Comparative evaluation of 2 resin materials in luting composite inlays

Abstracts

Abstracts from the Academy of Dental Materials Conference,

Siena, Italy, October 2001

1. Effect of orthodontic stripping on enamel demineralization after

storage in cariogenic solution.

An SEM investigation; M. Zanarinip, S. Marchionni, G. Borea, C. Prati

(University of Bologna, Italy)

Introduction. Many studies show how orthodontic stripping should be

responsible for damaging the enamel structure and interproximal caries.

The aim of our study was to evaluate the ultrastructural aspect of the

stripped interproximal enamel after demineralization with cariogenic

solution (Lactic Acid buffer solution of pH 4.4) by SEM. We also wanted

to evaluate role of saliva in the demineralization and its ability to protect

enamel from the acid attack.

Materials and methods. Nineteen human incisor teeth extracted

were selected and stored in distilled water (pH 7.0) at 4 8C for not

more than 30 days. Each of the incisors was stripped interproximally

with an Horico strip. Teeth were than carefully cleaned under water

for 15 s and incubed at 37 8C. Ten of the selected incisors were stored

in a cariogenic solution alterned with distilled water buffered (H2Ob)

by pH 7.0 with Ammonium hydroxide for 3 days. Other five teeth

were stored in a cariogenic solution alterned with human saliva (Sal)

for the same time. After a storage of 72 h, a vertical section was made

to obtain 38 samples. These were fixed in 4% glutaraldeyde in 0.2 M

phospate buffer, deydrated in alcohol then gold sputtered before SEM

evaluation. Pictures were taken at a magnification of between 200 and

5000 £ .

Results and discussion. SEM analysis shows the following differences.

Samples stored in H2Ob show deep grooves on the enamel surface (2–

3m) but no removal of enamel prisms or exposed interprismatic enamel

matrix. It is also possible to see somewhere the smear layer, consequence of

stripping procedures. Samples stored in cariogenic solution and H2Ob show

no grooves or smear layer on the enamel surface. Removed enamel prisms

and exposed interprismatic enamel matrix are observable. Samples stored

in cariogenic solution and saliva show no grooves or smear layer on the

enamel surface, the number of enamel prisms is higher than the one

observed in the samples stored in H2Ob while the exposed interprismatic

enamel matrix is less represented. No stripped samples stored in cariogenic

solution and H2Ob/saliva show a homogeneous enamel surface.

Material groups n Enamel

grooves

Enamel

prisms

Interprismatic

matrix

Stripping-H2Ob 4 þþþ 2 2

Stripping-cariogenic

sol.-H2Ob

20 2 þ þþþ

Stripping-cariogenic

sol.-saliva

10 2 þþ þþ

No stripping -cariogenic

sol.-H2Ob

4 2 2 2

Conclusions. Our study confirm that orthodontic stripping causes an

alteration of the integrity and morphology of the enamel surface. We also

observed a different behavior of the stripped enamel stored in acid solution

and H2Ob with respect to the one stored in cariogenic solution and saliva.

Saliva seems to prevent enamel demineralization and to play a protective

role on the enamel surface reducing the depth of demineralization and

preserving the integrity of prisms.

2. The color of the same shade in different composites: a

spectrophotometric analysis; M. Anselmip, G. Dondi Dall’orologio,

R. Lorenzi (University of Bologna, Bologna, Italy)

It has long been recognized that the color of the tooth is strongly

influenced by the color of the dentin and the thickness of the enamel. The

total color effect of natural teeth is a result of the combination of light

reflected from the enamel surface and light scattered in the enamel and

dentin and finally reflected back. The use of the recommended layering

technique with composite resins has provided the means to produce a highly

esthetic restoration but has presented some problems to the area of color

control.

The purpose of this study was to use a spectrophotometric analysis to

evaluate colorimetric data of composites of different manufacturers with

the same shade designation.

Three shades (A3,A3.5,B1) of three different composites were selected:

Filtek Z250(Z), (3M); Charisma (C), (Heraeus Kulzer); Esthet X (E)

(Dentsply).

Samples of the materials were prepared on the same resin tooth, where a

cavity, 3.0 mm in diameter, 3 mm thick, was done. Each sample was

measured using a reflectance spectrophotometer on black and white

backings. For the white background resin tooth cavity had L p 87.8, a p 4.8,

b p 26.2, T 27% colorimetric values. For the black background a black

varnish was applied on cavity walls. Colorimetric values for the black

cavity were: L p 21.8, a p 20.7, b p 23.2 and T 93%.

A layer of glycerin was used on the walls for an easier removal of the

material. Each sample was light cured from the top for 40 s with a visible

light unit, having 7 mm diameter tip. Colorimetric analysis was performed

with a reflection spectrophotometer (Pikkio, M.H.T.) with a 358/0 type

illuminating and viewing geometry; with a 3 mm measuring port and

1.5 mm detector area: the measure was automatically reported after three

identical recordings.

All the data were directly measured in CIELAB coordinates, with

respect to the standard light source A. The manufacturer states that the

precision of the machine in within 1%.

The CIELAB color difference metric (CIE 1986) was used to determine

the size of color shift. Means for CIE L p a p b p and translucency for the

shade A3 are listed in the following table.

A3 L p a p b p T (%)

Charisma 59.0 4.0 21.0 70

Esthet X 56.1 2.3 20.2 66

Z250 57.9 2.1 18.8 69

DECE ¼ 5:37; DECZ ¼ 3:1; DEEZ ¼ 2:69: For the shade A3.5

PII: S0 10 9 -5 64 1 (0 2) 00 0 44 -1

Dental Materials 18 (2002) A1–A23

www.elsevier.com/locate/dental

http://www.elsevier.com/locate/dental

DECE ¼ 9.4, DECZ ¼ 5:7; DEEZ ¼ 4:1; for the shade B1 DECE ¼ 8:5;

DECZ ¼ 6:9; DEEZ ¼ 8:9:

The difference was significant, p , 0.01 for all the shades of the three

systems.

For the brands and the shades measured, the following conclusions can

be made:

1. The CIELAB color system and spectrophotometer provide an objective

technique for evaluating color.

2. Corresponding shades of different composites can produce perceivably

different colors that are mostly a result of differences in all three color

directions.

3. For a more scientific approach to color selection, the clinician should

increase his information about colorimetric data for a color matching

more reproducible.

3. Low-temperature aging of transformation-toughened zirconia, Y-

TZP, for dental inlays, crowns and bridges; B.I. Ardlinp (Department

of Odontology, Umea University, Umea, Sweden)

One concern, for transformation-toughened zirconia, Y-TZP, is their

liability to low temperature aging with accompanying degrading of

properties such as strength and toughness. The loss in strength is related

to the amount of transformation of tetragonal grains to monoclinic. The

transformation is related to factors such as loading of the ceramic

reconstruction, temperature and time of exposure to surrounding media

(aging) and the manufacturing processes of Y-TZP.

Objectives. The purpose of this investigation was to study the flexural

strength, chemical solubility, surface texture, crystal structure and low-

temperature aging (4% acetic acid at 80–83 8C for 168 h) of two shades, P0

and P17, of a Y-TZP ceramic used for dental inlays, crowns and bridges.

The hypotheses to be tested were that both shades of the dental Y-TZP

ceramic have high strength and chemical solubility, and that the strength,

surface texture and crystal structures of the ceramic were not effected by

aging.

Methods. Forty specimens of Y-TZP, 20 of the shade P0 and 20 of

the shade P17 were ground and polished. Ten specimens of each shade

were exposed to low-temperature aging. The flexural strength of all 40

specimen was registered. Surfaces of the specimens were evaluated by

using SEM, XRD and roughness recorder. The chemical solubility was

determined by weight loss. Wilcoxon Signed Rank test was used for

statistical analysis.

Results. As expected, the two shades, P0 and P17, of the studied dental

Y-TZP had high strengths that were not effected by low temperature aging

and high chemical solubility. Contrary to what was assumed the crystal

structure and surface texture of P0 and P17 were effected. Transformation

from tetragonal to monoclinic structures occurred and small elevations on

the ceramic surfaces were observed after aging.

Conclusion. The dental Y-TZP ceramic used for dental inlays, crowns

and bridges has high strength and low chemical solubility.

4. Stability measurements of osseointegrated implants in the treatment

of partially edentulous upper jaws; P. Ballerip, A. Cozzolino, L. Ghelli

(Universita degli studi di Siena)

Introduction and purpose:

In the upper jaw, the risk of failure for implants supporting partial

prostheses, is increased by the property of bone and by anatomical limits,

and this is quite evident when the implants are placed in postero-lateral

regions without using grafts or bone augmentations techniques.

The aim of the present study was to test the stability of implants

supporting partial prosthesis in the upper jaw, after one year of loading,

when the fixtures comes to the steady state.

Materials and methods:

The implants were inserted in according to Branemark protocol.

A group of 7 patients were selected for study and the patients had a total

of 21 implants placed. The stability of each implant was tested with

Resonance Frequency and the analysis was performed by Osstelle

(Integration Diagnostics, Gothenburg, Sweden). The resonance frequency

of a trasducer, connected directly with the implant, can measure the

stability of an implant and the obtained values are reported in a reference

scale called I.S.Q. (implant, stability, quotient).

Results and statistical analyses:

All the I.S.Q. values was up to 60, the critical limit for implant loading.

The level of marginal bone around each implant is investigated by

radiography and there was no sign of bone resorption.

Stability measurements indicate the absence of a direct correlation

between implant length and resonance frequency ðR ¼ 20:026Þ:

Conclusions:

I.S.Q. values are always encouraging and they show a good result in

postero-lateral sites too.

The outcome of the study indicate that, in partially edentulous upper

jaws, safe and predictable results can be obtained with Branemark implant

technique and that the placement of short implants to give a good support to

the prosthesis is possible in poor quality bone.

The results support the hypothesis that the bone augmentations and graft

techniques are not always necessary for implant placement, even if the

width and the quality of bone do not show the right property.

5. Effect of different polymerization methods on marginal leakage of

composite restorations; M.F. Bernardop, J. Portugal, J. Leitao

(University of Lisbon, Lisbon, Portugal)

Stress generated by polymerization shrinkage of composites may, in

some instances, be high enough to produce debonding of the restoration or

even enamel microcracks. Both these events result in marginal leakage.

Several polymerization methods have been proposed in order to minimize

polymerization shrinkage stress.

Objective: The objective of this ‘in vitro’ study was to assess the

marginal leakage occurring at the margins of composite restorations, using

five different polymerization methods.

Materials and methods: Two composite resins, Z100 (3M Dental

Products) and Surefil (Caulk/Dentsply), were used to restore 80 restorations

made in the buccal and lingual surfaces of 40 recently extracted human

permanent molars. Five polymerization methods were tested: (1) low

intensity light—40 s at 300 mW/cm2; (2) medium intensity light—40 s at

650 mW/cm2; (3) high intensity light—PAC—10 s at 1900 mW/cm2; (4)

ramp intensity light—10 s at 100–1000 mW/cm2 þ 10 s at 1000 mW/cm2

and (5) pulse-activation—3 s at 300 mW/cm2 þ 4–5 min delay þ 40 s at

300 mW/cm2. Following restorative procedures, the teeth were kept in de-

ionized water for 24 h and then thermocycled between 5 and 55 8C for 500

cycles with a dwell time of 20 s. After thermocycling teeth were isolated

with bright color nail varnish and dental compound up to a distance of

1 mm to the restoration margins and then, immersed in 2% methylene blue.

Teeth were cut twice, in a buccal-lingual direction, with a slow speed

ultramicrotome. Determination of marginal leakage was performed in each

of the eight cross-sectioned restoration margins, using the following ordinal

scale: 0—no marginal leakage; 1—marginal leakage confined to the

gingival/occlusal wall; 2—marginal leakage extending to the axial wall.

Statistical analysis of the results was performed using a non-parametric

ANOVA (Kruskal–Wallis test) at a 95% significance level.

Results: Median scores for each group are presented in the following table:

Low

intensity

Medium

intensity

High

intensity

Ramp Pulse-

activation

Z100 0.75 0.25 1 0.5 1

Surefil 1 0.25 1 1 1.25

Abstracts / Dental Materials 18 (2002) A1–A23A2

The statistical analysis of the results showed significant differences

between the five polymerization methods ( p , 0.05).

Conclusion: Results suggest that the presence of marginal leakage is

strongly influenced by the method of polymerization.

6. Comparative evaluation of 2 resin materials in luting composite

inlays; M. Biasottoa,p, O. Cotarcaa, F. Rusina, M. Cadenaroa,

G. Merlatib, R. Di lenardaa (aUniversita’degli Studi di Trieste, Trieste,

Italy; bUniversita’degli Studi di Pavia, Pavia, Italy)

The aim of this study was the comparative evaluation of a photocuring

resin composite (Z100, 3M) and a selfcuring resin cement (C&B, Bisco Inc.) in

luting composite inlays on human teeth: microleakage at the tooth/inlay

interface and microhardness of the luting materials were evaluated. For the

infiltration test 28 occlusal cavities on human molars extracted for periodontal

reasons were prepared with butt margins using a diamond bur for inlays. After

the application of two layers of Lab-Separator Coltene on the cavity walls 28

inlays were prepared with an incremental technique using Z100 (3M) resin

composite. Each layer of the material (max thickness 2 mm) was polymerized

exposing the occlusal surface to the Apollo 95E curing light (D.M.D.S. Ltd)

for 9 s. After removal from the cavities, the inlays were accurately rinsed with

water and post-polymerized for 9 min in a Coltene D.I. 500 oven; then they

were lightly reduced on the pulpal and axial surfaces with a diamond bur,

respecting the margins. The inlays were sandblasted with Al2O3 for 5 s at

2 atm (Danville Microetcher) and covered with a layer of One Step (Bisco Inc.)

polymerized with Apollo 95E for 9 s. The cavities were total etched for 30 s

with 37% phosphoric acid (3 M), washed for 30 s, gently dried and covered

with two layers of One Step,polymerized with Apollo 95E for 9 s. The samples

were divided into four groups (group 1 and 2, n ¼ 7; group 3 and 4, n ¼ 5). In

groups 1 and 3 inlays were luted with Z100 while in groups 2 and 4 they were

luted with C&B. Inlays were placed into the cavities and luting materials were

polymerized with the Apollo 95E lamp, applying the curing tip occlusally,

buccally and lingually for 1 min each, after removing the material’s excesses.

