scientific/technical flaws or lack of a significant message are rejected before proceeding for formal review. Manuscripts that are found suitable for publication in JPDM are sent to two or more expert reviewers. The selection of these reviewers is at the sole discretion of the Editor. The journal follows a double blind review process, wherein the reviewers and the authors are unaware of each other's identity. Every manuscript will be assigned to a member of the editorial team, who based on the comments from the reviewers takes a final decision on the manuscript. The authors will be asked to modify the manuscript if needed. The comments and suggestions received from the reviewers are conveyed to the corresponding author.

Manuscripts (single word document file with) typed in British English should be

sent to the editor via mail at [email protected] Text should be made in MS Word. Size 12 of 'Times New Roman' font with double spacing is recommended for the main text. Title page should be in a separate word file with NAME OF THE ARTICLE, NAME AND DETAILS OF CONTRIBUTORS and NAME, EMAIL & MOBILE NUMBER OF CORRESPONDING AUTHOR. For Headings, Size 16 and 20 can be used. Images, graphs and tables should be included in the main text. References from articles in journals, books and other monographs should be in the formats used by the Vancouver system. References should be numbered consecutively in the order in which they are first mentioned in the text (not in alphabetic order). Scanned image of signed Copyright transfer statement by corresponding author should be attached as a separate file.

THE JOURNAL OF


Title Page/covering letter:

1. The type of manuscript (original article, case report, review article, Letter to editor, Images, etc.) title of the manuscript, running title, names of all authors/ contributors (with their highest academic degrees, designation, and affiliations) and name(s) of department(s) and/ or institution(s) to which the work should be credited. All information that can reveal your institute affiliation should be here. Use doc files.

2. Registration number in case of a clinical trial and where it is registered (name of the registry and its URL)

3. The name, address, e-mail, and telephone number of the corresponding author, who is responsible for communicating with the other authors about revisions and final approval of the proofs, if that information is not included in the manuscript itself.

Number of authors:

a. Original article and Review articles: Maximum of 6 authors. The decision of the editor/ editorial board is final and binding in all situations.

b. Case report, innovations – Maximum of 3 authors. If it is more than 3 authors, justification on the same must be provided in writing by the corresponding author to the editor on the contribution of each author. Prior approval on the same must be obtained by the authors before publication. The decision of the editor/ editorial board is final and binding in all situations.

Manuscript:

The main text of the article, beginning from Abstract until References (including tables) should be in this file. The file must not contain any mention of the authors' names or initials or the institution at which the study was done or acknowledgments. Do not add any header here. Please incorporate images, tables and graphs in the manuscript file along with the appropriate legends. The pages should be numbered consecutively, beginning with the first page of the blinded article file. The font style should be Times New Roman and font size should be 12 for the main text file.

Mandatory plagiarism check would be done before publication of the selected articles, so authors are requested to follow the recommended guidelines for the same.

Submit good quality colour images. The size of the image can be reduced by decreasing the actual height and width of the images (keep up to 1600 x 1200 pixels or 5-6 inches).

The contributors' / copyright transfer form (template provided below) should be attached in the mail.

The e-mail to the Editor should have these files: 1. Title page (word file) 2. Manuscript (includes Images, graphs and tables) (word file) 3. Copyright transfer statement

INDIAN PROSTHODONTIC SOCIETY MUMBAI/NAVI MUMBAI BRANCH MEMBERSHIP FORM

1. IPS Number (Head Office): 2. Membership applied: Student Member (SM)/Life Member(LM)/ Associate Member(AM)/

Honorary Member (HM) 3. Name: __________________________________________________________________________

Surname First name Middle name 4. Address:_________________________________________________________________________

________________________________________________________________________________ ________________________________________________________________________________

5. Contact No. Cell: ___________________________ Landline: ______________________________ 6. Email:___________________________________________________________________________ 7. Date of birth: _____________________________________________________________________ 8. Marital Status: Single / Married _________________ 9. Qualifications: Degree Year College/ University

i) _________ ________ __________________________________ ii) _________ ________ __________________________________ iii) _________ ________ __________________________________ iv) _________ ________ __________________________________

10. State Dental Council Reg No.: __________________________________________________ 11. Membership fee: i) Student -Rs 500/-

ii) Life member- Rs 2950/- (inclusive of GST) iii) PGs from IPS MNM to life member – Rs 2500/-(inclusive of GST) Payment details:

(A) For NEFT/ RTGS (B) For Cheques Name: IPS Mumbai Navi Mumbai Name: IPS Mumbai Navi Mumbai

A/c No.: 50200014529042 Cheque No. _______________________ Type: Saving account Bank: ____________________________ Bank: HDFC Branch: __________________________ Branch: Andheri west IFSC code: HDFC0000114 (send the copy of transaction)

FOR OFFICE USE ONLY IPS Number checked: ________________________ Cheque cleared: _____________________________ Application approved at EC meeting held on: ______________ Membership status: SM/LM/AM/HM Receipt No.: ____________________________ issued on _________________________________ IPS MNM no.: ___________________________ Signed by: ______________________________ _________________________________

Hon. Secretary: Name: Treasurer: Name:

IPS MNM Correspondences: i)Dr Saloni Mehta Mistry, Hon Secretary 9821020083 Email: [email protected] ii) Dr Parmeet Singh Banga, Treasurer 9960433834 iii)Dr Sharat Shetty, President 9820418986 Address: Secretariat Office - B-3 Velentine Apts D/304,Pimplipada,Off Jerry Verghese Compound ,

opp Tarmat . Malad (East ). Mumbai 400097

Recent Photo

From the IPS MNM President's Desk

Greetings to all of you and best wishes on the digital celebrations of all festivals. The recent Covid 19 outbreak has changed our routine dramatically, affecting our lives and work and exposing our inabilities to handle this unprecedented crisis effectively. The virus has also affected the functionalities of all organizations across the world. As we pass through these grave unpredictable pandemic times, there is still a need to build a stronger future for ourselves and next-generation using all our knowledge, ideas, and resources wisely. There has been a paradigm shift already seen in various sectors in their operations, both domestically and internationally. Hence, we, too, need come together and plan with creative and innovative approaches, in spite of many still being hesitant. There should be an alternate global networking platform for students, faculties, and practicing clinicians to achieve their professional goals. Our Branch of Indian Prosthodontic Society Mumbai-Navi Mumbai (IPS MNM) is in its infancy, but its belly is filled with fire to rise high with professional accomplishments. It has earmarked safe yet implicit programs for the year 2020-21 with a very dynamic team for advancing education. We will grab the available opportunities, and my mission as the President is focussed on to

1. Bolster the legacy of the pioneer prosthodontists of the Mumbai region 2. Improve the value delivered to our members 3. Use current technological advances to further our goals 4. Refresh the harmony of academia, practitioners, and the dental industry

The webinars organized witnessed a strong subscription pan-India, and the smiling faces on our monitors reflect interest from the comforts of their homes for the added values, and we do not want to miss this exciting digital opportunity. We are handpicking seldom spoken topics that are very clinically relevant and brought to our doorsteps by the likes of luminaries like Dr. Shankar Iyer, Dr. V Rangarajan, Dr. Ali Tunkiwala, and Dr. Ajit Shetty. There are many in the pipeline taking shape in our planning room now. Our branch needed a voice to reflect the strength of their research, educational pursuits, and exclusive clinical cases. And The Journal of Prosthodontics and Dental Materials (JPDM) is born this year. This official journal of the IPS MNM is released here with great efforts of our enthusiastic editor Dr. Naisargi Shah and her team, and I am sure that it will scale to indexed version soon. We welcome

all our members to contribute to the journal and discover their talent and experience and appropriately express them. We are also not forgetting our student friends as they are the future of our specialty. And in spite of facing the effects of the pandemic, we are not losing sight of this fact and are arranging enough competitive and mentoring events for them. Mini conferences, essay writing, e-poster makings, case presentations, and exclusive lectures through the new ProsthoCoach channel by celebrated teachers are some of them. Our Immediate Past President, Dr. Omkar Shetty, and the team are incessantly working on compiling educational resources of quality for easy access for our students and add value to their momentum of pursuing a post-graduate course. In today's world, websites have become an essential part of any organization for easy accessibility and for lasting expression of their potential. We also made our customized and dynamic website this year to enable quick engagement at your fingertips, which will expose our presence to the world, display all information of our branch, inclusive of our team, our past, current, and future activities, access to journal contents, educational resources, updates, blogs, etc. There will be links to many advertising dental and medical companies, dental suppliers, and dental laboratories, and members can avail of advantages provided by them only to us. My vision is to have a highly resourceful and trustworthy website of our branch with regular contributions from all our members and visited by prosthodontists across the globe for its valued content. Dr. Guarang Mistry and his team should be credited for their immense perseverance and efforts to create this informative website. Besides the names mentioned above, it has been rewarding for me to have an ever-cheerful, tirelessly working, and talented Executive Committee team on-board in the incoming President Dr. Rathin Das, dedicated and dependable Secretary Dr. Saloni Mistry, hardworking treasurer Dr. Parmeet Banga, and other capable and committed members Dr. Anuradha Nemane, Dr. Praveen Badwaik, Dr. Sankalp Bhandarkar, Dr. Sumit Bedia and Dr. Anita Gala-Doshi, to carry out the mission activities of our branch. We have fruitfully met on many occasions, both virtually and physically, with due safeguards to effectively deliberate avenues to move our profession forward and optimistically plan the seamless implementation of our initiatives. We would like to build this vibrant and zealous organization further by increasing our membership, and I wish to invite suggestions from all of you. Come and join us in this exciting and motivating endeavor, and together we will fulfill our dream and grow intellectually and academically. I, on behalf of our branch, would also like to thank the Head Office presided by Dr. J R Patel with Secretary Dr. Rupesh P L for their continuous support, guidance, and encouragement through their wonderful programs and communications. SAMPARK 2020 was a stand-out event. Kudos, HO team. "Nothing in life is to be feared; it is only to be understood. Now is the time to understand more, so

that we may fear less." said Madam Curie. How apt and true in these times. Respectfully submitted,

Dr. Sharat Shetty President, IPS MNM

Advisor's Note

Powered by disruption-contextual education & oral health practice

Recent times have been challenging to the dental profession as a whole and Prosthodontics in particular. We have witnessed a massive slowdown in practice. Both dental surgeons and patients are apprehensive of being infected with Covid-19 disease. We do hear about dental practitioners down with Covid-19 and sometimes with fatal consequences. Disruption and challenges faced by the dental profession are much higher than any other health profession due to closely working in and around the highest aerosol generation areas. Dental institutions had to commence online classes despite various studies and research showing institutions and faculty's unpreparedness. Moreover, our curriculum design does not fully support distance learning. Innovative teaching, learning, or blended learning practices are not prevalent, especially in our country. Though most institutions have quickly adapted to the virtual platforms, few have established centralized 'LEARNING MANAGEMENT SOFTWARE' (LMS). Another challenge is a clinical practice, which is the core of Dentistry as well as Prosthodontic and requires the development of psychomotor skills. Finding a silver lining for dental education during the pandemic is critical. We need to focus on Preventive Therapeutics, better integration with medical practice, greater emphasis on innovative thinking, dealing with safe practices for overcoming clinical challenges for the benefit of all stakeholders.

Dental procedures should change to include expanded case history covering recent travel details, medical conditions of the patient and their family, pretreatment photographs and videos, shorter clinical guidelines, practice by appointment only, little or no waiting time, pre and postoperative workplace sanitization, and all of these at an affordable cost. Clinical acumen, smart communication skills, and strong ethical values will be very crucial. This challenging time will impact our profession in insignificant ways. So, how do we make the most of our learning during the pandemic? Can we leverage our strengths to take full advantage of this disruption?

It has reminded us; we are human first, vulnerable, and can support each other in times of need. Many dental schools & associations are sharing online webinars. There is exquisite talk on how to improve participation & learner's engagement during these online sessions. Group tasks and participation by attendees provide better peer experience and learning opportunities. Faculty development programs need to retool their approach to enhance student engagement with the curriculum. We all have experienced participating in online meetings and conferences. It saves time, but the involvement of participants is questionable. Online classes combined with contact classes will be the trend, and they are here to stay. Hence, we need to innovate methods to maximize student engagement and learning opportunities. During this pandemic, Prosthodontists have had an opportunity to carefully consider the risk versus benefits of immediate versus the deferred procedural treatment and re-visit minimally invasive treatment such as atraumatic restorative techniques, adhesive bridges, removable partial dentures, and use of conventional speed motors to avoid aerosols. Many are including strict infection control protocols aligned with recommendations from the center for infection control of diseases. Here we recall the early eighties during the HIV & AIDS pandemic when the dental profession was declared as high risk demanded strict clinical infection control procedures and practices. Stress on Universal precaution, mandatory special training for dental surgeons for infection control equipment & procedures including biomedical waste management. Importance of history sheets social history with confidentiality, counseling, record-keeping, legal aspects is a few aspects that every dentist had to learn. The protective equipment was not devised with comfort and ease of performing clinical procedures. Once again, we need to consider practicality and feasibility with safety in our PPEs. To summarize, it needs the hour to be compliant with technology, adapts our teaching sessions to engage learners effectively, and maximize learners' participation. Institutions need to have their learning management software. Focus continues to be procedures – skills backed with knowledge and the right attitude. As we get ready to start our clinics for full-fledged oral healthcare, we must understand patients will have varying medical risk factors that affect their susceptibility to aerosolized micro-organisms. Hence let us adapt to the new normal and practice safely. Online patient history, shorter clinical procedures, minimally invasive procedures, and preventive care will help transition until the world sees a proven approved safe vaccine, herd immunity, and effective Covid treatment. We are standing on the threshold of overhauling our curriculum and educational program based on the new normal demand. Dr. Suhasini Nagda Advisor to Editor, JPDM Founder President, IPS MNM

THE JOURNAL OF


The Official e-publication of Indian Prosthodontic Society


TABLE OF CONTENT Page No.

EDITORIAL 1-2

REVIEW

1. Effect of different finish line preparations on the marginal and internal adaptation of

cobalt - chromium metal copings fabricated using CAD CAM technology - A Scoping

Review.

Dr. Naisargi Shah, Dr. Praveen Badwaik, Dr. Vidhi H Sheth, Dr. Vishrut Bhatnagar, Dr. Nikhil

Bhanushali, Dr Prashant Patil.

3-9

2. JAW IN A DAY A Fibular Reconstruction of The Mandible.

Dr. Saloni Mistry, Dr. Omkar Shete, Dr. Shalu Shah, Dr. Gauraja Kadam, Dr. Ankita Walke.

10-18

3. Margins in restorative dentistry - a review

Dr. Samruddhi Shinde, Dr. Padmini Chandrasekhar, Dr. Shishir Singh, Dr. Rajesh Podar, Dr.

Roshan Shetty, Dr. Avinash Salgar

19-31

4. The right perspective of practicing prosthodontics in post COVID - 19 era.

Dr. Jayesh Banswani, Dr. Naisargi Shah, Dr. Praveen Badwaik, Dr. Rahul Malu, Dr. Kaveri

Chakrabortty, Dr. Arshad Idrisi.

32-41

5. Magnets in prosthodontics - An Overview

Dr. Hrishikesh Mahapatra, Dr. Sumit Bedia

42-50

6. The implant - abutment connection and its relation to crestal bone - a review

Dr. Rahul Ravi, Dr. Adnan Kheyroolla, Dr. Omkar Shetty, Dr. Rubina Tabassum, Dr. Gaurang

Mistry, Dr. Kunal Mehta.

51-59

ORIGINAL RESEARCH

7. Efficacy of citronella oil as an antifungal agent on denture soft liner.

Dr. Banashree S. Sankeshwari, Dr. Pranav R. Tulle, Dr. Raghavendra V. Adaki, Dr. Dayanand

A. Huddar, Dr. Deepti S. Fulari, Dr. Mokshada M. Badadare.

60-64

8. Evaluation of golden proportion in males and females in chhattisgarh population: a

clinical short study.

Dr. Preeti Tiwari, Dr. Saumya Sharma, Dr. Sanjeev Singh, Dr. Vivek Lath, Dr. Priyabrata Jena

65-71

CLINICAL TIP

9. Steps for disinfection of impression

Dr. Rathin Das

72-73

CASE REPORTS

10. Immediate Functional Loading of Completely Edentulous Arches with a Screw

Retained Definitive Prosthesis on Corticobasal Implants: A Case Report

Dr. Anita Gala Doshi, Dr. Vivek Gaur, Dr. Janani Iyer

74-81

11. Neutral zone: a novel approach for resorbed ridge management-a case series

Dr. Ankita Savaliya, Dr. Janani Iyer, Dr. Jyoti Nadgere.

82-89

12. Smile designing using all ceramic laminates guided through aesthetic pre-evaluative

temporaries: a case report.

Dr. Pinak Rathi, Dr. Janani Iyer, Dr. Jyoti Nadgere

90-95

1

Editorial

"A journey of thousand miles begins with a single step."

Lao Tzu

It is my great pride and pleasure to announce the launch of "Journal of Prosthodontics and Dental Materials" (JPDM), the official publication of the Indian Prosthodontic Society, Mumbai- Navi Mumbai branch. It has long been felt that the ever-burgeoning Prosthodontic community of Mumbai and Navi Mumbai needed an outlet to communicate and showcase their talent and skills. To address this requirement, Branch President, EC members, and seniors mooted the idea of having a Branch journal. It was envisaged that the Journal would provide a holistic, inclusive platform that incubates and articulates branch members' passion for learning, innovating, and collaborating. Our vision of making the Journal the first choice of reference and widespread indexing will only be possible by quality research and clinical work submissions by our branch members. This requires focusing on continuous improvement, embracing new ideas and technology, and leveraging the existing depth of knowledge and experience for evolving paradigms. Just as the idea was being crystallized, the Covid-19 pandemic struck. However, it made our resolve even firmer, and the lack of infrastructure or supportive ecosystem did not deter us from achieving our goal. You will be glad to know that the Journal has already created a buzz and excitement among its members. It has received manuscript submissions from individuals and institutes across India. This is both a recognition and testament of the intent and content of the Journal. The issue covers a broad spectrum of prosthodontics and dental materials, including reviews, original research, case presentations, clinical tips, and much more.

2

I am proud to share that the editorial team has gone beyond the normal in the prevailing difficult times to prioritize the Journal roll out. The articles have been painstakingly reviewed, revised, and edited for publishing. The editorial team meticulously curated all Journal aspects, right from artwork, design, layout, and sequencing. The tremendous support from IPS Head Office President Dr. J R Patel, Secretary Dr. Rupesh P L and Editor Dr. N. Gopi Chander, Branch President Dr. Sharat Shetty, Secretary Dr. Saloni Mistry, and our advisors and senior branch members' Dr. Suhasini Nagda, Dr. Sabita M. Ram and Dr. Suresh Meshram, Dr. Jyoti Karani have been very encouraging and humbling. I would also like to thank my editorial team and my department's staff at Terna Dental College, Navi Mumbai, for their endless enthusiasm and tireless efforts in making this project a resounding success. Finally, I would like to thank all our well-wishers, sponsors, and partners who have supported the Journal in its infancy. I wish that our members (students, faculties, and practitioners) take maximum advantage of this opportunity to showcase their abilities as researchers and clinicians. The JPDM will be published biannually for the benefit of the branch members. Issues 1 and 2 covering the period January to June and July to December 2020 are being launched simultaneously.

Arise, awake, and stop not till the goal is reached Swami Vivekanand

Dr. Naisargi Shah Editor, IPS MNM

The JPDM I Vol 1 I Issue 1 and 2 I 2020 3

THE JOURNAL OF PROSTHODONTICS AND DENTAL MATERIALS

The Official e-publication of Indian Prosthodontic Society MUMBAI - NAVI MUMBAI BRANCH

ABSTRACT Purpose: This scoping review aimed to evaluate the effect of different finish line preparations on the

marginal and internal adaptation of cobalt-chromium metal copings fabricated using computer-aided

designing and computer-aided manufacturing (CAD-CAM) technology.

Material and Methods: The Arksey and O’Malley methodological framework has been followed for

this scoping review. The research question and the PIO criteria were established accordingly. An

electronic search of the PubMed database for articles published from 1st January 2010 to 31st July 2020

was conducted using a combination of MeSH terms and free-text terms.

Results: 9 articles were eventually identified after applying the inclusion and exclusion criteria and were

included in this scoping review. A better overall marginal adaptation was reported in deep chamfer finish

line preparation followed by shoulder and chamfer finish line preparations respectively, whereas a better

overall internal adaptation was reported in shoulder finish line preparation as compared to chamfer and

deep chamfer finish line preparations.

Conclusions: Different finish line preparations and the CAD-CAM method of fabrication seem to

influence the marginal and internal adaptation of single-unit tooth-supported cobalt-chromium metal

copings. A more detailed search of the available literature is required, preferably a systematic review

and meta-analysis, to come to a more definitive conclusion regarding the effect of different finish line

preparations on the marginal and internal adaptation of cobalt-chromium metal copings fabricated using

CAD-CAM technology.

Effect of Different Finish Line Preparations on The Marginal and Internal Adaptation of Cobalt – Chromium

Metal Copings Fabricated Using CAD – CAM Technology – A Scoping Review

Dr Naisargi Shah1, Dr Praveen Badwaik2, Dr Vidhi H Sheth3, Dr Vishrut Bhatnagar4, Dr Nikhil

Bhanushali5, Dr Prashant Patil6

1Professor and Head of Department, 2Professor,

3Post-graduate Student, 4Reader,

6Lecturer,

Department of Prosthodontics, Crown & Bridge, 5Reader

Department of Public Health Dentistry.

T.P.C.T’s Terna Dental College, Navi Mumbai

5Reader, Department of Public Health Dentistry,

T P C T’s Terna Dental College, Navi Mumbai.

Shah N. et al: Finish Line Preparations – A Scoping Review


Key-words: Finish line preparations, chamfer, deep chamfer, shoulder, rounded shoulder, marginal

adaptation, internal adaptation, cobalt-chromium metal copings, CAD-CAM technology

Introduction

The advent of computer-aided designing and computer-aided manufacturing (CAD-CAM)

technology has greatly improved the efficiency and accuracy of prosthetic treatment when compared to

conventional methods.1 One of the most widely used applications of this technology in the dental field

has been in the manufacturing of cobalt-chromium metal copings for fixed dental prosthesis. These are

one of the most widely used materials today due to their high strength, good esthetic results, and

longevity.2

The success of these prostheses greatly depends upon their marginal and internal adaptation,

amongst other factors.3 Marginal adaptation has been considered as the distance between the finish line

preparation and the coping margin. The internal adaptation has been considered as the distance between

the intaglio surface of the coping and the axial and occlusal surface of the prepared tooth. The presence

of discrepancies in this adaptation can lead to increased plaque accumulation, alterations in the

distribution of microflora, and gingival irritation.4 This can further contribute to a higher risk of dental

caries, possibly leading to secondary decay, followed by endodontic complications, leading to eventual

failure of the prosthesis.5,6 Thus, marginal and internal adaptation of cobalt-chromium metal copings is

considered an essential criterion for assessing clinical quality and success of fixed dental restorations.

Various factors can affect the marginal and internal adaptation of these metal copings, one of

them being the finish line preparation. Currently, there is no clear consensus as to which finish line

preparation can provide the best marginal and internal adaptation in the case of cobalt-chromium metal

copings.

Thus, this scoping review aims to evaluate the effect of different finish line preparations on the

marginal and internal adaptation of Cobalt-chromium metal copings fabricated using CAD-CAM

technology. This scoping review was conducted as a part of the pilot search for an ensuing systematic

review.

Methodology

The Arksey and O’Malley methodological framework was followed for this scoping review (Figure 1).7

Figure 1: Arksey and O’Malley methodological framework for conducting a scoping review



Stage 1: Identifying the research question

The research question defined for this scoping review was, “Do different finish line preparations

influence the marginal and internal adaptation of cobalt-chromium metal copings fabricated using CAD-

CAM technology?”

The PIO criteria was established based on the research question as follows:

Population: Cobalt-chromium metal copings fabricated using CAD-CAM technology.

Intervention: Different finish line preparations (chamfer, deep chamfer, shoulder, rounded shoulder).

Outcome: Discrepancy in marginal and internal adaptation.

Stage 2: Identifying relevant studies

An electronic search of the PubMed database for articles published from 1st January 2010 to

31st July 2020 was conducted. The search was conducted using a combination of various controlled

vocabulary terms (i.e., MeSH terms) as well as free text terms related to the research question. The

MeSH terms used were Crown, Computer-Aided Design, Tooth preparation, Prosthodontic and Dental

Marginal Adaptation. The free text terms used were cobalt-chromium metal copings, computer-aided

designing, computer-aided manufacturing, CAD-CAM, finish line design, chamfer, deep chamfer,

shoulder, rounded shoulder, internal fit, internal adaptation, marginal fit and marginal adaptation.

Various combinations of the MeSH terms and the free text terms were used to conduct the searches.

Stage 3: Study selection

Articles published from 1st January 2010 to 31st July 2020 were included. Only those studies

evaluating effect of different finish line preparations (chamfer, deep chamfer, shoulder, rounded

shoulder) on the marginal and/or internal adaptation of single-unit tooth-supported cobalt-chromium

metal copings fabricated using CAD-CAM technology were included. Also, articles published in the

English language only were included.

Case reports, case series, finite element analysis, review articles and surveys were excluded from

this scoping review. Studies evaluating single-unit metal-ceramic restorations after ceramic veneering,

multi-unit restorations, all-ceramic restorations, full-metal restorations, implant-supported prosthesis,

partial-coverage restorations, or temporary restorations; or cobalt-chromium metal copings fabricated

by techniques not involving CAD-CAM technology were also excluded. Studies with sample size less

than or equal to 5 were also excluded.

A total of 64 articles were obtained in the searches. 36 articles were excluded after the title and

abstract screening, followed by the further exclusion of 19 articles after full text evaluation. 9 articles

were eventually identified after applying the inclusion and exclusion criteria and were included in this

scoping review (Figure 2).

Stage 4: Charting the data

The data was then extracted from the 9 selected studies and was entered into a Microsoft Excel

spreadsheet (Figure 3). The data items that were extracted and charted were:

1. Author.

2. Year of publication.

3. Study setting.

4. Sample Size.

5. Finish line preparation design.

6. CAD-CAM method used for manufacturing the Cobalt-chromium copings.

7. Method of measurement of marginal and/or internal fit.

8. Marginal and/or internal fit with mean and standard deviation values (in microns).



Figure 2: Flow-chart for the search strategy

Figure 3: Study Characteristics



Stage 5: Collating, summarizing and reporting the results

Out of the 9 articles included, Kim et al., Xu et al., Park et al., Lövgren et al., and Dong-Yeon

Kim et al. evaluated the chamfer finish line design.8-10,12,13 Out of these 5 articles, Kim et al. and Xu et

al. used the direct metal laser sintering method for coping fabrication.8,9 Park et al. used the hard and

soft milling method for coping fabrication whereas Lövgren et al. used the direct metal laser sintering

and hard milling method for coping fabrication.10,12Dong-Yeon Kim et al. used the direct metal laser

sintering and soft milling method for coping fabrication.13

The marginal adaptation with respect to the chamfer finish line preparation seemed to be better

when soft milling was used for coping fabrication followed by the direct metal laser sintering. Hard

milling methods showed the worst marginal adaptation. No conclusions could be drawn regarding the

internal adaptation of the chamfer finish line preparation.

Out of the 9 articles included, only Vojdani et al. evaluated the shoulder finish line preparation.11

Vojdani M et al. used the hard and soft milling method for coping fabrication and reported a better

marginal and internal adaptation with hard milling as compared to soft milling.

Seong-Bin Kim et al. evaluated the deep chamfer finish line and used the hard milling method

for coping fabrication, whereas Rödiger et al. evaluated the rounded shoulder finish line and has also

used the hard milling method for coping fabrication.14,15 No conclusions could be drawn with respect to

these two finish lines due to a lack of comparative studies.

Maaz Adel Al et al. evaluated the chamfer, deep chamfer and shoulder finish line preparations

and used the direct metal laser sintering method for coping fabrication.16 They reported a better overall

marginal adaptation in deep chamfer finish line preparation followed by shoulder and chamfer finish

line preparations. However, they found a better overall internal adaptation in shoulder finish line

preparation. This was followed by the chamfer and deep chamfer finish line preparations.16

Discussion

Scoping reviews represent an increasingly popular approach to reviewing health research

evidence.17 They present a great tool to help rapidly map the already available literature with respect to

a particular subject matter, thereby enabling researchers to identify the research potential and

subsequently plan future researches.18,19 Similarly, this scoping review was primarily conducted as a part

of a pilot search to assess the range and nature of research available, and to determine the necessity to

conduct a systematic review on this topic in the future.

The Arksey and O’Malley methodological framework was followed for this scoping review.7

This was decided based upon the scoping review conducted by Pham MT et al. in which they found that

the Arksey and O'Malley (2005) framework had been used in 62.6% (109/174) of the scoping reviews

they evaluated and was thus the most frequently used framework design used for conducting scoping

reviews.20 Levac et al. also reported that this framework provided an excellent methodological

foundation for conducting scoping reviews.19

The advent of CAD-CAM technology has paved the way for a highly precise and efficient digital

workflow.21 The application of this technology for the manufacturing of cobalt-chromium metal copings

for fixed dental prosthesis via additive and subtractive manufacturing and the quality of its marginal and

internal accuracy has been well documented.22 However, there remains some amount of uncertainty with

respect to the effect of finish line preparations on the marginal and internal adaptation of single-unit

tooth-supported cobalt-chromium metal copings fabricated using CAD-CAM technology. Hence, this

subject was chosen for defining the research question of this scoping review.

The chamfer, deep chamfer, shoulder and rounded shoulder finish line designs were taken into

account since these are the most widely used finish line preparation designs for metal-ceramic fixed

dental prosthesis. A PIO format was chosen based on the research question. All the finish line designs

https://onlinelibrary.wiley.com/doi/full/10.1002/jrsm.1123#jrsm1123-bib-0002



were considered in the intervention group, and no comparison group was established to ensure maximum

inclusion of data for this scoping review.

As enlisted in the results, a better marginal adaptation was reported in deep chamfer finish line

preparation followed by shoulder and chamfer finish line preparations respectively. In contrast, a better

internal adaptation was reported in shoulder finish line preparation as compared to chamfer and deep

chamfer finish line preparations.