Teeth in groups 1 and 2 were thermocycled for 9 12

h (Thermocycler FCA14;

500 5/50 8C cycles). All the 28 teeth were then immersed in 0.05% basic

fuchsine for 48 h, embedded in resin and sectioned in buccal–lingual direction

with a microtome cooled with tap water. The sections were analyzed with a

64X stereomicroscope to assess the microleakage at the tooth/inlay interface.

The depth of dye penetration was evaluated using a scale ranging from 0 to 4.

For the Vickers microhardness (VH) test other 12 M were selected and inlays

prepared as mentioned above. Six inlays were luted with Z100 (group 5), while

the other six were luted with C&B (group 6). Teeth were embedded in resin

and sectioned in buccal–lingual direction with a microtome cooled with tap

water. VH of the luting materials was measured on the bottom of the cavity

sections and on the resin composite in the middle of the inlays; microhardness

was correlated with the cavity depth. All data were statistically analyzed with

the Mann–Whitney test. There was no statistical difference between the two

luting materials in the dye infiltration degree both in thermocycled and no

thermocycled samples, although the highest infiltration was observed in the

samples luted with the self-curing cement in group 4. Z100 showed higher

Vickers microhardness (VH) values than C&B ( p , 0.05), but lower than the

inlay material. A significant correlation ( p , 0.05) between VH and cavity

depth was found only for Z100. Microinfiltration was low for both materials,

while the microhardness was higher in the Z100 samples, associated with an

easier material manipulation than C&B. Resin inlays luted with a photocuring

composite represent an excellent choice for the restoration of posterior teeth.

7. In vivo evaluation of new calcium hydroxide points for intracanal

medications; G. Gambarini, G. Bologninip, A. Lupi, L. Testarelli,

M. Bossu’, Polimeni, A., Ottolenghi, L., Barbato, E., De Biase, A.,

(University of Rome, Dental School)

A new formulation of calcium hydroxide has recently been developed

(CaOH Plus, Roeko, Germany) for easy placement and removal of the

intracanal medicament. Since the clinical properties of calcium hydroxide

can change depending on the different vehicles, the purpose of the present

study was to compare in vivo tissue response with the new material and

chemically pure Ca(OH)2 pastes. Twenty patients scheduled for extraction

for periodontal disease were selected for this study and divided into two

homogeneous groups. The written consent of the patients was obtained after

the nature of the procedures and the possible discomfort and risks had been

fully explained. Chemio-mechanical preparation of the endodontic space

was performed using a crown-down instrumentation technique and

irrigation with 5% NaOCl and 17% EDTA. The two different intracanal

medications were then placed in the root canals. After 14 days all teeth were

extracted and processed for histopathological evaluation. Tissue response

to the intracanal medicament was scored as follow: (1) none/mild; (2)

moderate; (3) severe. Data were collected and assessed using the Mann–

Whitney–Wilcoxon test. Results for Group A (CaOH Plus) were 80%

none/mild and 20% moderate. The same score was reported for Group B

specimens (Ca(OH)2). No statistically significant differences ( p . 0.05)

were noted between the two groups. Overall, histological sections showed

that tissue response to CaOH Plus cones appeared not to be distinguishable

from the response to chemically pure Ca(OH)2.

8. Effect of burnout schedule on thermal expansion of phosphate-

bonded investments; L. Borchersp, J. Heine, P. Ohnmacht, U. Schmitt

(Medical University of Hannover, Hannover, Germany)

Modern phosphate-bonded investments are suited for accelerated

bench-set and burnout schedules offering substantial savings in laboratory

time. Some of these materials may as well be processed according to the

conventional, considerably more time consuming technique. Since the

effective heating rates applied in both cases differ by approximately two

orders of magnitude, the reactions and phase transitions within the

investment might well be completed to a different extent. Thus, the

associated volume changes and the fit of cast restorations would be different

for both techniques. In order to verify this hypothesis and to find an

explanation for recently reported differences in fit of crowns made

according to both methods, we studied the effect of burnout schedule on

thermal expansion of six commonly used and one experimental investment

for high gold crown and bridge alloys.

The materials used in this study are listed in Table 1. Cylindrical

specimens (diameter 5 mm, length 20 mm) were prepared in silicone

molds. The specimens were demolded 60 min after start of mixing, and

drying at (23 ^ 1) 8C for an additional 60 min. Immediately thereafter, they

were transferred to a computer-controlled, calibrated, horizontal quartz rod

dilatometer and heated to 950 8C using one of the following schedules:

constant heating rates of (a) 5 K/min, (b) 50 K/min, and (c) 200 K/min, (d)

thermal shock in dilatometer preheated to 950 8C for simulating accelerated

burnout, and (e) conventional schedule as recommended by the

manufacturer. Final readings of expansion were taken after the end

temperature had been held constant for 15 min. Measurements were

corrected for offset errors and converted to percentage values with respect

to the initial length. Three specimens were tested per material and schedule.

ANOVA and Scheffe tests were performed in order to reveal significant

influences of schedule type on expansion.

The mean values reported in Table 1 are ranging between 0.60 and

1.15% and do not show much variation for a given material. Maximum

expansion is always accomplished either with the slowest heating rate or

with the conventional procedure, whereas shock heating or one of the

higher heating rates leads to lower expansion. Though differences between

shock and conventional heating are significant in all cases with the

exception of Experimental, they amount to only 0.21% at the most, which is

of minor importance clinically. Therefore, with respect to thermal

expansion alone, all materials tested seem to be suited for preparing well

fitting casts using either accelerated or conventional burnout schedule.

Abstracts / Dental Materials 18 (2002) A1–A23 A3

9. Surface analysis of 5 esthetic materials after polishing;

M. Cadenaroa,p, M. Biasottoa, R. Chiesab, R. Di Lenardaa, E. Dorigoa

(aUniversita’degli Studi di Trieste, Trieste, Italy; bPolitecnico di

Milano, Milano, Italy)

Obtaining a smooth surface is a prime objective for composite resin

restorations, in order to avoid plaque retention and surface staining and

improve esthetics. Curing the material against a Mylar strip produces the

smoothest surface, however, the removal of excess material or recontouring

of restorations is often necessary clinically. It has been suggested that a

perfectly smooth surface is virtually unattainable with current polishing

techniques. Bollen et al. (1996) indicated the existence of a threshold

roughness (0.2 mm) below which no influence on the bacterial adhesion

should be expected. The aim of this study was the in vitro evaluation of the

surface roughness of five esthetic materials (Surefil, Dentsply; Definite,

Degussa; Ariston pHc, Vivadent; Solitaire, Kulzer; Z100, 3M) polymerized

with an halogen curing light (VIP, BISCO Inc.) and a plasma arc lamp

(Apollo 95E, Dental/Medical Diagnostic System Inc.), following finishing

and polishing. Using a metal mold, 10 block specimens (5 £ 5 £ 2 mm3)

were prepared from each material. A Mylar strip was placed on both sides

of the mold. Five specimens from each material were cured applying the

curing tip of VIP on the top surface for 40 s (group 1), while the other five

were polymerized with Apollo 95E for 9 s (group 2). In both groups the

surface exposed to curing light was finished and polished with the

ENHANCEw system (Dentsply). The opposite surface was not treated and

served as a control. Both surfaces of each specimen were analyzed with a

laser profilometer (UBM microfocus): the roughness average (Ra) was

evaluated. The Vickers microhardness of the polished surfaces was also

calculated. All data were statistically analyzed with the Mann–Whitney

test. The regression test was carried out to evaluate the possible correlation

between roughness and microhardness. All surfaces polymerized against

the Mylar strip presented in both groups a mean Ra lower than 0.2 mm.

Roughness was significantly increased in both groups in the treated

surfaces, with a mean Ra higher than 0.2 mm. The plasma cured non-

polished surfaces presented lower Ra values than in the halogen light group.

It was observed that the higher the Ra values, the lower the microhardness

values, although a significant correlation was obtained only for Ariston pHc

and Solitaire. These two materials presented very low microhardness

values, clinically inadequate for posterior restorations if compared to the

conventional composite Z100.

10. Effect of sodium hypochloride on dentin: a high resolution SEM

study; L. Breschia, S. Chersonia,p, L. Montebugnolia, M. Toledanob,

R. Osoriob, G. Mazzottia, C. Pratia (aUniversity of Bologna, Italy;bUniversity of Grenada, Spain)

The use of sodium hypochloryde (NaOCl) to remove the collagen fibrils

(CF) on dentin as to improve the dental adhesion is controversial. The

purpose of this study was to evaluate the effect of different times of

application of a 5% solution of sodium hypocloride on the dentin surface

after application of different acids solutions.

Eighteen extracted human molars were selected and randomly assigned

to the tested etching treatments. Dentin disks were obtained with a low

speed diamond saw and treated with: (1) 10% maleic acid, (2) 10% citric

acid, (3) 2.5% oxalic acid, (4) EDTA, (5) 35% phosphoric acid, (6) no

etching. Acids were left on the dentin surface for 15 s, then NaOCl was

applied for 2 and 5 min. Control specimens without the NaOCl application

were also prepared. Dentin disks were then fixed, dehydrated, mounted on

stubs and finally observed under a high resolution SEM (Jeol JSM-890).

The application of sodium hypochloride on dentin showed different

morphological features depending upon the etching agent previously applied

to demineralize the dentin surface. In particular, the application of maleic and

citric acid on the dentin surface revealed similar features, such as complete

removal of the smear layer and smear plugs and the exposure of the acid of

several CF on the intertubular (ITD) and peritubular dentin. After the

application of NaOCl for 2 min most of the CF of the ITD were completely

removed, while residual CF were evident only in small areas; on the other hand

no evidence of CF was present in any of the maleic and citric acid etched

specimens after 5 min application of NaOCl. Oxalic acid resulted in the

formation of several crystal salts on the ITD. The use of NaOCl revealed minor

modifications of the dentin surface. EDTA surface conditioning resulted in

uncompleted opening of the tubules and a very superficial demineralization of

the ITD. After the use of NaOCl at both times of application tested, a very

compact ITD as well as residual CF were observed under a thick mineral

coating. On the other hand the use of NaOCl on phosphoric acid etched dentin

revealed an enlargement of the tubule orifices particularly evident after the

5 min application, while the treatment with NaOCl produced minor changes

on the dentin surface of the unetched specimens.

Conclusions. The application of different acid treatments is responsible

for different morphological modifications of dentin surface that can greatly

influence the effectiveness of NaOCl. The combined application of acids

and NaOCl may represent the correct approach in the preparation of dentin

surface to obtain a thin and effective hybrid layer. After 2 min application

of a solution of 5% NaOCl residual collagen fibrils were evident, while no

organic remants were observed after 5 min application on phosphoric,

maleic and citric acid etched samples.

11. Analysis of leachable monomers of composites by NMR1H in

solution; I.C. Correap, M.I.B. Tavares, W.G. Miranda Jr (Dental

Materials-University of Sao Paulo and IMA-UFRJ-Brazil)

Several studies used infrared spectroscopy to evaluate the degree of

conversion by the detection of remaining CyC. This remaining double bond

was due to non-reacted and pendant monomers. The presence of unreacted

monomers after photo-activation of dental composites causes mechanical

and biological properties to decrease and could be detected by NMR

analysis. The aim of this study was to evaluate the percentage of leachable

monomers of light curing composites under the effect of variations of

exposure time of photoactivation by nuclear magnetic ressonance of

hydrogen in solution (NMR1H). Cilindrical specimens (d ¼ 5 mm and

h ¼ 3 mm) of Z250. FillMagic (hybrid composites), Durafill and A110

(microparticles composite), of shade A3, were light-cured for 20, 40 and

80 s with Optilux 401 curing unit (500 mW/cm2). The unreacted monomers

Table 1

Thermal expansion (%) for different investments and temperature schedules ðn ¼ 3Þ

Material Manufacturer 5 K/min 50 K/min 200 K/min Shock Conventional

Bellavest SH Bego, Germany 0.98 0.82 0.80 0.84 1.04

Fujivest Super GC, Japan 1.02 0.98 1.01 1.00 1.12

Heravest Speed Heraeus, Germany 0.98 0.84 0.81 0.78 0.93

PowerCast WhipMix, USA 1.13 0.92 0.93 0.93 1.10

Presto-Vest Siladent, Germany 1.15 1.13 1.13 1.07 1.15

Experimental Dentaurum, Germany 1.03 0.83 0.88 0.95 1.02

FastFire 15 WhipMix, USA 0.86 0.71 0.60 0.62 0.83


of each specimen were extracted after a 1-day and 7-days immersion in

deuteraded chloroform, and analyzed in a spectrometer VARIAN

MERCURY 300. The 1H spectra of all specimens showed leachable

monomers unreacted after extracting (shown in the table), by the detection

of 5.6 and 6.1 ppm signals of CH2y groups. After 7 days, only the

specimens of manufacturer time of exposure were immersed in a new

deuteraded chloroform for 2 weeks, to optimize the monomers extraction.