The limitations of this scoping review are that the search was limited to a single database and a

select few MeSH terms, and free text terms were used in the search, due to which some of the available

literature might have been overlooked.

Despite the limitations, a decent amount of homogenous literature does seem to be available on

this subject. This scoping review also found that the effect of different finish line preparations on the

marginal and internal adaptation can be due to multiple factors that need to be further elaborated. Thus,

a systematic review and meta-analysis needs to be conducted on this subject to come to a more definitive

conclusion.

Conclusion • Finish line preparations and the CAD-CAM method of fabrication seem to influence the marginal

and internal adaptation of single-unit tooth-supported cobalt-chromium metal copings.

• A better overall marginal adaptation was reported in deep chamfer finish line preparation followed

by shoulder and chamfer finish line preparations.

• A better overall internal adaptation was reported in shoulder finish line preparation as compared to

chamfer and deep chamfer finish line preparations.

• The marginal adaptation seemed to be better when soft milling was used for coping fabrication

followed by the direct metal laser sintering and hard milling methods with respect to the chamfer

finish line preparation.

• The marginal and internal adaptation was reportedly better with hard milling as compared to soft

milling with respect to the shoulder finish line preparation.

• A more elaborate search of the available literature is required, preferably a systematic review and

meta-analysis, to come to a more definitive conclusion regarding the effect of different finish line

preparations on the marginal and internal adaptation of cobalt-chromium metal copings fabricated

using CAD-CAM technology.

References:

1. Boitelle P, Mawussi B, Tapie L, Fromentin O. A systematic review of CAD/CAM fit restoration

evaluations. J Oral Rehabil 2014;41(11):853-74.

2. Svanborg P, Hjalmarsson L. A systematic review on the accuracy of manufacturing techniques for

cobalt chromium fixed dental prostheses. Biomater Investig Dent 2020;7(1):31-40.

3. Papadiochou S, Pissiotis AL. Marginal adaptation and CAD-CAM technology: A systematic

review of restorative material and fabrication techniques. J Prosthet Dent 2018;119(4):545-51.

4. Valderhaug J, Birkeland JM. Periodontal conditions in patients 5 years following insertion of fixed

prostheses. Pocket depth and loss of attachment. J Oral Rehabil 1976;3(3):237-43.

5. Valderhaug J, Heloe LA. Oral hygiene in a group of supervised patients with fixed prostheses. J

Periodontol 1977;48(4):221-4.

6. Lang NP, Kiel RA, Anderhalden K. Clinical and microbiological effects of subgingival restorations

with overhanging or clinically perfect margins. J Clin Periodontol 1983;10(6):563-78.

7. Arksey H, O'Malley L. Scoping studies: towards a methodological framework. Int Jour of Soc Res

Method 2005 Feb 1;8(1):19-32.



8. Kim KB, Kim JH, Kim WC, Kim HY, Kim JH. Evaluation of the marginal and internal gap of

metal-ceramic crown fabricated with a selective laser sintering technology: two- and three-

dimensional replica techniques. J Adv Prosthodont 2013;5(2):179-86.

9. Xu D, Xiang N, Wei B. The marginal fit of selective laser melting-fabricated metal crowns: an in

vitro study. J Prosthet Dent 2014;112(6):1437-40.

10. Park JK, Kim HY, Kim WC, Kim JH. Evaluation of the fit of metal ceramic restorations fabricated

with a pre-sintered soft alloy. J Prosthet Dent 2016;116(6):909-15.

11. Vojdani M, Torabi K, Atashkar B, Heidari H, Torabi Ardakani M. A Comparison of the Marginal

and Internal Fit of Cobalt-Chromium Copings Fabricated by Two Different CAD/CAM Systems

(CAD/ Milling, CAD/ Ceramill Sintron). J Dent (Shiraz) 2016;17(4):301-8.

12. Lövgren N, Roxner R, Klemendz S, Larsson C. Effect of production method on surface roughness,

marginal and internal fit, and retention of cobalt-chromium single crowns. J Prosthet Dent

2017;118(1):95-101.

13. Kim DY, Kim JH, Kim HY, Kim WC. Comparison and evaluation of marginal and internal gaps

in cobalt-chromium alloy copings fabricated using subtractive and additive manufacturing. J

Prosthodont Res 2018;62(1):56-64.

14. Kim SB, Kim NH, Kim JH, Moon HS. Evaluation of the fit of metal copings fabricated using

stereolithography. J Prosthet Dent 2018;120(5):693-98.

15. Rödiger M, Schneider L, Rinke S. Influence of Material Selection on the Marginal Accuracy of

CAD/CAM-Fabricated Metal- and All-Ceramic Single Crown Copings. Biomed Res Int

2018;2018:2143906.

16. Al Maaz A, Thompson GA, Drago C, An H, Berzins D. Effect of finish line design and metal alloy

on the marginal and internal gaps of selective laser melting printed copings. J Prosthet

Dent2019;122(2):143-51.

17. Davis K, Drey N, Gould D. What are scoping studies? A review of the nursing literature. Int J Nurs

Stud 2009;46(10):1386-400.

18. Peterson J, Pearce PF, Ferguson LA, Langford CA. Understanding scoping reviews: Definition,

purpose, and process. J Am Assoc Nurse Pract 2017;29(1):12-16.

19. Levac D, Colquhoun H, O'Brien KK. Scoping studies: advancing the methodology. Implement Sci

2010 Dec 1;5(1):69.

20. Pham MT, Rajić A, Greig JD, Sargeant JM, Papadopoulos A, McEwen SA. A scoping review of

scoping reviews: advancing the approach and enhancing the consistency. Res Synth

Methods2014;5(4):371-85.

21. Serag M, Nassar TA, Avondoglio D, Weiner S. A Comparative Study of the Accuracy of Dies

Made from Digital Intraoral Scanning vs. Elastic Impressions: An In Vitro Study. J

Prosthodont 2018 Jan;27(1):88-93.

22. Baroudi K, Ibraheem SN. Assessment of chair-side computer-aided designand computer-aided

manufacturing restorations: a review of the literature. J Int Oral Health 2015;7:96-104.

https://www.ncbi.nlm.nih.gov/pubmed/?term=Serag%20M%5BAuthor%5D&cauthor=true&cauthor_uid=27149542

https://www.ncbi.nlm.nih.gov/pubmed/?term=Nassar%20TA%5BAuthor%5D&cauthor=true&cauthor_uid=27149542

https://www.ncbi.nlm.nih.gov/pubmed/?term=Avondoglio%20D%5BAuthor%5D&cauthor=true&cauthor_uid=27149542

https://www.ncbi.nlm.nih.gov/pubmed/?term=Weiner%20S%5BAuthor%5D&cauthor=true&cauthor_uid=27149542

https://www.ncbi.nlm.nih.gov/pubmed/27149542

https://www.ncbi.nlm.nih.gov/pubmed/27149542


THE JOURNAL OF PROSTHODONTICS AND DENTAL MATERIALS The Official e-publication of Indian Prosthodontic Society


Jaw in A Day A Fibular Reconstruction of The Mandible

Dr Saloni Mistry 1, Dr Omkar Shete 2, Dr Shalu Shah3, Dr Gauraja Kadam3, Dr Ankita Walke4

1Professor and HOD, 2Associate Professor,

3Second year Post Graduate Student, 4First year Post Graduate Student.

Y.M.T Dental College and Hospital, Kharghar.

ABSTRACT: The goals in reconstructing mandibular discontinuity defects are to provide architectural

support to restore and preserve lower facial contour and occlusal relationships. Patients with

unrestored mandible have cosmetic disfigurement, compromised function, and difficulty in

socializing.

A wide variety of methods have been reported to reconstruct these defects with osseous grafts

harvested from various donor sites like ilium, radius, metatarsal, scapula, and fibula.

However, each of these donor sites has significant limitations related to the length of available bone

or the reliability of the associated soft tissue.

The advantages of the fibula as a donor site are not limited to the surgical aspect, but with the use of

technology as an adjunct to a surgical procedure in the form of a 3D printed stent; the prosthetically

driven placement of the fibular graft is now possible. Computer-aided design/computer-aided

manufacturing (CAD/CAM) technology has recently opened new frontiers in maxillofacial bone

reconstruction.

The crucial role of a Prosthodontist is to guide the fabrication of surgical stents manually or by 3D

printing, which helps oral surgeons to contour the fibular grafts for favorable functional and

harmonious prosthodontic rehabilitation in terms of occlusion.

This article overviews the metamorphosis of rehabilitation procedures from the conventional free

fibular grafts approach to a novel approach of rehabilitating the mandible with pre osseointegrated

implants using a 3D printed stent.

Introduction Resection of a part or complete mandible is a treatment modality for many pathological conditions. Patients with unrestored mandible have cosmetic disfigurement, compromised function and difficulty in socializing. The microvascular fibula free flap popularized by Hidalgo1 has become one of the most significant advances in reconstructing the maxillofacial region. The

Mistry S. et al : Jaw in A Day: Fibular Reconstruction of Mandible

The JPDM I Vol 1 I Issue1 and 2 I 2020 11

conventional process of rehabilitation demands time and meticulous sequential procedures to be followed. However, with the use of technology as an adjunct to a surgical procedure in the form of 3D printed

stents and virtual planning, the prosthetically driven placement of the graft and implants makes this

approach more accurate, predictable and also considerably decreases the time required.

Rehabilitation goals

A] Choice of graft

The ultimate goal in mandibular reconstruction cases is the restoration of both form and function. We

can achieve this through various surgical techniques, mainly non-vascularized bone grafts (NVBGs)

and vascularized grafts. Direct comparisons of NVBGs and vascularized bone flaps (VBFs) have

shown the superiority of the latter in terms of bony union (69% for NVBGs vs. 96% of VBFs)2 as

well as superior functional and aesthetic scores for diet, speech, and midline symmetry.3 Superiority

of VBGs compared to NVBGs increases significantly in mandibular defects greater than 6 cm or

previously irradiated tissue.2 Vascularized flaps withstand irradiation better. Available options for

VBGs are the fibula, radial forearm, scapula, and iliac crest.4-7

B] Why fibula is the choice of graft?

➢ The use of free vascularized fibula has become the “gold standard” for mandibular

reconstruction since its introduction by Hidalgo in 1989,1 due to various advantages over other

VBGs.

➢ It provides the longest bone segment with 20 to 30 cm long, 14 mm wide with a bicortical

plate, allowing implant placement and osseointegration.

➢ A reasonably long vascular pedicle with large diameter vessels, mainly peroneal artery, and

the segmental blood supply of the bone permits multiple osteotomies.8

➢ The most reliable septocutaneous perforators are located in the middle and distal third of the

fibula.9

➢ We can harvest Soleus muscles with the fibula if additional bulk is required.

➢ We can use proximity of the sural nerve for the reconstruction of the inferior alveolar nerve.

➢ Minimal donor site morbidity and ease of harvesting.

C] Two ways to get there

The complete rehabilitation of the mandible can be carried out in 2 different approaches the

conventional and digital namely, depending on the method followed for the reconstruction.

1. Conventional approach: The conventional approach is completely based on the expertise and

experience of the clinician. It includes simultaneous resection of the mandibular pathology as well as

the harvesting of the fibular graft. This is done based on of manual measurements, making it not

100% accurate. The resection is then followed by the surgical reconstruction of the mandible by

harvesting the fibular graft. Before the placement of implants, the patient has to wait for a period of

3-5 months for the graft to get accepted.

After the acceptance and healing of the graft, we can conduct a second surgery to place the implants;

followed by another waiting period of 3-6 months for the osseointegration of the implants. The



process of fabrication for the prosthesis beings after this, thereby increasing the time frame required

for the complete rehabilitation to 9-12 months.

Drawbacks of a conventional approach

1) Long waiting period till satisfactory function and aesthetics are achieved.

2) Formation of a thick layer of soft tissue post the first surgery hampers the placement

of implants; in such cases “Debulking” of the soft tissue is necessary.

3) Manual measurements used for resection make it difficult to reach the optimal

positioning of implants.

4) Each surgical intervention increases the risk of infection.

A study10 of 56 patients has reported 92% implant success versus only 42.9% prosthetic success. The

reasons proposed by the authors are patient’s poor cooperation (30.4%), tumour recurrence (14.3%),

and surgery-related factors (10.8%) in which the authors include both implant failure and an

unfavorable relationship between the maxilla and the reconstructed mandible. One should consider

that a high implant osseointegration rate is not significant if the functional prosthetic result is bad.10

Thus, from this study, it is inferred that the success of such cases is predicted from the standpoint of

final occlusion achieved and duration needed for the complete reconstruction ,which necessitates the

use of digital methods.

2. Digital approach

3D printing is a rapidly growing technology in the medical field, which can provide adapted solutions.

After resection of malignant tumours, mandibular reconstruction using a free fibular flap and a 3D

printed resection guide is considered to be more accurate than conventional reconstruction. Moreover,

this technique is expected to contribute to shorter surgical times and overall cost savings.

Working a case from the digital stand point begins with a CT – scan of the mandible with the

pathology and a CT-angiography for the fibula. A CT- angiography is done to check for the peroneal

artery’s patency, to be harvested along with the graft. These files are provided in DICOM formats.

After the scan, various software e.g.- Geoform, MAGICS etc are used to convert the DICOM file into

STL format, which is essential for the virtual planning of the case. The files are uploaded onto the

software; the various tools are then used to analyze the extent of the lesion and create a personalized

treatment plan. The accessed pathology is virtually resected by keeping safety margins (Figure 1).11

Following which a resection stent is designed to be used at the time of surgery for the accurate

excision of the pathology (Figure 2).

Figure 1 Figure 2

Figure 1. - Virtual Delineation of The Part to Be Resected



Figure 2 - Virtual Image Of Pathology Resection Stent

Simultaneously the fibula is analyzed for the area to be resected depending on the anatomical

considerations. Those include using the middle portion of the bone, not including the distal end of

the bone to maintain its vascularity. Cases,which include the resection of the anterior section of the

mandible are more difficult to rehabilitate as it entails the reconstruction of the anatomical curvature.

This can be achieved via virtual planning (Figure 3A,3B).

Figure 3 A Figure 3 B

Figure 3 - Virtual Images f The Fibula Sectioning Using The Fibular Stent

3A - Three Segments Aligned

3B - Three Segments Aligned to Achieve the Anterior Curvature of The Mandible.

The cutting planes for the fibula are decided based on the amount of graft needed for the

reconstruction. The angles between these cutting planes act as a guide to achieve the anterior

curvature of the mandible. Along with the angles the resected pieces help us gauge the height, width

and placement of the implants (Figure 4), thereby guiding us to rehabilitate the occlusal harmony

post-surgery. Post the planning two more stents are designed, one for the resection of the fibula and

another for the implant placement (Figure 5A, 5B).

Figure 4 - Virtual Image of Resected Pieces Gauging the Height, Width and Placement Of The

Implants



Figure 5A- Mandibular Resection Stent 5B - Fibular Resection And Carrier Stent

The resection stent has a snap-fit onto the bone, thus making the resection accurate and easy. The

designed stents are then 3D - printed and sterilized by UV radiation and H2O2 plasma. A 3D printed

model of the mandible can also be printed to contour the reconstruction plate (Figure 6).1

Figure 6 – Digital Approach, 3D Printed Implant Placement Stent

On the day of the surgery, two surgical teams simultaneously resect the mandible and harvest the

fibular graft using the previously printed stents, attach the reconstruction plate to the harvested fibular

graft , and attach it to the remnant mandible; implants are placed thereafter using the stent (Figure

7A). Following the implant placement, there is a waiting period of 3-6 months for the graft to get

accepted and implants to Osseointegrate simultaneously. A prosthesis is then fabricated (Figure 7B).

Figure 7A - Mandible with Accepted Graft 7B- Prosthodontic Rehabilitation – The 3D Printed Way

JAW IN A DAY: 13-15

Introduced by Levine in 2013, this approach proposes the complete reconstruction and rehabilitation

of the maxilla and mandible in the same surgical intervention. This technique used digital technology

to plan, design, fabricate and deliver a comprehensive reconstruction for an ablative mandibular

defect using a fibular free flap that included immediate implant placement and a provisionalized fixed



dental prosthesis. As a result, the reconstructive surgeon now has the ability to place dental implants

and deliver a temporary fixed prosthesis on the same day as the jaw resection and free flap

reconstruction, fully restoring the patient surgically and prosthetically to form and function in a single

operation.

Patient Selection - It is crucial to know the pathology and to have a biopsy confirming the diagnosis

to plan the resection with adequate margins, comorbidities that could affect the success of a

microvascular reconstruction, such as vascular or autoimmune disease. ‘Jaw in a Day’ is limited to

using an osseous fibula flap with no significant soft tissue component. To avoid further complications

this technique is currently used for non-cancerous benign lesions.

Radiographic assessment – Maxillofacial CT and a CT angiogram of the bilateral lower extremities,

with resolution scans with image slice of 1mm or less. These help us to plan the surgery, virtually,

allowing us to “work backwards” and have a prosthetically driven approach.

Technique – Imaging of dentition with either Digital impression using an intraoral scanner or laser

scanning of traditional alginate impression is done, which is merged with Maxillofacial and CT

angiogram of lower extremities. These images are imported to the surgical planning software using

DICOM format. Using software systems, virtual surgical planning (VSP) is done. Virtual surgery is

then performed by a biomedical engineer. By identifying the pathology on the model, a resection is

planned with acceptable margins and resection guide is designed. It has predictable holes correlating

to holes for reconstruction plates, which are drilled before resection to ensure their accurate placement

of the bony segment using a reconstruction plate as an index. These resection guide can be tooth-

borne or bone-borne. Tooth borne being more accurate due to the absence of soft tissue between bone

and guide. Following which, the appropriately sized segment of the fibula is chosen ,and the number

and position of implants are planned and incorporated into the same fibular resection cum implant

placement guide. This guide has to be secured with a monocortical screw to prevent movement. Then,

custom reconstruction plates are designed. The design of the plates and cutting guides are finalized

and approved by the surgeon, and the cutting guides and hardware are fabricated and delivered for

surgery. The provisional prosthesis can be designed virtually as well and milled prior to surgery.

Placing dental implants into fibula bone is similar to placing implants in to dense type 1 mandible.

Osteotomies should be slightly overprepared, paying close attention to widening the cortices with the

final drill. Following final drill, the osteotomy site is thoroughly irrigated and inspected for soft tissue

remains.

The implants are then screwed into the bone and hand-torqued to the appropriate value and primary

stability is determined, following which prosthetic abutments with screw retained temporary

cylinders are placed and torqued. While still pedicled to the leg, the fibula/reconstruction

plate/provisional construct is tried into a pre-prepared stereolithic model of the segmental defect site

and checked. Once accurate occlusion is achieved, the prosthesis is luted to provisional cylinders.

Then the whole assembly is transferred to the site and maxillomandibular fixation is carried out to

ensure satisfactory occlusion prior to osteosynthesis of the osseous fibular flap to the jaw.

D] Choice of prosthesis

➢ Fixed Prosthesis- might stimulate the bone but can be more difficult to adapt because of

anatomical conditions, especially a reduced mouth opening. It also requires a high number of

implants, which is not always possible in these patients. It is recommended in case of short

grafts (Figure 8). 16

➢ Removable Prosthesis - necessitate fewer implants. The rehabilitation, follow up and oral

hygiene are easier. The procedure is cheaper. It can also easily compensate for an aesthetic

defect, especially in the anterior part of the mandible.17 However, hyposalivation might lead



to mucosal irritations and the significant decrease of blood vessels in the oral mucosa renders

soft tissues more susceptible to traumas.

➢ The main problem with prosthesis remains the unfavorable implant–crown ratio and axis of

the implants, which is not always the same as an axis of the prosthesis, leading to torque forces

that may endanger implant survival.

➢ Use of image-guided surgery and surgical guides decreases the risk and minimises the

angulation between the prosthetic axis and implant axis and also allows precise planning and

accuracy of the rehabilitation.18,19

➢ When the placement of five implants or more is possible, a fixed ceramic prosthesis can be

placed. A fixed hybrid ‘‘Branemark-like’’ prosthesis can be a good alternative for permanent

rehabilitation. A bar framework (Figure 9) can also be proposed for patients wearing a

removable denture, as well as O-ring retained dentures or telescopic retention.20

Figure 8 - Fixed Implant Supported Prosthesis with Multiple Implants (Implant guides are planned

into the fibula cutting guide. Left: fibula guide overlayed on fibula. Right:fibula guide with planned

implants).

Figure 9 - REMOVABLE IMPLANT SUPPORTED PROSTHESIS (Dental Prosthetic

Rehabilitation Of A Class III Defect With Oral Implants In The Fibula And Supraconstruction

Using A Bar Supported Denture).

Merits of Digital Approach – ➢ “Reverse engineering” helps to achieve accurate and predictable results.

➢ Occlusal driven planning increases the efficiency of the final prosthesis.

➢ Decreases time and number of surgeries.

➢ Decreased trauma to tissues.

➢ Decreases chances of infection.

Like with almost any other process, there are also drawbacks of 3D printing technology, which

should be considered before using this process. These drawbacks include High Energy

Consumption, 3D printing technology is not cost-effective, limited materials, chances of harmful

emissions, copyright infringements etc.



Future scope The advent of 3D printing has opened many avenues to the field of medical science. Further Use of

this technology will help us evolve our treatment options in the future. The new emerging ideas to be

considered for mandibular rehabilitation includes-

➢ Prefabricated free fibular grafts – introduced by Rohner21 in 2013, includes the prior

osseointegration of the implants in the fibula followed by the resection and reconstruction.

➢ Titanium frameworks – in cases with extensive resection, an alternative to use of fibular grafts

is the use of 3D printed titanium frameworks to hold and give shape to the mandible.

➢ Tissue engineering approaches utilizing collagen-based scaffolds combined with bone

marrow-derived stromal cells and growth factors. Additionally, off-label use of bone

morphogenetic protein-2 (rhBMP-2) in a collagen carrier has been described as a new

alternative to various types of autogenous bone grafting procedures.22

Conclusion Disfigurement of the face, impaired speech and inability to chew are stigmas that are significant in

the social world. Rehabilitation of patients with maxillofacial defects poses a challenge to the able

clinician. Medical imaging and computer-assisted surgery help in improving these surgical

techniques. The digital approach discussed in this article not only overcomes the demerits of the

conventional approach but also proves its own merits in numerous ways to achieve harmonious

occlusion, function and aesthetics. Precise knowledge and the blend of biological principles and

technology is the key to defining success in rehabilitating patients with maxillofacial defects.

References:

1) Hidalgo DA: Fibula free flap: A new method of mandible reconstruction. Plast Reconstr Surg

1989;84:71.

2) Foster RD, Anthony JP, Sharma A, Pogrel MA. Vascularized bone flaps versus non-

vascularized bone grafts for mandibular reconstruction: an outcome analysis of

primary bony union and endosseous implant success. Head Neck 1999;21(1):66-71.

3) King TW, Gallas MT, Robb GL, shalani Z, Miller MJ. Aesthetic and functional

outcomes using osseous or soft-tissue free flaps. J Reconstr Microsurg 2002;18:365-

71.

4) Taylor GI, Townsend P, Corlett R. Superiority of the deep circumflex iliac vessels

as the supply for free groin flaps. Plast Reconstr Surg 1979;64:595-604.

5) Soutar DS, Scheker LR, Tanner NS, Gregor Mc. The radial forearm flap: a versatile

method for intra-oral reconstruction. Br J Plast Surg 1983;36:1-8.

6) Swartz WM, Banis JC, Newton ED, Ramasastry SS, Jones NF, Acland R. The

osteocutaneous scapular flap for mandibular and maxillary reconstruction. Plast

Reconstr Surg 1986;77:530-45.

7) Taylor GI, Miller GD, Ham FJ. The free vascularized bone graft: a clinical extension

of microvascular techniques. Plast Reconstr Surg 1975;55:533-44.

8) Daya M. Peroneal artery perforator chimeric flap: changing the perspective in free

fibula flap use in complex oromandibular reconstruction. J Reconstr Microsurg

2008;24:413-8.

9) Chen ZW, Yan W. The study and clinical application of the osteocutaneous flap of

fibula. Microsurgery 1983;4:11-6.

10) Smolka K, Kraehenbuehl M, Eggensperger N, Hallermann W, Thoren H, Iizuka T,

et al. Fibula free flap reconstruction of the mandible in cancer patients: evaluation of

a combined surgical and prosthodontic treatment concept. Oral Oncol

2008;44(6):571–8.



11) Liu YF, Xu LW, Zhu HY, Liu SSY. Technical procedures for template-guided

surgery for mandibular reconstruction based on digital design and manufacturing

BioMedical Engineering OnLine 2014, 13:63.

12) Cohen A, Laviv A, Berman P, Nashef R, Abu-Tair J. Mandibular reconstruction

using stereolithographic 3-dimensional printing modelling technology. OOOOE

2009 Nov;108(5):661-666.

13) Levine JP, Bae JS, Soares M, Brecht LE, Saadhe PB, Ceradini DJ, Hirsch DL. Jaw in a day:

Total maxillofacial reconstruction using digital technology. Plast Reconstr Surg

2013June;131:1386.

14) Levine JP, Patel A, Saadeh PB, Hirsch DL. Computer-aided design and manufacturing in

craniomaxillofacial surgery: the new state of the art. J Craniofac Surg. 2012;23(1):288-293.

15) Patel A, Harrison P, Cheng A, Bray B, Bell RB. Fibular Reconstruction of the Maxilla and

Mandible with Immediate Implant-Supported Prosthetic Rehabilitation: Jaw in a Day. Oral

Maxillofac Surg Clin North Am 2019;31(3):369-386.

16) Raoul G, Ruhin B, Briki S, Lauwers L, Haurou Patou G, Capet JP, et al.

Microsurgical reconstruction of the jaw with fibular grafts and implants. J Craniofac

Surg 2009;20(6):2105–17.

17) Gürlek A, Miller M, Jacob R, Lively J, Schusterman M. Functional results of dental

restoration with osseointegrated implants after mandible reconstruction. Plast

Reconstr Surg 1998;101(3):650–9.

18) Siessegger M, Schneider BT, Mischkowski RA, Lazar F, Krug B, Klesper B, et al. Use of an

image-guided navigation system in dental implant surgery in anatomically complex operation

sites. J Craniomaxillofac Surg 2001;29(5): 276–81.

19) Valente F, Schiroli G, Sbrenna A. Accuracy of computer-aided implant surgery: a clinical and

radiological study. Int J Oral Maxillofac Implants 2009;24(2):234–42.

20) Wu Y, Huang W, Zhang Z, Zhang Z, Zhang C, Sun J. Clinical outcome of dental implants

placed in fibula-free flaps for orofacial reconstruction. Chin Med J 2008;121(19):1861–5.

21) Rohner D, Bucher P, Hammer B: Prefabricated fibular flaps for reconstruction of defects of

the maxillofacial skeleton: Planning, technique, and long-term experience. Int J Oral

Maxillofac Implants. 2013Sept-oct;28(5):e221-9.

22) Numajiri T, Tsujiko S, Morita D, Nakamura H, Sowa Y. A fixation guide for the accurate

insertion of fibular segments in mandibular reconstruction JPRAS Open 2017;12:1-8.

ACKNOWLEDGMENTS We are very grateful of Dr. Guruprasad Rao (Director, 3D Imaginarium) and his team for their

guidance and Dr. Kartik Bhanushali(4 Quadrant Dental Solution.Pvt.Ltd) for his continuous support.




ABSTRACT

Tooth-restoration margins are the most essential and critical link between the tooth structure and the

restoration. Sufficient understanding regarding the margin selection and preparation is of paramount

importance to ensure the restoration longevity and success. Although there are various advances in

regards to the materials in restorative dentistry, selecting the margin type remains a crucial decision.

This paper aims to assertively compile the appropriate margin design, configuration, and location

concerning various restorative materials. Factors determining the periodontal considerations about the

margins and marginal discrepancies are also addressed.

Keywords: Bevelled margins; Flares; Chamfer; Shoulder; Butt joint; Finish lines

Introduction

The ultimate goal of restorative dentistry is to recover biomechanics of the original tooth, prevent further

decay, and restore optimal function. The selection of an appropriate restorative material with its proper

clinical technique is essential for the success of the restorative treatment. An adequate seating and

specific adaption of the restorative material to the preparation margins contribute to its success. This

margin between the restoration and the tooth structure, which is one of the weakest links in the tooth

restoration complex, should be prepared with particular attention to ensuring it transitions with the tooth.

Any gap or interference in this portion of the tooth can lead to harmful effects like difficulty in recording

impression, stress build-up at the margins, increased susceptibility to fracture of the restorative material,

reduced strength and esthetics, and periodontal deterioration.1-3 The marginal design effect is an

underrated factor in the clinical success of the restoration. A greater understanding of the margin design

and placement is essential to achieve maximum results in restorative practice.

Margins In Restorative Dentistry – A Review

Dr Samruddhi Shinde1, Dr Padmini Chandrasekhar2, Dr Shishir Singh3, Dr Rajesh Podar4, Dr Roshan

Shetty 2, Dr Avinash Salgar2

1Post-graduate Student,

2Reader, 3Dean, Professor and Head of Department,

4Professor.

Department of Conservative Dentistry and Endodontics,

Terna Dental College

Shinde S. et al: Margins in restorative dentistry


Ideal requisites for a successful tooth restoration interface: Preparation margins resting on enamel should fulfill all the requirements advocated by Noy4 to possess

enough strength to withstand massive occlusal forces without disrupting tooth structure and the

restoration. It must be smooth enough to allow proper seating of the final restoration and must be located

in an area that is self-cleansing or can facilitate easy plaque removal. The margins' location should be

aesthetically acceptable but must not adversely affect the periodontium's health, and hence, care should

be taken to maintain the biologic width.3 The peripheral extension of a tooth preparation must be easy

to prepare and duplicate, conservative, and provide sufficient strength to the restoring material. The

restoration margin should fit as closely as possible to the finish lines of the preparation to minimize

exposed cement width to prevent microleakage and secondary caries.

Features of peripheral marginal anatomy for various direct and indirect

restorations: Bevels are the extensions placed on the occlusal and the gingival enamel and dentinal walls which can

function to involve the surface defects, aid in the removal of unsupported enamel rods (gingival bevel

in amalgam), mask the restoration margins (for anterior composites), provide enough metal bulk (for

cast metal restorations) and reduce cement dissolution.4-6 Beveling minimizes seating discrepancy by

lowering the marginal metal angle.7 In intracoronal cast restorations, flares are placed on the facial and

the lingual walls, which perform a function similar to that of the bevels.

Skirts are placed as thin extensions on the facial or lingual proximal margins to involve defects, impart

resistance and retention, and increase retention. They are indicated when contacts and contours are to

be changed in the contemplated restoration. In tilted teeth, they allow for the bulk, resistance, and

retention of the occlusal cast material required in building the occlusal table.5

Facial or lingual collar preparation also increases the retention and resistance forms on a weakened

tooth and prevents it from cuspal fracture. A collar can accommodate both alloy and porcelain bulk and

facilitate marginal seating of the castings circumferential tie.

Bevels, flares, skirts, and collars form a part of the circumferential tie.4,5

Various finish lines are used for the extra - coronal cast restorations. Based on the configuration, they

could be

Feather edge (knife-edge), which provides the least strength, is difficult to locate on the cast and

fabricate. However, it offers an excellent marginal seal and is the most conservative type. It is indicated

in full metal crowns and mandibular molars if they are lingually tilted or have convex axial surfaces.

Chamfer type is distinct and assures bulk with little tooth involvement. It is the universally used design

for cast metal restorations and lingual margins of PFM crowns (Class I, II, and III cast material). It is

prepared with a round end tapered diamond bur. This preparation provides a diameter of 0.5 to 1 mm.

Heavy chamfer exhibits a 90° cavosurface angle with a rounded internal angle. It is indicated for all-

ceramic crowns and is prepared with a round end tapered diamond. A bevel is added for use with metal

restorations.

The shoulder provides resistance to masticatory forces, produces space for healthy contours, good

esthetics, and less distortion. However, it is difficult to prepare; the least conservative lacks the sliding

joint fit and has inferior marginal integrity. It is best for all-ceramic crowns and facial margins of PFM

crowns. It is prepared by flat end tapered diamond bur. This preparation has a diameter of 1.5 to 2 mm.

(Fig.1k,2k)



Shoulder with bevel has a bevel created on the marginal end of the unprepared tooth structure. It is

indicated for a proximal box of inlays, onlays, occlusal shoulders of onlays and mandibular three fourth

crowns, facial aspect of PFM crowns, and acrylic facing full cast veneers.

The radial shoulder is a shoulder with a rounded gingivoaxial line angle 90º cavosurface angle and is

indicated for porcelain restorations. It provides lesser stress and good support for porcelain.

The sloped shoulder possesses a 120° sloped shoulder margin. It is indicated on the facial margin of

the metal-ceramic crown. This configuration removes unsupported enamel but provides enough bulk for

thinning of metal framework for esthetic purpose.8

Preparation features specific to various restorations material-wise:

A. Margin configuration for direct restorations:

Amalgam restorations:

The location of the margin for amalgam is determined by its property of high compressive strength and

weak tensile strength. Occlusal margins should be located on smooth surfaces, inclined cuspal planes,

marginal ridges, and crossing ridges. Enamel cavosurface margins of 90°- 110° (butt joint) prevent

enamel fracture and help marginal amalgam tolerate masticatory forces. (Fig.1a,1b,1c,2a,2b,2c) Beveled

occlusal margins are not recommended as masticatory stresses acting on them will lead to elastic

deformation of the tooth, resulting in tensile stress build-up at the amalgam at the bevel leading to

fracture of the restoration. For the same reason, the removal of amalgam flash is also mandatory. For

class II restorations, the finished gingival margins should be located in the gingival sulcus' occlusal

portion. (Fig.1c, 2c) If it is gingival to the CEJ, the gingival cavosurface angle of 90° to the external root

surface is needed. Proximal clearance of 0.5 mm should be given; since it compensates for setting the

amalgam. 20° declination gingivally is given; if the gingival seat is in enamel. The bevel should not be

given if the gingival margin is apical to the CEJ and primary teeth. A recent instrument named "PACE"

(Perfected for Amalgam Cavity Evaluation) guides the attainment of a 110° cavosurface angle, allowing

the clinician to achieve a minimum of 70° amalgam margin angle.9

Glass ionomer restorations:

Glass ionomers show good adhesive property with the tooth structure due to ionic bonding. Advances

like resin-modified GIC has superior properties like marginal adaptation and esthetics for restoring non-

carious cervical lesions.10 Therefore, bevelling of the margins is usually not recommended.

Composite restorations:

Bevelling the enamel margin in composites can be advantageous as it will help remove aprismatic

enamel, increase the area for acid etching and therefore improve bonding, and reduce microleakage.11-

13

In class I, the facial and lingual margins should be extended as needed to remove all carious tooth

structure and should form at least a 90˚ cavosurface margin or more. (Fig.1d,2d)

In class II, facial and lingual margins are placed. All carious structure is removed. No unsupported

enamel rods exist; there is accessibility for the placement and adaptation of the restoration on cavity

margins, and plaque removal from the interdental area is facilitated. Thus, clearance in the proximal box



depends on the individual clinical situation. The gingival floor should be prepared flat and create a 90°

cavosurface margin.5 (Fig.1e,2e)

In slot preparations, the occlusal, facial, and gingival cavosurface margins of 90˚ or greater should be

placed. For a vital asymptomatic extensively carious tooth, bevel placement is not required on occlusal

cavosurface margin unless there are unsupported enamel rods.

In class III and class IV, starburst bevel camouflages the restoration margin; thus, providing superior

esthetics and removal of unsupported and frail enamel structure (Fig1f,2f). Preservation of enamel

margin on the gingival seat is of utmost importance as it is critical for bonding.

Extensive class III and class IV preparations might need additional bevel on the enamel walls for

adequate retention. If the preparation extends gingivally onto the root surface, a 90˚ cavosurface margin

should be provided in class III and class IV preparations. Flame shaped or round diamond instrument

can be used to create a bevel of 45˚ angle to the external surface with a width ranging from 0.5–2 mm.5

For class V restorations, there is no need for enamel bevel for prevention of microleakage.14 In

maxillary incisors, bevel on lingual aspect may be contraindicated if it would cause the restoration

marginal interface to be placed at the incisal contact area.

B. Margin configuration for indirect restorations:

Metal inlay:

According to Marzouk, the margins of inlays should fulfill all requirements for an extension for

prevention.4 Occlusal and gingival marginal bevels and placement of the secondary flare on the

distolingual and distofacial walls result in a 30 to 40˚ marginal metal on the inlay. This seals and protects

the margins and creates a healthy enamel margin of 140–150˚. The desirable metal angle at the inlays'

margins is always 40˚ except at the gingival margins, which in 30˚facilitating burnishable metal and a

lap sliding fit. The gingival bevel should blend with the secondary flare (Fig 1h,2h). Bevelling is

performed by No. 8862 bur. Secondary flare is prepared by No.8862 bur or No.169L bur. It is indicated

in the indirect wax pattern, broad contact areas, wide extension of caries buccolingually, and to

overcome undercuts in the cervical aspect of the facial and lingual proximal walls. It is omitted in the

mesiofacial wall of maxillary premolars and molars as it impacts the resistance form and smile esthetics.

Metal Onlay:

On the practical side, facial and lingual margins should be located gingivally and away from the contact

area to include the facial and the lingual cuspal elements and the grooves. They should be parallel to the

contour of the cusp tips and crests of the adjacent ridges. Whereas, on the non-functional side, the facial

and the lingual margins should be just gingival to the tip and crest of the ridge of the involved cusps and

away from the occlusal contact. Proximal margins will be located similar to that of an inlay margin.

Placing skirts provides a conservative and atraumatic way to increase resistance and retention form. A

slender, flame-shaped, fine-grit diamond instrument is used for giving skirts. For the same intention,

collars are placed on the weakened tooth for a MOD onlay with No. 271 carbide bur at high speed. A

functional cusp bevel provides sufficient metal in zones of heavy occlusal contact. It is prepared with a

round-end tapered diamond at 45˚ with the axial wall and depth of 1.5 mm.15

Posterior maxillary three-quarter crown:

Occlusal finish bevel of 0.5 mm is given along the occlusofacial line angle, extending from the central

groove on the mesial to the central groove on the distal. This provides space for metal on the lingual-



facing incline of the lingual cusp to match the space on the buccal-facing incline created by the occlusal

reduction. No. 171L bur is used to smooth the bevel. Chamfer finish line provides periodontal

preservation, marginal integrity.

Three-quarter crown preparation on a mandibular molar or premolar:

Occlusal finish line must be given on the facial surface, gingival to occlusal contacts. The occlusal

shoulder on the buccal aspect of the buccal cusp(s) knots the grooves and strengthens the nearby Bucco-

occlusal margin.

Seven-eighth crown:

The vertical distobuccal margin is placed slightly mesial to the middle of the buccal surface. Margin

finishing is easy, and hygiene maintenance for patients is also facilitated.

Porcelain fused to metal:

There should be a continuity of the shoulder or the beveled shoulder margin and the chamfer margin in

the interproximal region.8 This is often referred to as a winged preparation.

Ceramic inlay:

Porcelain fracture has been reported as a primary reason for restoration failure.16,17

Butt joints are preferred. Bevels are not placed in ceramic inlays because ceramics tend to fracture at the

margins due to low tensile strength. Placement of margins in enamel and rubber dam isolation during

the luting procedure provides a good survival rate.18

Ceramic Onlay:

Beveled margins are contraindicated because the bulk is needed to prevent fracture. Cavosurface

margins should be 90(Fig 1i,2i). A well-defined heavy chamfer is the recommended margin. Margins

in enamel must be smooth and distinct for a ceramic restoration to fit accurately.8

All-Ceramic crown

A uniform margin thickness circumferentially with a width of 1-1.5 mm is necessitated for better

aesthetics. A butt joint will enable proper stress distribution and thus minimize ceramic fracture due to

tensile stress. The beveled margin is not recommended as it does not support the porcelain. The margin

must be smooth for appropriate fabrication.

Zirconium based crowns:

A 0.8-1mm wide, 360 deep chamfer with no sharp internal line angles is recommended as it allows

room for the zirconium coping and overlying veneering ceramic.

Finishing the margins can be done by finishing grit diamonds followed by a 30-fluted carbide bur and

polishing pastes. Shoulder and chamfer preparations provide adequate accuracy because they offer good

detectability of the finish line for scanning devices in the case of CAD/CAM-fabricated zirconia

copings.19

Laminate veneers:

Veneer interproximal margins should extend into the facial and gingival embrasures without engaging

an undercut and should be located just facial to the proximal contacts.5



Window preparation is recommended for most direct composite veneers, indirectly fabricated veneers

where the canine's outline form is intact, and the patient is canine guided. The incisal edge of the tooth

is preserved. This reduces the accelerated wear of the opposing tooth.

Feather preparation is indicated in patients with a normal overbite and avoids direct contact of ceramic

veneers with their antagonistic tooth structure. The incisal edge of the tooth is prepared Bucco-palatally,

but the incisal length is not reduced. This can cause weak veneer, ceramic chipping, difficulty with the

veneers' seating, marginal discoloration, and poor marginal adaptation.20

For incisal overlap preparation, the butt joint (Fig 1l,2l) is used in worn or defective areas on the

incisal edge's lingual aspect. It provides an increased adaptation of veneer to the lingual margin

providing a 'lap sliding' fit.

Palatal chamfer preparation can be used when the incisal edges are thin buccolingually or when an

increase in crown length is needed. This design increases the surface area for bonding, provides rounded

angles and adequate ceramic thickness.

The gingival extent of the veneer's margin depends on the size of caries, discoloration, and the amount

of tooth structure visible while smiling. If the tooth's cervical portion is discolored, carious, or defective,

a subgingival margin needs to be placed. Margin should be placed at the crest of tissue in a high smile

line, fluorosis stains for esthetic reasons.

Vertical preparation:

A preparation without a finish line is a less-invasive substitute to a horizontal margin, allowing enamel

preservation in the cervical area. It is indicated when periodontally compromised teeth are used as

abutments for fixed prostheses. This is referred to as the biologically oriented preparation technique

(BOPT). A Batt-Bur, which is a round-ended tapered diamond bur with a non-cutting end, is used.21,22

Fig 1. a-l



a) Class I amalgam

b) Class I amalgam palatal extension

c) Class II amalgam

d) Composite

e) Class II composite

f) Starburst bevel

g) Class II composite inlay

h) MOD metal inlay

i) Ceramic onlay

j) Margins for PFM crown

k) All shoulder margins

l) Veneer preparation

Fig 2. a-l

a) Class I amalgam

b) Class I amalgam palatal extension

c) Class II amalgam

d) Composite

e) Class II composite

f) Starburst bevel

g) Class II composite inlay

h) MOD metal inlay

i) Ceramic onlay

j) Margins for PFM crown

k) All shoulder margins

l) Veneer preparation



DIRECT RESTORATIONS

RESTORATION CAVOSURFACE

CONFIGURATION

PURPOSE

AMALGAM

Class I and Class II

Butt joint Prevents enamel fracture, helps

marginal amalgam to tolerate

masticatory forces

Class II 20° gingival bevel Removal of unsupported enamel

rods

COMPOSITES

Class I, II, V, box only and

slot preparations

90˚ cavosurface margins

No occlusal or gingival bevel

Removal of unsupported enamel

rods

Class III

Class IV

45˚ on the facial surface, a

width of 0.5–2 mm

Starburst bevel

Unsupported enamel rods removal,

increase retention by bonding

Conceal restoration margin

GLASS IONOMER

CEMENTS

Bevels not recommended

INDIRECT RESTORATIONS

METAL INLAY The occlusal bevel of width -

1/4th the depth of the

respective wall.

40˚ marginal metal and the

140° occlusal marginal

enamel

Increases the strength of the marginal

enamel and helps seal the margins.



Gingival bevel with 30˚

marginal metal

Burnishable marginal metal

ONLAY Similar to inlay margins,

skirts

Skirts increase the resistance and

retention form

FULL METAL CROWN Chamfer, knife-edge,

shoulder with a bevel of 0.5 to

1 mm

Marginal integrity and structural

durability

ALL CERAMIC Shoulder/ Bevelled shoulder /

Sloped shoulder/90˚ heavy

chamfer margin of 1.5 to 2

mm

Material thickness and material strength

and esthetics

PORCELAIN FUSED TO

METAL

Labially – Shoulder of 1.5 to

2 mm

Lingually – Chamfer of 0.5 to

1 mm (winged preparation)

Marginal integrity and structural

durability, material thickness, material

strength, and esthetics

Effect of tooth preparation margins concerning pulpal health: Immediate changes in dental pulp vary with different types of preparations depending upon remaining

dentin thickness. However, crown preparation of up to 2 mm depth is considered within a safe limit, and

it does not lead to reversible or irreversible pulpitis.23 The crown preparation procedure leads to dentinal

tubules' exposure, which causes minute fluid shifts across dentin due to tactile, thermal, osmotic, or

evaporative stimuli. This permits mechanoreceptors' activation and initiates mild to moderate

inflammatory response in the pulp and odontoblast injury24. Pulpal injuries lead to the release of several

inflammatory mediators that may have direct or indirect effects via modulation of trigeminal sensory

nerve fibers on pulpal vasculature. Vasodilatation and increased blood flow are the two significant

actions seen in the initial phase of pulpal inflammation37 Dentin hypersensitivity following tooth

preparation is a common issue in dentistry.33 The application of dentin bonding agents can control root

sensitivity. An important point to be understood here is that remaining dentin thickness, which is

inversely proportional to the pulpal response tooth preparation near the pulp, should be avoided.25,8



Effect of peripheral marginal anatomy on periodontal health: The margin location can influence periodontal health, esthetics, finishing, and retention of the restoration

and stump shade of the underlying tooth.26 Association between the margin placement, supracrestal fiber

attachment, and location of the sulcus base is majorly vital for gingival health. Margins placed within

biologic width breach the biologic principle leading to alveolar bone resorption, periodontal breakdown,

aggregation of subgingival microflora, and the chronic inflammatory process followed by iatrogenic

periodontal disease and restoration failure.3,27

Supragingival finish line configuration proposed by Orban facilitates predictable impressions, ease in

excess cement removal, convenience to prepare and finish by the operator, optimum periodontal health,

oral hygiene maintenance and proper fitting and should be welcomed favorably in non-esthetic areas.26,28

- 30 So, margins must be placed 1-2 mm supragingival if possible. However, innovations in translucent

restorative materials, adhesive dentistry, and resin cement has allowed supragingival margin placement

in esthetic areas.3,28

Equigingival finish line as suggested by Marcum accredits for marginal finish, esthetics, and

accessibility.31 The success of this configuration is due to the presence of keratinized epithelium.32 They

are placed at the marginal gingiva crest; they are more plaque retentive and impact the periodontium.

Subgingival margins are indicated for esthetic concerns, subgingival caries, cervical erosion, and when

crown-lengthening is not shown.8 They are placed below the marginal gingiva and are at most significant

biologic risk since they may violate the gingival apparatus.33 Mechanical, chemical, rotary gingival

curettage, and surgical methods are employed to expose the subgingival finish line.34 However,

"intracrevicular finish lines" are limited within the gingival sulcus and favor periodontal health and

esthetics.28 Provisional restoration can be placed, and tissue reaction was observed several weeks before

the final restoration placement. Flemmig et al. advocated using 0.12% chlorhexidine gluconate for two

weeks before the tooth preparation procedure. This aids in decreasing gingival inflammation around the

teeth and will ultimately provide a healthy working environment.35 Healthy tissue after this indicates no

violation of the biologic width and that the periodontium will respond well to the final restoration

margins.5

Importance of marginal fit: Well adapted margins to finish lines of preparation provide longevity to the restoration serving marginal

integrity. Configuration of finish line decides the shape and bulk of marginal metal, affects the marginal

adaptation and degree of seating. The junction between a cemented restoration and the tooth is a potential

site for recurrent caries. Metal casting fits within 10 μm, whereas the porcelain margin fits within 50

μm.8 Clinically acceptable marginal gap must be less than 120 μm.36,37 Improperly adapted margins act

as an area of plaque accumulation, increase cement dissolution, and are correlated with the severity of

inflammation.5,6 It may make the tooth surface susceptible to caries. Hence, marginal adaptation is

essential as it may result in biological or mechanical failure of the restoration.6 Finish line configuration

remarkably affects the marginal seal and occlusal seating of the crowns. Shoulder margins provide a

good seat but a wider marginal seal. Chamfer, long chamfer, and feather edge margin permit superior

sealing of the margins regardless of poor seating. However, the finish line does affect the fit of the

cemented crowns. The beveled margin does not show significant superiority in a marginal fit after

cementation.38,39



Marginal discrepancies: Errors like over-extended and under-extended margins, rough, incomplete, non-uniform, J shaped

margins, pseudoshoulders, margins with sharp internal line angles should be avoided for optimum

results.40 Rough, irregular, or "stepped" margins restoration subsequently increases the overall margin

dimension and decreases the restoration's adaptation accuracy. Smooth margins allow the subsequent

steps like tissue displacement, impression making, laboratory communication, die formation, waxing,

and finishing much more straightforward and ultimately result in longer-lasting restorations. Smooth,

accurately placed preparation margins are of great importance in the repairs that are fabricated using

computer-aided design and computer-aided manufacturing (CAD/CAM) process.8

Conclusion: The success of a dental restoration largely depends on the accurate margin placement, adaptation, and

integrity. The restorative margin placed plays an essential role in the long-term prognosis and outcome

of the restoration. Thus, proper knowledge of the gingival and periodontal response to the restoration

from a biomechanical perspective is essential. Though more research is needed, this paper has

highlighted the different tooth margins that work for the broad array of restorative materials in use.

Research is progressing at a fast pace. We need to update the emerging restorative material's knowledge

and their respective margins and adapt as per the latest groundwork.

References: 1. Shetty R, Bhat S, Srivatsa G. Rectifying the tooth preparation errors in all-ceramic restorations.

World J Dent 2010 Oct;1:181-5.

2. Chatterjee U. Margin designs for esthetic restoration: An overview. Journal of Advanced Oral

Research 2012 Jan;3(1):5-9.

3. Shenoy A, Shenoy N, Babannavar R. Periodontal considerations determining the design and

location of margins in restorative dentistry. Journal of Interdisciplinary Dentistry. 2012 Jan

1;2(1):3.

4. Marzouk MA, Simonton AL, Gross RD. Operative dentistry. Modern theory and practice

5. Gopikrishna V. Sturdevant's Art & Science of Operative Dentistry: Second South Asia Edition.

Elsevier Health Sciences; 2018 Sep 3.

6. Hunter AJ, Hunter AR. Gingival margins for crowns: a review and discussion. Part II:

Discrepancies and configurations. The Journal of prosthetic dentistry. 1990 Dec 1;64(6):636-42.

7. Pascoe DF. Analysis of the geometry of finishing lines for full crown restorations. J PROSTHET

DENT 1978;40:157-62.

8. Rosenstiel SF, Contemporary Fixed Prosthodontics, 4th edition, USA, Mosby, 2006, pp 166-201.

9. Arora A, Acharya SR, Ballal V, Sharma P. A self-designed instrument to evaluate cavosurface

angle for class I amalgam cavity preparation: A learning aid. Journal of conservative dentistry: JCD.

2012 Jul;15(3):253.

10. Hussainy SN, Nasim I, Thomas T, Ranjan M. Clinical performance of resin-modified glass ionomer

cement, flowable composite, and polyacid-modified resin composite in noncarious cervical lesions:

One-year follow-up. Journal of conservative dentistry: JCD. 2018 Sep;21(5):510.

11. Sharpe AN. Influence of the crystal orientation in human enamel on its reactivity to acid as shown

by high resolution microradiography. Arch Oral Biol. 1967;12:583-92.

12. Coelho-de-Souza FH, Camacho GB, Demarco FF, Powers J. Influence of restorative technique,

beveling and aging on composite bonding to sectioned incisal edges. J Adhes Dent. 2008;10:113-7

13. Opdam NJM, Roeters JJM, Kuijs R, Burgersdijk RCW. Necessity of bevels for box only Class II

composite restoration. J Prosthet Dent. 1998;80:274-9



14. Effect of Cavosurface Margin Configuration of Class V Cavity Preparations on Microleakage.

9(2):1–8.

15. Shillingburg HT, Hobo S, Whitsett LD, Jacobi R, Brackett SE. Fundamentals of fixed

prosthodontics Third edition

16. Hayashi M, Tsuchitani Y, Kawamura Y, Miura M, Takeshige F, Ebisu S. Eight-year clinical

evaluation of fired ceramic inlays. Oper Dent. 2000;25(6):473–481.

17. van Dijken JW, Hasselrot L, Ormin A, Olofsson AL. Restorations with extensive dentin/enamel-

bonded ceramic coverage. A 5 year follow-up. Eur J Oral Sci. 2001;109(4):222–22

18. Fuzzi M, Rappelli G. Ceramic inlays: clinical assessment and survival rate. J Adhes Dent.

1999;1(1):71–79.

19. Winkelmeyer C, Wolfart S, Marotti J. Analysis of tooth preparations for zirconia-based crowns and

fixed dental prostheses using stereolithography data sets. The Journal of prosthetic dentistry. 2016

Nov 1;116(5):783-9.

20. Chai SY, Bennani V, Aarts JM, Lyons K. Incisal preparation design for ceramic veneers: A critical

review. The Journal of the American Dental Association. 2018 Jan 1;149(1):25-37

21. Agustín-Panadero R, Solá-Ruíz MF, Chust C, Ferreiroa A. Fixed dental prostheses with vertical

tooth preparations without finish lines: A report of two patients. The Journal of Prosthetic Dentistry.

2016 May 1;115(5):520-6.

22. Imburgia M, Canale A, Cortellini D, Maneschi M, Martucci C, Valenti M. Minimally invasive

vertical preparation design for ceramic veneers. Int J Esthet Dent. 2016 Dec 1;11(4):460-71.

23. Ahmed A, Ilyas MS, Chaudhry S, Fahim A, Malik AA, Baig MZ. Morphological changes in dental

pulp with different depths of tooth preparation. J Univ Med Dent Coll. 2017 Jun 3;8(3):23-33.

24. Katoh Y, Suzuki M, Kato C, Shinkai K, Ogawa M, Yamauchi J. Observation of calcium phosphate

powder mixed with an adhesive monomer experimentally developed for direct pulp capping and as

a bonding agent. Dental materials journal. 2010;29(1):15-24.

25. Sorensen JA. A rationale for comparison of plaque‑retaining properties of crown systems. J Prosthet

Dent 1989;62:264‑9.

26. Sarandha DL. Effects of location of gingival finish lines on periodontal integrity. Journal of Nepal

Dental Association| Vol. 2013 Jan;13(1).

27. Nugala B, Kumar BS, Sahitya S, Krishna PM. Biologic width and its importance in periodontal and

restorative dentistry. Journal of conservative dentistry: JCD. 2012 Jan;15(1):12.

28. Newsome P, Owen S. Improving your margins. Int Dent SA. 2009; 11:36-42.

29. Becker CM, Kaldahl WB. Current theories of crown contour, margin placement, and pontic design.

The Journal of prosthetic dentistry. 1981 Mar 1;45(3):268-77.

30. Christensen GJ. Marginal fit of gold inlay castings. Journal of Prosthetic Dentistry. 1966 Mar

1;16(2):297-305.

31. Marcum JS. The effect of crown marginal depth upon gingival tissue. Journal of prosthetic

Dentistry. 1967 May 1;17(5):479-87.

32. Michael F. Margins of complete crowns-Literature review. J Prosthet Dent. 1982;48(4):396–400.

33. Paniz G, Nart J, Gobbato L, Mazzocco F, Stellini E, De Simone G, Bressan E. Clinical Periodontal

Response to Anterior All-Ceramic Crowns with Either Chamfer or Feather-edge Subgingival Tooth

Preparations: Six-Month Results and Patient Perception. International Journal of Periodontics &

Restorative Dentistry. 2017 Jan 1;37(1).

34. Klugman R, Revah A, Kohavi D, Rehany A, Stern N. Finish lines in fixed prosthodontics. Refu'at

ha-peh veha-shinayim (Tel Aviv, Israel: 1969). 1978 Oct;27(4):31.

35. Flemmig TF, Sorensen JA, Newman MG, Nachnani S. Gingival enhancement in fixed

prosthodontics. Part II: Microbiologic findings. J Prosthet Dent 1991;65:365‑72

36. Fransson B, Oilo G, Gjeitanger R: The fit of metal-ceramic crowns, a clinical study. Dent Mater

1985;1:197-199 17.



37. McLean JW, von Fraunhofer JA: The estimation of cement film thickness by an in vivo technique.

Br Dent J 1971;131:107-111

38. Nemane V, Akulwar RS, Meshram S. The effect of various finish line configurations on the

marginal seal and occlusal discrepancy of cast full crowns after cementation-an in-vitro study.

Journal of clinical and diagnostic research: JCDR. 2015 Aug;9(8): ZC18.

39. Halawani SM, Al-Harbi SA. Marginal adaptation of fixed prosthodontics. IJMDC. 2017;1(2):78-

84.

40. Christensen GJ. Marginal fit of gold inlay castings. Journal of Prosthetic Dentistry. 1966 Mar

1;16(2):297-305.


THE JOURNAL OF PROSTHODONTICS AND DENTAL MATERIAL The Official e-publication of Indian Prosthodontic Society


Introduction The recent spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and

its associated coronavirus disease has seized the entire international community and has caused

widespread public health concerns. Despite comprehensive efforts to contain the disease spread, the

outbreak is still on the rise because of the community spread pattern of this infection.1 On 31st

December 2019, 27 cases of pneumonia of unknown etiology were identified in Wuhan City, Hubei

province, in China.2 The causative agent was identified from throat swab samples conducted by the

Chinese Centre for Disease Control and Prevention (CCDC) on 7th January 2020 and was

The Right Perspective of Practicing

Prosthodontics in The Post COVID-19 Era

Dr Jayesh Banswani1, Dr Naisargi Shah2, Dr Praveen Badwaik3, D. Rahul Malu4, Dr Kaveri

Chakrabortty4, Dr Arshad Idrisi4

1Post-Graduate Student, 2Professor and Head of Department,

3Professor, 4Lecturer,

Department of Prosthodontics, Crown & Bridge,


ABSTRACT

The COVID-19 global pandemic continues to have catastrophic health, economic, and social

effects and is significantly affecting the delivery of services in dental care. Initial guidelines

have been provided only for minimal treatment for emergency cases. However, there is a lack

of definitive universal guidelines for performing routine dental procedures. This lack of

guidelines can on the one hand increase the nosocomial infection spread and, on the other hand,

deprive patients in need of the necessary dental visit. Because of the infection risks associated

with aerosol generated procedures, such as the use of high-speed drills, dental care across much

of the world have been essentially on halt since late March 2020. However, Dental operatories

are now gradually and hesitantly beginning to re-open, although there is a substantial disparity

in the guidance being issued on the safety procedures required. This literature overview

describes standard operating protocols that can be followed in prosthodontics to reduce

COVID-19 transmission.

Keywords: SARS-CoV-2; coronavirus; COVID-19; Dental Care; Guidelines; Prosthodontics;

Pandemic.

Banswani J. et al: Practicing Prosthodontics in Post Covid19 Era


subsequently named COVID-19 by the World Health Organization (WHO).3 Here in India, the first

confirmed case of the COVID-19 infection on 30th January 2020 was reported in Kerala. On 30th

January 2020, the WHO declared the outbreak of SARS-CoV-2 a Public Health Emergency of

International Concern.4 As we are aware of widespread transmission of SARS-CoV-2 in medical health care

professionals, on similar lines Dental health Care professional those who work in proximity to

patients oropharyngeal region are also at very high risk. Dental professionals could also become

potential carriers of the disease. Dentistry practice involves the use of rotary dental and surgical

instruments, such as air turbine handpieces, ultrasonic scalers, and air-water syringes. These

instruments generate aerosols containing particle droplets of water, saliva, blood, microorganisms,

and other debris. Also, if adequate precautions are not taken, the dental office can potentially

expose patients to cross contamination. According to the CDC recommendation, dental settings

should prioritize urgent and emergency visits only. However, as the pandemic continues to evolve,

dental settings may also need to deliver non-emergency dental care.5

Different branches of dentistry deals with various Dental emergencies, and those related to

the branch of Prosthodontics include repair of broken complete dentures, post denture insertion

adjustment of complete denture, adjustment of Cast partial / interim partial dentures, removal of old

FDPs, provisional or definitive restoration for already prepared teeth/ implant abutments, implant

prosthesis related issues and Peri-implant infections. It is crucial for Prosthodontists to develop

specific protocols to deal better with the current situation of Covid-19 while performing these

procedures.