The table shows the percentage of non-reacted monomers leached after

different exposure times.

The shadow values correspond to the manufacturer’s time of photo-

activation.

Z250 and FillMagic obtained similar values of unreacted monomers (%) at

photocuring time suggested by the manufacturer and values were also lower

than Durafill and A110 concentrations. A 1-day extraction time was efficient to

quantify the total amount of residual monomers for Z250, FillMagic and A110.

PRONEX-CNPq 0327.00/00 e CAPES

12. Clinical evaluation of esthet-x composite resin; J.R. Dunnp, C.A.

Munoz, R. Kinzer, D.E. Tan, J. Sy-Munoz, A. Wilson (Loma Linda

University, Loma Linda, CA)

This Clinical Trial evaluated the clinical performance of a new

polychromatic high density composite resin (Esthet, X., L.D. Caulk) over a

two year period. Forty-three anterior and posterior restorations were placed

in 27 subjects (36 at 1 Year). Following cavity preparation the teeth were

etched, restored, and polished following manufacturer’s instructions.

Marginal adaptation (MA), Anatomic Form (AF), color match (CM),

secondary caries (SC) marginal discoloration (MD) and polishability (PO)

were evaluated. At 2 years, using a modified USPHS grading systems the

following results were found in percentages (%) (BL ¼ Base Line):

At the 2-year recall: (1) categories MA, AF, and SC were unchanged from

baseline; (2) MD showed a decrease in restoration quality, (3) PO showed that

restorations polished adequately at baseline but showed increase in the surface

polish over time, while restorations polished inadequately at baseline had a

decrease in surface polish and (4) Overall clinical performance is acceptable

for routine clinical use. Study supported by L.D. Caulk/Dentsply.

13. The influence of cold working and thermal treatment of the fit of

implant-supported fixed partial dentures; Salman Lakhani, Carlo

Ercolip, Gerald N. Graser, Ross H. Tallents, Mark E. Moss (University

of Rochester Eastman Dental Center, Rochester, NY, USA)

Purpose. The fit of porcelain-fused-to-metal frameworks has been

shown to substantially change after porcelain application. It has been shown

that a significant reduction in metal distortion was evident, in single

castings, when the oxidation cycle was completed before the prosthesis was

cold worked (finished). This study compared the fit of implant-supported

porcelain-fused-to-metal fixed partial dentures when different thermal

treatments are performed.

Material and methods. Fifteen implant-supported porcelain-fused-to-

metal fixed partial denture frameworks were fabricated on a machined

aluminum base and randomly divided in three groups: Group 1. Cold

working and unrestrained thermal oxidation. Group 2. Unrestrained thermal

oxidation, cold working, unrestrained thermal oxidation. Group 3.

Phosphate-bonded investment-restrained thermal oxidation, cold working,

unrestrained thermal oxidation. After this treatment, porcelain was applied

to all frameworks. Three-dimensional changes (x, y, and z ) were monitored

by measuring the frameworks (three times) after each step (oxidation, cold

working, opaque porcelain application, dentin porcelain application, and

glaze stages) with a digital Mitutoyo caliper (error ¼ ,1 mm). Intraobser-

ver reliability was determined by measuring two fixed partial dentures at 4

weeks interval (coefficient of variation ¼ 0.05–0.13). Data was analyzed

with repeated ANOVA and Tukey studentized range test. Statistical

significance was set at P ¼ ,0.05. Distortion trends in each group

(Positive ¼ away from the measuring references; Negative ¼ toward the

measuring references) were also assessed.

Results. Mean total absolute distortion was not significantly different

among groups (P . 0.05). No significant difference among groups was

found in the distortion after thermal treatment (P . 0.05). Absolute values

of distortion at each step were not significantly different among groups

(P . 0.05). Specific patterns of distortion were found in each group. These

trends of distortion were somehow maintained throughout the experiment.

Indeed, group 1 castings generally deformed in a positive direction (away

from the measuring references) while castings in group 2 deformed in a

negative direction (toward the measuring references). Group 3 frameworks

showed the greatest amount of negative distortion (toward the measuring

references).

Conclusions. Heat treating implant-supported porcelain-fused-to-

metal fixed partial denture frameworks before cold working (finishing)

did not decrease the absolute distortion. Specific patterns of distortion

are found when different heat treatments are performed. The authors

therefore suggest that, if the purpose of the heat treatment is to allow

casting stress relief and recrystallization of the alloy with minimal

distortion, it is important to select a restraining material that has

pattern and magnitude of thermal expansion similar to those of the

metal.

This project was partially supported by a 1999 American Academy of

Fixed Prosthodontics Stanley D. Tylman Research Grant.

Z250 FillMagic Durafill A110

20 s 40 s 80 s 20 s 40 s 80 20 s 40 s 80 s 20 s 40 s 80 s

1 d 2.45 1.98 1.55 4.5 2.48 2.22 7.27 5.9 4.74 7.76 4.24 3.36

7 d 2.34 1.96 1.97 6.25 2.49 2.22 8.30 7.57 6.89 8.57 4.48 3.29

þ14 d 0 – – – 0 – 0 – – – 0

MA AF CM SC MD PO

BL 1Y BL 1Y BL 1Y BL 1Y BL 1Y BL 1Y

Alpha 54 50.0 84 92.1 53 50 100 100 100 73.7 47 73.7

Bravo 46 50.0 16 7.9 47 47.4 0 0 0 23.7 43 21

Charlie 0 0 0 0 0 2.6 0 0 0 2.6 0 0

Delta 0 0 0 0 0 0 0 0 0 0 0 5.2


14. The influence of bur wear on cutting efficiency and heat production

during osteotomy preparation for dental implants: A study of bur

durability. Ercoli Carlop, P.D. Funkenbusch, T.D. Greene, H.J. Lee,

M.E. Moss, U. Ben-Hanan, G.N. Graser, R.H. Tallents, K.S. Hebel

(Department of Mechanical Engineering, University of Rochester

Eastman Dental Center, Rochester, NY)

Introduction. Excessive surgical trauma is considered an important

cause of implant failure. During bone drilling, most of the energy not used

in the cutting process is transformed into heat, and the amount of heat will

depend on several factors (i.e. drill flute geometry and sharpness, torque,

chip removal rate, bone density etc.). Repeated use of drills progressively

increases their wear and decreases their cutting efficiency, thus producing

more frictional heat. A review of the literature has shown that there are no

scientific established guidelines on the durability of drills used to prepare

osteotomies.

Purposes. (1) To determine the maximum number of osteotomies that

can be prepared with several implant drills without causing a temperature

increase damaging to the bone. (2) To determine the relationship between

osteotomy depth and heat production during consecutive osteotomies.

Cutting efficiency and heat production of different drill designs (i.e. spade,

twist, tri-flute, TiN coated) were evaluated and compared during 100

successive osteotomies. Materials and methods. Bovine ribs were used in

this study. Two positioning holes were drilled at the base of each bone

piece. Two thermocouple holes were also drilled at 1 mm distance from the

future osteotomy site. Two chromega/constantan thermocouples were

inserted into the bone block to the predetermined depths of 5 and 15 mm.

Parallelism between the thermocouple canal, the future implant site and

positioning holes was achieved by positioning the bone to a bi-directional,

micrometer-controlled (x,y ) translation slide secured to a press stand base.

A silicone heat-transfer compound was injected into the thermocouple

canals to facilitate heat transfer. The bone block was positioned in the

cutting apparatus holder by placing metal pins in the positioning holes. The

handpiece was secured to a pneumatic cylinder-driven translation slide so

that the drill was kept in a horizontal position (force ¼ 2 kg). The rotational

speed, torque and amount of room temperature water (external cooling)

were, respectively, 1500 rpm, 37 N cm, and 40 ml/min. An electronic valve

allowed a back and forth motion of the translation slide/handpiece assembly

to simulate the clinical setting. Drill position was monitored with a LVDT.

A computer software program controlled the handpiece back and forth

motion and recorded the handpiece displacement (depth of cutting),

temperatures, and drilling time. Total drilling depth was 15 mm. The

computer-driven assembly performed this drilling in four progressive

cycles (respectively, 2, 3, 5, and 5 mm advancements). Tested drills were:

Nobel Biocare, Implant Innovations, Steri-Oss, Paragon, Implamed,

Lifecore, and ITI. Initial drilling was performed with a 2 mm-diameter

drill. The osteotomy was then enlarged with a 3 mm-diameter drill. When

these bur diameters were not available (Steri-Oss, Paragon, and ITI), the

closest diameter was used. Data analysis. After outliers were removed (they

were defined as observations more than three standard deviations away

from the group mean), single factor ANOVA and Tukey Multiple Range

Test (P ¼ ,0.05) were used to compare removal rates among groups. Data

is reported for the 2 mm burs. Temperature data was analyzed with a T-Test

(start, peak and increase in temperature for all groups) and with ANOVA

and Tukey Studentized Test (among groups). Temperature data in the first

and last five osteotomies is presented.

Results. Nobel Biocare and 3I drills mean removal rate was significantly

greater than the other drills (P , 0.05). TiN-coated drills (Steri-Oss,

Paragon) showed statistically significant (P , 0.05) lower removal rates

than non-coated drills. Two-flute twist drills (Nobel Biocare, Lifecore, 3I,

ITI, Implamed) showed statistically greater removal rates compared to tri-

flute (Paragon) and spade drills (Steri-Oss). Mean starting temperature for

the two thermocouples were 28.46 (15 mm) and 30.45 8C (5 mm). Mean

peak temperatures (15 mm: 30.98 8C; 5 mm: 31.94 8C) and increases in

temperature (15 mm: 2.52 8C; 5 mm: 1.49 8C) were not statistically

different. Temperature increase for Paragon drills at 15 mm depth was

significantly higher than the other groups; this increase (4.57 8C), however,

was not clinically significant. Temperature increase at 5 mm depth was not

statistically different among the groups.

15. Operator variability influence on marginal seal of Class II resin

restorations; A. Fabianellip, M. Ferrari, A. Dagostin, S. Grandini

Aim of this study was to evaluate the effect of the operator variability on

the marginal sealing of resin composite restorations bonded using an

experimental dual-curing bonding system under laboratory conditions.

Eighty freshly extracted sound posterior teeth were prepared according to

standardized procedure obtaining mesio-occlusal Class II cavities. The

samples were randomly divided into four groups and the composite

restorations were made by four operators, having different levels of clinical

experience. An experimental dual-curing adhesive system (Excite DSC)

was used in its self-activating and light-curing version (Subgroup a and b),

in combination with a microhybrid resin composite (Tetric Ceram). A

microleakage evaluation was performed and the scores recorded were

tested for statistical significance by Newman Keuls and Kruskal-Wallis

multi-comparison test at p , 0.001. Three samples of each group were

selected and prepared for SEM observation. Score 0 ( ¼ no leakage) was

detected in a higher number of samples of Subgroup a than of Subgroup b.

In Subgroup a, the non-parametric one-way analysis of variance showed a

non-significant difference in the extent of leakage on enamel site among the

four groups and a significant difference between Group 1 and Group 2, 3

and 4 at the dentin–cementum site. In Subgroup b, there was no significant

difference among groups on enamel; on dentin, Groups 1 and 2 differed

significantly from Groups 3 and 4. The SEM observations showed gap

formation in Groups 1 and 2 at the interface between adhesive resin and

resin composite and/or adhesive resin and dentin. In the samples of Groups

3 and 4 the specimens did not show gaps along the adhesive interface and

rarely a gap was noted between hybrid layer and resin composite. It can be

concluded that even with less technique-sensitive bonding systems of last

generation, like the one tested in this study, a persistent operator variability

existed.

16. Verification jig for implant-supported prosthesis: a comparison of

standard impressions with verification jigs made of different materials;

Jorge E. De La Cruz, Paul D. Funkenbusch, Carlo Ercolip, Mark

E. Moss, Gerald N. Graser, Ross H. Tallents (University of Rochester—

Eastman Dental Center and Department of Mechanical Engineering,

Rochester NY, USA)

Purpose. Non-passive implant prostheses are associated with a greater

occurrence of screw loosening and fracture. Verification jigs are clinically

used to verify the accuracy of the master cast and correct eventual errors

after impression making. While the fabrication of verification jigs is an

additional step during the fabrication of implant-supported prosthesis, jigs

are widely used and several techniques and materials have been suggested

for their fabrication. There is, however, no evidence in the literature

confirming their greater accuracy relative to impression making, nor

comparing the dimensional accuracy of verification jigs made of different

materials. This study compared the dimensional accuracy of verification

jigs with that of conventional impression procedures, and to measure the

dimensional accuracy of three resin materials used to fabricate verification

jigs.

Methods/materials. A master stone base was fabricated with a

preexisting implant-supported fixed partial denture metal framework

(Master Framework). The master base had three implants (Center: C,

Left: L, and Right: R). Thirty verification jigs and 20 impressions

were fabricated from this master base according to the following

groups: Group 1. Jig: GC pattern resin. Group 2. Jig: Duralay resin.

Group 3. Jig: Triad Gel resin. Group 4. Impression: Closed-tray


impression copings. Group 5. Impression: Open-tray impression

copings. X and Y coordinates of each implant center were used to

calculate inter-implant distances (CL, RL, LC) based on Pythagorean

theorem. Z measurements were calculated relative to the master

framework and to the center implant (fixed point). Distortion in the Z-

plane was measured at two locations (ZR; ZL) corresponding to the

right and left terminal implants. Mean three-dimensional accuracy of

the experimental bases obtained from each jig or impression group

was compared with the master base with a traveling microscope and a

Mitutoyo caliper (error ¼ ,1 mm). Data was analyzed with ANOVA

and Tukey Studentized Range test. Statistical significance was set at

p ¼, 0:05:

Results. All the results are expressed in microns with standard

deviations in parenthesis, and groups with the same letter are not

significantly different:

Conclusions. The accuracy provided by verification jigs was not

superior to standard impression procedures. Therefore, we suggest that jig

fabrication does not improve the accuracy of stone casts. Open-tray

impression copings showed a significant greater inaccuracy in the vertical

plane.

This project was supported by the 2000 American Academy of Fixed

Prosthodontics Stanley D. Tylman Research Grant.

17. Hydrolytic instability of dental glass-ionomer cements; L. Fanop,

M. Bonanini, S. Pizzi, V. Fano (University of Parma, Italy)

When restorative materials take up water, their dimensions and

structural integrity may be affected. In this work, glass-ionomer cements

(GIC) and resin modified glass-ionomer cements (RMGIC) were analyzed

by laser beam scanning micrometer during the setting reaction. After

mixing in room atmosphere and storage in water or in lactic acid solution,

the porosity, filler distribution and gel layer, which was formed at the

filler/matrix interface, were tested by stereomicroscope and confocal laser

spectroscope. To observe the microstructure with this last technique, the

specimens were treated with fluorescent dye solution before the test. After

45 days in water, the uptake of water by the matrix clearly showed a

swelling process. The degradation of the materials involved two processes:

one was related to the matrix and induced swelling of the surface, opening

of surface bubbles, diffusion of entangled molecules, and subsequent

formation of gelatinous layers both in water and acid environment; the other

involved the removal of the gel layer and the missing of the filler particles

from the surface. The first process was the same for all maturated matrixes.

The second process was affected by the setting mechanism. For Fuji II,

setting by acid-base mechanism, this lifetime in water was about 45 days,

and was several months longer for other materials. After 45 days in acid

environment at pH3.5, only Vitremer showed unchanged filler structure.

18. Influence of sodium fluoride in watery solution on dentin

permeability; A. Fondip, G. Lorenzini, S. Parrini (University of Siena,

Siena, Italy)

Dentin permeability and its related tooth hypersensitivity is a common

and important problem since it can effort oral comfort.

The purpose of this study was to investigate desensitizing activity of a

sodium fluoride in watery solution to reduce dentin permeability and tooth

pain. The study group involved 29 patients (14 male and 15 female) which

presented spontaneous hypersensibility (cervical wear), or secondary

hypersensitivity (prosthetic preparations or conservative therapy); in total

sixty-five sites were evaluated: 30 were represented by Class I or II cavity

preparation, 24 by prosthetic abutments and 11 by cervical lesions.

Teeth were cleaned using a medical solution to remove smear layer and

then the exposed dentin was abudantly covered with sodium fluoride

emulsion by micro-sponge.

Dentin sensitivity was evaluated by cold air jet before the application of

fluoride varnish, the same test was repeated after 30 s. The degree of tooth

sensibility was expressed by the patient according to a Visual Analogic

Scale (V.A.S.) with 0–10 subdivision. When we used anaesthesia the

evaluation was performed after normal sensibility reappearance.

The results were submitted to statistical analysis by T-Student test. A

critical reduction of dentin sensitivity was observed after the application of

fluoride varnish (P , 0.001).

19. Osteoblast-like cell adhesion on bioactive glasses: surface reactions

and resistance to trypsinization; S. Foppianoa,p, A.P. Tomsiab, G.W.

Marshalla, T. Breuniga, D.J. Rowea, S.J. Marshalla (aUniversity of

California San Francisco; bLawrence Berkeley National Laboratory

Berkeley, CA, USA)

We have developed bioactive glass coatings of Ti alloys that

provide good metal adhesion while retaining bioactivity. Two of the

glasses (6P1 and 6P8) proved to be suitable substrates for the

attachment of osteoblast-like cells. Osteoblast-like cells, when seeded

on glass 6P8, showed remarkable resistance to detachment by

trypsinization. The purpose of this study was to investigate two

possible mechanisms underlying trypsin resistance of MG63 osteoblast-

like cells on glass 6P8: (1) trypsin inactivation by solubility products

released from glass 6P8 in tissue culture medium; (2) differential

protein adsorption on the substrates. Glass discs of the same dimensions

(B ¼ 12 mm) were finished through 0.05 mm alumina slurry, cleaned

by ultra-sonication in alcohol, sterilized in dry heat at 250 8C, and

placed in 12-well tissue culture plates (N ¼ 5 per material). Human

osteosarcoma (osteoblast-like) cells (MG63) were cultured in a-MEM

with 10% fetal calf serum and antibiotics. 4 £ 105 cells in a 20 ml

aliquot were plated on each glass or titanium alloy (Ti6Al4V), as a

control. Cells were allowed to settle for 1 h prior to flooding with

medium. After 30 min cells were treated with 1.5 ml of trypsin, either

fresh or previously incubated for 1 h with a disc of glass 6P8. Cells

were completely detached from Ti6Al4V at 5 min and glass 6P1 at

10 min. After 15 min cells were still adhering onto glass 6P8, as

previously observed. Therefore, cell adherence does not seem to be due

to glass 6P8 reactivity products inactivating trypsin. Then specimens of

the same two glasses and Ti6Al4V (control) (N ¼ 4) were prepared, as

described above, and incubated with 2 ml of fetal calf serum for 2 h at

37 8C. Samples were gently rinsed with PBS to remove weakly

adsorbed proteins and desorbed with 10 rinses of 500 mL of 0.1%

sodium dodecyl sulphate (SDS). The SDS rinses were collected and

analyzed for protein concentration, using a spectrophotometric assay

(BioRad Laboratories, and Molecular Devices n max kinetic microplate

Group C-L L-R R-C ZR ZL

Group 1 0.055(0.042) BA 0.049 (0.028) A 0.038 (0.027) B 0.097 (0.026) B 0.06 (0.025) B

Group 2 0.059 (0.045) BA 0.046 (0.04) A 0.09 (0.035) A 0.10 (0.044) B 0.053 (0.024) B

Group 3 0.078 (0.082) A 0.048 (0.05) A 0.049 (0.043) BA 0.087 (0.045) B 0.07 (0.03) B

Group 4 0.012 (0.013) B 0.04 (0.029) A 0.03 (0.024) B 0.065 (0.055) B 0.05 (0.036) B

Group 5 0.034 (0.034) BA 0.057 (0.031) A 0.039 (0.049) B 0.262 (0.157) A 0.33 (0.189) A


reader) with serum albumin as the standard. Data normalized to sample

surface area showed significant differences in the amount of protein

adsorbed per unit of surface area among substrates (6P8 . 6P1 .

Ti6Al4V, one-way ANOVA p , 0.001). Aliquots of the same samples were

fractionated by SDS–polyacrylamide gel electrophoresis, and the proteins

visualized by staining with Coomassie blue. The distribution of the bands

indicated differential protein adsorption between the bioactive glasses and

Ti6Al4V. Glass surfaces were analyzed by Fourier transform infrared

spectroscopy (FTIR) before and after the protein adsorption experiments to

identify surface reactions and residual adsorbed proteins. FTIR surface

analysis showed that glass 6P8 readily reacted in solution, forming silanols,

while glass 6P1 did not. These results indicate that resistance to

trypsinization of osteoblast-like cells from glass 6P8 may be due to

differential protein adsorption but not to trypsin inactivation. Supported by

NIH/NIDCR Grant DE 11289.

20. Ability of NiTi instruments to shape endodontic walls: a comparison

with manual and mechanical techniques; F. Foschip, S. Marchionni,

M. Mercuri, C. Prati (Department of Dental Sciences, Alma Mater,

University of Bologna, Italy)

Introduction. The aim of this study was to evaluate the ability to

shape apical and medium third of endodontic dentin walls using two

different mechanical NiTi techniques and one manual crown-down

conventional technique.

Materials and methods. The study was conducted upon a sample of

30 extracted human teeth (incisors with straight or slightly curved,

,58, single canal). After coronal removal, each root was firstly

prepared with a #10 K file for the evaluation of working length. Three

different instruments and techniques were used (10 teeth for each

group): crow-down/K file with manual technique (FKG), mechanical

technique with NiTi Hero 642 (Micromega) and mechanical technique

with NiTi Race (FKG). NaOCl 5% and EDTA irrigations were used in

each technique. After the preparation, each sample was split vertically

into two halves with chisel. Each sample was fixed in 4%

glutaraldeyde in 0.2 M sodium cacodylate buffer, dehydrated in graded

concentration alcohol, air dried, then gold sputtered and observed

with SEM. Observations were obtained at a magnification of

£1000– £ 5000. Each specimen was evaluated in its three main

area (coronal, middle and apical third), comparing its aspect with a

predefined scale of values regarding four different parameters (smear

layer, presence of pulpal and inorganic debris, homogeneous surface

profile) in order to have a score to all the area of each one. Not-

parametric statistic analysis for the type of instrument employed was

made.

Results. No significant difference was found among the two mechanical

instrumentation, instead a significant difference was found among HeRo

642-Race and the manual instrumentation with K file. It was evident that the

main difference could be observed at the apical third: manual instrument

allows a more precise surface profile, showed a thin not-layered smear

layer, the lack of pulpal and inorganic debris in comparison with

mechanical instruments.

Conclusion. Conventional manual technique with K file permits better

results in comparison with mechanical techniques with NiTi instruments

(HeRo 642 and RaCe), because of the well known importance of an

adequate cleansing of canal surface to avoid relapses and failure of the

endodontic treatment.

21. A new histological technique to study the interface between tooth

tissues and adhesives restorative materials; M. Grandep, F. Ricciardi,

L. Cianconi (University of Rome Tor Vergata, Italy)

In the past years, diverse microscopic techniques have been used to

investigate the interfacial relation between restorative materials and dental

tissue. SEM is the most widely used device to study the ultrastructure of the

hybrid layer, but the procedure which is necessary to prepare the specimens

could produce artifacts.

The cofocal microscope allows for an observation of the specimen

under less critical conditions. However, the traditional methodologies

utilized to prepare the hystological sections need procedures like

decalcification, dehydration, embedding and wearing, which can give

artifact as well.

The authors tested this new technique defined ‘fresh cut’ which allowed

the specimen to be cut immediately without its dehydration or embedding.

In this study, class V cavities have been restored with adhesive amalgam,

compomer and flowable composite. The samples were fixed on a stub and

cut longitudinally in three or four sections about 100 mm thick by a

diamond saw (Exact, Bio Optica). Each section was grounded using a

diamond disk (3M, Dental Products St Paul, MN 55144), cleaned with

phoshoric acid 37% for 15 in. and washed with distilled water. The

specimen were stained with toluidine blue (pH 4.4) and methilene blue (pH

7.3), and observed with a cofocal microscope (LSM, C. Zeiss, 73428 Aalen,

Germany) in conventional light, in bright field or in differential interference

contrast (DIC).

From the samples reserved for the SEM observation negative replicas

were prepared using a low viscosity polyether.

The ‘fresh cut technique’ showed a perfect preservation of the soft and

hard tissue of the tooth, and restorative materials. The technique allowed for

the evaluation of gaps, adaptation of the material to the dental structures and

the microscopical morphology of the hybrid layer. The staining technique

allowed for a differentiation of the dental structure, restorative materials,

hybrid layer and resin tags as well.

The SEM observations have been invalidated by the presence of notable

detachments which were not noted in the negative replicas. This is due to

the dehydration and contraction of the dental structure, and to the

observations in high vacuum, which are critical points for the study of

the biological tissues. For these reasons SEM cannot be used for the study

of marginal adaptation and gaps of restorative materials to the dental

structures.

22. SEM investigation of the surface of fiber posts after cutting

procedures; S. Grandinip, P. Narducci, P.F. Porciani, M. Ferrari

(School of Dental Medicine, University of Siena, Italy)

Aim of this study was to evaluate the surface of different types of fiber

posts after cutting with different methods, and to investigate if different

cutting procedures can affect the integrity of the posts. Among those available

in the market, six types of fiber posts were selected for this study: (1) Carbon

Smear layer Pulpal debris Inorganic debris Correct surface profile

Apical Middle Coronal Apical Middle Coronal Apical Middle Coronal Apical Middle Coronal

K file þ 2 2 þ 2 2 þ þ 2 þþ þþ þþþ

Hero 642 þþþ þ þ þþþ þ þ þ þ þ 2 þ þ

RaCe þþ þ þ þþ þ þ þ þ þ - þ þ


Fiber Posts (RTD), (2) Quartz Fiber Posts (RTD), (3) Aesthetic Posts (RTD),

(4) Aesthetic Plus Posts (RTD), (5) Translucent Posts (Dentatus), (6) FRC

Pertac Posts (Vivadent). Fifteen posts of each type were used as a single group.