Therefore, an attempt has been made in this article to discuss challenges faced by the

Prosthodontists and the strategies to overcome them.

Prosthodontic Procedures6

Emergency vs. Non-

Emergency

Clinical condition

Emergency care

Denture adjustments on radiation/oncology patient,

Denture adjustments or repairs when function impeded,

Crown and Fixed dental prosthesis removal,

Suture removal,

Final crown/bridge cementation if the temporary restoration is lost,

broken or causing gingival irritation

Peri-implant infections endangering stability

Elective care Routine complete dentures for complete edentulism, Removable or

fixed prosthodontics including implantology for partial edentulism

and maxillofacial prosthodontics.

Non-emergency care Aesthetic dental procedures like laminate and veneers



Patient screening During the dental visits, pre-screening of patients should be done in order to minimize the exposure

of covid-19. Triaging of patients is done by brief survey and investigating signs and symptoms of

cough, respiratory issues, dyspnea, body temperature of 38°C (100.4°F) or higher, and oxygen

saturation levels below 94%, before dental examination is conducted. If patients show these

symptoms, then an antibody screening tests should be done. Patients who test positive should be

treated in the hospital, with equipment and facility to deal with contagious diseases. Patients

answering ‘no’ to the survey questions and who doesn’t show any signs and symptoms can be

treated, but specific procedures may need to be altered to prevent the risk of covid-19 transmission.

Prosthodontic procedures can be categorized into Two Categories:

1. Non-aerosol generating procedures. (Non-AGP)

2. Aerosol generating procedures (AGP)

1. Non-aerosol generating procedures (Non-AGP) In prosthodontics, Non-aerosol generating procedures include fabrication of complete

dentures, removable partial dentures, implant prosthesis, and maxillofacial prostheses.

Prosthodontists can manage all these Non-AGPs using dental protective equipment, which

include a surgical gown, N95 mask, face shield, double gloves, and plastic disposable covers.

2. Aerosol generating procedures (AGP) Aerosol generating procedures (AGP) involve tooth preparation for crowns and fixed dental

prostheses, Implant osteotomies and its placement. While performing these AGPs, it is

mandatory that the minimum of 90 GSM personal protective equipment (PPE) is used by the

dental surgeon and dental assistant, which includes gloves, gown, head cover, shoe cover, eye

protection including goggles or a disposable/reusable face shield that covers the front and sides

of the face, and an N95 or higher-level respirator.

Hazards of aerosols When performing Tooth preparation with a high-speed handpiece, friction between the tooth

and the rapidly rotating diamond points would create excessive heat. Without a coolant, the heat

could cause damage to hard dental tissue and lead to pathological changes to the dental pulp.

Therefore, to prevent heat gain, it is a universal consensus to use a water coolant when performing

tooth preparation. The water coolant, however, could generate aerosols. When combined with

bodily fluids in the oral cavity, such as blood and saliva, bioaerosols are created. These bioaerosols

are commonly contaminated with bacteria, fungi, and viruses, and have the potential to float in the

air for a considerable amount of time and put the Prosthodontist at an extremely dangerous risk of

inoculating themselves, their dental assistants, other office staff members, and other patients too.

Aerosol Particles are classified based on size: coarse particles are 2.5–10 microns, fine

particles are less than 2.5 microns, and ultrafine particles are less than 0.1 microns. The nose

typically filters air particles above 10 microns. If a particle is less than 10 microns, it can enter the

respiratory system. If it is less than 2.5 microns, it can enter the alveoli.The current scientific

consensus is that most transmission via respiratory secretions happens in the form of small aerosols

rather than large respiratory droplets.Droplets are often heavy enough that they do not travel very

far; instead, they fall from the air after traveling up to six feet.The problem occurs when viral

particles are aerosolized by a cough, sneeze, or dental care. In these instances, particles can



potentially travel across far greater distances, with estimates up to 20 feet, from an infected person,

and then incite secondary infections elsewhere in the environment. Also, the smaller particles of an

aerosol have the potential to penetrate and lodge in the smaller passages of the lungs and thus carry

the greatest potential for transmitting infections.7

Because of these inherent dangers to the operator, team members, and patients, the

Occupational Safety and Health Act (OSHA) have released a report called “Guidance on Preparing

Workplaces for COVID-19.” According to OSHA, occupational risk can be categorized as very

high, high, medium, and lower risk. Procedures that involve aerosol production fall into a very

high-risk category.8

Preventive measures for Aerosol Transmission 1. Prosthodontists should install airborne infection isolation rooms or negative-pressure rooms

for operatory in which procedures involving aerosol will be performed. The airflow must be

planned in a way to facilitate the clearing of the contaminated aerosol within the dental

operatory with adequate provision of ventilation to allow a minimum of 6 ACH (Air

Changes per Hour). Airflow can be managed by introducing additional positive air flow

from less contaminated to a more contaminated zone using pedestal or tabletop fans and

placing exhaust fans to evacuate the contaminated air to the external environment.

2. During aerosol-generating procedures, we should follow four-handed dentistry, extra-oral

suction and rubber dams to minimize droplet spatter and aerosols. The number of Dental

health care practitioners (DHCP) present during the procedure should be limited to only

those essential for patient care and procedure support.

3. The commonly employed air-water syringe should also be used with caution due to its

potential to create droplets with the forcible ejection of air and/or water.

4. Ideally, dental treatment should be provided in individual patient rooms whenever possible.

For dental facilities with open floor plans, to prevent the spread of pathogens, there should

be: At least 6 feet of space between patient chairs should be maintained. Physical barriers

between patient chairs would be an added advantage.

5. Prosthodontist should use an N95 respirator or a respirator that offers a higher level of

protection such as other disposable filtering facepiece respirators (an N/R/P99, or N/R/P100,

R/P95), powered air-purifying respirator (PAPRs), or an air-purifying elastomeric (e.g.,

half-face or full-face) respirator. We should not perform any AGP without a surgical mask

and a full-face shield.

6. Consider using portable air purifiers with HEPA-14 or true HEPA air filtration unit while

the patient is actively undergoing, and immediately following, an aerosol-generating

procedure.Air purifiers with HEPA filtration efficiently capture particles the size of (and far

smaller than) the SARS-CoV-2 virus.

7. To clean and disinfect the dental operatory after each and every patient. We should wait a

minimum of 10 minutes after completion of clinical care and exit of each patient to begin

with cleaning and disinfection of the operatory. This time will allow for droplets to

sufficiently fall from the air after a dental procedure, and then be disinfected properly.

8. Few recent studies have recommended the use of Spraying or Fogging with disinfectants.

Rooms treated by disinfectants applied as fog, mist, or vapor should be empty and sealed off

to avoid human exposure to the potentially harmful treatments. However, it is not the most

effective way of disinfection for environmental surfaces and may pose harm to individuals.



If disinfectants are to be applied, manual surface cleaning with detergent and water using

applied friction (e.g., brushing, scrubbing) must be performed first to ensure physical

removal of organic materials, followed by the use of a cloth or wipe which is soaked in the

disinfectant (Eg. 0.5% to 0.1% sodium hypochlorite or 70% alcohol for sensitive surfaces).

Strategies Recommended in Prosthodontics

I. To reduce droplet / Aerosol generation9

1. During Tooth preparation:

a. Treatment alteration may be considered to incorporate rubber dam application.

b. Design supra-gingival margins for posterior Fixed Dental Prosthesis or use a split-

dam technique.

c. Most widely recommended are the Anti-retraction dental handpiece with specially

designed anti-retraction valves or other anti-reflux designs as an extra preventive

measure for cross-infection. Also, it is recommended to use electric handpieces with

torque of 1:5 for tooth preparation.

d. Clinical micro motor and a contra angled handpiece with latch type burs without

water or irrigation can also be used instead of air turbine handpieces.

2. During Removable Prosthodontics:

a. After contacting the patient, the Prosthodontist should avoid touching other objects

in the dental office. It is recommended to take the help of a dental assistant. Staff

should be educated to use personal protective equipment (PPE).

b. Upon removal from the patient’s mouth, dental prosthesis, impressions, and other

prosthodontics materials (e.g., bite registration) should be thoroughly disinfected by

a disinfectant approved by EPA (Solutions like sodium hypochlorite, 2%

Glutaraldehyde) which are effective against SARS-CoV-2.

3. During impression making:

a. Digital impressions are preferred in order to prevent the spread of infection through

cross-contamination by making impressions and pouring casts.

b. In conventional impressions, salivary suction must be performed with care to avoid

gagging.

c. Select and adjust trays to the right size to avoid cough reflex.

d. For highly sensitive patients, consider applying surface anesthesia on the palate

before impression making or use the triple tray impression technique to reduce

gagging.

e. For impressions of fixed dental prosthesis, Cordless techniques should be preferred

over the conventional Cord technique of gingival displacement.

II. Impression trays

Impression trays should be rinsed thoroughly under running water to remove residual blood

and saliva. Precleaning removes additional bioburden and any adherent impression material.

Consistent with dental infection-control guidelines for semicritical instruments, chrome-plated and

aluminum impression trays can be cleaned, packaged, and heat-sterilized. Single-use, plastic

impression trays provide a disposable alternative to heat sterilization.10



III. Disinfection of impressions

The importance of cross infection control cannot be overemphasized during this

Covid-19 era. In order to avoid the spread of disease, dental impressions require a high level

of disinfection. Impressions should be rinsed thoroughly under running tap water before

disinfection to remove as much bioburden as possible. Impressions must be decontaminated

through chair side disinfection immediately after removal from the patient`s mouth.

Personal protective equipment must be utilized while disinfecting the impressions.10, 11

The proper criterion for impression disinfection involves:

1. The most suitable method (spray or immersion).

2. Appropriate application (time of contact).

3. Periodic check for efficacy.12

The factors to be considered for any disinfection protocol for dental impression are

effectiveness, chemical stability, and efficacy of the disinfectant solution. The disinfection

procedure should not alter the dimensions and surface details of the impression and resultant cast.13

According to the CDC, The most appropriate method for reducing the burden of SARS-CoV-2

is Chemical disinfection.14 Irreversible hydrocolloid impressions can be effectively disinfected

against SARS-CoV-2 and other pathogens with minimal distortion by immersion in a 1% sodium

hypochlorite solution for 10 minutes.10 Rubber-base silicone impressions can be disinfected

adequately by immersion in a 1% sodium hypochlorite solution, chlorine dioxide, or complex

phenol for adequate time. However, the method of disinfection should be verified with the material

manufacturer to prevent distortion of the impression or loosening of the adhesive bond between the

impression tray and the impression material. Phenols with high alcohol content, for example, can

desiccate some impression materials.11Wax rims and wax bites are disinfected using a sodium

hypochlorite spray and a "spray-wipe-spray" technique. Following the second spray, the wax bites

can be enclosed in a sealed plastic bag for the proper contact time. The bites should remain wet with

disinfectant for the time recommended by the manufacturer.10

IV. Alternative Therapy to Aerosol Generating Procedures

1) Resin-bonded Fixed dental prosthesis: Conventional fixed partial dentures can be avoided

since they require extensive tooth preparation that requires a high-speed drill with a copious

amount of water coolant. Instead, bonded restorations should be considered for the

replacement of missing anterior teeth, including first premolars.15,16 The following are types

of lab-made bonded bridges that can be fabricated with minimal or no tooth preparation.

1. Maryland bridge (Metal wings)

2. Fiber-reinforced bridge (Composite resin and splinting fibers)

3. Lithium disilicate bonded bridge

It is recommended to follow minimal tooth preparation for gaining restorative space or

improving the path of insertion using diamond points, under Rubber Dam isolation. Digital

impressions are preferred over conventional impressions. If at all conventional impression is made,

it can be made using elastomeric impression material. Opposing impression can be made using

irreversible hydrocolloid impression material. Disinfection and dispatch of impression is done after



following the above-mentioned guidelines of chemical disinfection. Lab fabricated bonded FDPs

can be made entirely in Lithium disilicate or using composite resin with resin-reinforced splinting

fiber or using metal wings and a bonded ceramic pontic. Proper Bonding protocol should be

followed for these restorations.17

2) Removable Prosthodontics: An effort should be made to manage patients using Non-AGP

procedures as much as possible. If the patient can wait for few months, an interim

removable partial denture could be fabricated instead of a fixed dental prosthesis or

Fabrication of cast partial denture to delay the second stage implant surgery, and definitive

implant prosthesis could also be done. Flexible dentures could be fabricated instead of

acrylic dentures to avoid appointments due to broken dentures. Polymer-based RPDs (like

polyethylene glycol, polymethyl methacrylate, and aryl-ketone polymers,

polyetheretherketone polymer) fabricated using CAD-CAM can be considered as an

alternative to conventional Cast partial dentures made of metal. Also, extra-oral radiographs

should be preferred over intra-oral radiographs to prevent coughing or vomiting reflexes and

consequently, aerosol generation.

V. Strategies Recommended In Implantology

Following the CDC guidelines, we can plan and schedule implant surgeries in select clinical

situations. It is mandatory that the highest level of personal protective equipment (PPE) should be

used. Experience and clinical judgement, apart from thorough interpretation of CBCT data, is

mandatory for carrying out implant placement surgeries during this period.

Traditionally implant site preparations require drilling speeds of 500-2000rpm depending on the

density of bone and the manufacturer’s recommendations. Internal or external irrigation is advised

for preventing heat generation during osteotomy preparation. However, implant site preparations

can also be accomplished in select bone situations at speeds as low as 50-100 rpm without the

copious use of saline for irrigation.18 Slow, intermittent drilling using a sharp set of drill and

following the sequence suggested by the implant manufacturer is essential. It is prudent to choose

implant sites that have lower bone density like D2,D3,D4 bone types.

1. Bone expansion: In cases with a softer bone (D3, D4) and narrow ridges, bone expansion

procedures can be accomplished using expansion screws or convex osteotomes. This may

lead to the thinning of the labial bony wall, which can be augmented by performing a GBR

(Bone grafting) procedure.19

2. Immediate placements: Most immediate implant placements do not require too much

osteotomy site preparation. Apical preparation for achieving primary stability can be

achieved using the same protocol explained above.

3. Indirect Sinus Lifts: Can be performed using concave osteotomes followed by bone

augmentation.20

4. Ridge augmentation and socket grafting procedures can be performed as always.

5. During second stage surgery, Standard surgical protocol can be performed with Blade.

Avoid using tissue punch with the motor. Depending on a case per se, wherever possible, try

and avoid two-stage surgeries.

VI. Guidelines for Lab Procedures



Dental laboratory technicians have a high risk of infection by direct exposure to

contaminated laboratory materials. All impressions, bite registrations, casts, prostheses, or

other items placed in the patient’s mouth should be disinfected before sending them to the

lab or utilizing the Department’s lab. Lab personnel should strictly handle all lab equipment

as well as clinic transfers, including impressions, casts & frameworks using gloves. The

dental office and laboratory must reliably communicate the disinfection status of each case.

If the status is uncertain, the process should be repeated. The same infection control

protocols must be followed in the dental laboratory as in the dental office. Laboratory

surfaces must be disinfected using the disinfectant spray or surface wipes. The dental

laboratory should be fumigated on a regular basis. Dental prostheses should be stored in

diluted mouthwash and not in disinfectants prior to insertion. If a manufacturer’s

recommended contact time is exceeded, there are potential corrosion risks for metal

components. The lathe in a dental laboratory presents unique safety and infection control

risks. Protective barriers must always be worn when working with a lathe. Never use a

polishing lathe, rag wheel, brushes or pumice in the laboratory without first disinfecting the

appliance. Rag wheels should be heat sterilized every day. Pumice must not be used for

more than one case and must be discarded after use. Articulators should be disinfected by

spraying with a hospital-level disinfectant followed by wiping.

Adhering to Standard Precautions, using aseptic technique, following proper

disinfection and sterilization procedures, and wearing appropriate personal protective

equipment can prevent disease transmission from contaminated items entering the dental

laboratory.

VII. General Strategies & Measures

Apart from the detailed guidelines provided by the CDC, IDA, OSHA, DCI, and other

principal bodies, several strategies and measures can be implemented to mitigate the risks of

disease transmission.

Prosthodontists and their staff should regularly use 0.5% Povidone-iodine oral rinse for 15

seconds to decrease the risk of transmission associated with viral shedding from asymptomatic

individuals.This solution serves as an adjunct to personal protective equipment for dental and

surgical specialties during the COVID-19 pandemic.21

Aerosol adjuncts (additional recommendations): All aerosol-generating procedures (AGP)

should be performed in a closed room if available. 1: 100 dilution of 5.25- 6.15%, i.e. 0.01% of

sodium hypochlorite for Dental Unit Waterline, should be used to ensure continuous disinfection

while performing AGP. Freshly prepared sodium hypochlorite solution should be used, and remnant

diluted solution, Hydrogen peroxide should be discarded. Vapor fumigation with 30% hydrogen

peroxide can also be performed.

Avoid overcrowding in waiting rooms by scheduling the appointment with an adequate time

frame between appointments. Also, teledentistry consultations allow clinicians to triage patients and

identify the urgency of each case in order to reduce the need for in-person appointments if the issue

can be resolved virtually.22 Verbal informed consent is obtained and consultation details are

documented in the patient’s electronic dental chart. When an urgent intervention is deemed

necessary, teledentistry also helps clinicians determine whether the intervention can be safely

performed with available equipment. If the intervention requires the use of aerosol generating

procedures, these cases will be referred to hospital-based clinics with higher standard infrastructure.



Follow-up appointments can also be done using teledentistry to minimize contact while

ensuring patient safety and well-being. Maintenance of a small multidisciplinary and multi-

specialty team of essential clinicians and support staff helps reduce risks of spread in the event of

contamination. Last, when onsite intervention is necessary, the use of private operatory rooms

instead of open area operatories, and staggered patient schedule further minimize risks of viral

transmission.23

Conclusion

The impact of COVID-19 on a dental practitioner’s daily practice has been profound.

Prosthodontists are considering safe alternative options to treat their patients during Covid-19. This

article is an overview of the current guidelines issued by specialty bodies and learned societies to

tackle post covid-19 era in the field of prosthodontics. While COVID-19 continues to make its

presence felt in healthcare all over the world, Dental health care personnel will no doubt adapt to

altered guidelines for providing optimum dental care in the crucial fight against the COVID-19

pandemic.

References: 1. Ather A, Patel B, Ruparel NB, Diogenes A, Hargreaves KM. Coronavirus Disease 19

(COVID-19): Implications for Clinical Dental Care. J Endo 2020; 46(5):584-595. 2. Lu H, Stratton CW, Tang Y. Outbreak of Pneumonia of Unknown Etiology in Wuhan

China: the Mystery and the Miracle. J Med Virol 2020; 92(4):401-402.

3. World Health Organization, WHO Director-General’s remarks at the media briefing on

2019-nCoV on 11 February 2020. https://www.who.int/dg/speeches/detail/who-

directorgeneral-s-remarks-at-the-media-briefing-on-2019-ncov-on-11-february-2020.

4. Coronavirus disease (COVID-19) Situation Report – 138 SITUATION IN NUMBERS

total and new cases in last 24 hours. https://www.who.int/docs/default-

source/coronaviruse/situation-reports/20200606-covid-19-sitrep-

138.pdf?sfvrsn=c8abfb17_4

5. Centers for Disease Control and Prevention, Interim Infection Prevention and Control

Guidance for Dental Settings during the COVID-19 Response, Centers for Disease

Control and Prevention, Atlanta, GA, USA, 2019.https://www.cdc.gov/

6. ADA, What Constitutes a Dental Emergency? American Dental Association, Chicago,

IL, USA, 2020.

7. Harrel SK, Molinari J. Aerosols and splatter in dentistry: a brief review of the literature

and infection control implications. J Am Dent Assoc 2004; 135(4):429-37.

8. OSHA-Occupational Safety and Health Act “Guidance on Preparing Workplaces for

COVID 19.”https://www.osha.gov/Publications/OSHA3990.pdf

9. Ge ZY, Yang LM, Xia JJ, Fu XH, Zhang YZ. Possible aerosol transmission of COVID-19 and

special precautions in dentistry. J Zhejiang Univ Sci B 2020; 21(5):361-368. 10. Poulos JG, Antonoff LR. Disinfection of impressions. Methods and effects on accuracy.

N Y State Dent J 1997; 63(6):34-6.

11. Lepe X, Johnson GH. Accuracy of polyether and addition silicone after long-term

immersion disinfection. J Prosthet Dent 1997; 78(3): 245-9.

12. Maillard JY, McDonnell G. Selection and use of disinfectants. In Prac 2012; 34(5):292-

9.

https://www.who.int/docs/default-source/coronaviruse/situation-reports/20200606-covid-19-sitrep-138.pdf?sfvrsn=c8abfb17_4



https://www.cdc.gov/

https://www.osha.gov/Publications/OSHA3990.pdf



13. Abdullah MA. Surface detail, compressive strength, and dimensional accuracy of

gypsum casts after repeated immersion in hypochlorite solution. J Prosth Dent 2006;

95(6):462-8.

14. Centers for Disease Control and Prevention, Interim Infection Prevention and Control

Recommendations for Patients with Suspected or Confirmed Coronavirus Disease 2019

(COVID- 19) in Healthcare Settings, Centers for Disease Control and Prevention,

Atlanta, GA, USA, 2019, https://www.cdc.gov/coronavirus/2019-ncov/hcp/infection-

controlrecommendations.html.

15. Durey KA, Nixon PJ, Robinson S, Chan MF. Resin bonded bridges: techniques for

success. Br Dent J 2011;211(3):113-8.

16. Lam WYH, Chan RST, Li KY, Tang KT, Lui TT, Botelho MG. Ten-year clinical

evaluation of posterior fixed-movable resin-bonded fixed partial dentures. J Dent2019

;86:118-125.

17. Indian Dental Association ‘Towards Aerosol Free Dentistry’

https://www.ida.org.in/pdf/20200425_TowardsAerosolFreeDentistry.pdf

18. Delgado-Ruiz RA, Velasco Ortega E, Romanos GE, Gerhke S, Newen I, Calvo-Guirado

JL. Slow drilling speeds for single-drill implant bed preparation. Experimental in vitro

study. Clin Oral Investig 2018;22(1):349-359.

19. Starch-Jensen T,Becktor JP. Maxillary Alveolar Ridge Expansion with Split-Crest

Technique Compared with Lateral Ridge Augmentation with Autogenous Bone Block

Graft: a Systematic Review. J Oral Maxillofac Res 2019;10(4):e2.

20. Nedir R, Nurdin N, Vazquez L, Abi Najm S, Bischof M. Osteotome Sinus Floor

Elevation without Grafting: A 10-Year Prospective Study. Clin Implant Dent Relat Res

2016 ;18(3):609-17.

21. Bidra AS, Pelletier JS, Westover JB, Frank S, Brown SM, Tessema B. Rapid In-Vitro

Inactivation of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2)

Using Povidone-Iodine Oral Antiseptic Rinse. J Prosthodont 2020;29(6):529-533.

22. Khan SA, Omar H. Teledentistry in practice: literature review. Telemed J e

Health2013;19:565–567.

23. Wu KY, Wu DT, Nguyen TT, Tran SD. COVID‐19’s Impact on Private Practice and

Academic Dentistry in North America. Oral Dis 2020.

https://www.cdc.gov/coronavirus/2019-ncov/hcp/infection-controlrecommendations

https://www.cdc.gov/coronavirus/2019-ncov/hcp/infection-controlrecommendations

https://www.ida.org.in/pdf/20200425_TowardsAerosolFreeDentistry.pdf




ABSTRACT

In Prosthodontics, magnets have created great interest, and their applications are various, primarily as

retentive aids. Magnets are common because their small size and their attractive or repulsive forces

allow them to be positioned within the prosthesis without becoming obtrusive in the mouth.

Conventionally magnets have been used as retentive devices for removable partial dentures, obturators,

and maxillofacial prosthesis. The retentive properties and the rare earth magnets' compactness have

contributed to their widespread use in the last few decades. This article reviews the types of magnetic

devices available, their applications in various fields of Prosthodontics, advantages, and disadvantages

followed by newer magnetic systems.

Keywords: Metals, Rare Earth, Overlay, Implant retained overdentures, Magnetic Phenomena,

Maxillofacial prosthesis

Introduction

For several decades now, magnetic phenomena have been known, and their applications in

diverse fields have been various. In dentistry, magnetism is not new, though it has not been closely

investigated. Its most prevalent use has been in the field of prosthetic dentistry, where both its repulsive

and attractive properties have been used.1

Magnets that have been initially in use were bulky, and questions about their potential toxic

effects were raised. The currently available literature, however, does not display such evidence. The

cause for magnets' popularity is their small size and strong, attractive forces, which facilitates them to

be positioned in the prosthesis without being obtrusive in the mouth. Despite many benefits, including

ease of washing, positioning for both dentist and patient, automatic reseating, and continuous retention,

magnets have a low resistance to corrosion within oral fluids and thus require encapsulation within a

relatively inert alloy such as stainless steel or Titanium. Action with saliva quickly results in corrosion

and loss of magnetism when such casings are breached.2

Brief history The very first documentation of magnets was around 2500-3000 years BC. It was labelled as

Load Stone by the ancients. Their origin is first noted in a large area in Asia Minor called Magnesia,

where the locals called it 'Magnetite'3. In 1953, Freedman initially used a magnet to improve retention

Magnets in Prosthodontics – An Overview

Dr Hrishikesh Mahapatra1, Dr Sumit Bedia2

1Post Graduate student,

2Associate Professor,

Department of Prosthodontics and Crown & Bridge,

Bharati Vidyapeeth Deemed to be University Dental College and Hospital, Navi Mumbai,

Mahapatra H et al: Magnets in Prosthodontics


and seating of complete denture against the alveolar ridges by using mutual repulsion at the time of

closing the jaw.4 In 1956, Nadeau used magnets in combined extraoral and intraoral prosthesis.5 In 1960,

Behrman used the technique of incorporating magnets in the jaw to increase the prosthesis's retention.6

In 1976, Federick used magnets in a sectional denture.7 Magnets were also used in the maxillofacial

prosthesis in eyelid and lip closure at the fabrication of obturators.8

CLASSIFICATION9:

A. Based on Alloys used

• Those comprising cobalt Examples are Alnico, Alnico V, Cobalt-Platinum (Co-Pt), Cobalt-

Samarium (Co5Sm)

• Those not containing cobalt Examples are Neodymium-Iron-Boron (Nd-Fe-B), Samarium Iron

Nitride.

B. Based on the type of magnetism

• Repulsion

• Attraction

C. Based on Capability to retain magnetic properties (intrinsic coercivity or hardness)

• Soft (easy to magnetize or demagnetize but less permanent): Palladium-Cobalt-Nickel (Pd-Co-

Ni) alloy, Palladium-Cobalt (Pd-Co) alloy, Palladium-Cobalt-Chromium (Pd-Co-Cr) alloy,

Palladium-Cobalt-Platinum (Pd-Co-Pt) alloy, Magnetic stainless steels, Permendur (an alloy of

Fe-Co), Chromium-Molybdenum (Cr-Mo) alloy.

• Hard (retain magnetism permanently): Alnico alloys, Co-Pt, Co5Sm, Nd-Fe-B.

D. By the number of magnets in the system

• Single

• Paired

E. Based on Type of surface coating (materials may be stainless steel, Titanium, or palladium)

• Coated

• Uncoated

F. Based on the type of magnetic field

• Open field

• Closed field — Rectangular closed-field sandwich design

— Circular closed-field sandwich design

G. Based on the number of magnets in the system:

• Duo-system open field

• Mono-system open field

• Mono-system closed field

H. Based on the arrangement of the poles

• Reversed poles

• Non reversed poles



Commercially Available Magnetic Systems3 Table 1: Few commercially available magnetic systems for use in Prosthodontics

OPEN FIELD SYSTEM CLOSED FIELD SYSTEM

The first magnetic devices to be used were

the open-field type where one magnet each

was placed in the jaw and the denture

Closed-field devices were developed because

of concerns about the potential impact of

magnetic fields on oral tissues

This configuration offered unshielded

magnetic fields inside the oral cavity. This

unshielded, encapsulated magnet uses only

one retention pole and is therefore known as

an open field device.

When a soft ferromagnetic substance (keeper)

connects the two poles of a magnet, the actual

magnetic field is shunted through the keeper,

thereby suppressing the actual magnetic

fields; a greater magnetic force may be

obtained. This attachment form is referred to

as the 'closed field type.

DYNA INNOVADENT

GOLDEN SOLID STATE

MAGNEDENT

SCHINNER

GILLINGS

JACKSONS- Regular and mini

Types of Magnetic Materials Used in Prosthodontics: 1) Rare earth permanent magnets2: a) Samarium-Cobalt Magnets (Sm-Co)

b) Neodymium-Iron-Boron Magnets (Nd-Fe-B)

• Rare elements consist of seventeen elements with atomic numbers 21, 39, and from 57 to

71.

• These elements have a strong affinity for the non-metallic elements, due to which they are

used for producing alloys, which are used in metallurgical industries.

• Made from alloys of rare earth elements, rare earth magnets are strong permanent magnets

producing higher magnetic fields.

• Due to magneto crystalline anisotropy, rare earth magnets can generate high forces relative

to their size. This property enables the preferential alignment of single crystals in one

direction (along the C-axis), which increases the magnetism.

• Another beneficial aspect of rare earth magnet, relative to Alnico magnets, is their very

strong coercivity. Strong coercivity means a superior capacity for these magnets to resist

demagnetization.