All fiber posts had a diameter between 1.2 and 1.4 mm and a standardized

length (between 14 and 16 mm). Each single group was divided into three

subgroups, according to the cutting method: (a) Diamond bur, (b)

Carborundum disk and (c) Scissors. The samples were then processed for

SEM investigation. Analysis of fiber posts cut surfaces showed different

features mainly due to the cutting procedures. Uniform results were

found according to the type of cutting procedure. At low magnifications,

no microscopic differences were found among the samples of groups 1–

4 and 6. Only samples of group 5 showed more irregular surfaces after

being cut with the two procedures providing rotary instruments

(subgroups a and b). All groups showed evident differences between

cut surface of subgroup c samples and those of groups a and b. In

subgroup a, the posts showed regular surfaces after cutting with diamond

bur. Cutting with a carborundum disc (subgroup b) brought to an almost

regular surface, but sometimes with some irregularities more evident

close to the surface borders. In subgroup c the cut surfaces of all samples

showed two plane and convergent flanges; also due to formation of

fracture lines, these posts loose their integrity not only at the cutting

surface but also along their length. The results of this study indicated

that fiber posts can be cut using a diamond bur mounted in a handpiece

under copious water coolant. Although carborundum disc cutting

procedure (subgroup b) showed a less regular post surface, it can be

speculated that it might be clinically acceptable. The cutting procedure

using scissors must be avoided.

23. The role of fluoride in the antibacterial activity of Glass Ionomer

cements; A. Guidaa,p, S. Eramob (aUniversity of Limerick Ireland;bUniversity of Perugia, Italy)

Glass-ionomer cements (GICs) have been shown to possess antibacter-

ial properties. Fluoride released by the materials and low pH have been

reported to be the most important factors involved in these properties. The

aim of this study was to investigate whether or not fluoride was responsible

for the antibacterial activity of GICs. The antimicrobial properties of three

groups of GICs (fluoride and non-fluoride containing cements, commercial

GICs and cements with different fluoride release characteristics) were

tested against Streptococcus mutans and Actinomyces Viscous. Materials

were evaluated in both the freshly mixed and pre-set state. The inhibition of

bacterial growth by fluoride and poly(acrylic acid) solutions at different

concentrations was also evaluated. Standard agar diffusion assay method-

ology was applied in the study. The fluoride concentration of the agar

adjacent to the materials was also determined in order to investigate any

correlation between fluoride ion release and inhibition of bacterial growth.

An ion selective electrode was used for the fluoride measurement. Results

indicated that all materials tested were effective against both bacterial

strains in the freshly mixed state. Conventional GICs were totally

ineffective against either micro-organism in the pre-set state. In this state

only a number of light-activated GICs produced inhibition zones. A strong

correlation was observed between the fluoride concentration of the agar

adjacent to the cements and width of the inhibition zones produced by them.

It was concluded that fluoride was one factor directly responsible for the

antibacterial activity of GICs. The low pH of the materials while setting

appeared to play a decisive role in this activity.

24. Fracture strength of 3-unit inlay bridges after thermo-mechanical

fatigue in a chewing simulator; P. Hahnp, A. Peemoller, H.F. Kappert,

E. Hellwig (Department of Operative Dentistry and Periodontology,

University of Freiburg, Freiburg, Germany)

The purpose of this pilot study was to evaluate the fracture strength of

posterior inlay bridges after thermomechanical fatigue. The cavities were

cut with a newly invented device for standardized preparation of teeth

intraorally.

Eighty human caries free premolars and molars were used for the

experiments. Each two teeth were mounted a distance of 10 mm into

an acrylic base, roots coated with an artificial periodontal membrane

made from gum resin. The models were randomly divided into five

groups. In four groups standardized slots (small proximal inlay boxes)

were cut into the teeth with the new preparation device, and 32 slot-

retained bridges were fabricated (Remanium EH, non-precious alloy).

The size of the cavities was 2.5 mm mesio-distally and buccal-orally,

while the occlusal-cervical height, and the angle of diamond bur

differed.

The four slot retained groups were: (1) preparation angle 5.28,

occlusal-cervical height 3.5 mm, (2) preparation angle 5.28, occlusal-

cervical height 2.5 mm, (3) preparation angle 2.88, occlusal-cervical

height 3.5 mm, (4) preparation angle 2.88, occlusal-cervical height

2.5 mm, respectively. The slot bridges were treated tribochemically

(Rocatec), and adhesively fixed with Panavia F cement. In group (5)

eight partial-coverage crown bridges were prepared, and cemented

with zinc oxide phosphate cement. They served as control.

All samples were subjected to a dynamic load with synchronized

thermocycling (5/55 8C) in a dual-axis chewing simulator (250.000

chewing cycles). Afterwards the samples were quasi statically loaded

under 08 loading direction until fracture.

Except for group 4 (one bridge failed), survival rate after testing in the

artificial oral environment was 100%. The mean fracture strengths [N ] were

in: group (1) 2681.29 (^526.56), group (2) 2046.23 (^241.85), group (3)

2953.69 (^504.15), group (4) 2307.76 (^737.85), and group (5) 2722.93N

(^873.55), respectively.

ANOVA revealed significant differences concerning fracture strength

between the five groups ( p ¼ 0.025). There was no significant difference

between the control group (partial crown retained bridges) and the slot

retained bridges. Tukey’s test revealed significant higher fracture strength

values for the bridges with preparation size 2.88 angle and 3.5 mm cavity

height (group 3) than with 5.28 angle and 2.5 mm height (group 2,

p ¼ 0:013).

Within the limitations of this in vitro pilot study, the results indicate that

non precious alloy inlay bridges, adhesively fixed, could be an alternative to

conventional partial-coverage crown retained 3-unit bridges.

25. Class V preparation design and restoration materials analysis

in the first maxillary premolar through the finite element analysis;

Angelica Reis Hannasa,p, Estevam de Las Casasb, Tulimar

Cornacchiaa, Marcos Dias Lanzaa, Fabiano Carvalhob

(aDepartment of Restorative Dentistry, School of Dentistry;bDepartment of Structures, School of Engineering, Federal

University of Minas Gerais, Brazil)

The purpose of this study was to discuss a two-dimensional finite

element analysis in a class V preparation with and without retention groove

and restored either with composite resin or the sandwich technique (glass

ionomer þ composite resin).

Method. A numerical plane strain finite element study was carried

out, for which the maxillary first premolar tooth was used. All tissues

were assumed to be isotropic linear elastic—with the exception of

enamel, which was considered orthotropic. First, a model for the

sound premolar was developed. Then, the cavity class V was modeled

in the cervical area with and without a retention groove in the gingival

wall. The cavity was then filled with microhybrid composite resin and

an additional model was analyzed with glass ionomer under composite

resin restoration, simulating the sandwich technique. The models

contained between 6700 and 7200 linear strain triangular elements. A

unit horizontal load was applied and the resulting distribution of

tensile, compressive and shear stresses were analyzed. Results. Under


horizontal load, the obtained stress distribution in the cervical region

indicated that, for the empty preparation, there was shear stress

concentration in the retention groove and tensile stress in the class V

axial wall. Comparing the sound tooth and the restored one, the

restoration and the presence of the retention groove made no

significant difference in the stress distribution. When the tooth

restored with composite resin was compared with that restored with

the combination composite resin and glass ionomer, the latter

produced an increase of 18% in tensile stresses. Conclusions. It can

be concluded that either when filled with resin or using the sandwich

technique, did not result in new stress concentration areas. The groove

was not relevant in the stress distribution in the presence of the

restoration, as the mechanical properties of the resin are similar to the

dentine. When analyzing the stresses in the unfilled preparation, the

groove increased the stresses by approximately 18%.

26. Availability as a dental polymers of aromatic dimethacrylates

synthesized from bis(4-hydroxyphenyl)sulfone and bis(4-

hydroxyphenyl)ketone; Y. Hashimotop, M. Kawaguchi, K. Miyazaki,

M. Nakamura (Osaka Dental University, Osaka, Japan, Fukuoka

Dental College, Fukuoka, Japan)

The purpose of this study was to investigate the availability as dental

polymers of aromatic dimethacrylates synthesized from bis(4-hydroxyphe-

nyl)sulfone (BPS) and bis(4-hydroxyphenyl)ketone (BPO), which showed

little estrogenicity in our previous study.

Bis(4-(2-hydroxy-3-methacryloyloxypropyl)phenyl) sulfone (BPS-

GMA) and bis(4-(2-hydroxy-3-methacryloyloxypropyl)phenyl)ketone

(BPO-GMA) were synthesized from glycidyl methacrylate and BPS,

BPO, respectively, and characterized by IR spectrometer. Two monomers,

together with Bis-GMA were dissolved with DMSO and then diluted with

cell culture medium with 1% fetal bovine serum to final concentrations

ranging from 15.6 to 500 mM. HgCl2 as a positive control, was dissolved

with ddH2O and then diluted with cell culture medium with 1% fetal bovine

serum to final concentrations ranging from 1.56 to 50 mM. Human pulp

cells (HPCs) were seeded into 96- and 12-well multi-plate at

5 £ 103/100 ml and 5 £ 104 cells per well/1 ml of cell culture medium

with 10% fetal bovine serum, respectively, and then cultured for 72 h. The

medium in each well was changed to the specimens of six different

concentrations and cultured for another 24 h. The cell survival ratios seeded

into a 96-well multi-plate were calculated by WST-8 assay. IL-6 and IL-8

release from cells seeded into a 12-well multi-plate was investigated using

an ELISA test system according to the manufacturer’s instructions

(BIOSOURCE). Each aromatic dimethacrylate was diluted with triethylane

glycol dimethacrylate in a major ratio of 1/1. Photosensitizer was added to

the monomer to prepare three types of visible light-cured unfilled resin

systems. The unfilled resins were poured into a stainless ring and irradiated

for 40 seconds each. Knoop hardness (KHN) was determined using a

hardness tester.

Cell responses after exposure to BPS-GMA were very similar to those

observed with BPO-GMA. BPS-GMA and BPO-GMA showed cytotoxicity

at concentrations of more than 125 and 250 mM, respectively. An elevated

level of IL-6 was not found in cultures exposed to both types among the

concentrations tested. BPO-GMA slightly elevated IL-8 level only at

concentration of 250 mM compared to untreated control; however, BPS-

GMA showed no effect. Bis-GMA was cytotoxic at the concentration of

more than 3.13 mM. IL-6 level was elevated after exposure to 31.3 and

62.5 mM, compared to untreated control. The highest amounts of IL-8 were

released from the HPCs at a concentration of 31.3 mM among those of

15.6–250 mM, which increased the IL-8 level compared to untreated

control. A positive control HgCl2 was cytotoxic at 25 and 50 mM. IL-6 and

IL-8 levels were elevated after exposure to 1.56–12.5 and 1.56–25 mM

compared to untreated control, respectively, and they were completely

absent at 50 mM, which was severely cytotoxic. BPO-GMA showed the

lowest KHN among the three types, followed by BPS-GMA and Bis-GMA,

the highest, although the latter two were not significantly different.

In summary, the present data suggest that one of the aromatic

dimethacrylates, BPS-GMA, might be available for use as a dental

polymer.

27. Polymerization contraction strain and thermal load of resin based

composites following boost vs. ramp halogen irradiation; N. Hofmannp,

T. Markert, B. Hugo, B. Klaiber (University of Wuerzburg, Germany)

The aim of the present study was to compare polymerization shrinkage

strain and thermal load of resin composites after high energy (‘boost’) as

compared to slow-start (‘ramp’) halogen irradiation.

Shrinkage strain was determined using the ‘deflecting disk technique’

described by Watts and Cash [Dent Mater 1991;7:281–7]. Composite

specimens of standardized volumes (ca. 65 mm3) and 1.5 mm height were

irradiated using two different halogening curing lights (Astralis 10, Vivadent;

Optilux 501, Kerr). In the high-energy mode, the units provide irradiation

intensities of 1200 mW/cm2 (Curing Radiometer, Demetron, equipped with

ND filters) for 10 s [A10 Boost, OLBoost]. In the ‘Pulse’ mode the Astralis

10 unit provides a radiation intensity exponentially increasing to

1200 mW/cm2 during 10 s and subsequently alternating between three

periods of 2 s at 1200 mW/cm2 and two periods of 2 s at 700 mW/cm2 [A10

Ramp]. The ‘Ramp’ mode of the Optilux 501 unit features a similar increase

during 10 s followed by 1200 mW/cm2 for another 10 s [OLRamp]. All

experiments were carried out at a temperature of 37 8C. Polymerization

contraction strain was recorded after 60 min using an inductive displacement

transducer and expressed as a percentage of the original specimen height. In

addition to the original experimental setup described by Watts and Cash, a

thermocouple was incorporated into the resin composite to record the thermal

load during polymerization. The test materials included the fine hybrid

composites Herculite XRV (Kerr) [Herc], Solitaire 2 (Kulzer) [Soli2], Tetric

Ceram (Vivadent) [TC] and Filtek Z250 (3M ESPE) [Z250] and the micro-

filled composite Filtek A110 (3M ESPE) [A110]. For each combination of

resin composite and curing mode, six specimens were tested. Results were

statistically analyzed using two-way ANOVA. Differences between the

levels of the main factors were analyzed using the Tukey test at a level of

p , 0.05. Following results were observed:

The highest shrinkage strain was observed for Soli2 followed by TC and

Herc, which were not significantly different. A110 and Z250 featured lower

strain values, respectively. The boost modes produced a higher shrinkage

strain than the ramp modes, and strain was higher for the Optilux 501 as

Mean(SD) Contraction strain after 60 min (%) Maximum thermal load (8C)

A10Boost A10Ramp OLBoost OLRamp A10Boost A10Ramp OLBoost OLRamp

TC 2.7(0.08) 2.6(0.04) 2.8(0.07) 2.9(0.09) 25.3(1.4) 19.8(1.9) 21.9(1.4) 20.6(1.5)

Herc 2.7(0.10) 2.5(0.10) 2.9(0.08) 2.8(0.08) 25.6(3.4) 20.9(2.2) 19.6(1.1) 18.6(1.5)

Soli2 3.3(0.13) 3.3(0.11) 3.3(0.14) 3.3(0.06) 28.8(1.5) 24.9(2.0) 21.3(2.6) 21.8(2.2)

A110 2.2(0.08) 2.2(0.05) 2.4(0.05) 2.3(0.09) 22.5(1.7) 20.2(1.9) 16.5(1.8) 16.5(2.0)

Z250 2.1(0.06) 2.1(0.05) 2.3(0.04) 2.2(0.09) 21.4(1.1) 17.6(0.9) 16.8(1.7) 14.4(1.5)


compared to the Astralis 10 unit. OLRamp and A10 Boost were not

significantly different. Regarding maximum rise of temperature, the

ranking between the resin composites was the same as stated above. The

highest thermal load was observed for the Astralis 10 unit used in the power

mode, followed by the ramp mode of the same unit. The Optilux 501

produced lower temperatures with both curing modes.