• Sm-Co can be embedded in heat polymerizing resin when fabricating dentures as its curing

temperature is above 7000C, and their magnetic properties are stable below 2000C.3

• Nd-Fe-B has a curing temperature, which is low about 3000C and magnetic properties

deteriorate above 800C. Therefore, care should be taken not to overheat the magnet.3

2) Soft Ferromagnetic alloys3: a) Palladium Cobalt Magnets (Pd-Co)

b) Palladium Cobalt-Chromium Magnets (Pd-Co-Cr)

c) Palladium Cobalt Nickel Magnets (Pd-Co-Ni)

• Materials of rare earth magnets are too hard to be shaped into a form suitable for each patient.

• To overcome this problem, soft magnets were introduced in 1984 for use in the root face.

Components of The Magnetic System9:

A two-component device is the standard magnetic retention unit: the magnetic retention element

and the keeper element. The magnetic retention element consists of paired magnets, an attached keeper,

and two protective plates covering the paired magnets' faces. The oval shape of the magnetic retention

element is 5 mm long, 3.2 mm wide, and 3 mm high. The keeper element is a detachable, oval-shaped,

magnetizable preferred disk or a cast root cap. The keeper element is prepared with a magnetizable alloy,

which is not a magnet. Still, it acts as a magnet (induced magnet) when it comes in contact with the

element's magnetic retention. The alloy used is Pd-Co-Ni alloy or stainless steel alloy.

Selection of keeper10

• Cement-in keeper: It should be used where available denture space is limited. It is not suitable

for small roots because of the danger of lateral root perforation or for patients with high caries

susceptibility. It is 5 mm long, 3 mm wide, and 1.2 mm thick, and the root face should be large

enough to accommodate a cavity of this size. It is fitted in one appointment.

• Screw-on keeper: It can be used where ample denture space is available or where the root face

is too small for a cement-in keeper to accommodate. As it can be easily removed and replaced,

it is used where the root may require shortening. Its most extensive measurements are 6 mm long

and 4 mm wide and typically covers much of the root face. It is fitted in a single appointment.

• Cement-on keeper: Other than its retention by a soldered-in wire loop, it is comparable to the

screw-on holder. It's hard to remove, but the easiest one to match with all keepers. It is possible

to finish the procedure in minutes. It is the most favored type.

• Cast root cap and dowel keeper: Due to the risk of dental caries, it should be used where

complete root face coverage is needed. It must be cast in a magnetizable alloy, and techniques

are required for cobalt-chromium casting.

Biocompatibility and Their Effects on Tissues

The magnetic intensity of the dental attachment on the magnetic assembly surface is about 0.8

Tesla. The leakage flux in contact with the keeper on the magnet assembly is around 0.01-0.03 Tesla

and about 0.005 Tesla outside the abutment tooth. Thus, there is no influence of the static magnetic field

generated by a dental magnetic attachment on the human body and tissues. However, the potential ways

in which a magnet might result in tissue injury are:

• The physical effects triggered by the ambient steady magnetic fields (magnetism)

• Chemical effects of alloys and their corrosion materials

In 1960, Behran11 studied the physical effects of magnetism on both bone and soft tissues in 450

subjects and concluded that tissues were harmless. It is shown that, as compared to an open field system,

the closed-field system has improved tissue compatibility.



Late back in 1979, Tsutsui12 and his colleagues stated that Cobalt-Samarium does not have

harmful chemical effects. Cobalt has also been an essential dietary trace element in remnants. Samarium

salts are not considered toxic.

Nevertheless, Walmsley13 suggests that there is a need to encapsulate the magnets. He also found

that the magnet will contact saliva as the coating wears out, resulting in magnetic corrosion. It was also

shown that the presence of bacteria such as Streptococcus sanguinus increases the corrosion rate. The

lifetime of the magnet will thus be shortened. Coated magnets have also been shown to have little effect

on human dental pulp, gingiva, osteoblasts, or blood flow. Only uncoated magnets have shown that

cytotoxic effects on cells are generated. Oral mucosal fibroblasts are among the most susceptible to the

impact of these rare earth magnets. It is concluded that the magnetic potential produced by intraoral

magnets in the surrounding blood vessels is very negligible (2*10-5V) compared to the resting

membrane potential of cell membranes (60-100V).11

Clinical Applications of Magnets: 1) Magnets in Complete dentures based on Magnetic Repulsion and Attraction

• Magnets have been used because they are small and are easy to incorporate into a denture.

• The first attempt to use magnets to hold dentures involved implanting them into the mouth;

because of their large size and insufficient powers, issues ensued. Improvements in magnetic

materials have allowed magnetic attachments to be smaller and stronger.

• The first recorded use of magnets in prosthetic dentistry involved using the repulsion of like

poles of magnets to maintain and improve the seating of complete dentures. The magnetic

material used was Alnico type that has been discontinued because of the large bulk necessary for

magnetic strength.12

• The use of attractive force retention was reported in the early 1960s.13 This first attempt was

made with Al-Ni-Co V, which was surgically implanted in the mandible of edentulous patients.

Because of the distance between the two magnets, they provided the inadequate force to aid in

retention.

• After that, the smaller and stronger Co-Pt magnets were implanted. Several disadvantages,

including high cost, limited availability, difficult fabrication was associated.

2) Tooth Supported Overdenture retained by magnetic attachments

• The first reported use of magnets for the retention of overdentures took place in the 1960s with

a patient's rehabilitation with a cleft lip and palate.14 Magnetic Co-Pt alloy was used to produce

crowns for three remaining teeth with cast Co-Pt also built into the denture.

• This was soon followed by cementing magnets within the retained roots for the retention of

overdentures.15 A Sm-Co was cemented into a prepared cavity in the root surface, and a similar

magnet was placed in the denture.

• Magnetically retained overdentures are virtually maintenance-free and inexpensive to fabricate,

and the technique lies within every dentist's scope.

• The primary purpose is to preserve the alveolar bone by retaining teeth or/and roots underneath.

Magnetically retained overdentures transfer no detrimental lateral forces to those supporting

elements that help in maintaining a favorable clinical situation.

• An overdenture with a magnetic attachment is a useful choice for an abutment tooth with chronic

periodontal disease because the magnetic attachment dissipates the lateral stress component on

the abutment teeth and improves poor clinical crown-to-root ratios.



3) Implant-supported overdenture with Magnetic attachments

• The various problems reported by the complete denture wearers can be eliminated with implant-

supported fixed prostheses or removable overdentures.

• Magnetic attachments used to retain dentures are typically shorter than mechanical attachments,

which is particularly useful for patients with restricted interocclusal space and challenging

aesthetic demands. They can also accommodate a moderate divergence of alignment between 2

or more abutments since they do not depend on the path of insertion.16

• Magnets in Implant retained overdentures are particularly useful for elderly or disabled patients

who may have difficulty in inserting and removing removable prosthesis.

• Various types of attachments have been developed for the use of implant overdenture, including

O-ring, Locator, magnetic attachment, and bar type. The choice of the higher abutment and self-

adjusting type magnet provides significant higher stability and retention of implant overdenture.

Patients' satisfaction is expected to be greater by increased retention and stability of implant

overdenture.17

4) Magnets in Maxillofacial Prosthesis

• Magnets have been effectively used for the retention, maintenance, and stabilization of combined

maxillofacial prostheses, and they are effective for this purpose.

• Magnets in coin form have more advantages in maxillofacial prosthetics than the other forms;

the magnet can be chosen according to the size of the defect and in any diameter that is needed.18

• Cheek plumper, a single unit prosthesis that adds on to the weight of the denture, increases the

mesiodistal width of the prosthesis, thereby making its insertion difficult in patients with limited

mouth opening and can also cause muscle fatigue. Thus, to combat this situation, a detachable

cheek plumper prosthesis using magnets was fabricated in a completely edentulous patient with

sunken cheeks.19

• Robinson used horseshoe magnets for the retention of an upper denture and obturator for a patient

with a complete maxillectomy. A sectional prosthesis can be used for patients with large

maxillary defects. Two magnetic pairs are commonly used for connecting the sections. The

magnets are embedded in the respective contacting surfaces at a depth of 0.5 mm. Because Sm-

Co magnets are small, the obturator can be made hollow to reduce its weight. The size of ferrite

or alnico magnets often prevents the use of a hollow obturator.20

• Magnets are also used in an orbital prosthesis, auricular prosthesis, large and small maxillary

defects, and intra oral-extra oral combination prosthesis.21

Failure of Dental Magnets Corrosion is the key issue connected with the use of magnets as retentive devices. SmCo5 and

Nd-Fe-B magnets are both extremely susceptible to corrosion, particularly in environments containing

chloride. Therefore, before being used in dental applications, magnetic materials must be separated

securely from oral fluids. While some existing magnet assemblies are encapsulated in stainless steel or

Titanium, due to corrosion and lack of retention provided by the attachment, some devices fail in about

18 months of clinical use.22



Advantages and disadvantages of magnets: (Table 2)

Table 2: Advantages and Disadvantages of using magnets in Prosthodontic applications

ADVANTAGES DISADVANTAGES

Magnets provide both retention and stability Low corrosion resistance

Magnets allow 24 degrees of abutment

divergence, which allows for easy insertion

and removal of the prosthesis in a non-critical

way

Cytotoxic effects of the leachants

The roots or implants do not need to be

parallel; soft-tissue undercuts may be

engaged

High cost

Potentially pathologic lateral or rotating

forces are eliminated, providing maximum

abutment protection

Short track record

Enables automatic reseating of the denture if

dislodged during chewing

If misaligned placement occurs, then the

orthodontic movement of the root will result

in correct contact being reached

Roots with as little as 3mm of bone support

are adequate for use as abutments with

magnetic appliances

They do not directly induce stress to root

abutments

Newer Magnetic Systems: MAGFIT - New Generation Magnetic Attachment: This is a revolutionary dental magnetic

attachment device made up of a strong but ultra-compact embedded magnet that maintains a prosthesis

on an attractive magnet keeper set on the abutment tooth. It has the following advantages-

• Protection of the abutment tooth from excess stress

• Easy instrumentation and easy maintenance



• Superior aesthetics

• Strongest Retention in its class with an ultra-compact size

• No Corrosion

Recommended applications • Natural tooth

• Implant

Conclusion Dentistry is a discipline that is ever-changing. Changes in treatment are needed as new research and

clinical practice expand our understanding. Some decades ago, magnets were only rarely used for dental

purposes. Intraoral magnets have been influencing the course of aesthetics and retention for both

complete and removable partial dentures since the advent of rare earth magnet alloys.

Their advantages include convenience, low cost, self-adjustment, inherent stress breaking, comparative

lateral freedom of movement, and the minimum trauma to the retained root while eliminating the need

for adjustment in services.

Magnetic attachments will offer new possibilities in the field of removable prosthesis retention. Over

the last five years, magnet technology and engineering have improved significantly, and it is now

possible to manufacture much smaller magnets that give the keeper a better position.

These enhancements need long-term clinical studies to evaluate the durability of the upcoming

generation of clinically working magnets. There is no doubt, however, that if magnets are chosen for a

specific clinical situation, they act as a good introduction and can prove to be extremely effective in

many cases.

References: 1. Laird WR, Grant AA. The use of magnetic forces in prosthetic dentistry. Journal of Dentistry, 9,

No. 4, 1981, pp. 328-335.

2. Bhat VS, Shenoy KK, Premkumar P. Magnets in dentistry. Arch Med Health Sci 2013; 1:73-9.

3. Rohit Raghavan et al. Magnets in Complete Dentures. International Journal of Oral Health

Dentistry, July - September 2015;1(3):133-137.

4. Moghadam BK, Scandrett FR. Magnetic retention for overdentures. J Prosthet Dent 1979; 41:26-

9.

5. Nadeau J. Maxillofacial prosthesis with magnetic stabilizers. J Prosthet Dent 1956; 6:114-9.

6. Behrman SJ. The implantation of magnets in the jaw to aid denture retention. J Prosthet Dent

1960; 10:807-41.

7. Federick DR. A magnetically retained interim maxillary obturator. J Prosthet Dent 1976; 36:671-

5.

8. Meenakshi A. et A Meenakshi A. et al. l. Magnets in Prosthodontics. Int J Oral Health Med Res

2015;2(4):81-84.

9. Gillings BR. Magnetic denture retention systems: inexpensive and efficient. International Dental

Journal 1984:34; 184-97.

10. Rassawet RR, Mittal S, Kalra H. Magnets – Role in prosthodontic rehabilitation: A review.

Indian J Dent Sci 2020; 12:168-71.

11. Behrman SJ. The implantation of magnets in the jaw to aid denture retention. J Prosthet Dent

1960; 10:807–41.

12. Tsutsui H, Kinouchi Y, Sasaki H, Shiota M, Ushita T. Studies on the Sm-Co magnet as a dental

material. J Dent Res 1979; 58:1597–606.

13. Walmsley AD. Magnets in Restorative Dentistry. www.priory.com/mags.htm.



14. Brewer AA, Robert M. OVERDENTURES. 2nd Ed, The CV Mosby Company: 1980. p. 376-

97.

15. Overdentures with magnetic attachments. Dental clinics of North America. 1990; 34(4):683-709.

16. Ceruti P, Bryant SR, Lee JH, MacEntee MI. Magnet-retained implant-supported overdentures:

review and 1-year clinical report. J Can Dent Assoc 2010, 76: a52.

17. Richard Leesungbok. The change of stability and retention on magnet-retained overdentures

according to abutment height and attachment design. Presented at the 24th Annual Scientific

Meeting of the European Association of Osseointegration, Stockholm, Sweden.

18. Javid N. The use of magnets in a maxillofacial prosthesis. J Prosthet Dent. 1971:25;334-40.

19. Rewari A et Al. Case Report Esthetic Rehabilitation Using Magnet-Retained Cheek Plumper

Prosthesis. Case Reports in Dentistry Volume 2020, 2769873.

20. Robinson JE. Magnets for Retention of a Sectional Intraoral Prosthesis. J Prosthet Dent 13: 1167-

1171, 1963.

21. Bhat V: A close-up on obturators using magnets: Part 11. J Indian Pros Soc Sep 2006:6(3); 148-

53.

22. Highton R, Caputo AA, Kinni M, Matyas J. The interaction of a magnetically retained denture

with osseointegrated implants. J Prosthet Dent 1988; 60:486-490.



The Official e-publication of Indian Prosthodontic Society


The Implant - Abutment Connection and Its Relation to Crestal Bone — A Review

Dr Rahul Ravi1, Dr Adnan Kheyroolla1, Dr Omkar Shetty2, Dr Rubina Tabassum3, Dr Gaurang Mistr4,

Dr Kunal Mehta5

1P.G Student, 2Dean and Professor,

3Professor, 4HOD,


Department of Prosthodontics and Implantology,

D.Y Patil University, School of Dentistry, Navi Mumbai, India

ABSTRACT: Implant therapy offers increased longevity, improved function, bone preservation and quality of life. This

article discusses the literature related to the dynamics in effect when an implant is placed in the bone.

Osseous and soft tissue changes take place around the implant subsequent to their placement. These

changes determine the esthetic outcome of the implant.

Keywords: Implants, osseointegeration, esthetics, implant-abutment connection, platform switching

Introduction Dental implants is a widely accepted device used as a predictable and reliable tool for dental

reconstruction, however, it is still necessary to ensure that the height of the peri-implant crestal bone is

maintained. Directly after insertion of a dental implant, a cascade of biological events occurs during the

bone healing process.1 The change in bone shape and continuity is a result of this bone healing process,

contrary to a possible pathological bone loss.2–5 Osseointegration is considered to be the phenomenon of

direct apposition of bone on an implant surface, which subsequently undergoes structural adaptation in

response to a mechanical load. Over time the shape of crestal bone around the implant changes both

horizontally and vertically.6,7

One of the criteria for the success of dental implant treatment is the amount of crestal bone change.

Albrektsson et al.8 proposed that a dental implant can be considered successful if peri-implant crestal bone

loss is less than 1.5 mm during the first year after implant placement and less than 0.2 mm annually after

that. Numerous theories are put forward to explain the crestal bone loss around implants including,

surgical trauma due to excessive heat and pressure generation while preparing the osteotomy for the

implant and periosteal flap elevation, or secondary to the attachment of prosthetic components due to

occlusal overload and the presence of a micro gap between the implant and the abutment & its positioning

in relation to the crestal bone. Although the success of a dental implant is probably multifactorial and

dependent on some or all of the above factors, this review specifically addresses the relationship of the

implant-abutment connection and its relation to crestal bone changes.

https://paperpile.com/c/jZzNvQ/v9BX

https://paperpile.com/c/jZzNvQ/3MSRT+ZABQ9+1UK6D+adkOm

https://paperpile.com/c/jZzNvQ/Bd4Yt+0GhIo

https://paperpile.com/c/jZzNvQ/l8YsF

Ravi R. et al. Implant-abutment connection and crestal bone


Implant-Abutment Connections and Micro gaps: In the two-stage implant placement technique, the implant is placed at the bone crest level. After 3-

6 months, a prosthetic abutment is installed on the implant to connect the implant to future prosthetic

restorations (crowns, bridges or dentures). It is postulated that a potential microscopic space exists at the

abutment/implant interface, along the abutment screw threads and at the base of the screw chamber known

as micro gaps. Three main factors are identified as possible causes for the formation of micro gaps:

occlusal load during physiological function9, manufacturing tolerance10 and micromotion between the

implant–abutment connections. Microorganisms occupy this gap and set up a bacterial reservoir, resulting

in an area of inflamed soft tissue facing the fixture abutment junction.11,12 This microbial leakage at the

implant-abutment interface is a chief challenge for the constructing the two-stage implant systems & is a

major contributing factor for peri-implant inflammatory reactions.

Fig 1: Microgaps at the Implant-abutment connection

Microleakage: Many studies have shown that this microscopic space between implant and abutment (micro gap)

facilitates the infiltration of fluids and macromolecules from crevicular fluid and saliva, enabling bacterial

invasion and proliferation,11,13,14 even in patients with good oral hygiene.15–18

On the other hand, bacterial infiltration may also arise during the first stage or the second stage of implant

surgery.19,20 Moreover, findings from several studies have documented that bacterial infiltration may occur

both from an external source to the inner area of an implant, and in reverse.17,21,22 This migration of

bacteria is probably facilitated through the unavoidable presence of micro gaps between the fixture and the

abutment components of the assembled system.

The bacterial contamination may be correlated with gap sizes or misfits. Gap dimensions ranging

from 20μm to 168μm have been reported.23,24 The level of contamination depends not only on the

precision of fit but also on the degree of the applied micromovement and torque. The incidence of loads

and unscrewing of the prosthetic abutment can increase infiltration, whereas optimal adaptation, minimal

micromovement and exceptional prosthetic and occlusal planning are factors which can minimize

microleakage,9,25 but do not seem to prevent it completely.12,26 The presence of a micro gap in close

relation to bone plays a role in developing of peri-implant inflammation and bone loss. Put merely,

bacterial invasion of the micro gaps can interfere with the osseointegration of an implant during the

healing phase of the surgical intervention and cause peri-implantitis. Pathogenic bacterial microflora may

also influence the outcome of guided bone regeneration in the treatment of peri-implantitis.19,27,28

https://paperpile.com/c/jZzNvQ/VfKHU

https://paperpile.com/c/jZzNvQ/xVCSC

https://paperpile.com/c/jZzNvQ/S5FlE+bH9mH

https://paperpile.com/c/jZzNvQ/0ebg2+iqSvn+S5FlE

https://paperpile.com/c/jZzNvQ/h6Anz+hTr9G+TjwAM+W6pgd

https://paperpile.com/c/jZzNvQ/W5yDF+xV12r

https://paperpile.com/c/jZzNvQ/kATlS+snXEC+TjwAM

https://paperpile.com/c/jZzNvQ/h8ill+IA3cp

https://paperpile.com/c/jZzNvQ/VfKHU+03OMt

https://paperpile.com/c/jZzNvQ/bH9mH+DxDki

https://paperpile.com/c/jZzNvQ/JpLuw+W5yDF+NW4ON



Broggini et al.29 demonstrated an increase in inflammatory cells in the peri-implant soft tissues at

the level or slightly coronal to the implant–abutment junction due to the bacterial presence, which when

combined with osteoclasts formation results in alveolar bone loss.30 This is in contrast to an implant

system with a lack of implant-abutment interface that shows little evidence of the presence of

inflammatory cells. This infiltration of inflammatory substances is irrespective of the amount of plaque

accumulation.31

Comparison of Microleakage in Different Implant-Abutment Connections: Verdugo CL et al. used external connection implant and conical internal connection (Morse taper)

implants. The results of the study showed that less microleakage was shown by Morse taper connection

implants than external connection implants. A gap of 10 μm was presented by external connection

implants more than Morse taper implants with a gap of 2-3 μm.32

Canullo L et al. conducted a five year follow-up study on humans for different implant connections

under functional loading. The results showed that microbial contamination was seen in all the connections.

Internal Hex and conical connection implants showed less leakage of bacteria at the peri-implant sulcus

and inside the connection than external hexagon implants.33

Do Nascimento C et al., in their in vitro study, used 43 microbial species, which were very

common in the human oral cavity. They evaluated prostheses supported by External Hexagon or Morse

Cone implants under dynamic loading conditions. Results revealed that higher microbial count was found

in External Hexagon implants than Morse Cone implants. Many microbial species including, peri-implant

diseases causing organisms were detected in internal part of External Hex implants. Internal surfaces of

Morse Cone implants showed no colonization of microorganisms, as micro gaps present in conical

connections were much smaller at the implant-abutment interface.34

Baggi L et al. in their study, found that tube-in-tube interface implants were more resistant to

colonization than flat to flat interface.34,35 Contradictory results were obtained by Al-Jadaa A et al. where

they found, implants with a flat-to-flat interface (internal hexagonal) mating surfaces showed the best

performance with regard to leakage under both static and dynamic conditions. This study also proved that

if implants under static conditions were tight and would provide better sealing ability under dynamic

conditions.36

Koutouzis T et al. evaluated microleakage of internal Morse-taper connection and found that there

was minimal penetration of bacteria down to the implant-abutment interface.37

Dynamic loading increases the penetration of bacteria as there was micro movement at the implant-

abutment interface, which causes a pumping effect and leads to detrimental effects on marginal bone

stability.13Contradictory results were obtained by Harder S et al. where conical implant-abutment

connections do not prevent microleakage on a molecular level in even unloaded conditions.25

From the studies mentioned above, it is possible to draw the inference that internal implant-

abutment connections and conical (Morse Taper) implant-abutment connections show lesser microleakage

than external implant-abutment connections. The external connections, of which the external hexagonal

connection is the most common, provides a short and narrow connection with the abutment and provides

for only limited screw engagement and a short fulcrum arm, which together allow for frequent screw

loosening. The instability of the external connection leads to open the micro gaps. Besides, it is often

challenging to seat components on the hex easily and with confidence, especially in the posterior parts of

the mouth, even for an experienced clinician. Minute rotational changes at a single abutment location can

result in the misfit of the superstructure. Increasing the flat-to-flat width and the height of the connection

has reduced these complications but not eliminated them. Internal connections, due to their design, have a

more stable implant-abutment connection resistant to joint- opening forces. Lateral forces are distributed

deep within the implant, and the long internal wall engagement with the implant shields the abutment

screw and buffers vibrations. Internal connections are therefore, less prone to micromovements and

opening of the implant-abutment connection. Conical connections, specifically, have the advantage of the

smallest inherent micro gaps due to frictional fit of the abutment into the implant, virtually removing any

https://paperpile.com/c/jZzNvQ/4OlAF

https://paperpile.com/c/jZzNvQ/CbpSc

https://paperpile.com/c/jZzNvQ/OmQlz

https://paperpile.com/c/jZzNvQ/iFeVT

https://paperpile.com/c/jZzNvQ/p92Oq

https://paperpile.com/c/jZzNvQ/dwgIv

https://paperpile.com/c/jZzNvQ/dwgIv+LU67g

https://paperpile.com/c/jZzNvQ/A3hKC

https://paperpile.com/c/jZzNvQ/WVqG0

https://paperpile.com/c/jZzNvQ/0ebg2

https://paperpile.com/c/jZzNvQ/03OMt



gap between the two. However, no implant-abutment interface can completely prevent microleakage in

either loaded or unloaded states.

Position of the Implant-Abutment Connection in Relation to Crestal Bone: Numerous studies have shown that bone resorption around the implant neck does not start until the

implant is uncovered and exposed to the oral cavity. It is hypothesized that bacterial contamination of this

micro gap during the second stage surgery results in peri-implant inflammation, leading to bone

remodeling.30 Bone remodeling will progress until the biologic width has been created and stabilized to

seal off the connective tissue from the colonized micro gap. Not only does this width progress apically,

along the vertical axis, but according to studies conducted by Tarnow et al.38 there is also a horizontal

component amounting to 1–1.5 mm.

Fig. 2: Establishment of Biologic Width after second stage implant surgery

So, the position of the implant-abutment connection in relation to the crestal bone determines the amount

of bone loss around an implant. A study by Broggini et al.39 revealed that as the apical position of the

implant-abutment interface was progressively increased, the total number of peri-implant inflammatory

cells was increased in parallel, i.e., the deeper the interface, the greater the magnitude of peri-implant

inflammation. Further, the maximum density of neutrophils adjacent to supracrestal implants was

significantly less than for crestal and subcrestal implants. Moreover, the peri-implant location with

maximum neutrophil density was also dependent upon the depth of the implant-abutment interface. Thus,

for supracrestal implants, this location was near the implant-abutment interface (ie, above the original

bone crest), whereas for subcrestal implants, this location was immediately coronal to the implant-

abutment interface (below the original bone crest).

In parallel with differences in peri-implant inflammatory cell accumulation, the apico-coronal

dimension of connective tissue was also progressively expanded as the depth of the implant-abutment

interface was increased. This primarily reflected increases in the connective tissue compartment apical to

the original alveolar crest (ie, alveolar bone loss). Specifically, there was significantly greater bone loss

associated with subcrestal implants as compared to supracrestal position.

Therefore, this study demonstrated that moving the interface supracrestally, effectively changing

the location of the inflammatory stimulus, also reduces peri-implant bone loss. Thus, minimal

inflammation (and bone change) occurred when the interface was above the original bone crest, whereas

the greatest inflammation (and bone loss) occurred when the interface was below the alveolar crest. These

clinical observations are highly relevant, since the maintenance of crestal bone height appears to be an

https://paperpile.com/c/jZzNvQ/CbpSc

https://paperpile.com/c/jZzNvQ/hkupJ

https://paperpile.com/c/jZzNvQ/0vHjt



important predictor of soft tissue margins in both natural dentition40,41 and implants.42 These findings have

several important clinical implications relative to limiting inflammation and bone loss around implants.

First, implant design could be either one-part or transmucosal to eliminate the interface. Second, the

interface could be positioned supracrestally. Third, the interface might be made in such a way that

excludes microbes, i.e. a more stable interface with smaller micro gaps. In these scenarios, inflammation

would not be expected to develop near the alveolar crest, consequently reducing the potential for bony

changes. Support for this speculation comes from another animal study in which implants were placed

with the interface approximately 3mm above the original alveolar crest. Bone loss around these implants

was minimal.43 Further, in patients with transmucosal implants placed so that the implant interface was

approximately 3 mm above the original alveolar crest, minimal bone loss was observed over an eight-year

period.44

Platform Switching Concept: Platform switching or platform shifting is a method used to preserve the alveolar bone around

dental implants. The platform switching effect was first observed in the mid-1980s. At the time, larger-

diameter implants were often restored with narrower abutments (Ankylos Dentsply, Friadent, Germany;

Astra-Zeneca, Sweden; Bicon, Boston), as congruent abutments were often still unavailable.45 As it later

turned out, this was a remarkable coincidence. The abutments used with conventional implant types are

generally flush with the implant shoulder in the contact zone. This results in the formation of micro gaps

between the implant and the abutment. The bacterial contamination of these micro gaps adversely affects

the stability of the peri-implant tissues and leads to a reduction of horizontal and vertical marginal bone

levels. If the microcrack is located close to the bone, the creation of the biologic width will occur at the

expense of the bone.13,46 The platform-switching concept requires that this microcrack be placed away

from the implant shoulder and closer toward the axis in order to increase the distance of this microcrack

from the bone.47–49 This generally implies the use of a reduced-diameter abutment. The inward, horizontal

repositioning of the abutment inflammatory cell infiltrate (right) will move the abutment inflammatory

cell infiltrate away from the crestal bone and into a more confined area.

Fig. 3:Soft Tissue Level Implants a

supracrestal IAI

Fig.4: Bone Level Implant have an epicrestal

IAI

https://paperpile.com/c/jZzNvQ/rYKm8+NryMz

https://paperpile.com/c/jZzNvQ/CFEG9

https://paperpile.com/c/jZzNvQ/AFgOY

https://paperpile.com/c/jZzNvQ/NOPZr

https://paperpile.com/c/jZzNvQ/8s7xr

https://paperpile.com/c/jZzNvQ/0ebg2+FhZXI

https://paperpile.com/c/jZzNvQ/Nq4W1+0XZDD+8uoLl



Fig. 5: A comparison of non-platform switched (left)

and platform switched (right) Implant-Abutment Interface

Fig. 6: Platform switching moves the inflammatory cell infiltrate away from the bone

There appear to be two results of the horizontal inward repositioning of the implant-abutment

interface. First, with the increased surface area created by the exposed implant seating surface, there is a

reduction in the amount of crestal bone resorption necessary to expose a minimum amount of implant

surface to which the soft tissue can attach. Second, and perhaps more important, by repositioning the

implant-abutment interface inward and away from the outer edge of the implant and adjacent bone, the

overall effect of the inflammatory cell infiltrate on the surrounding tissue as described by Ericsson et al.7

and Abrahamsson et al.50,51 may be reduced, thus decreasing its resorptive effect on crestal bone. It is

further suggested that platform switching repositions the inflammatory infiltrate further away from crestal

bone and locates it within an approximate ≤90-degree confined area of exposure instead of a ≤180-degree

area of direct exposure to the surrounding hard and soft tissues. As a consequence, the reduced exposure

and confinement of the platform-switched abutment inflammatory cell infiltrate may result in a reduced

inflammatory effect within the surrounding soft tissue and crestal bone.