28. Influence of adhesive resin removal procedures on quality of cement

at the margin; L.L. Pace, S.K. Hummelp, V.A. Marker (Baylor College

of Dentistry-TAMUS, Dallas, TX, USA)

Purpose. To compare the effects of cement removal time on the quality

of the cement at the margin using four new adhesive resin cements and one

established resin cement as a control.

Materials and methods. A simulated clinical situation was used to test

the cement removal as a function of time of four new resin adhesives and a

control cement. Stainless steel crowns were fit to ivorine dies to simulate

both open and closed margins. One clinician performed all the cementing

and cleanup procedures. Removal of the excess cement at the margin was

done at two periods: (a) immediately after seating and (b) a delayed time

specified in the handling instructions. Four independent evaluators rated the

cement conditions for: (a) amount of excess cement, (b) quality of the

cement at the margin and (c) number of specimens with cement pull outs.

The results between the time periods and among the cements were

evaluated by both non-parametric and parametric statistics ( p , 0.05).

Paired t-test was used to compare parameters evaluated on the same

specimen.

Results. Handling assessment at the early removal time revealed little

difference among the cements. When the cement removal was delayed,

there were major distinctions among the cements in ease of manipulation.

Variation in the scores obtained for the amount of excess cement showed

little consistency between the two test conditions. Only Panaviae F

specimens in selected comparisons exhibited more excess cement than the

other new resin adhesives. In conclusion, this study demonstrated that the

cements tested could be removed at an early time, immediately after

seating, and there was no apparent adverse affect compared to waiting or

light-curing the cement prior to removal as long as the crown accurately fit.

Clinical significance. Early excess cement removal of adhesive resin

cement may be desirable because of ease of elimination but caution should

be used if the clinical situation dictates seating a crown with an open

margin, as it is likely you will get cement pulling out from these areas.

29. Bond strength of dual cure resin cement to bovine root canal dentin;

T. Kanno, R.M. Foxton, M. Nakajima, J. Tagami, H. Miura (Tokyo

Medical and Dental University, Tokyo, Japan)

Several studies have demonstrated that metallic posts and cores

cemented with no-bonding dentin cements (inorganic cements) were not

able to reinforce endodontically treated teeth. Recently, the use of dentin

adhesive systems have been recommended for post-cementation. However,

there are few studies that have evaluated bond strength to root canal dentin

using dual cure resin cement. The aim of this study was to evaluate the bond

strengths of dual cure resin cement to bovine root canal dentin.

Using bovine teeth, the crowns were removed, and then post cavities

(3 mm in base diameter, 12 mm in depth) in root canal were prepared by

means of a carborundum point (Shofu, HP20) with copious water spray.

Two dual cure resin cements (BistiteII, Tokuyama; Panavia F, Kuraray)

were used in this study. The root canal dentin in the post cavity was treated

with the primer and the cavity then filled with the resin cement according to

the manufacturer’s instructions. The cemented specimens were further

divided into two sub groups; with light-cure (light) and without light-cure

(no-light) groups. The light group specimens were photo-irradiated for 60 s

from a coronal direction, while the no-light group specimens were placed in

darkness for 30 min. After water storage for 24 h at 37 8C, a chemical-cure

resin composite (Clearfil FII; Kuraray) was placed on the cementum to

make grips for testing. The specimens were then serially sectioned

perpendicularly to the long axis of the root into approximately 0.7 mm thick

slabs. The slabs were then trimmed to an hourglass shape with a cross-

sectional area of approximately 1 mm2 for the microtensile bond strength

(mTBS) test. The specimens were attached to a testing apparatus with a

cyanoacrylate adhesive, and subjected to tensile stress in a universal testing

machine at a crosshead speed of 1.0 mm/min. The data were divided into

two groups by the coronal and apex side regions in the cavity.

The data (mean(SD)(n ), MPa) were analyzed by three-way ANOVA

and Fisher’s PLSD test ( p , 0.05).

NS ¼ not significantly different ( p . 0.05).

Three-way ANOVA revealed that there were significant differences

among the material (Panavia, F. vs. Bistite II) ( p ¼ 0.0136) and the

polymerization methods (with vs. without light irradiation) ( p ¼ 0.0079).

On the other hand, there was no significant difference among the regions

(coronal vs. apex side) ( p ¼ 0.1097). For both materials, the mTBS of the

coronal side region with light irradiation were higher than those of the other

groups, although there were no significant differences ( p . 0.05).

30. Setting reaction kinetics of different glass ionomer cements;

U. Lohbauerp, P. Sahrmann, S. Nikolaenko, J. Neubauer, A. Petschelt,

P.Greil (University of Erlangen-Nuremberg, Erlangen, Germany)

The setting reactions of different glass ionomer restorative cements

(GIC) were examined. Starting with the mixing of the components (mixing

time) the setting kinetics were analyzed (net setting time) according to the

criteria specified in ISO standard 9917.

The needle (i ¼ 1 mm) of an indentor (400 g) was set vertically on the

freshly mixed cement surface ðn ¼ 11Þ: The time elapsed between end of

mixing until the needle fails to make a complete circular indentation was

recorded as net setting time.

The grain size was measured by laser light scattering method

(Granulometre 517, Cilas Corp., France) and the reactive surface was

determined by isothermal nitrogen adsorbance method according to

Brunauer–Emmert–Teller (Asap 2000; Micrmeridics Corp., USA).

A microcalorimeter (Kuzel 1984, University of Erlangen, Germany)

was used to observe heat flow during setting of the cement. The measuring

principle of the highly sensitive equipment is based on the determination of

the voltage difference of two thermo columns (71 serial BiTe semi

conductors) which are placed under both, sample and reference. Calibration

of the voltage difference gives the heat flow of the sample. Mixing of the

cement components was done outside the calorimeter. The heat of reaction

Q was determined by integration of the heat flow Q/t from t1 ¼ 45 s (after

mixing was finished) to t2 ¼ 3600 s:

Ketac Molar (hand-mix, 3MEspe Corp., Germany), Ketac Molar Quick

PANAVIA F BISTITE

Coronal side Apex side Coronal side Apex side

Light 22.1(7.0)(10) NS 17.5(7.0)(10) 16.2(5.0)(8) NS 14.0(6.1)(10)

NS NS NS NS

No-light 17.3(6.1)(10) NS 12.3(5.5)(10) 11.1(4.7)(9) NS 13.9(6.3)(10)


(capsule, 3MEspe Corp., Germany), Fuji IX GP Fast (capsule, GC Corp.,

Japan) and an experimental cement G111/4 (hand-mix, University of

Erlangen, Germany) were examined.

The results are listed below:

The results reveal a direct correlation between the powder grain size,

e.g. BET surface and the reaction kinetics. The larger reactive surface area

of G111/4 show a correlating higher heat flow maximum. Although the heat

flow maximum is a double, the resulting heat of reaction was in the same

range like Ketac Molar cement. The measured net setting times may also be

correlated directly with the heat flow.pKuzel, H.-J., Ein leistungsfahiges Warmeleitungskalorimeter. TIZ—

Fachberichte 1984;108(1):46–51.

31. Development of reactive fiber reinforced glass ionomer cements;

U. Lohbauerp, J. Walker, S. Nikolaenko, A. Petschelt, P.Greil

(University of Erlangen-Nuremberg, Erlangen, Germany)

The main disadvantage of glass ionomer cements (GIC) is the

sensitivity to brittle fracture. Improvement of fracture strength can be

achieved by reinforcement with fibers.

The purpose of this study was to develop a new glass system and to

manufacture reactive glass fibers. The glass fibers were added to the glass

ionomer cements. The compressive strength of the reinforced glass ionomer

cements was measured.

A glass called ‘G111/4’ was melted at 1400 8C (viscosity

h1400 ¼ 102:023 dPa s) for 1 h. The following components were selected:

SiO2: 33.3, Al203: 16.7, AlF3 £ 3 H20: 5.5, CaCO3: 24.97, NaF: 3.35,

Na3AlF6: 16.18 (wt%). For comparison, commercial GIC’s were tested: Ketac

Molar (hand-mix, 3MEspe Corp., Germany), Ketac Molar Quick (capsule,

3MEspe Corp., Germany), Fuji IX GP Fast (capsule, GC Corp., Japan).

The glass powder was milled to a grain size of d50 ¼ 2:4 mm ðd97 ¼

7:3 mmÞ so that a BET surface of 10.4 m2/g was reached. The glass powder

was treated by acid washing and tempering. Fibers were drawn from the

glass melt by a bushing process at 1200 8C (viscosity h1200 , 105 dPa s).

The fibers showed a thickness of 26 mm and a length of 500 mm. A ratio of

length to thickness was approximately 20:1.

The specimens ðn ¼ 15Þ to determine the compressive strength

were manufactured according to ISO standard 9917. The ratio of

powder to liquid for preparation of the cements was varied depending

on the amount of reactive glass surface. The GICs were stored for up

to 30 days in nanopure water at 38 8C. The compressive strength was

determined using a universal testing machine (Instron Mod. 4204, England).

The data were statistically treated by an analysis of variance technique

(ANOVA,mod. LSD test, p , 0.05). The results are listed below:

All results show sufficient compressive strength according to the ISO

standard. The highest experimental strength data were measured for a 20% fiber

loading. Specimens of Ketac Molar and G111/4 leached for 30 days showed a

significant increase of compressive strength compared to the 1 day results.

32. Use of posterior composite resin restorations by Dutch dental

practitioners; B.A.C. Loomansp, N.J.M. Opdam, F.J.M. Roeters,

R.C.W. Burgersdijk (College of Dental Science, University of

Nijmegen, The Netherlands)

Introduction.

Posterior composite resin restorations (PCRs) have been reported to be

of clinical use in controlled clinical trials (review: Hickel Am J Dent

2000;13(spec issue):41—54). Reported reasons for failure are secondary

caries, marginal deficiencies, fracture and wear. Dental practitioners (DPs)

report problems in placing PCRs, which might be related to inadequate

materials and application techniques. Aim of this study was to investigate

the type of materials and application techniques and problems encountered

by Dutch dental practitioners in placing PCRs.

Materials and methods.

A 31 items questionnaire was sent to a random sample of 750 clinicians,

stratified for age and region in the country. Data were collected regarding

the period 1999–2000. A reminder was sent after 6 weeks to increase the

response rate.

Results.

The response rate was 35% ðn ¼ 252Þ: Equally distributed over the

stratification criteria.

Materials and techniques.

Composites. Ten percent of the DPs only used packable composites,

54% only used traditional composites and 31% used packable as well as

traditional composites. Z100, TPH and Herculite XRV were the materials

used most frequently.

Adhesives. One-bottle systems were used by 46%, multi-bottle

systems by 33% and self-etching primers by 21% of the responding

dentists.

Curing lights. Eighty-six percent of the dentists used a conventional

halogen light, 12% used a plasma light.

Rubberdam. Fifty percent of the respondents never used rubberdam,

35% only in selected cases, 17% in almost all restorative procedures.

Matrices. Automatrix 24%, Tofflemire 27%. Sectional matrices 27%.

Seventy-six percent never used special separation rings for improvement of

the proximal contact.

Lining technique. Fifty percent used a total-etch technique and 50%

used a sandwich technique including GIC-lining. Twenty-eight percent

applied a first layer of flowable composite resin.

Composite application. Seventy-four percent used an injection

Ketac Molar Ketac Molar Quick Fuji IX GP Fast G111/4

Grain size (d10/d50/d97) (mm) 0.7/2.7/10.7 0.7/2.7/10.7 1.1/4.2/24.0 0.9/2.4/7.3

BET surface (mm) 2.99 2.99 1.75 10.43

Mixing time (s) 45 10 10 45

Net setting time (s) 243 117 155 105

Heat flow max. Q/t (J/s g) 91.96 – – 221.09

Heat of reaction Q (J/g) 67.53 – – 73.47

Material [Mean (SD)] Comp. strength (1 d) (MPa) Comp. strength (30 d) (MPa)

Ketac Molar Quick (Capsule) – 326.57 (22.57)

Fuji IX GP Fast (Capsule) – 316.91 (22.3)

Ketac Molar (Hand-mix) 154.6 (42.3) 305.0 (29.96)

G111/4 100.0 (7.5) 169.0 (14.11)

F111/4 (20% fiber loading) 134.2 (4.0) –

F111/4 (40% fiber loading) 98.0 (3.7) –

F111/4 (60% fiber loading) 81.7 (6.1) –


technique and 22% used hand instruments for PCRs application. Ninety-

two percent placed PCR’s in layers, 6% placed them in bulk.