It is important to note that to benefit from the platform-switching bone preservation technique,

reduced-diameter components, beginning with the healing abutment, must be used from the moment that

the implant is exposed to the oral environment, because the process of biologic width formation begins

immediately following exposure to the oral environment. Thus, whether an implant is placed using a one-

or two-stage surgical procedure, the first component placed on the implant must be of a smaller diameter

if a horizontally repositioned biologic width is to be accomplished. This is important because after crestal

https://paperpile.com/c/jZzNvQ/0GhIo

https://paperpile.com/c/jZzNvQ/LRdrz+ZwvpT



bone has remodeled to a post-restorative resting position around the top of an implant, it will not return to

its presurgical level if platform-switching principles are implemented at a later time.

Conclusion The long-term predictability of dental implants is now a well-documented fact. Virtually all the major

manufacturers can document success rates greater than 90%, and the more refined systems have achieved

well above that number for more than ten years. A grey area has been the long-term stability of the

abutment and prosthesis. Tremendous progress has been made in this area mainly, due to improved

clinical machining tolerances. The transition to internal connections has been gradual but profound. The

internal connections available today are far more stable, physically stronger, easier to restore, more

amenable to excellent esthetics, and definitely more user-friendly.

References: 1. Terheyden H, Lang NP, Bierbaum S, Stadlinger B. Osseointegration--communication of cells. Clin

Oral Implants Res. 2012 Oct;23(10):1127–35.

2. Cochran DL, Nevins M. Biologic width: a physiologically and politically resilient structure. Int J

Periodontics Restorative Dent. 2012 Aug;32(4):371–3.

3. Hermann JS, Buser D, Schenk RK, Higginbottom FL, Cochran DL. Biologic width around titanium

implants. A physiologically formed and stable dimension over time. Clin Oral Implants Res. 2000

Feb;11(1):1–11.

4. Hermann JS, Cochran DL, Hermann JS, Buser D, Schenk RK, Schoolfield JD. Biologic Width

around one- and two-piece titanium implants. A histometric evaluation of unloaded nonsubmerged

and submerged implants in the canine mandible. Clin Oral Implants Res. 2001;12(6):559–71.

5. Linkevicius T, Apse P. Influence of abutment material on stability of peri-implant tissues: a

systematic review. Int J Oral Maxillofac Implants. 2008 May;23(3):449–56.

6. Ericsson I, Nilner K, Klinge B, Glantz PO. Radiographical and histological characteristics of

submerged and nonsubmerged titanium implants. An experimental study in the Labrador dog. Clin

Oral Implants Res. 1996 Mar;7(1):20–6.

7. Ericsson I, Persson LG, Berglundh T, Marinello CP, Lindhe J, Klinge B. Different types of

inflammatory reactions in peri-implant soft tissues. J Clin Periodontol. 1995 Mar;22(3):255–61.

8. Albrektsson T, Zarb G, Worthington P, Eriksson AR. The long-term efficacy of currently used dental

implants: a review and proposed criteria of success. Int J Oral Maxillofac Implants. 1986

Summer;1(1):11–25.

9. Steinebrunner L, Wolfart S, Bössmann K, Kern M. In vitro evaluation of bacterial leakage along the

implant-abutment interface of different implant systems. Int J Oral Maxillofac Implants. 2005

Nov;20(6):875–81.

10. Shareef N, Levine D. Effect of manufacturing tolerances on the micromotion at the Morse taper

interface in modular hip implants using the finite element technique. Biomaterials. 1996

Mar;17(6):623–30.

11. do Nascimento C, Barbosa RES, Issa JPM, Watanabe E, Ito IY, Albuquerque RF. Bacterial

leakage along the implant–abutment interface of premachined or cast components. Int J Oral

Maxillofac Surg. 2008;37(2):177–80.

12. Teixeira W, Ribeiro RF, Sato S, Pedrazzi V. Microleakage into and from two-stage implants: an in

vitro comparative study. Int J Oral Maxillofac Implants. 2011 Jan;26(1):56–62.

13. Hermann JS, Schoolfield JD, Schenk RK, Buser D, Cochran DL. Influence of the size of the

microgap on crestal bone changes around titanium implants. A histometric evaluation of unloaded

non-submerged implants in the canine mandible. J Periodontol. 2001 Oct;72(10):1372–83.

14. Byrne D, Houston F, Cleary R, Claffey N. The fit of cast and premachined implant abutments. J

Prosthet Dent. 1998 Aug;80(2):184–92.

http://paperpile.com/b/jZzNvQ/v9BX

http://paperpile.com/b/jZzNvQ/v9BX

http://paperpile.com/b/jZzNvQ/3MSRT

http://paperpile.com/b/jZzNvQ/3MSRT

http://paperpile.com/b/jZzNvQ/ZABQ9



http://paperpile.com/b/jZzNvQ/1UK6D



http://paperpile.com/b/jZzNvQ/adkOm

http://paperpile.com/b/jZzNvQ/adkOm

http://paperpile.com/b/jZzNvQ/Bd4Yt



http://paperpile.com/b/jZzNvQ/0GhIo

http://paperpile.com/b/jZzNvQ/0GhIo

http://paperpile.com/b/jZzNvQ/l8YsF



http://paperpile.com/b/jZzNvQ/VfKHU



http://paperpile.com/b/jZzNvQ/xVCSC



http://paperpile.com/b/jZzNvQ/S5FlE



http://paperpile.com/b/jZzNvQ/bH9mH

http://paperpile.com/b/jZzNvQ/bH9mH

http://paperpile.com/b/jZzNvQ/0ebg2



http://paperpile.com/b/jZzNvQ/iqSvn

http://paperpile.com/b/jZzNvQ/iqSvn



15. Jansen VK, Conrads G, Richter EJ. Microbial leakage and marginal fit of the implant-abutment

interface. Int J Oral Maxillofac Implants. 1997 Jul;12(4):527–40.

16. Ricomini Filho AP, Fernandes FS de F, Straioto FG, da Silva WJ, Del Bel Cury AA. Preload loss

and bacterial penetration on different implant-abutment connection systems. Braz Dent J.

2010;21(2):123–9.

17. Rimondini L, Marin C, Brunella F, Fini M. Internal Contamination of a 2-Component Implant

System After Occlusal Loading and Provisionally Luted Reconstruction With or Without a Washer

Device. J Periodontol. 2001;72(12):1652–7.

18. Dias ECL de C e. M, Bisognin EDC, Harari ND, Machado SJ, da Silva CP, Soares GD de A, et al.

Evaluation of implant-abutment microgap and bacterial leakage in five external-hex implant systems:

an in vitro study. Int J Oral Maxillofac Implants. 2012 Mar;27(2):346–51.

19. Quirynen M, Alsaadi G, Pauwels M, Haffajee A, van Steenberghe D, Naert I. Microbiological and

clinical outcomes and patient satisfaction for two treatment options in the edentulous lower jaw after

10 years of function. Clin Oral Implants Res. 2005 Jun;16(3):277–87.

20. Quirynen M, Bollen CM, Eyssen H, van Steenberghe D. Microbial penetration along the implant

components of the Brånemark system. An in vitro study. Clin Oral Implants Res. 1994

Dec;5(4):239–44.

21. Gross M, Abramovich I, Weiss EI. Microleakage at the abutment-implant interface of

osseointegrated implants: a comparative study. Int J Oral Maxillofac Implants. 1999 Jan;14(1):94–

100.

22. Piattelli A, Scarano A, Paolantonio M, Assenza B, Leghissa GC, Di Bonaventura G, et al. Fluids

and microbial penetration in the internal part of cement-retained versus screw-retained implant-

abutment connections. J Periodontol. 2001 Sep;72(9):1146–50.

23. Hamilton A, Judge RB, Palamara JE, Evans C. Evaluation of the fit of CAD/CAM abutments. Int J

Prosthodont. 2013 Jul;26(4):370–80.

24. Sumi T, Braian M, Shimada A, Shibata N, Takeshita K, Vandeweghe S, et al. Characteristics of

implant-CAD/CAM abutment connections of two different internal connection systems. J Oral

Rehabil. 2012 May;39(5):391–8.

25. Harder S, Quabius ES, Ossenkop L, Kern M. Assessment of lipopolysaccharide microleakage at

conical implant-abutment connections. Clin Oral Investig. 2012 Oct;16(5):1377–84.

26. do Nascimento C, Miani PK, Watanabe E, Pedrazzi V, de Albuqerque RF Jr. In vitro evaluation of

bacterial leakage along the implant-abutment interface of an external-hex implant after saliva

incubation. Int J Oral Maxillofac Implants. 2011 Jul;26(4):782–7.

27. Esposito M, Hirsch JM, Lekholm U, Thomsen P. Biological factors contributing to failures of

osseointegrated oral implants. (II). Etiopathogenesis. Eur J Oral Sci. 1998 Jun;106(3):721–64.

28. Quirynen M, Vogels R, Peeters W, van Steenberghe D, Naert I, Haffajee A. Dynamics of initial

subgingival colonization of “pristine” peri-implant pockets. Clin Oral Implants Res. 2005;17(1):25–

37.

29. Broggini N. Periimplant Inflammation Defined by the Implant-abutment Interface. 2003. 42 p.

30. Broggini N, McManus LM, Hermann JS, Medina RU, Oates TW, Schenk RK, et al. Persistent

acute inflammation at the implant-abutment interface. J Dent Res. 2003 Mar;82(3):232–7.

31. Mawhinney J, Connolly E, Claffey N, Moran G, Polyzois I. An in vivo comparison of internal

bacterial colonization in two dental implant systems: Identification of a pathogenic reservoir. Acta

Odontol Scand. 2014;73(3):188–94.

32. Larrucea Verdugo C, Jaramillo Núñez G, Acevedo Avila A, Larrucea San Martín C. Microleakage

of the prosthetic abutment/implant interface with internal and external connection: in vitro study.

Clin Oral Implants Res. 2014 Sep;25(9):1078–83.

33. Canullo L, Penarrocha-Oltra D, Soldini C, Mazzocco F, Penarrocha M, Covani U. Microbiological

assessment of the implant-abutment interface in different connections: cross-sectional study after 5

years of functional loading. Clin Oral Implants Res. 2015 Apr;26(4):426–34.

http://paperpile.com/b/jZzNvQ/h6Anz

http://paperpile.com/b/jZzNvQ/h6Anz

http://paperpile.com/b/jZzNvQ/hTr9G



http://paperpile.com/b/jZzNvQ/TjwAM



http://paperpile.com/b/jZzNvQ/W6pgd



http://paperpile.com/b/jZzNvQ/W5yDF



http://paperpile.com/b/jZzNvQ/xV12r



http://paperpile.com/b/jZzNvQ/kATlS



http://paperpile.com/b/jZzNvQ/snXEC



http://paperpile.com/b/jZzNvQ/h8ill

http://paperpile.com/b/jZzNvQ/h8ill

http://paperpile.com/b/jZzNvQ/IA3cp



http://paperpile.com/b/jZzNvQ/03OMt

http://paperpile.com/b/jZzNvQ/03OMt

http://paperpile.com/b/jZzNvQ/DxDki



http://paperpile.com/b/jZzNvQ/JpLuw

http://paperpile.com/b/jZzNvQ/JpLuw

http://paperpile.com/b/jZzNvQ/NW4ON



http://paperpile.com/b/jZzNvQ/4OlAF

http://paperpile.com/b/jZzNvQ/CbpSc

http://paperpile.com/b/jZzNvQ/CbpSc

http://paperpile.com/b/jZzNvQ/OmQlz



http://paperpile.com/b/jZzNvQ/iFeVT



http://paperpile.com/b/jZzNvQ/p92Oq





34. do Nascimento C, Ikeda LN, Pita MS, Rafael Cândido Pedroso, Pedrazzi V, de Albuquerque

Junior RF, et al. Marginal fit and microbial leakage along the implant-abutment interface of fixed

partial prostheses: An in vitro analysis using Checkerboard DNA-DNA hybridization. J Prosthet

Dent. 2015;114(6):831–8.

35. Baggi L, Di Girolamo M, Mirisola C, Calcaterra R. Microbiological evaluation of bacterial and

mycotic seal in implant systems with different implant-abutment interfaces and closing torque

values. Implant Dent. 2013 Aug;22(4):344–50.

36. Al-Jadaa A, Attin T, Peltomäki T, Heumann C, Schmidlin PR. Impact of Dynamic Loading on the

Implant-abutment Interface Using a Gas-enhanced Permeation Test In Vitro. Open Dent J. 2015 Mar

31;9:112–9.

37. Koutouzis T, Mesia R, Calderon N, Wong F, Wallet S. The Effect of Dynamic Loading on

Bacterial Colonization of the Dental Implant Fixture–Abutment Interface: An In Vitro Study. J Oral

Implantol. 2014;40(4):432–7.

38. Tarnow DP, Cho SC, Wallace SS. The effect of inter-implant distance on the height of inter-

implant bone crest. J Periodontol. 2000 Apr;71(4):546–9.

39. Broggini N, McManus LM, Hermann JS, Medina R, Schenk RK, Buser D, et al. Peri-implant

inflammation defined by the implant-abutment interface. J Dent Res. 2006 May;85(5):473–8.

40. Gargiulo AW, Wentz FM, Orban B. Dimensions and Relations of the Dentogingival Junction in

Humans. J Periodontol. 1961;32(3):261–7.

41. Tarnow DP, Magner AW, Fletcher P. The effect of the distance from the contact point to the crest

of bone on the presence or absence of the interproximal dental papilla. J Periodontol. 1992

Dec;63(12):995–6.

42. Hermann JS, Buser D, Schenk RK, Schoolfield JD, Cochran DL. Biologic Width around one- and

two-piece titanium implants. Clin Oral Implants Res. 2001 Dec;12(6):559–71.

43. Hermann JS, Cochran DL, Nummikoski PV, Buser D. Crestal bone changes around titanium

implants. A radiographic evaluation of unloaded nonsubmerged and submerged implants in the

canine mandible. J Periodontol. 1997 Nov;68(11):1117–30.

44. Buser D, Mericske-Stern R, Dula K, Lang NP. Clinical experience with one-stage, non-submerged

dental implants. Adv Dent Res. 1999 Jun;13:153–61.

45. Hermann F, Lerner H, Palti A. Factors influencing the preservation of the periimplant marginal

bone. Implant Dent. 2007 Jun;16(2):165–75.

46. Maynard JG Jr, Wilson RD. Physiologic dimensions of the periodontium significant to the

restorative dentist. J Periodontol. 1979 Apr;50(4):170–4.

47. Gardner DM. Platform switching as a means to achieving implant esthetics. N Y State Dent J.

2005 Apr;71(3):34–7.

48. Lazzara RJ, Porter SS. Platform switching: a new concept in implant dentistry for controlling

postrestorative crestal bone levels. Int J Periodontics Restorative Dent. 2006 Feb;26(1):9–17.

49. Baumgarten H, Cocchetto R, Testori T, Meltzer A, Porter S. A new implant design for crestal bone

preservation: initial observations and case report. Pract Proced Aesthet Dent. 2005 Nov;17(10):735–

40.

50. Abrahamsson I, Berglundh T, Lindhe J. Soft tissue response to plaque formation at different

implant systems. A comparative study in the dog. Clin Oral Implants Res. 1998 Apr;9(2):73–9.

51. Abrahamsson I, Berglundh T, Lindhe J. The mucosal barrier following abutment dis/reconnection.

An experimental study in dogs. J Clin Periodontol. 1997 Aug;24(8):568–72.

http://paperpile.com/b/jZzNvQ/dwgIv




http://paperpile.com/b/jZzNvQ/LU67g



http://paperpile.com/b/jZzNvQ/A3hKC



http://paperpile.com/b/jZzNvQ/WVqG0



http://paperpile.com/b/jZzNvQ/hkupJ

http://paperpile.com/b/jZzNvQ/hkupJ

http://paperpile.com/b/jZzNvQ/0vHjt

http://paperpile.com/b/jZzNvQ/0vHjt

http://paperpile.com/b/jZzNvQ/rYKm8

http://paperpile.com/b/jZzNvQ/rYKm8

http://paperpile.com/b/jZzNvQ/NryMz



http://paperpile.com/b/jZzNvQ/CFEG9

http://paperpile.com/b/jZzNvQ/CFEG9

http://paperpile.com/b/jZzNvQ/AFgOY



http://paperpile.com/b/jZzNvQ/NOPZr

http://paperpile.com/b/jZzNvQ/NOPZr

http://paperpile.com/b/jZzNvQ/8s7xr

http://paperpile.com/b/jZzNvQ/8s7xr

http://paperpile.com/b/jZzNvQ/FhZXI

http://paperpile.com/b/jZzNvQ/FhZXI

http://paperpile.com/b/jZzNvQ/Nq4W1

http://paperpile.com/b/jZzNvQ/Nq4W1

http://paperpile.com/b/jZzNvQ/0XZDD

http://paperpile.com/b/jZzNvQ/0XZDD

http://paperpile.com/b/jZzNvQ/8uoLl



http://paperpile.com/b/jZzNvQ/LRdrz

http://paperpile.com/b/jZzNvQ/LRdrz

http://paperpile.com/b/jZzNvQ/ZwvpT

http://paperpile.com/b/jZzNvQ/ZwvpT


THE JOURNAL OF PROSTHODONTICS AND DENTAL MATERIALS The Official e-publication of Indian Prosthodontic Society


Efficacy of citronella oil as an antifungal agent on denture soft liner

Dr Banashree S. Sankeshwari1, Dr Pranav R. Tulle2, Dr Raghavendra V. Adaki3, Dr Dayanand A. Huddar4, Deepti

S. Fulari1, Dr Mokshada M. Badadare5


2Post graduate student,

3Professor and Head,

4Professor, 5Assistant Professor

Department of Prosthodontics

Bharati Vidyapeeth Dental College and Hospital, Sangli.

ABSTRACT Purpose: To investigate the antifungal activity of citronella oil by incorporating in acrylic based soft

liner

Materials and method: Varying concentrations of citronella oil is incorporated in acrylic based soft

liner and its antifungal activity is evaluated at 1 day and 1 week and adherence of Candida albicans to

the soft liner is measured at 1 day, 1 week and 15 days.

Results: Soft liner with citronella oil incorporation showed mean inhibitory zone of 10.5 mm with 400

μl, 19.8 mm with 600 μl and 33 mm with 800 μl after 1 day whereas after 1 week it showed 9.4 mm, 18

mm and 31.2 mm with 400 μl, 600 μl and 800 μl respectively.

On intergroup comparison for adherence test, after 1 day group 2 showed highest mean cell count

whereas group 4 showed least mean cell count. After 7 and 15 days, group 1 showed highest mean cell

count whereas group 4 showed the least mean cell count.

On intragroup comparison for adherence test, the mean cell count had decreased for all the groups

except the control group when measured after 1 day, 7 days and 15 days.

Conclusion: This in-vitro study shows that citronella oil can be used as antifungal agent.

Key-words: Citronella, essential oil, antifungal activity, soft liner

Introduction Denture soft liners are mainly used for therapeutic purpose in patients who are not able to

tolerate denture induced stresses. The most commonly used soft liners are acrylic based or silicone

based which help to absorb the masticatory forces and its distribution.[1] Fungal growth on the surfaces

of soft liners is a common phenomenon due to lack of antifungal property and increased surface

roughness. The fungal growth on the surfaces of liners leads to tissue irritation and mucosal pain. The

colonization and adherence of microorganisms to the surfaces leads to denture stomatitis.1

The etiology of denture stomatitis though is multifactorial; the most commonly associated

microorganism is Candida albicans. Treatment option includes maintenance of oral hygiene, systemic

and topical application of antifungal agents.1 Systemic application has few disadvantages and to

Sankeshwari BS. et al: Citronella oil efficacy on candida albicans biofilms


overcome these, antifungal agents are now incorporated in denture liners. Antifungal agents like

ketoconazole, itraconazole, fluconazole have been used but the disadvantages include side effects of

these drugs and developing resistance to these drugs.1

Hence, there is a need to reduce the fungal activity without hampering the properties of soft liners with

the use of natural antimicrobials. Cymbopogon nardus, popularly known as citronella, is a grass

cultivated in subtropical and tropical regions of Asia, Africa, and America.2 The major chemical

constituents are geraniol, citral, citronellal, and citronellol. Essential oils of Cymbopogon species are

known to possess antifungal properties.3 Although, citronella provides good antifungal properties, its

use in dental applications is very minimal. Therefore, the purpose of this study is to evaluate citronella

as an antifungal additive to acrylic based soft liner.

MATERIALS AND METHODOLOGY

This study comprised the use of acrylic based soft liner (GC). The soft liner was processed according to

the manufacturer’s instructions (2.2 gm/1.8 gm) (table 1).

Table 1: Preparation of soft liner

Evaluation of antifungal activity:

Strains of Candida albicans were inoculated into Sabouraud Dextrose Agar in plates and incubated at

37°C. After 8 hours of incubation, the Candida albicans suspension was standardized by dilution with

sterile broth. Approximately 0.5 ml of diluted Candida albicans solution was dispensed onto a sterile

Sabouraud agar plate and a lawn culture was made. After the inoculum dried, a 6 mm diameter well

was punched to a depth of 5 mm with a sterile punch cork borer. The punched wells were filled with

soft liner with varying concentrations of citronella oil. After the wells were filled, the plates were

incubated at 37°C in an incubator. The mean inhibitory zone (MIZ), in millimeters, for each test punch

well was measured at 1 day and 1 week (fig 1).

Fig 1: Mean inhibitory zone after 1 week (800 μl)

Specimen preparation for adherence test:

Specimens of dimensions (25 mm diameter x 2 mm thickness) (fig 2) were prepared by adding

citronella oil in different concentrations to soft liner and were processed by conventional compression

molding technique.

Soft liner polymer Citronella oil + monomer

1 gram 400μl + 0.79 ml

1 gram 600μl + 0.79 ml

1 gram 800μl + 0.79 ml



Fig 2: Mold for specimen fabrication

A total of 12 samples were made and randomly divided into 4 groups based on different concentrations

of citronella oil.

Group 1- Control

Group 2- 400 µl

Group 3- 600 µl

Group 4- 800 µl

Total sample size- 3 samples per group

All the specimens were prepared to a uniform size with smooth surfaces by placing polyester film over

them. The prepared specimens were allowed to polymerize for 30 minutes at room temperature.

Adherence test:

The standard strain of Candida albicans was inoculated into 25 ml of Sabouraud Dextrose broth in a

sterile petri dish and incubated at 37°C for 8 hours. After 30 minutes of setting, the disks were retrieved

from the mold, placed in Sabouraud dextrose broth, and incubated at 37°C. At the end of 1 day, 7 days

and 15 days storage in the broth, the disks were washed twice with sterile broth for 1 minute. The

washed disks were dried, and the adherent yeast cells were fixed in methanol and stained with Crystal

violet for 1 minute. Subsequently, the disks were washed with distilled water for 30 seconds and

examined under light microscopy. Adherent yeast cells were quantified at 10 different fields on the

disks and reported as yeast cells per mm2 (fig 3 and 4).

Fig 3: Adherence test after 1 day (Group 1) Fig 4: Adherence test after 15 day (Group 1)

RESULTS

The mean inhibitory zone after 24 hours was 33 mm for 800 μl and least was 10.5 mm for 400 μl

(table 2).

Table 2: Zone of inhibition after 24 hours

Soft liner polymer Citronella oil + monomer Zone of inhibition after 24

hours (in mm)

1 gram 400μl + 0.79 ml 10.5

1 gram 600μl + 0.79 ml 19.8

1 gram 800μl + 0.79 ml 33



After 1 week, MIZ was 31.2 mm and 9.4 mm for 800 μl and 400 μl respectively (table 3).

Table 3: Zone of inhibition after 1 week

On intergroup comparison for adherence test, after 1 day group 2 showed highest mean cell count (509

cells per mm2) whereas group 4 showed least mean cell count (69 cells per mm2) (table 4).

Table 4: Adherence test after 1 day

After 7 days, group 1 showed highest mean cell count (807.33 cells per mm2) whereas group 4 showed

the least mean cell count (36 cells per mm2) (table 5).

Table 5: Adherence test after 7 days

After 15 days, group 1 showed highest mean cell count (699.33 cells per mm2) whereas group 4

showed the least mean cell count (15.33 cells per mm2) (table 6).

Table 6: Adherence test after 15 days

On intragroup comparison of group 1, the highest mean cell count was seen after 7 days (807.33 cells

per mm2) whereas with groups 2, 3 and 4, the mean cell count was highest after 1 day (509, 148 and 69

cells per mm2 respectively) and gradually reduced till 15th day (231.66, 105 and 15.33 cells per mm2

respectively).

Soft liner polymer Citronella oil + monomer Zone of inhibition after 1

week (in mm)

1 gram 400μl + 0.79 ml 9.4

1 gram 600μl + 0.79 ml 18

1 gram 800μl + 0.79 ml 31.2

After 1 day (measured in cells per mm2)

Sample no. Group 1 (Control) Group 2 (400µl) Group 3 (600µl) Group 4 (800µl)

1 210 501 126 75

2 180 475 189 73

3 250 551 129 59

Mean 213.33 509 148 69

After 7 days (measured in cells per mm2)


1 1082 424 119 46

2 558 338 118 31

3 782 373 113 31

Mean 807.33 378.33 116.66 36

After 15 days (measured in cells per mm2)


1 676 222 102 20

2 733 225 98 14

3 689 248 115 12

Mean 699.33 231.66 105 15.33



DISCUSSION

Soft liners do not possess significant antifungal activity by themselves. The antimicrobial effect

of citronella originates from the natural biological activity of its chemical constituent, such as

citronellal. Citronella essential oil is thought to disrupt cell membranes and degrade other organic

structures.4 Hence, when essential oil was incorporated in acrylic liner, there was an increase in the

zone of inhibition as the concentration of oil was increased. There was a decrease in mean inhibitory

zone for all the groups after 1 week as compared to that after 1 day.

On intragroup comparison for adherence test, the mean cell count per mm2 had decreased for all

the groups except the control group when measured after 1 day, 7 days and 15 days respectively.

On intergroup comparison for adherence test, after 1 day- group 2 showed highest cell count as

compared to other groups. After 7 days and 15 days- control group showed highest cell count followed

by group 2, 3 and 4 respectively. Group 4 showed the least cell count after 1, 7 and 15 days indicating

that it had the highest antifungal activity followed by group 3 and group 2 respectively.

CONCLUSION

This study concludes that as the concentration of citronella oil increases, there is an increase in

the mean inhibitory zone (MIZ). However, after a period of 1 week the MIZ is seen to decrease.

Similarly, as the concentration of citronella oil increases, the adherence of Candida albicans cells

decreases when measured after 1, 7 and 15 days.

References: 1. Srivatstava A, Ginjupalli K, Perampalli NU, Bhat N, Ballal M. Evaluation of the properties of a

tissue conditioner containing origanum oil as an antifungal additive. J Prosthet Dent

2013;110(4):313-9.

2. De Toledo L, Ramos M, Spósito L, Castilho E, Pavan F, Lopes É et al. Essential oil of

Cymbopogon nardus (L.) Rendle: a strategy to combat fungal infections caused by Candida

species. Int J Mol Sci 2016;17(8):1252.

3. Ata JP, Manalo MM. In vitro Evaluation of Cymbopogon nardus Essential Oil against Leaf

Disease Fungus of Narra (Pterocarpus indicus Wild). Int J Biol Sci 2014;3(8):56-9.

4. Almeida LD, Paula JF, Almeida RV, Williams DW, Hebling J, Cavalcanti YW. Efficacy of

citronella and cinnamon essential oils on Candida albicans biofilms. Acta Odontol Scand

2016;74(5):393-8.




Evaluation of Golden Proportion in Males and Females in Chhattisgarh Region: A Clinical Short

Study Dr Preeti Tiwari1, Dr Saumya Sharma2, Dr Sanjeev Singh3, Dr Gulab.C. Baid4, Dr Vivek Lath4, Dr

Priyabrata Jena5

13rd year PG student, 2 Professor, Head of Department,

3Professor, 4Reader,

5 Senior Lecturer,

Department of Prosthodontics, Crown & Bridge,

MCDRC

ABSTRACT: Purpose: The objective of our work is to evaluate and investigate the occurrence and prevalence of

the much-discussed Golden Proportion provided by Levin on perceived widths of maxillary anterior

teeth among the people of Chhattisgarh region with natural and pleasing smiles by measurements

made on digital images.

Material and method: The material of this study consists of digital photographs taken of subjects

with natural and aesthetic teeth. We took photos of 100 subjects (50 males and 50 females), between

18 and 30 years. Using a computer program, each maxillary tooth was digitally measured. Once the

measurements are recorded, theory was applied and data was compared as well as analysed

statistically.

Results: The Golden Proportion between the lateral and central incisor occurs in a higher proportion

than between the canine and the lateral incisor. The values obtained by analysing the golden

proportion differ slightly from those proposed by Levin and Snow.

Conclusions: Results of the current study have shown that golden proportion in Males and Females in

Chhattisgarh region was not present between the widths of the maxillary anterior teeth in individuals

who had an aesthetic smile.

Keywords: Golden proportion, aesthetic, smile analysis.

Introduction The principles that make up the aesthetics are subtle.1 Methodological analysis has revealed

that principles can be applied to evaluate and alter dental aesthetics with predictability.2 Each principle

can be considered, recognized, assessed and developed individually in aesthetic management.3 Among

the aesthetic principles the proportion can be predicted with a formula that determines the ratio of

Tiwari P. et al: Golden Proportion In Population of Chhattisgarh Region


component from one constituent to next. The Golden Proportion (1.618:1.0) is a mathematically

constant ratio that defines the dimensions between the larger and smaller length. This specific relation

is unique, perfect, ideal and desirable. It has been used from studying beauty to design aesthetic

restorations.4,5 It is also a valuable tool for evaluation of symmetry, dominance and proportion in the

diagnosis of tooth arrangement and aesthetic dental treatment.6 The uncertainty of golden proportion in

aesthetic analysis and in smile design intended this study to evaluate the existence and comparison of

presence of golden proportion in the population of Chhattisgarh region.

Aim To investigate and evaluate the existence of the Golden Proportion between the widths of the

maxillary anterior teeth among males and females in individuals of Chhattisgarh region having an

aesthetic smile with natural permanent dentition with the aid of digital photographs and computer

analysis.

Material and methodology This study was conducted at Maitri College of Dentistry and Research Centre, Durg,

Chhattisgarh. Hundred subjects were taken and were divided into 2 groups Male -50, Female – 50

(mean age 24 years). An inclusion criterion for the study was as follows:

a) Age between 18 and 30 years.

b) Skeletal and Dental Class I relation with well-balanced orthognathic profiles.

c) No crowding, spacing or rotation in anterior teeth.

d) No history of previous orthodontic treatment or anterior restorations.

e) No previous history of trauma to the dentition.

f) Presence of all anterior teeth from canine to canine.

Subjects with any visual abnormalities with hard and soft tissues (crowding, rotations, malformations,

fractures, abnormalities, etc) and teeth posterior to canine during natural smiling were excluded. A

written, informed consent/ approval were obtained from all subjects and the Institutional Review

Board. The subjects were informed that their participation in the survey was completely voluntary. A

frontal photograph was taken of each individual with an aesthetic smile by Digital camera (SONY

Cyber-shot DSC-W810, 20.1 mp) in natural head position. The subject was instructed to sit in an

upright and comfortable position. Lighting and staging were kept constant. The camera was positioned

and adjusted so as to obtain a sharp image of the face, from the tip of the nose to the tip of the chin.

The distance between the camera and the subject was fixed at a working distance of 60 cm. The

camera was stabilized with the help of a tripod, at this fixed distance. The photos were clicked while

patient was smiling with the head in the natural position, so that the bipupilar line was parallel to the

floor



.

Figure 1: Operator taking the photograph of volunteer

Figure 2: Digital photograph of a smiling female Figure 3: Digital photograph of a smiling male

The photos were transferred to a computer, and software Adobe Photoshop CS5 (photo editing

software) was used to perform the necessary measurements. Using the software vertical lines were

drawn at the mesio-distal line angles of all the anterior teeth as seen from the frontal view. We

measured the number of pixels per cm, using the zoom function of the program, so that we could

measure the apparent mesio-distal width more accurately. For each patient we measured the width of

each of the 6 crowns: from canine on the right side (r) to the one on the left side(l): Canine(right) [13],

Lateral Incisor (right) [12], Central Incisor (right) [11], Central Incisor (left) [21], Lateral Incisor (left)

[22], Canine (left) [23]. The distance between these lines was measured and used to calculate the

Golden Proportion for both sides by one individual. After obtaining the results, the calculations were

performed corresponding to theories (golden ratio and golden percentage). The resulting data was

analysed with the Microsoft Excel and SPSS 17 programs. For processing the data, the paired samples

T test was used to analyse the differences in the golden number between the left and right side for each

subject’s anterior teeth.

Results

The existence of the Golden Proportion was found to be nearly similar in the left and right side

and for both genders. It was found that the difference in Golden Proportion was statistically

insignificant between females and males for central incisor/lateral incisor and lateral incisor/canine.

For both the genders as well as collectively, a significant difference (p<0.001) from golden proportion

was observed for all the three ratios being evaluated.

Statistical analysis: A master file was created with the data, and it was statistically analysed by using

the Statistical Package for Social Sciences Software Version 17 (SPSS Inc. Released 2008. Chicago:

SPSS Inc). The data was subjected to descriptive analysis for mean, standard deviation, and 95%



confidence interval. ‘p’ value less than 0.05 was considered to denote a statistically significant

association. For comparison of gender groups independent sample ‘t’-test was performed.

TABLE 1: Minimum and maximum width of teeth along with standard deviation and standard error

obtained for females.

S.NO. TOOTH NO. MEAN SD SE MINIMUM MAXIMUM

1 11 9.87 0.47 0.095 8.72 10.92

2 12 6.57 0.48 0.096 5.64 7.46

3 13 5.39 0.59 0.119 4.28 5.84

4 21 9.93 0.37 0.074 9.04 10.68

5 22 6.71 0.47 0.094 5.88 7.21

6 23 5.24 0.44 0.089 4.34 6.16

TABLE 2: Minimum and maximum values of ratio of width of teeth along with standard deviation and

standard error obtained for females.

S.NO. RATIO BETWEEN MEAN SD SE MINIMUM MAXIMUM

1 11:12 1.50 0.11 0.022 1.33 1.66

2 12:13 0.82 0.10 0.021 0.66 1.05

3 21:22 1.47 0.09 0.020 1.31 1.67

4 22:23 0.78 0.07 0.016 0.67 0.99

TABLE 3: Minimum and maximum width of teeth along with standard deviation and standard error

obtained for males.

S.NO. TOOTH NO. MEAN SD SE MINIMUM MAXIMUM

1 11 9.76 0.36 0.065 9.48 10.72

2 12 6.66 0.52 0.105 5.61 7.64

3 13 5.52 0.47 0.094 4.32 6.12

4 21 10.10 0.27 0.055 9.28 10.48

5 22 7.35 0.51 0.102 5.68 7.68

6 23 6.19 0.65 0.131 4.44 6.88



TABLE 4: Minimum and maximum values of ratio of width of teeth along with standard deviation and

standard error obtained for males.

S.NO. RATIO BETWEEN MEAN SD SE MINIMUM MAXIMUM

1 11:12 1.51 0.14 0.028 1.25 1.77

2 12:13 0.81 0.08 0.026 0.67 0.91

3 21:22 1.50 0.14 0.028 1.31 1.63

4 22:23 0.81 0.10 0.020 0.64 0.98

TABLE 5: Significance values obtained

S. NO. RATIO BETWEEN TEETH MALES FEMALES P VALUE

1

11:12 1.51 ± 0.14 1.50 ± 0.11 0.875

2

12:13 0.81 ± 0.14 0.82 ± 0.10 0.653

3

21:22 1.50 ± 0.14 1.47 ± 0.10 0.355

4

22:23 0.81 ± 0.10 0.78 ± 0.08 0.179

Discussion Determination of a symmetric or geometrical relation among the anterior teeth is important to

achieve an aesthetic result. Existence of statistically reliable results will help to support these existing

theories. However, the results of this investigation found no reliable relationships in the average

natural dentition. These findings are supported by other investigations.7-9

The Golden Proportion (1.618: 1.0) describes the ratio between the dimensions of a larger and a

smaller length. Many previous pieces of research have used this mathematical proportions in dentistry

like, Levin in 1978 identified the Golden Proportion between the width of central incisor, lateral

incisor and the canine.4 The golden proportion is founded to be a reliable predictor for determining the

width of the maxillary central incisors.10 In 1993, Preston presented that 17% of his study samples had

a golden proportion between the width of the maxillary central and lateral incisors.8

On the other hand, other authors found that the golden proportion did not exist between the

widths of the maxillary anterior teeth.2,9,11

In this study, relative proportions of central and lateral incisors and canines’ dimensions were

recorded according to the golden proportion of 1.618 and no relationship was found. So, the results of

the current study concurred with previous studies, that golden proportion did not exist in the study

sample of Chhattisgarh region, similar to the results of a study carried out by Wolfart et al., 2006, who

reported a width-to-length proportion of 82%. 12

The rule of the Golden Proportion in dentistry is as follows: The width of the maxillary

anterior teeth from the frontal view shows that the visible width of maxillary lateral incisor is 62% of

central incisor and the visible width of canine is 62% of lateral incisor.

Gillen et al.9 found no correlation existing between tooth dimension and Golden Proportion.

Although in their study the values of tooth width were not measured from frontal view as the theory

implies –



The Golden percentage was proposed as a simple and objective tool to assess dental aesthetic

measures across the midline, and the regressive proportions.13 The largest study done on the Golden

Proportion involved 376 dental students in Jordan. The authors found that average ratio of the

maxillary central incisor, the lateral incisor, and the canine was 1.53:1:0.8.14 The golden section occurs

in a higher proportion between the Lateral incisor and Central Incisor, than between the Canine and

the Lateral Incisor. The average proportion in our study obtained for canine and lateral incisor is 0.84

in females and 0.81 in males, and for the lateral incisor and central incisor proportion found is 1.51 in

females and 1.45 in males, so, in comparison with this study done by Snow SR13 in 1999, we found a

greater difference between the proportion of teeth studied and the golden proportion. Therefore, these

results do not prove that the Golden Proportion would be the average proportion characteristic for this

group of teeth. The variation of views among the current studies and previous studies could be

explained due to the lack of the standardization of the protocol used to evaluate the gold proportion.

Besides, the differences in racial characteristics might influence such variation.15

Many articles have showed that the Golden Proportion was not seen in a majority of observed

aesthetic smiles. In the current study the existence of the golden proportion was found to be nearly

similar in the left and right side and for both genders. This was also seen in other studies done on

golden proportion.16,17 It is clear from the above mentioned result that individual variations are not

seen in the Golden Proportion as the width of teeth perceived in maxillary anterior region on both

sides are nearly the same unless some malformation or deformity is seen.18,19 Results of the current

study have shown that Golden Proportion was not present between the widths of the maxillary anterior

teeth in individuals who had an aesthetic smile. This may be mainly due to individual variations in

each individual. Genetics also plays a major role in tooth sizes. Change in environment and lifestyle

from childhood also may affect the size of the teeth and development of the facial soft tissues. Many

studies reported that to produce a satisfactory appearance instead of concentrating on a single ratio,

such as the Golden Proportion, other ratios reflecting harmony among tooth lengths should be

considered.7,11,20 Further research on this topic is required to obtain clarity on this matter.

Conclusion Results of the current study have shown that golden proportion was not present between the widths of

the maxillary anterior teeth in individuals who had an aesthetic smile. This may be mainly due to

individual variations in each individual. Genetics also plays a major role in tooth sizes. Esthetics in

dentistry cannot be justified mathematically; individuals should not be standardized in the same way

as suggested by other authors earlier also.

Although we dentists should follow some fundamental guidelines in esthetic treatment planning, it

should be acknowledged that esthetics varies greatly from person-to-person. It is, therefore, important

to consider the dento-facial specificities of each individual and the various natural teeth proportions

during restoration or replacement of the maxillary anterior teeth. In addition, individual cultural

characteristics and perceptions of beauty must be considered.

Change in environment and lifestyle from childhood also may affect the size of the teeth and

development of the facial soft tissues.

Further research on this topic is required to obtain clarity on this matter.

References: 1. Lombardi RE. The principles of visual perception and their clinical application to denture

esthetics. J Prosthet Dent 1973;29:358-82.

2. Ward DH. Proportional smile design using the recurring esthetic dental (red) proportion. Dent

Clin North Am 2001;45:143-54.

3. Morley J, Eubank J. Macroesthetic elements of smile design. J Am Dent Assoc 2001;132:39-45.

4. Levin EI. Dental esthetics and the golden proportion. J Prosthet Dent 1978;40:244-52.



5. Snow SR. Esthetic smile analysis of maxillary anterior tooth width: the golden percentage. J

Esthet Dent 1999;11:177-84.

6. Ricketts RM. The biologic significance of the divine proportion and Fibonacci series. Am J

Orthod 1982;81:351-70.

7.Mahshid M, Khoshvaghti A, Varshosaz M, Vallaei N. Evaluation of “golden proportion” in

individuals with esthetic smile. J Esthet Restor Dent 2004;16:185-192.

8.Preston JD. The golden proportion Revisited. J Esthet Dent1993;5:247–251.

9. Gillen RJ, Schwartz RS, Hilton TJ, Evans DB. An analysis of selected normative tooth

proportions. Int J Prosthodont 1994;7:410–417.

10. George S, Bhat V. Inner canthal distance and golden proportion as predictors of maxillary central

incisor width in south Indian population. Indian J Dental Res 2010;21(4):491-495.

11. Rosenstiel SF, Ward DH, Rashid RG. Dentists' preferences of anterior tooth proportion–a web-

based study J Prosthodont 2000;9(3):123-136.

12. Wolfart S, Thormann H, Freitag S, Kern M. Assessment of dental appearance following changes

in incisor proportions. Eur J Oral Sci 2005;113(2):159-165.

13. Snow SR. Esthetic smile analysis of maxillary anterior tooth width: the golden percentage. J

Esthet Dent 1999;11: 177-84.

14. Ali Fayyad M, Jamani KD, Agrabawi J. Geometric and mathematical proportions and their

relations to maxillary anterior teeth. J Contemp Dent Pract 2006;7: 62-70.

15. Hasanreisoglu U, Berksun S, Aras K, Arslan I. An analysis of maxillary anterior teeth: Facial

and dental proportions. J Prosthet Dent 2005;94(6):530–8.

16. Morley J. Smile design--specific considerations. J Calif Dent Assoc 1997;25(9):633-7.

17. Dong J-K, Jin T-H, Cho H-W, Oh S-C. The esthetics of the smile: a review of some recent

studies. Int J Prosthodont 1999;12: 9-19.

18. Bukhary SM, Gill DS, Tredwin CJ, Moles DR (2007) The Influence of Varying Maxillary

Lateral Incisor dimensions on perceived Smile Aesthetics. Br Dent J 2007;203:687-93.

19. Pini NP, de-Marchi LM, Gribel BF, Ubaldini AL, Pascotto RC (2012) Analysis of the golden

proportion and width/height ratios of maxillary anterior dentition in patients with lateral incisor

agenesis. J Esthet Restor Dent 2012;24:402-14.

20. Shrinzad M, Ahmady B. Evaluation of golden proportion of upper anterior teeth in dental

students of Hamedan Dental School-Iran (2003-2004). J Mashhad Dental School 2006;30(3,4): 255-

262.




ABSTRACT Dental Impressions can act as a mean for different types of micro-organisms like Hepatitis B, C,

HIV, Mycobacterium, Herpes simplex, MERS-CoV and the recent one SARS-CoV 2, etc. the most

effective way to prevent their spread could be to properly Disinfect them just after taking out of

patient’s mouth. This clinical tip would give an effective way to mange the steps to be followed for

Disinfection of the Impression. It will also provide information of the concentration of usage along

with different available disinfectants.

Keywords: Disinfection, Impression, SARS-CoV 2.

Introduction

In this post COVID-19 era, we should take extra care while handling the impressions from clinic to

laboratory as to prevent the Cross-Infection. Most of the bacterias or Viruses could be inactivated by

various Chemical Disinfectants.1-3 The ideal disinfectants should have these following properties:

• Broad Spectrum Activity

• Act Rapidly

• Non-Corrosive

• Environment Friendly

• Free of Volatile Organic Compounds

• Non-Toxic

• Non-Staining

According to CDC Guidelines, the best method to reduce the viral load from Impressions is

Chemical Disinfection. Various Chemical Disinfectants used are Glutaraldehyde, Sodium

Hypochlorite, Complex Iodophors, Phenols, Chlorhexidine, Alcohols, Quaternary Ammonium

Compounds and Simple Detergents. The second most important point of any disinfectant is the

appropriate application and contact time.4,5 So, the recommended steps for Disinfection of

Impression are as follows

1. Personal protective equipment must be worn.

2. Wash all Impressions thoroughly in running water.

3. Immerse the impression in 5% solution of Sodium Hypochlorite (NaOCl2) for 10 minutes. Ensure

the solution is freshly prepared.

Steps for Disinfection of Impression

Dr. Rathin D. Das1

MDS Prosthodontics Center head at Illusion training and Education Center

Ex Professor and HOD YMT Dental College, Navi Mumbai

Das R. et al: Steps in Disinfection


4. Re-Wash the impression thoroughly in running water then proceed to pour impression.

The recommended guidelines for preparing 1 litre of the said NaOCl2 solution is

For 5% NaOCl2 – Use 10 ml of NaOCl2 in 990 ml of Water.

For 2.5% NaOCl2 – Use 20 ml of NaOCl2 in 980 ml Water.

References:

1.Centres for Disease Control and Prevention, Interim Infection Prevention and Control

Recommendations for patients with suspected or confirmed Corona Virus Disease 2019

(COVID-19) in health care settings, centres for disease control and prevention, Atlanta, GA,

USA,2019,

https://www.cdc.gov/coronavirus/2019-ncov/hcp/infection-controlrecommendations.html

2. Poulos JG, Antonoff LR. Disinfection of Impressions. Methods and effects on Accuracy. N. Y.

State Dent J 1997;63(6):34-6.

3. Maillard JY, Mcdonnell G. Selection and use of disinfectants. In Prac 2012; 34(5):292-9

4. Abdullah MA. Surface detail, Compressive strength, and dimensional accuracy of gypsum casts

after repeated immersion in hypochlorite solution. J Prosth dent 2006; 95(6):462-8.

5. National Guidelines For Infection Prevention and Control In Healthcare Facilities, MoHFW,

Govt of India.




ABSTRACT Conventional implants require osseointegration to be successful, and often this process takes nearly 2-

4 months. If this process is interrupted, it delays the restorative procedures. These implants have

further complications, such as peri-implantitis due to their rough surfaces. Moreover, placing

conventional implants into the atrophic maxilla or mandible requires prior extensive grafting

procedures and sometimes even a sinus lift procedure that can severely contribute to increased

appointments, chances of failures and treatment costs. The technology of Cortico-basal implantology

was developed to overcome these limitations, The Cortico-basal Implant works with the bone

differently compared to the conventional root-form implants. It follows the principles of orthopedic

surgery and traumatology. They also do not require integration into the cancellous bone and are placed

directly into the 2nd and 3rd (distant) cortical bone. Presented here is a case report of a 65- year- old

female where a new and unique smooth- surfaced single-piece cortico-basal implants (with multiunit

abutment) were placed. This enabled us to complete the restoration process within 72 hours using

immediate functional loading protocol. These implants were loaded with definitive screw- retained

prosthesis.

Key Words: Cortico-basal implant; Immediate functional loading; Single- Piece Dental Implants;

Cortical Implantology; Multi-Unit Abutment

Introduction

Current advances in the field of implantology involve aiming to reduce the number of appointments as

well as to simplify dental treatment procedures to increase patient acceptance and to decrease the risk

Immediate Functional Loading of Completely Edentulous Arches with A Screw Retained Definitive Prosthesis on Corticobasal Implants: A Case Report

Dr Anita Gala Doshi1, Dr Vivek Gaur2, Dr Janani Iyer3

1 Private Dental Practice, Prosthodontist,

Mumbai, Maharashtra, India 2 Private Dental Practice,

Etah, Uttar Pradesh, India 3 Reader,

Department of Prosthodontics,

MGM dental college and hospital, Navi Mumbai, Maharashtra, India

5Reader, Department of Public Health Dentistry,


Doshi AG. et al: Immediate Functional Loading of Completely Edentulous Arches


of complications.1-3 This is achieved through immediate loading of dental implants. Immediate

functional loading of oral implants is defined as a situation where the superstructure is attached to the

implants at the time of the surgery or until no more than 72 hours post-surgery and brought in to chewing

function. Immediate loading is desirable if the survival rate of the implant, as well as the outcome of the

treatment, is in accordance with that of conventional loading.4-6 Currently, two approaches towards the

immediate loading of dental implants exist. The first approach is based on the compression screw

principle, where the implant compresses the bone while being inserted into the undersized osteotomy.4,7,8

Lateral condensation of spongy bone is the guiding principle of these implants; Implant stability is

significantly increased by a mechanism that could be regarded as “corticalization” of the spongy bone.

The latter approach involves achieving cortical anchorage of strong and thin body screw implants,

cortico-basal Implants, or basal implants. They are placed into the bone in such a way that the apical

load transmitting threads of the implants are positioned (fixated) directly into the cortical plate distant

(opposite) to the oral cavity.

The basal bone is present throughout our life and is resistant to resorption in the mandible and maxilla

formed by macro trajectories. It is very solid, firm and forms the stress-bearing part of our skeleton.

Implants anchored in this bone, can be loaded (splinted) with fixed tooth restorations immediately. One

of the greatest challenges of restoring missing teeth in the posterior maxilla is due to the jaw bone

resorption that results in deterioration in the quality of the bone post-extraction, thus impeding the

process of implant placement in that region.9 To overcome this, the technology of Cortico-basal implants

is used since; their load transmitting threads are anchored into the native, residual, cortical bone areas.

The Cortico-basal implants not only avoids any additional surgical procedures but also provides a

reliable anchor in cortical bone. This is very helpful even in severely reduced vertical bone heights, and

it can (actually must) be loaded immediately without any waiting period.10-13 The cortical bone provides

excellent retention for these implants. Dental implants anchored in this bone, can be loaded (actually

splinted) with fixed restorations and brought to function immediately.

This paper presents a clinical case for immediate implant loading with a smooth surfaced single-piece

Corticobasal implants (BCES and BCS, Simpladent) with multiunit abutments (BECES® MU) to restore

fully edentulous maxillary and mandibular arches with a definitive screw-retained prosthesis within 72

hours. The protocol is to place six corticobasal implants in the anterior maxilla engaging into the nasal

cortical floor and two corticobasal implants in the posterior maxilla bilaterally engaging the

tuberoterygoid region. In the mandible, it is recommended to use four single-piece corticobasal implants

in the anterior region engaging the lower border (base) of mandible between the mental foramina and

two single-piece corticobasal implants in the distal part of the mandible on both sides engaging the

lingual/vestibular cortical plate.

Case report:

A 65-year-old, healthy female patient with completely edentulous maxillary and mandibular arches

presented to the clinic with a chief complaint of missing teeth in the upper and lower jaw. She expressed

a desire to have her missing teeth replaced with a fixed restorative option. The clinical examination

(Figure 1) showed complete edentulous mandibular and maxillary arches. Radiographic examination

(Figure 2) revealed an atrophic both arches. After discussing the various treatment options with the

patients, such as removable complete dentures or implant supported prosthesis, it was to use a single-

piece immediate loading smooth surface corticobasal implants with multi-unit abutment with screw-

retained prosthesis. Upon obtaining the informed consent of the patient, local anesthesia (lidocaine 2%

with adrenaline 1:100000) was infiltrated. The surgical procedure was performed as per the protocol.14

Following soft tissue cleaning with antiseptic 5% Betadine solution (water-based), a flapless preparation

of osteotomy sites was carried out using the sequential order of calibrated drills recommended by the



manufacturer, cooled with saline solution in external mode at a speed of 27000 rpm. The implant beds

were prepared with the use of a 2.0 mm drill (30 mm long). In the maxilla, two Pterygoid implants of

3.6mm diameter and 23mm and 26mm length were placed on each side. In the anterior region, one

implant 5.5mm in diameter and 14mm in length was placed on each side on the lateral wall of the nose

and two implants of 3.6mm diameter and 17mm length on both sides engaging the floor of the nose. For

the distal mandible, a straight handpiece and for the anterior implants, an angled handpiece 1:1 (blue)

was used to place implants. Two one-piece implants with a diameter of 3.6 mm and a length of 14 mm

were placed with help of an insertion tool (Figure 5) and were anchored into the lingual cortical plate

on both sides, where superior primary stability was achievable. Four Implants with a length of 23 mm

were placed, and anchored in the base of the mandible in the inter-foramina region. The implants were

bent to a favorable position of the internal thread with an angulation adapter (Figures 4, 5 and 6) so that

the screw access holes faced occlusally (Figures 7, 8 and 9). Immediate post-surgery, the final

impressions were made. Open tray multi-unit impression copings were placed onto the BECES® MU

implants, which were then splinted with a low shrinkage self-polymerizing resin. This ensured an

accurate transfer without accidental displacement of the impression copings. An open tray impression

was made with a rigid polyvinyl siloxane material to capture the positions of the implants and the soft

tissues. following this, jaw relation was recorded. A metal framework of Co-Cr-Alloy was fabricated,

and tried on the next day of implant placement (Figure 10). The bite, the vertical and the sagittal

relationship as well as the aesthetic appearance, were checked at this stage. Definitive metal fused to

ceramic prosthesis was screwed in onto the implants day after that is within 72 hours of implant

placement. It was possible to give screw-retained restoration with the advantage of retrievability due to

the use implants with MU abutments. The final tightening of all screws was done at 25N torque with

each implant. (Figure 12, 13). Access holes were blocked with Teflon and filled with composite resin

(Figure 14, 15). Treatment was completed with high patient satisfaction (Figure 16, 17). Following the

principles of corticobasal implantology, occlusion developed was similar to complete denture occlusion,

avoiding anterior contact in centric relation and in lateral excursion. This eliminates anterior patterns of

chewing and thereby, extruding forces on distal implants is avoided. The patient was seen every month

for the first six months, with special consideration to the occlusion and hygiene (the pontics were

relieved from gingival contact and there were open embrasures for purposes of cleaning). Thereafter,

the patient was followed up every six months for clinical and radiographic follow-ups for 3 years

(Figures 11 and 12).

Figure 1. Clinical intra-oral examination Figure 2. Radiographic pre-operative view.



Figure 3: Implant placement Figure 4. Bending of implants

Figure 5. Radiographic view post implant placement

Figure 6. Impression post splinted with pattern resin and before pick-up impression

Figure 7. T base placed for metal trial



Figure 8. Metal try-in

Figure 9. Final prosthesis

Figure 10. Pre and post-operative images

Figure 11. 1-year post-operative radiograph



Figure 12. 3-year post-operative radiograph

Discussion Cortico-basal Implantology is currently the most favored and trending treatment modality in the

field of dentistry owing to the fact that it is a minimally invasive technique. This technique is very

patient- friendly since it aims towards restoring the function and form along with aesthetics in the

edentulous maxilla and mandible. This technique is more advantageous in atrophic jaws where the

entire treatment can be fast-tracked and also avoid grafting, which increases treatment time with

unpredictable results.15-17 The Cortico-basal implant is anchored or engaged cortically by the surgeon

into the dense basal (2nd cortical) bone, and the process of establishing this anchorage has been termed

as “Osseo-fixation”. However, for primary stability, i.e., for the treatment’s success, the macro-

mechanic anchorage (Osseo-fixation) in the 2nd or 3rd cortical is imperative.18 Thereafter, a cross arch

rigid splinting is done with the help of a prosthetic framework within 3 days that can help promote

biological stability / osseointegration after remodeling of the bone within 6 months. Macro retention can

be increased by tilting the implants. Cortico-basal implantology is based on the principle of engaging

the basal bone from the nasal floor, maxillary sinus floor, walls of sinus, septa of sinus, wall of nasal

cavity, palatal bone, crest of alveolar bone, pterygoid bone and zygomatic bone via aggressive threads

that promote enhanced primary stability thus improving functional loading as well as through the smooth

and small peri-mucosal penetration that helps resist infection.

It is reported in the literature that bicortical anchorage, i.e., engagement into the cortical bones on

both the cervical and lateral sides, demonstrated better results when measured by resonance frequency

analysis.19 The inter-foraminal region at the base of the mandible (2nd cortical bone) is accessible with

long implants and lingual cortical engagement is more predictable since the bone is present in the

compressive stress zone. Hence it has a greater predilection towards remodeling thus achieving the

tenting effect. The guidelines involved in keeping a defined and bilateral balanced prosthetic situation

(loading) include that only when a bilaterally identical anterior AFMP-angle (Planas’ Masticatory

Functional Angles) is present, the chewing activity of the patient will be equal on both sides. Only if

balance is present on both the sides of the distal mandible, will the development of a preferred chewing

side be avoided. Otherwise. the side which is balanced during regular chewing, will be preferred sooner

or later.

Peri-implantitis has been defined as a disease that is more severe and is defined as a more profound

inflammatory lesion characterized by a deepened peri-implant pocket and loss of supporting bone

around a functional implant. In analogy to gingivitis and periodontitis affecting the periodontium of

natural teeth, the inflammation and destruction of soft and hard tissues surrounding dental implants is

termed as mucositis and peri-implantitis.20 One of the primary drawbacks or limitations with regard to

the use of conventional rough surface implants is the accompanying peri-implantitis disease, and

currently, no treatment options21 are available to address it. However, this disease usually stops as it

approaches the basal (i.e. resorption resistant) bone areas and since Corticobasal implants being smooth



surface implants are anchored into the basal bone, peri-implantitis cannot occur, which is one of the

major advantages associated with the use of corticobasal implants.

Conclusion

It can be inferred from the results of this case that Cortico-basal implants can be the treatment of choice

that can be successfully selected while treating the atrophic maxilla and mandible. In our case, we

achieved excellent results with regard to the immediate functional loading protocol. Furthermore, it

presents as a good alternative to conventional implantology where applicable, and the protocol is very

patient- oriented and friendly.

References:

1. Berczy K, Laszlo Z, Gondocs G et al. Changes of trends in the size of the dental implants in

recent years Part 1. The role of short implants in dental implantology The literature review.

Fogorv Sz 2016; 109: 136-140.

2. Schlegel D. [Dental implantology--a review of the literature]. Dtsch Zahnarztl Z 1974; 29: 176-

186.

3. Chattman R. Implantology: history and review. Bull Plainfield Dent Soc 1970; 2: 15-19.

4. Cao ZL, Li X, Lin LJ, Chen YH. Immediate or delayed loading protocols for two-implant

mandibular overdentures: A systematic review and meta-analysis of randomized controlled trials.

J Prosthet Dent 2020.

5. Abboud M, Rugova S, Orentlicher G. Immediate Loading: Are Implant Surface and Thread

Design More Important Than Osteotomy Preparation? Compend Contin Educ Dent 2020; 41:

384-386.

6. Gupta G, Gupta DK, Gupta N et al. Immediate Placement, Immediate Loading of Single Implant

in Fresh Extraction Socket. Contemp Clin Dent 2019; 10: 389-393.

7. Baruffaldi A, Baruffaldi A, Baruffaldi M et al. A suggested protocol to increase the accuracy of

prosthetic phases in case of full-arch model-free fully guided computer-aided implant placement

and immediate loading. Oral Maxillofac Surg 2020; 24: 343-351.

8. Levin BP. Immediate implant loading of single and multiple implants: where are we now. Alpha

Omegan 2005; 98: 22-33.

9. Lee SP, Paik KS, Kim MK. Anatomical study of the pyramidal process of the palatine bone in

relation to implant placement in the posterior maxilla. J Oral Rehabil 2001; 28: 125-132.

10. Ihde S, Sipic O. Esthetic Indication for Dental Implant Treatment and Immediate Loading (3).

Case Report and Considerations Regarding the Aspect of the Patient's Right to Self-

Determination in Medical Decision-Making. Ann Maxillofac Surg 2020; 10: 213-216.

11. Ihde S, Sipic O. Functional and Esthetic Indication for Dental Implant Treatment and Immediate

Loading (2) Case Report and Considerations: Typical Attitudes of Dentists (and their Unions)

toward Tooth Extractions and the Prevention of Early, Effective, and Helpful Dental Implant

Treatment in the European Union. Ann Maxillofac Surg 2019; 9: 470-474.