Reported problems.

59% reported postoperative sensitivity in more than 5% of the PCRs.

Eight percent reported postoperative sensitivity in more than 25% of the

PCR’s placed. Most DPs (82%) had problems obtaining a good proximal

contact as compared to amalgam.

Conclusion.

Dutch DPs apply a great variety of materials and techniques in placing

PCRs. Dental practitioners report significant problems in placing PCRs

regarding to postoperative sensitivity and creating adequate proximal

contact. These findings are not consistent with results of some controlled

clinical studies.

33. Quartz fiber posts: an in vitro evaluation on fatigue resistance;

S. Malferrarip, P. Baldissara, R. Scotti (Department of Prosthodontics,

University of Bologna, Bologna, IT)

The use offiber posts for the reconstruction of endodontically treated teeth

is nowadays quite common. Different posts and clinical procedures have been

proposed in the literature. A new clinical ‘one step’ post and core

reconstruction procedure has been suggested in order to achieve a simpler

and less time consuming clinical technique, by using a dual composite resin

both for luting the post- and for core reconstruction. By doing this a post-core

uniform complex can be obtained. The aim of this study is to compare the

fatigue resistance of two different quartz fiber posts. Thirty sound human

incisors, canines and premolars extracted for periodontal reasons were

endodontically treated. The coronal portion of the teeth was removed 1 mm

above the CEJ, and a quartz fiber post was inserted to a depth of 9 mm into the

root leaving at least 3 mm of apical guttapercha seal. The teeth were randomly

divided in three groups of 10 samples each according to the type offiber post or

to the luting cement utilized. Group A was assigned to Endo Light-Post (RDT,

St Egreve, France), while group B and C to DT Light Post (RDT, St Egreve,

France). The cementation of the posts in groups A and B was performed with

the adhesive All Bond 2 (Bisco, Schaumburg, IL, USA) and with the

composite resin Bisfil 2B (Bisco, Schaumburg, IL, USA) utilized as a resin

cement. Posts of group C were cemented with the adhesive One Step (Bisco,

Schaumburg, IL, USA) and Duo Link Cement (Bisco, Schaumburg, IL, USA).

Each group was equally subdivided in an experimental sub-group and in a

control one. Specimens from experimental groups underwent two-million

8 Hz frequency load cycles in distilled water at 37 ^ 3 8C. The load applied on

the post with a 458 direction, ranged from 3 to 21 N during each cycle. The

control specimens were stored in distilled water at 37 8C. Failure was defined

as fracture or de-cementation of the post, or fracture of the root. At the end of

the loading cycles all the posts have completed the fatigue test with no

macroscopic failures. According to these results, and considering the limits of

this study, it is possible to conclude that the quartz fiber posts are resistant to

fatigue test and that the one step reconstruction procedure was successful.

34. Marginal quality and microleakage of InTen-S composite in class II

cavities after artificial aging; J. Manhartp, A. Albrecht, R. Hickel

(Restorative Dentistry, LMU University, Munich, Germany)

This study determined the marginal quality and microleakage of a new

composite restorative material (InTen-S, Ivoclar-Vivadent, Schaan, FL) in

class II cavities after artificial aging. Standardized class II inlay cavities

were cut in 24 freshly extracted, caries-free molars with one proximal box

limited within enamel (1-1.5 mm above CEJ) and one proximal box

extending into dentin (1–1.5 mm below CEJ). Teeth were assigned to three

groups ðn ¼ 8Þ; etched with 37% phosphoric acid (total etch), bonded, and

restored with incrementally placed direct composite restorations (Table 1).

After polishing, the teeth were stored for 48 h in Aqua dest. at 37 8C

before subjected to artificial aging by thermal stress (5/55 8C; 2000 £ ;

30 s) and mechanical loading in an artificial oral environment (50 N;

50,000 £ ). Teeth were replicated with an epoxy resin. The replicas were

gold-sputtered and analyzed in the SEM (200 £ ) according to the criteria of

the quantitative and qualitative margin analysis. Segments of marginal gap

formation were recorded as a percentage of the total length of the proximal

margins in enamel and dentin. The original specimens were isolated with

nail polish and immersed in 5% methylene blue for 24 h. After sectioning,

the specimens were evaluated for leakage (ordinal scale: 0–4) at the enamel

and dentin margins under a microscope. SEM (Table 2) and dye penetration

(Table 3) results were analyzed using Kruskal–Wallis H-test and Mann–

Whitney U-tests with adjusted Alpha-level for pairwise multiple compari-

sons. Superscripts indicate statistically different subsets.

Both InTen-S groups showed significantly more perfect margins and

less gap formation in the SEM than the control group Tetric Ceram, in

enamel and dentin, respectively. Both InTen-S groups exhibited signifi-

cantly less microleakage in enamel than the control group, whereas no

significant difference could be detected in dentin. The adhesive properties

of InTen-S in combination with a high power LCU seem to be superior to a

well-established control. Supported by Ivoclar-Vivadent.

35. Effects of amorphous calcium phosphate on dentin bond strength;

A.C.B.F. Martinelip, S.R.L. Teixeira, M.S. Tung, C.E. Francischone,

R.F.L. Mondelli (Bauru School of Dentistry, University of Sao Paulo,

Brazil and Paffenbarger Research Center, NIST, Gaithersburg, MD,

USA)

Solutions of calcium and phosphate have been used to treat dentin

hypersensitivity because they result in the precipitation of amorphous calcium

phosphate (ACP), thus obstructing dentinal tubules. The total or partial

remission of the symptoms of dentin hypersensitivity may not be obtained after

a single treatment with a desensitizing agent, so an adhesive restoration should

be indicated. The aim of this study was to compare the bond strength of a

composite resin to dentin with and without pre-treatment with amorphous

calcium phosphate (ACP) using the microtensile test. Four extracted human

third molars were prepared by reducing the occlusal surface in order to expose

a flat dentin surface. In the control group, the dentin was conditioned with 37%

H3PO4 gel for 15 s, then washed and blot dried (moist technique), followed by

the application of the adhesive system (Single Bond—3M Dental) according

to the manufacturer’s instructions. In the experimental group, the dentin

surface was treated with a solution of 1.5 mol/l calcium chloride ðpH ¼ 5:1Þ

for 5 s, and kept wet for 20 s. Then, a solution of 1.0 mol/l potassium

phosphate ðpH ¼ 12:7Þwas applied for 2 s, and held wet for 10 s. After 1 min,

the dentin surface treated was washed and dried before acid etching, followed

by the application of the adhesive system, as it was done in the control group. A

6 mm ‘crown’ was then built using a composite resin (Z100—3M Dental).

Each 1 mm resin composite increment was light cured for 40 s. After a 24 h

storage in deionized water at 37 8C, the teeth were sectioned transversally to

the bonded interface in both mesio-distal and facial–lingual directions in order

to obtain several bonded beams, with cross-sectional bonded areas of

Table 1

Group Composite DBA Light polymerization

1 InTen-S Excite Astralis 10 LCU (DBA 10 s with low power, each composite increment 10 s with high power)

2 InTen-S Syntac Classic Astralis 10 LCU (DBA 10 s with low power, each composite increment 10 s with high power)

3 (control) Tetric Ceram Syntac Classic Elipar Highlight LCU (DBA 10 s standard, each composite increment 40 s with standard mode)


approximately 1 mm2. Each beam was attached to the Bencor-Multi T testing

device with cyanocrilate adhesive and tested in an EMIC DL 500 testing

machine. The values recorded in Kgf were used to calculate the bond strength

expressed in MPa. The data were submitted to Student-t test. The results

showed that the adhesion strength values obtained in the experimental group

(33.23 MPa ^ 13.71 SD) were higher than those obtained in the control group

(27.55 MPa ^ 11.71 SD), but such difference was not statistically significant

( p . 0.05).pSupported by NIST.

36. Affect of operator variability upon surface roughness of resin

composite finished in vitro; B.B. Maxsonp, A.L. Neme, N. Kashani

(University of Detroit Mercy, Detroit, MI)

Surface roughness has been used as an in vitro parameter for

evaluating various techniques for finishing and polishing resin

composite materials. A standardized technique, which considers time

and handpiece speed (rpm), has been used to provide consistency and

limit operator variability between samples. Previously, a single

operator has been used with the assumption that this will provide

control of such confounding variables as handpiece pressure and

manipulation. It was the aim of this study to evaluate the effect of

multiple operators using a standard protocol for time and handpiece

speed on the surface roughness of resin composite materials finished

with bur or disk. Eight cylindrical resin samples of 10 mm diameter

were prepared in sections of acrylic rod for both a microhybrid and

packable material (Point 4, Prodigy Condensable). The two-sided

samples were condensed and light-cured in 2 mm increments against

Mylar sandwiched between two glass plates. The resin disks were

punched out of the rod with finger pressure and polished on two sides

with a water-cooled 600-grit abrasive wheel to produce a baseline

surface. Three operators finished one side of each disk with a carbide

finishing bur and the other side with a series of abrasive disks. Resin

disks were polished to baseline surface between operators. Baseline,

bur, and disk surfaces were analyzed three times with a Surfanalyzerw

5400(Federal Corp.) to obtain mean roughness for each surface. Data (Ra)

were analyzed with ANOVA and Tukey HSD ða ¼ 0:05Þ: A significant

difference was found between the disk and bur surfaces. No difference was

found among operators except between operators 1 and 2 with the bur on the

packable composite only. Standard deviations using both bur and disk were

similar among all operators. The data do not support the need for a single

operator to control potentially confounding variables when testing roughness

after polishing resin composite with a series of abrasive disks, but bur-finished

surfaces may produce operator variation due to differences in operator

technique. Mean roughness values, mm (std. dev.) are given below:

Operator Tool Microhybrid Packable

#1 Disk 0.090 (0.02) 0.108 (0.02)Bur 0.526 (0.05) 0.548 (0.07)

#2 Disk 0.078 (0.01) 0.102 (0.01)Bur 0.476 (0.07) 0.501 (0.07)

#3 Disk 0.077 (0.02) 0.089 (0.02)Bur 0.476 (0.07) 0.446 (0.06)

37. Duplicating dentures: an in vitro dimensional evaluation study;

G. Merlatip, G. Magenes, A. Manuello, D. Cattaneo, P. Menghini (Pavia

University—Department of Odontostomatology, Department of

Bioengineering, PAVIA-I, e-mail: [email protected])

The patient’s opportunity as well as the practitioner utility for a

denture duplicate in some prosthetic procedures has been pointed out

by several studies; at the same time the evaluations of the duplicating

systems has been discussed with regard to different clinical and

technological problems [1]. Even in the recent CAD/CAM appli-

cations, the desirable dimensional precision is considered the most

important concern and the measuring system accuracy is also under

discussion [2]. The aim of this ‘in vitro’ study has been to asses the

feasibility of a dentures duplicating laboratory system (MDPq, Apex

Dental S.r.l., Milano-I) with regard to the dimensional evaluation by

the means of a new measuring procedure compared to the standard

dial caliper measurement.

Six dentures (three maxillary—and three mandibular—dentures)

were duplicated three times each with three different heat-polymeriz-

able acrylic polymers by the use of the MDPq system. The existing

and the duplicated dentures were photographed by a reflex standard

camera at the same optical values in five different predefined positions

with respect to the three-dimensional axis in order to obtain shape-

related slides, then the images were digitized and recorded in a

calculator. A freeware software (‘Image Tool’w, UTHSCSA, TX-

USA), which provides a high resolution algorithm, was used to

process the images in the order to obtain resulting images which show

the discrepancy between the original and the duplicate denture

dimensions; then the linear discrepancy at three predefined locations

has been calculated and recorded. At the same predetermined

locations, the original and the duplicated dentures were measured by

the aid of a dial caliper and the values were recorded, then the linear

discrepancy has been calculated. All the discrepancy values were

reported and expressed as a percentage of the total length, then the

ANOVA test was applied.

No statistical significative difference resulted between the discrepancy

values calculated by the image processing software in comparison with the

dial caliper ones ( p . 0.005). The MDPq duplicate dentures, no matter

what resin was employed ( p . 0.005), showed all dimensions increased

with respect to the original, with an average linear discrepancy of

þ0.582083%.

This in vitro experience reveals that the computer-aided measuring

Table 2

Group 1 (%) Group 2 (%) Group 3 (%)

Enamel Perfect margin 91.5 (10.5)b 95.5 (3.8)b 72.2 (8.2)a

Marginal gaps 6.4 (9.0)a 4.1 (4.1)a 25.8 (9.9)b

Dentin Perfect margin 88.4 (15.1)b 90.7 (12.9)b 39.1 (11.4)a

Marginal gaps 7.7 (13.4)a 8.4 (13.3)a 60.9 (11.4)b

Table 3

3 Enamel Dentin

Score (n) 0 1 2 3 4 0 1 2 3 4

Group 1 19 3 10 13 4 2

Group 2 23 3 9 11 3 3

Group 3 13 16 1 8 13 5 4


system is effective in providing an accurate comparison testing. The

photo taking and the image digitizing may be considered complicated

procedures, but the following image processing analysis is fast and

easy to be handled, moreover many software tools can provide a

surface analysis and more detailed measurements. As a consequence of

this experience it can be concluded that the MDPq duplicating method

seems to be effective in the production of a reliable dentures duplicate

because of it is accepted by the literature a linear discrepancy of not

more than the 1% [3].