12. Ihde S, Sipic O. Dental Implant Treatment and Immediate Functional Loading (1). Case Report

and Considerations: Extended Treatment Options Using the Strategic Implant(R) and Indications

and Objectives for Comprehensive Dental Implant Treatment. Ann Maxillofac Surg 2019; 9:

465-469.

13. Ihde S, Palka L, Gaur V, Ihde A. Critical Appraisal Regarding the Publication "Implant Survival

between Endo-Osseous Dental Implants in Immediate Loading, Delayed Loading, and Basal

Immediate Loading Dental Implants: A 3-Year Follow-Up" as Published in Ann Maxillofac Surg



2017;7; 237-44, by the Authors R. Gharg (Corresponding Author), Neha Mishra, Mohan

Alexander, Sunil K. Gupta. Ann Maxillofac Surg 2018; 8: 101-107.

14. Gaur V DA, Ihde S, Fernandes G, Lysenko V “Immediate Loading of Implants in the Partially

Edentulous Maxilla: A Case Report of a Novel Technique with Strategic Implants .”. IOSR

Journal of Dental and Medical Sciences (IOSR-JDMS) (2018); 17: : 34-40.

15. Liu Z, Yuan X, Fernandes G et al. The combination of nano-calcium sulfate/platelet rich plasma

gel scaffold with BMP2 gene-modified mesenchymal stem cells promotes bone regeneration in

rat critical-sized calvarial defects. Stem Cell Res Ther 2017; 8: 122.

16. Fernandes G, Yang S. Application of platelet-rich plasma with stem cells in bone and periodontal

tissue engineering. Bone Res 2016; 4: 16036.

17. Fernandes G, Wang C, Yuan X et al. Combination of Controlled Release Platelet-Rich Plasma

Alginate Beads and Bone Morphogenetic Protein-2 Genetically Modified Mesenchymal Stem

Cells for Bone Regeneration. J Periodontol 2016; 87: 470-480.

18. Vivek Gaur AD, Stefan Ihde, Gabriela Fernandes . . Immediate Loading of Edentulous

Mandibular Arch with Screw Retained Final Prosthesis on Strategic Implants® With Single

Piece Multi Unit Abutment Heads: A Case Report. BAOJ Dentistry (2018) 4:.

19. Wang K, Li DH, Guo JF et al. Effects of buccal bi-cortical anchorages on primary stability of

dental implants: a numerical approach of natural frequency analysis. J Oral Rehabil 2009; 36:

284-291.

20. V Sequeira MT, V Abhyankar, G Fernandes. Prevention of Peri-Implantitis: A Narrative Review.

. J Dent Oral Care Med 2018.; 4: 106,.

21. Fernandes G, Vanyo ST, Alsharif SBA et al. Strontium Effects on Human Gingival Fibroblasts. J

Oral Implantol 2019; 45: 274-280.




ABSTRACT In complete denture prosthodontics, instability of lower denture is most common problem faced due

to long term edentulism. Various factors affect the stability of the denture, one of them being teeth

placed in proper position. Arrangement of artificial teeth in neutral zone and recording the correct

contour of the polished surface will reduce the interferences of teeth while functional movements.

Correct polished surface recording form favorable angle with cheek, tongue and lip. Teeth placed in

neutral zone enhances stability by equalizing forces exerted by muscles of tongue on one side and

muscles of cheek and lip on the other side. Different techniques and materials are used to record the

Neutral zone. The aim of this article is to understand this technique by practical implication in the

described case series.

Introduction

One of the major difficulties in complete denture wearer patient is the poor stability of the

mandibular denture. Mandibular ridge resorption is 4 times greater than that of maxilla.1–5 The denture

bearing area of maxilla is 24 cm2 and 14 cm2 in mandible.6 Presence of mobile tissues at the floor of

the mouth and tongue on the other side compromises the stability of the mandibular denture.7 The

potential space between the lips and cheeks on one side and tongue on other ;that area or position

where the force between the tongue and cheeks or lips are equal is called as “NEUTRAL ZONE”. It

is also referred as Dead space, Stable Zone, or Zone of Minimal Conflict.8,9

Sir Wilfred Fish in 1933 brought to the notice the importance of polished surface on stability

of the denture. Recording the correct contour of the polished surface and arrangement of artificial teeth

in neutral zone will reduce the interferences of teeth while functional movements and the muscular

forces from both sides will be equalized; which in turn will help in seating the denture in place.10 It is

indicated in patients with resorbed mandibular ridges and compromised neuromuscular control. The

aim is to fabricate a denture which is in harmony with the facial musculature to increase the stability

and retention.9,11

Case Report 1 A female patient aged 57 years reported with the chief complaint of loose mandibular denture. Patient

was wearing the same denture for last 7 years. On examination, hyperactive mentalis muscle activity

Neutral Zone: A Novel Approach for Resorbed Ridge Management - A Case Series

Dr Ankita Savaliya1, Dr Janani Iyer2, Dr Jyoti Nadgere3

1PG Prosthodontics,

2Professor, 3Professor and HOD,

Department of Prosthodontics and Crown and Bridge,

MGM Dental College and Hospital, Navi Mumbai

Savaliya A. et al: Neutral Zone – A Case Series


was seen which was responsible for repeated unseating of denture. (Fig 1) The patient was diagnosed

as a completely edentulous patient with a hyperactive mentalis muscle. (Fig 2) Therefore, it was

decided to fabricate a new set of dentures using the Neutral Zone technique.

Fig 1 Fig 2

Clinical Technique Primary Impression was made in stock tray using medium fusing impression compound (Prime

Dental Products). Border molding was done with low fusing impression material (DPI Pinnacle tracing

stick) and wash impression was made with Zinc Oxide eugenol paste (DPI Impression Paste).

Temporary denture base were made by auto polymerizing acrylic resin(DPI autopolymerising resin)

and wax rims of modeling wax were fabricated on it. Denture bases were checked in the patient’s

mouth for border extensions and stability. Maxillary rim orientation was analyzed by assessing the

esthetics, phonetics and function. Mandibular rim was adjusted at the established vertical dimension

and centric relation was recorded. Facebow transfer was done using mounted on semi-adjustable

Hanau articulator. (Fig 3)

Fig 3

A second new pair of denture bases were fabricated. Maxillary rim was duplicated with

medium fusing impression compound. A superstructure was constructed over the lower denture base

in the posterior region using auto polymerizing acrylic resin to maintain the established vertical

dimension. (Fig 4) 20-gauge orthodontic wire loops were incorporated over the crest of the lower

ridge to support the low fusing impression material to be used to record the neutral zone.



Fig 4

Patient was made to sit in an upright position and the duplicated maxillary rim was inserted in

the patient’s mouth. It was reassessed for occlusal plane and lip support. Low fusing impression

compound was tempered in hot water bath and adapted over the lower denture base around the

supporting wire loops and placed in the patient’s mouth.12

Patient was then instructed to perform the following series of actions for 10 minutes:

1. To have a sip of warm water and swallow.

2. Take frequent sips of water.

3. Pout and smile, grin, lick the upper lip and purse the lips (Fig 5).

. Patient is then told to talk aloud, pronounce the vowels and count from 60 to 70.

Fig 5

A wash impression is then made using soft liner(D-Soft tissue conditioner) by repeating all the above

movements (Fig 6).12,13

Fig 6

Neutral zone impression was seated on the master cast. Orientation grooves were carved in the ledge

area of the cast, 2 on the buccal side and one in the lingual area. Boxing of the master cast with boxing

wax was done. A thin layer of Separating media (Sodium alginate) was applied over the cast and



impression plaster was poured to form indexes. Buccally the indexes were separated at the midline for

easy removal. Lingually the index was fabricated in single piece (Fig 7). The indexes were labelled

according to their position and checked for accurate placement. A new denture base was fabricated

over the mandibular master cast. The indexes were seated in position and molted modelling wax was

poured in the space between the indices forming a new occlusal rim. Semi anatomic teeth were selected

according to SPA factor and teeth arrangement was done confining to the space and it was rechecked

by placing the plaster indices in place (Fig 8).14,15 Non balanced(Organic) occlusal scheme was

followed.

Fig 7 Fig 8

Try in was done and centric relation, esthetics and phonetics were verified. Neutral zone verification

was done during try in stage by flowing light body addition silicone (Flexceed light body) on polished

surface of upper and lower trial denture and asked patient to do all the movements. (Fig 9)

Fig 9

After all the movements exposed region of wax were removed and Patients approval was taken.

Denture was processed with heat cure acrylic resin by compression molding technique. After finishing

and polishing denture insertion was done and minor occlusal adjustment were made by selective

grinding technique. Patients follow up was done after 24 hours and minor modification was done (fig

10).

Fig 10

Case Report 2



A female patient aged 56 years reported with the chief complaint of ill-fitting lowered denture. Patient

was wearing the same denture for last 4 years. On examination, mandibular ridge resorption was seen

(Fig 1) Mandibular ridge was narrow in width with reduced height. Patient was diagnosed as

completely edentulous maxillary and mandibular ridges with moderate resorption of mandibular arch

Therefore, it was decided to fabricate a denture using a Neutral Zone technique.

Fig 1

Clinical Technique The primary impression, Final impression and Jaw relation was taken conventionally as described in

the previous case.

Lower mandibular denture base was prepared to record neutral zone same as described previously.

Patient was instructed to do all the movements as described in the previous case (Fig2)

Fig 2

In this case we used Zinc Oxide eugenol paste as a wash impression material to record the neutral

zone. (DPI Impression Paste) (Fig 3)



Fig 3

Teeth arrangement, Try in and denture insertion was done as described in the previous case. (Fig 4)

Non balanced (Organic) occlusion philosophy was chosen for this patient.

Fig 4

Discussion Neutral zone philosophy is well described in the literature to achieve stability and retention in

a severely resorbed cases.16 Various methods that can be used to record the neutral zone are

swallowing, phonetics, sipping of warm water, slicking and pursing upper lip smiling, whistling,

protruding tongue, opening and closing of mouth, blowing air and exercise movement of lip, cheek,

tongue and facial muscle. We used Phonetics and swallowing methods to record neutral zone as it

activates all the muscle involved in. Lott and Levin suggested that reading interesting topic loudly and

rapidly is the ideal method as this causes muscles to be increasingly strained, and saliva secretion

increases which will result in more swallowing action. This will record more natural movements of

muscle as it reduces the patient’s focus on the occlusal rim. Tench proposed the use of thermoplastic

low fusing impression compound material to record neutral zone as it has the advantages of being

easily available, ease of manipulation and low cost.17Low fusing impression compound is most

commonly used to record tissue while functional manipulation as in border molding to record

vestibule; hence we used this material to record neutral zone. Other materials that can be used are

tissue conditioners, modelling wax, light cure resins, silicone and auto-polymerizing acrylic resin.

Modelling wax is initially stable but gets distorted after some time, hence it is not used routinely.15,18

Resin (light cure / acrylic) can be used but it causes irritation due to residual monomer content. Tissue

conditioner, addition silicone (Light body), zinc oxide eugenol paste can be used as a wash impression

material. We used tissue conditioner and zinc oxide eugenol paste as a wash impression material



because of its adequate flow and slow setting time of the material. These materials can be used to

record neutral zone or as materials for wash impressions of neutral zone.19 The material should have a

body; so that it can stay over the denture base with wire as a supporting medium; And sufficient

viscosity so that oral musculature can shape it in proper contour and dimension via the functional

muscle movements. Whichever material is used two factors are mandatory 1) maintain the established

vertical dimension 2) slow setting time; so that the patient gets adequate time to mold it. For index

fabrication silicone, stone, plaster, or modeling plastic impression compound can be used. We used

dental plaster because of its rigidity, ability to record minute detail and ease of manipulation and

availability. Indexing helps in preservation of recorded neutral zone.20–22 Verification of neutral zone

at try in stage is an important step. Impression of an external surface (labial, buccal and lingual)

determine the correct contour, thickness and shape of the polished surface of the denture. Dentist or

the technician has a tendency to wax up the external surface of denture during wax up of the trial

denture. By making an impression of the external surface; the exposed areas need to be cut off or

reduces so as to maintain our neutral zone contour. Zinc oxide eugenol or light body addition silicone

can be used in 2 steps for this procedure. First buccal and labial surface is recorded and secondly

lingual surface is recorded. This procedure has two advantage 1)It forms a ledge lingually in the lower

anterior region; it should be replicated in final denture as tongue sits on this ledge and it keeps the

denture in position.2)External impression fills up the denture spaces and cheeks can easily push the

food towards the occlusal surface; hence reduces or eliminates food accumulation on the buccal aspect.

This technique is contraindicated in patients with long term edentulism as the tongue size increases

results in macroglossia and causes unseating of the lower denture. In severe neuromuscular

incoordination.10,23

Conclusion Atrophic mandibular ridges with poor denture stability and discomfort is the major problem in

complete denture prosthodontics. Neutral zone impression technique is highly effective in such cases.

This impression technique utilizes muscle forces to record the neutral zone. This technique defines the

polished surface of the denture and accurately place the teeth in the stable zone. It increases the stability

of the denture, esthetics and comfort of the patient. The neutral zone technique is also used in patient

with partial glossectomy, motor nerve damage, mandibular resection which have led to atypical

movement and less favorable denture bearing area. This technique requires extra clinical appointment

of the patient and chair side working time. Accurate methodology and material used improves

masticatory efficiency and prognosis of the case.

References: 1. Wical E, Swoope C. Studies of residual ridge resorption. Part I. Use of panoramic radiographs for

evaluation and classification of mandibular resorption. J Prosthet Dent.1974;32(7):7-12.

2. Wical E, Swoope C. Studies of residual ridge resorption. Part II. The relationship of dietary

calcium and phosphorus to residual ridge resorption. J Prosthet Dent.1974;32(7):13-22.

3. Saunders TR, Desjardins RP, Gillis RE. The maxillary complete denture opposing the mandibular

bilateral distal-extension partial denture:Treatment considerations. J Prosthet Dent. 1979;41(2).

4. Ortman LF, Hausmann E. osteopenia and residual ridge resorption. J Prosthet Dent.1989;61(3)

:321 5.

5. Qiufei X, Narhi T, Nevalainen JM, Wolf J, Ainamo A. Oral status and prosthetic factors related to

residual ridge resorption in elderly subjects. ACTA odontol scand.1997;55(24).

6. Klemetti E. A review of residual ridge resorption and bone density.J Prosthet

Dent.1996;75(5):512-514.



7. Morrow RM, Payne SH. The neutral zone in complete denture. J Prosthet Dent.1976;36(4) :356–

67.

8. Cagna DR, Massad JJ, Schiesser J. The neutral zone revisited : From historical concepts to modern

application. J Prosthet Dent. 2009;101(6):405–12.

9. Porwal A, Dds KS. Current status of the neutral zone : A literature review. J Prosthet Dent.

2013;109(2):129–34.

10. Srivastava V, Gupta NK, Tandan A, Kaira LS, Chopra D. The Neutral Zone : Concept and

Technique.Journal of orofacial research.2012;2(1):42–7.

11. Fahmy FM. . A study dentures of the importance zone in complete. J Prosthet Dent.1990;64 :459–

62.

12. Dds LS, Dds FG, Falahi S, Memarian M. Using neutral zone concept in prosthodontic treatment

of a patient with brain surgery : A clinical report. J Prosthodont Res. 2011;55(2):117–20.

13. Porwal A, Satpathy A, Jain P, Ponnanna AA. Association of Neutral Zone Position with Age ,

Gender , and Period of Edentulism.Journal of prosthodontics; 2016:1-8

14. Kelly E.Changes caused by a removable mandibular partial denture opposing a maxillary

complete denture. J Prosthet Dent. 1972;27(2):140–50.

15. Kishor K, Vikram S, Vero N, Ahmed H. Novel registration technique to register neutral zone. J

Oral Biol Craniofacial Res. 2012;2(3):198–202.

16. Gupta KL, Agarwal S. Salvation of a severely resorbed mandibular ridge with a neutral zone

technique.Indian journal of dental research. 2011;22(6):30–2.

17. Ohkubo C, Hanatani S, Hosoi T. Neutral zone approach for denture fabrication for a partial

glossectomy patient : A clinical report. J Prosthet Dent .2000;84(4),3–6.

18. Jain C, Goel R, Kumar P, Singh HP. CASE REPORT Neutral Zone approach for severely atrophic

ridges ; Avenues beyond implants and surgeries – A Case Report. International journal of clinical

dental science.2011;(August)2(3).

19. Suzuki Y, Ohkubo C, Hosoi T. Implant Placement for Mandibular Overdentures using the Neutral

Zone Concept.Prosthodont Res pract.2006;109–12.

20. Wee AG, Cwynar RB, Cheng AC. Utilization of the Neutral Zone Technique for a Maxillofacial

Patient.Journal of prosthodontics. 2000;9(1):2–7.

21. Yeh Y, Pan Y, Chen Y. Neutral zone approach to denture fabrication for a severe mandibular

ridge resorption patient : Systematic review and modern technique. J Dent Sci. 2013;8(4):432–8.

22. Rashid H, Vohra FA, Haidry TZ, Karmani GD. “stabilizing mandibular complete dentures using

the neutral zone impression technique.” J Pak Dent Assoc.2013;22(02):154–159.

23.Beresin V,Schiesser F. The neutral zone in complete dentures. J Prosthet Dent

.2006;(February);95(2):93–100.




ABSTRACT Ceramic veneers are indicated in a wide variety of cases, such as correcting malalignment, diastema,

tooth defects and tooth discolouration. Patient esthetics drastically changes even after minor alteration

of shape, shade, size and position of teeth. This can be achieved by using diagnostic wax-up and

aesthetic pre evaluative temporaries. Esthetic pre-evaluative provisional prepared from the diagnostic

wax-up permits the dentist and the patient to evaluate the appearance of the final restorations during

smile and function. This paper describes the esthetic rehabilitation and smile designing of a case which

has multiple spaces in upper anterior teeth.

Introduction The importance of cosmetic smile to the psychosocial well-being of an individual has been

well established.1 In an esthetic conscious society, ‘beautiful smile’ tends to create a perception of

more confident, successful and a good looking individual2. Smile contributes 47% of the overall

dentofacial attractiveness.3 Esthetics and function should be in harmony, creating restorations that are

indistinguishable from its natural counterpart.2

Advent of Lithium di-silicate and bonding protocols led to a conservative approach to correct

the appearance and unusual position of anterior teeth by minimising the amount of tooth preparation.4

All ceramic veneers are preferred when major corrections in colour and form of the tooth is to be done

because of its better strength after bonding, good marginal fit, biocompatibility and high esthetic

value.1,4

The following case focuses on significance of diagnostic wax up, use of Provisionals to guide

the tooth preparation and historically acknowledged smile designing principles.

Case Report A male patient of 38 years reported with spaces between his upper teeth and wanted closure of

those spaces. Patient had square facial form with straight profile. (Fig 1) Extra orally smile line was

observed to be medium with adequate lip support. (Fig 2) Intra orally spaces were seen between all six

maxillary anterior teeth. 11 and 21 were mesiopalatally rotated (fig. 3). Gingiva was firm and resilient

Smile Designing Using All Ceramic Laminates Guided Through Aesthetic Pre-Evaluative Temporaries: A

Case Report

Dr Pinak Rathi1, Dr Janani Iyer2, Dr Jyoti Nadgere3

1PG Student,

2Professor, 3Professor and HOD,

Department of Prosthodontics and Crown and Bridge,

MGM Dental College and Hospital, Navi Mumbai

Rathi P. et al: Smile Designing


with stippling of attached gingiva. Diagnosis was made as tooth size jaw size discrepancy causing

spacing.(Fig 4)

Fig 1 Fig 2

Fig 3. Fig 4.

Treatment options given to the patient were, orthodontic treatment to correct the spacing of teeth or

Smile designing with all ceramic laminates. Patient did not wanted to go for orthodontic correction of

teeth and therefore opted for all ceramic laminates.

Extra oral and intra oral smile analysis was done. After detail case history and clinical

examination, diagnostic impressions were made and facebow transfer was done. Diagnostic wax up

was done by using golden proportion as a guide (Fig 5). A putty index was made using condensation

silicone putty (C-silicon lab putty, ZERMAC). Wax up was transferred in the patients mouth using bis

acryl based provisional restorative material (Protemp; 3M-ESPE, St Paul,MN). These provisionals

were used to analyse patient’s esthetics, phonetics and function (Fig 6). Patient was re-evaluated after

2 weeks for comfort and function. Patient consent was recorded for final treatment. Impressions were

made after doing fine corrections of the provisionals intraorally which was to be used as a guide for

the ceramist. Shade selection was done by using spectrophotometer (VITA Easy Shade) by dividing

each tooth in three quadrants.



Fig 5 Fig 6 Final tooth Preparation was done using the Aesthetic Pre-evaluative Temporaries (APR) as guide.

Facially, grooves of 0.5 mm depth were made using depth cutting bur in 2 planes. Incisal depth grooves

of 1 mm were made. These grooves were highlighted using carbon pencil. The temporaries were then

removed and only the areas which were highlighted by the carbon pencil were reduced using round

ended tapered fissure bur (Fig 7). Remaining tooth structure was left as it is and thus a conservative

approach was followed. The preparation was extended palatally up to incisal 1/3 rd to make a

wraparound preparation design. Chamfer finish line of 0.5 mm depth was given at the level of marginal

gingiva. Finishing of the preparation was done using yellow banded tapered fissure burs. Chemico-

mechanical method of retraction was followed using double cord technique (MEDIPAK “00”) and

25% aluminium chloride (MEDICEPT) as a homeostatic agent. Retraction cord was placed in mouth

for 4 minutes. (Fig 8) Outer cord was removed from the sulcus and impression was made using a two

stage impression technique by Addition silicone impression material. (GC FLEXCEED)

Fig 7 Fig 8



Impression was poured in type IV gypsum product (Kallabhai) and dies were prepared. (Fig 9). Wax

pattern was fabricated and Lithium di silicate glass ceramic was pressed. Bisque trial of the laminates

was done to check the marginal fit, shape and contour of the laminate and once found satisfactory the

laminates were stained and glazed and made ready for cementation (Fig 10).

Bonding of laminates to the tooth structure was done with light cure adhesive resin cement by

following the below protocol. Adjacent teeth were isolated using Teflon. Etching the tooth surface was

done with 37% Phosphoric acid (GLUMA) for 20 seconds. Simultaneously etching of laminates was

done using 9.6% hydrofluoric acid (Ultradent) for 20 seconds. Frosty Appearance was seen on drying

the tooth and the laminates. A thin layer of bonding agent (Monobond 3M ESPE) was applied on the

etched tooth surface using applicator tip. Silane coupling agent (Primedent) was coated on the etched

laminate surface. Light cure adhesive resin cement was used to lute the laminates (Variolink

IVOCLAIR). Excess cement was removed and the prosthesis was light cured for 30 seconds each.

Dental floss was passed through each embrasure to remove small chunks of excess cement. The

margins of the laminates were finished and polished using yellow banded burs and polishing cups.

Result was a pleasing smile and patient was satisfied with the enhanced look and confident gesture.

(Fig 11, 12) Patient was recalled after 24 hours and then after 7 days to evaluate dentogingival

components and function.

Fig 9 Fig 10

Fig 11

Fig 12



Discussion The goal of esthetic rehabilitation is to develop a masticatory system where the teeth and the

supporting structures function in harmony as stated by Dawson.5 An attractive smile is a vital asset of

one’s personality. Manipulation of colour shape, line angles, contour, proportion and position of tooth

can be worked to create a pleasing smile.6–10 An appropriate white and pink balance must be

maintained in designing the smile of a patient. Diastema is a very common occurrence and in adults as it can distort the individual’s pleasing

smile.11 Orthodontic correction of spaces or restorative correction or combination of both can be used

to correct the problem of diastema.11,12 In the present case patient was reluctant for orthodontic

treatment and thus wanted a restorative solution for the problem. Closure of diastema with laminates

can result in increased mesiodistal dimensions of the tooth. Therefore, careful planning with the aid of

diagnostic wax up helps in maintaining the intradental proportions of tooth as well as inter dental

proportion of each tooth.12–14 Along with the aid of anatomic wax up, the esthetics and function was

achieved as desired by the patient.

Amendment of dental esthetic inconsistencies demands cautious examination, perfect

treatment planning and good communication between a prosthodontist and the ceramist.9,15 Anatomic

wax up is one of the most important step in designing the smile of an individual.3,9,16 Every tooth has

a unique anatomy and it must be harmonious with the dentofacial complex.10 Proportions of the central

incisor must be esthetically as well as mathematically correct. Various guidelines are proposed for

establishing the correct proportions of anterior teeth, such as Golden Proportion (Lombardi), Recurring

Esthetic Dental proportion (Ward), M proportion and Chu’s esthetic gauge. These ratios help to

determine the height and width of the teeth with respect to each other. Golden proportion

mathematically divides the tooth in the ratio of 1: 1.618 with its adjacent counterpart. This ratio was

achieved by dividing the anterior tooth into grids digitally and wax up was done taking golden

proportion as a guide.

Corrected provisionals which are also called as Aesthetic Pre-evaluative Temporaries (APR)

are used as guide for tooth preparation.3,9,17 The main goal of this technique is to reduce the actual

tooth structure as conservatively as possible.9,16,17 This helps to maintain the enamel layer of the tooth

and enhances the bonding ability of all ceramic laminates to the tooth structure.8–10,17 These

provisionals also act as a guide for the ceramist in fabrications of laminates.

Shade selection is an important step in smile designing.15 Tooth shade is never monochromatic

and therefore should be recorded by dividing the tooth in three parts horizontally.19 Clinical

spectrophotometer is a reliable device to evaluate the shade accurately.19,20 Not only the shade but also

the various characterisations present on the underlying tooth must be noted down and communicated

to the ceramist for its incorporation in the final prosthesis to give a natural appearance to the smile.19,21

Conclusion The smile we create should be esthetic and functionally sound. It is our duty to deliver the best to our

patients, after careful diagnosis and examination. Aesthetic pre evaluative temporaries provides

conservative tooth reduction and helps in better bonding. Even though utilising APT sounds like a

long and time-consuming procedure, it is not—and it is extremely beneficial to the final outcome.

References:

1. Bhuvaneswaran M. Principles of smile design 2020;1–9.

2. Article R. Anterior Teeth and Smile Designing : A Prospective View 2012;2:117–27.



3. Navigation A. Digital Smile Design for Computer-assisted Esthetic Rehabilitation 2020;1–22.

4. Series C. Smile Designing with Ceramic Veneers.

5. Drive WI. This ebooks is uploaded by dentalebooks . com This ebooks is uploaded by

dentalebooks.com.

6. Brunton P, Aminian A. Tooth preparation techniques for porcelain laminate veneers.

2000;(March 2014):7–10.

7. Cp L, Wh D, Sl E. Predictable and precise tooth preparation techniques for porcelain laminate

veneers in complex cases. 1999;9(1).

8. Dentistry I. Minimally invasive veneers : current state of the art. 2014;101–7.

9. Garcia PP, Goulart R, Gonzaga CC. Digital smile design and mock-up technique for esthetic

treatment planning with porcelain laminate veneers. 2020;8–11.

10. Hari M, Poovani S. Porcelain laminate veneers : A review. 2017;4:187–90.

11. Huang WJ, Creath CJ. The midline diastema: a review of its etiology and treatment. Pediatr

Dent. 1995;17(3):171–9.

12. Bhoyar A. Esthetic Closure of Diastema by Porcelain Laminate Veneers : A Case Report.

People’s J Sci Res. 2011;4(1):47–50.

13. Raj V. Esthetic paradigms in the interdisciplinary management of maxillary anterior dentition

- A review. J Esthet Restor Dent. 2013;25(5):295–304.

14. Giannetti L, Apponi R. Combined Orthodontic and Restorative Minimally Invasive Approach

to Diastema and Morphology Management in the Esthetic Area. Clinical Multidisciplinary Case

Report with 3-Year Follow-Up. Case Rep Dent. 2020;2020:5–9.

15. Farias-neto A, Maria E, Gomes F, Sánchez-ayala A, Sánchez-ayala A, Soares L, et al. Case

Report Esthetic Rehabilitation of the Smile with No-Prep Porcelain Laminates and Partial

Veneers. 2015;2015.

16. Calamia JR, Levine JB, Lipp M, Cisneros G, Wolff MS. Smile Design and Tre a t m e n t P l

a n n i n g With the Help of a C o m p re h e n s i v e E s t h e t i c Evaluation Form.

2011;55:187–209.

17. Reshad M, Cascione D, Magne P, Angeles L. Diagnostic mock-ups as an objective tool for

predictable outcomes with porcelain laminate veneers in esthetically demanding patients : A

clinical report. 2008;

18. Gu G. Porcelain Laminate Veneers : Minimal Tooth Preparation by Design. 2007;51:419–31.

19. Basavanna R, Gohil C, Shivanna V. Shade selection. Int J Oral Heal Sci. 2013;3(1):26.

20. Thomas MS, David K. esthetic smile design with ceramic veneers. 2014;(1):55–8.

21. Porcelain N, Preparation L, Driven A. Approach Driven by a Diagnostic Mock-up.

2004;(1):7–18.

Dental Chair with Unit

DOSHI MARKETING CORPORATION42, Shah Industrial Estate, Ground Floor, Deonar Village Rd, Deonar, Govandi (E),Mumbai - 400 088. Tel. : 2555 9374 / 2555 9383 Email : [email protected]

Exclusive Range of Dental Equipment Instrument Material

Jenin

Surgi Safe

Discover the Perfect Salutationfor your Dental Clinic

Discover the Perfect Salutationfor your Dental Clinic

Your Trusted Partner In Dentistry

Your Trusted Partner In Dentistry

“Nothing is impossible if you put your mind to it”

EDITOR’S OFFICE: Editor: Dr. Naisargi Shah Dept. of Prosthodontics, Terna Dental College, Navi Mumbai.

Contact us: +91 9819238483 +91 8976876779

Mail ID: [email protected]

Mr. Hemant Khot, Chief Technician And Owner

Contact no: +91 99200 30082, +91 79778 66297

EDITOR’S OFFICE :

The Journal of Prosthodontics and Dental Materials

Documents

Transcript of The Journal of Prosthodontics and Dental Materials