References

[1] Lindquist TJ, Ettinger RL. Patient management and decision making

in complete denture fabrication using a duplicate denture procedure:

a clinical report. J Prosthet 1999;82(5):499–503.

[2] Kawahata et al. Trial of duplication procedure for complete dentures

by CAD/CAM. J Oral Rehabil 1997;24(7):540–8.

[3] Kippax et al. How well are complete dentures copied? Br Dent J

1998;185(3):129–33.

38. Microleakage evaluation of the marginal adaptation of different

restorative-adhesive combinations in Class II composite restorations.

Raquel Lima Mouraoa, Angelica Reis Hannasb, Simone Grandinia,

Marco Ferraria (aDepartment of Dental Materials, School of Dental

Medicine, University of Siena, Italy; bDepartment of Restorative

Dentistry, School of Dentistry, Federal University of Minas Gerais,

Brazil)

Objectives. The aim of the present study was to evaluate the sealing

ability of different types of restorative–adhesive combinations in class II

composite restorations and the influence of the consistency of filling

materials on marginal seal. Methods. Fifty extracted human posterior teeth

were selected and stored. A standardized adhesive Class II preparation was

made in the mesial and occlusal surface. The interproximal cervical margin

box was placed 1 mm below the cementum enamel junction. Five groups of

10 samples each were selected and restored with five different combinations

of adhesive-restorative materials: Group 1: Prime & Bond NT, Dyract,

Spectrum TPH, Group 2: Syntac Single Component, Compoglass Flow (as

base) and Tetric Ceram, Group 3: Syntac Single Component, Tetric Flow

and Tetric Ceram, Group 4: One-Step, AelitFlow and Pyramid/ VIP and

Group 5: Excite LC, Tetric Flow and Tetric Ceram. The samples were

immersed in a dye solution and submitted to thermal cycling tests. After

embedding the samples, they were sectioned and were evaluated for

leakage scores at cervical and occlusal margins. The worst score for the

sections of each tooth area was selected for scoring. The results of the

staining measurements were statistically evaluated using the Kruskal–

Wallis non-parametric analysis of variance (ANOVA). Results. In the

cervical wall, group 2 showed better performance, followed by groups 4, 3

and 5 from the least to the highest leakage, respectively. In the occulsal

wall, groups 2 and 4 showed less leakage, followed by groups 5, 1 and 3

from the least to the highest leakage, respectively. Conclusions. Compomer

flowable material in combination with microhybrid resin composite showed

good sealing ability of Class II direct restorations.

39. Cyclic voltammetry an accepted method for corrosion

characterization for anybody W.-D. Mullerp, Chr. Schopf, K.-P. Lange

(Humboldt-University of Berlin, Berlin, Germany)

The modern analytical technique, cyclic voltammetry, is accepted now

for the characterization of the corrosion behavior of dental alloys by

publication of ISO standard 1021 “dental metallic materials—Corrosion

test methods”. It is more complicated to explain this method and the results

caused by the huge amount of data in comparison to the classical immersion

test by watching of the weight loss, but it has more information not only

concerning the corrosion behavior of a specimen. The aim of this work is to

present a special developed equipment for characterization of electro-

chemical behavior of dental alloys using the cyclic voltammetry. With help

of the named Mini-Cell-System it is possible to measure on any interesting

surface of a metallic dental device with a minimum area of 0.008 cm2, so a

special preparation of specimens is no longer necessary. Additional

advantages are the possibility to change the electrolyte very quickly and to

measure fast, with a scan rate of 10 mV/s. The measurements onto pure

elements could demonstrate that the design of the MCS does not produce

any systematic mistakes on the contrary with the developed measurement

routine results were performed comparable with data from reference books.

This special cell was developed for a direct characterization of the

electrochemical behavior of Nd–YAG Laser welding tracks. The

width of a laser track is more or less about 1 mm. By comparing the

results performed onto the surface of the bulks and the tracks it is

possible to make a decision about changes of the corrosion behavior.

The application of this cell starts with pure qualitatively descriptions

of changes in the electrochemical behavior, now it is also possible to

calculate the material loss from the characteristic data Rp (polarization

resistance) and io (exchange current density).

The performed I (current) vs. E (potential) curves can be collected and

summarized to a mean I vs. E curves range for each dental alloy in any

electrolyte to use as a finger print. Deviation and shifts from this reference

curve, spectra, can be interpreted as changes of the electrochemical

behavior with the special view to the corrosion stability. In this way

information about changing of the stability of the oxide layer, activity and

possible adsorption phenomena can be collected.

So different applications are possible besides the characterization of

welding tracks, also the characterization of soldered junctions and the

electrochemical assessment of modified metallic surfaces, like surfaces

of implants.

Last but not the least the application of the MCS can be helpful in

educational training of colleagues and dental students for a better

understanding of corrosion phenomena onto dental alloys and combination

of them.

40. Clinical evaluation of heliomolar HB for posterior restorations;

J.R. Dunn, C.A. Munozp, G. Bernal, J. Torres, A. Wilson (Loma Linda

University, Loma Linda, CA)

This investigation evaluated the clinical performance of a new heavy

body composite resin (Heliomolar, H.B., Ivoclar, N.A.) over a 12-month

period. Fifty posterior MOD and Class II restorations were placed in 32

subjects. Forty-three restorations were evaluated at 12 months. Following

conventional procedures for cavity preparation the teeth were etched,

restored, and polished following manufacturer’s instructions. The teeth

were then evaluated by two examiners for the following variables: Marginal

adaptation (MA), Interproximal anatomic form (IAF), proximal contact

(PC), secondary caries (SC) marginal discoloration (MD) Surface Gloss

(SG) and sensitivity (SE) were evaluated. At 12 months, using a modified

USPHS grading system the following results were found in percentages (%)

(BL ¼ Base Line, IY ¼ one year):

MA IAF PC MD SE

BL 1Y BL 1Y BL 1Y BL 1Y BL 1Y

Alpha 100 88 92 95 78 91 100 88 100 93

Bravo 0 12 8 5 22 7 0 12 0 7

Charlie 0 0 0 0 0 0 0 0 0 0

Delta 0 0 0 0 0 0 0 0 0 0

One year results: (1) Surface gloss on the restorations and secondary

caries remained unchanged (all Alpha) from baseline to one year. (2) Four

of the restorations had a slight degradation of the marginal adaptation

(MA). Those same restorations presented with marginal discoloration

(MD). (3) The interproximal anatomic form (IAF) and the proximal contact


(PC) showed improvement over time. (4) Surface gloss showed that the

restorations polished adequately at baseline and they maintained the surface

polish over time. (5) Two restorations still had some sensitivity at 1 year.

Overall clinical use of Heliomolar HB as a posterior restoration is

acceptable for routine clinical use.

Study supported by Ivoclar Vivadent.

41. Regional bond strengths to dog cuspid dentin in vivo;

M. Nakajimaa,b,p, I. Urabea,b, R.M. Foxtona,b, J. Tagamia,b, D.H.

Pashleya,b (aTokyo Medical and Dental University, Tokyo, Japan;bMedical College of Georgia, Augusta, GA, USA)

When applying adhesive systems to dentin, the variation of bond

strengths depends not only on the materials but also on many factors about

the substrate such as dentin depth, tubule orientation or with/without pulpal

pressure. The purpose of this study was to evaluate the regional bond

strengths to dentin in dog cuspids in vivo using the microtensile bond test.

Using anesthetized dogs, the cervical surfaces of intact cuspid teeth

were exposed by gingival flap surgery. Long dentin cavities from the incisal

to the gingival of the buccal surface were prepared by means of a diamond

point with copious water spray. The dentin surfaces were bonded with two

self-etching primer adhesive systems (Clearfil LinerBond 2; Kuraray and

Clearfil LinerBond 2V; Kuraray) and two total-etch wet-bonding systems

(Single Bond; 3M and One-Step; Bisco), and then covered with Protect

Liner F. One hour later, the teeth were surgically removed, and then stored

in water at 37 8C. After 24 h, the resin-bonded specimens were serially-

sectioned into 0.7 mm slabs perpendicular to the long axis of the tooth. The

slabs were trimmed to an hourglass shape with a cross-sectional area of

approximately 1 mm2. The specimens were attached to Ciucchi testing

apparatus with a cyanoacrylate adhesive, and subjected to tensile stress in a

universal testing machine at a crosshead speed of 1.2 mm/min.

Statistical analysis was performed using one-way ANOVA and Fisher’s

PLSD post-hoc tests. Statistical significance was considered as p , 0.05.

Materials Incisal Mid-coronal Cervical

LB2 33.8(11.7)(13) 38.2(9.8)(13) 34.8(12.8)(12)

LB2 V 31.0(5.8)(13) 35.8(7.6)(14) 38.6(5.4)(13)

OS 28.3(5.5)(9) 30.9(9.6)(10) 26.2(7.9)(9)

SB 25.5(5.6)(9) 29.0(5.4)(10) 31.6(5.0)(9)

The results were: mTBS(MPa) mean(S.D.)(N)

For mTBS of each material, there were no significant differences

among the three regions ( p . 0.05). For the SEM observation of the

debonded surface, the direction of the dentinal tubules of the incisal

group was relatively parallel, while in the cervical group, the dentinal

tubules were cross-sectioned perpendicular to the adhesive interface.

Therefore, pulpal fluid in the cervical groups may have influenced the

dentin subsurface more than in the incisal groups, although the

remaining dentin of the incisal group was thinner than that of the

cervical group. The condition of the dentin surface as an adhesive

substrate has been thought to be very different at the three regions. On

the other hand, the remaining dentin of the cervical group was

approximately 1.8–2.0 mm thick, through which it might have been

difficult for pulpal fluid to contaminate the dentin subsurface.

Moreover, the dentin surface was prepared using a coarse diamond

bur, resulting in the production of a thicker smear layer. This might be

a reason why the mTBS in this study did not show any differences

among not only the regions but also the materials.

42. Three months evaluation of fluoride release from dentin adhesives;

S. Phanthavonga,p, H. Sonodaa,T. Nikaidoa, P.N.R. Pereirab, J. Tagamia

(aTokyo Medical and Dental University, Tokyo, Japan; bUniversity of

North Carolina at Chapel Hill, USA)

Fluoride has been shown to be an effective agent for prevention of

dental caries. Recently, fluoride-releasing dentin adhesives have been

developed. The purpose of this study was to measure fluoride release

from three single-step adhesives: One-Up Bond F (OB, Tokuyama,

Japan), Reactmer Bond (RB, Shofu, Japan) and Xeno CF Bond (XB,

Sankin, Japan). Resin-modified glass ionomer cement, Fuji II LC-

improved (F LC-imp, GC, Japan), was used as a positive control. Each

material was applied to the vinyl mold (3 mm diameter, 0.36 mm

height), and light-cured for 20 s each on both sides. Specimens were

stored in either distilled water (DW) or demineralizing solution (DS,

pH 4.5) at 37 8C. Amount of fluoride release from each material was

measured with a fluoride ion-specific electrode (combination electrode

fluoride 960900; Orion, USA) up to three months. The data were

statistically analyzed using one way ANOVA and Fisher’s PLSD test

at 95% level of significance. Fluoride concentration was calculated in

ppm. The mean and standard deviation for five samples of each group

were calculated for each interval.

Cumulative amounts of fluoride release are summarized in the Table.

The total amounts of fluoride released from F LC-imp in DS were

significantly higher than that in DW ( p , 0.05). For One-Up Bond F, there

was no significant difference in amount of fluoride release between DW and

in DS ( p . 0.05). For Reactmer Bond, the amount of fluoride release in DS

was significantly higher than that in DW ( p , 0.05). For Xeno CF Bond,

the amount of fluoride release in DW was significantly higher than that in

DS ( p , 0.05). F LC-imp provided the highest amount of fluoride release

among the materials in each solution. For DW groups, the amount of

fluoride release from Xeno CF Bond was significantly higher than those of

One-Up Bond F and Reactmer Bond ( p , 0.05). There was no significant

difference in the amount of fluoride release between One-Up Bond F and

Reactmer Bond ( p . 0.05). For DS groups, the amount of fluoride release

from Reactmer Bond was significantly higher than those of One-Up Bond

and Xeno CF Bond ( p , 0.05). There were no significant differences in

amounts of fluoride release between One-Up Bond F and Xeno CF Bond

( p . 0.05). The single-step adhesives demonstrated the capacity for

fluoride release in both solutions, although these amounts of fluoride-

release were smaller than that of resin-modified GIC. Fluoride released

from each material up to 3 months (ppm) are given below:

Mean(SD), n ¼ 5. S—statistically significant, NS—not statistically

significant.

43. Micro-invasive cavity preparation: an in vitro microleakage study;

C. Poggiop, S. Bianchi, M. Chiesa, U. Genova, G. Merlati (Department

of Odontostomatology, Pavia University, PAVIA-I, e-mail:

[email protected])

The aim of this ‘in vitro’ study was to assess the microleakage behavior

of Class V composite resin restorations performed by means of a micro-

Solution F LC-imp One-Up Bond F Reactmer Bond Xeno CF Bond

DW 1.09(0.28) 0.18(0.04) 0.21(0.02) 0.42(0.06)

S NS S S

DS 1.94(0.35) 0.23(0.06) 0.32(0.04) 0.20(0.03)


invasive cavity preparation system (Durr Vectorw, Durr-Dental GmbH u.

Co.KG) vs. the standard operative technique performed by the usage of

diamond burs. Durr Vectorw improve the ultrasonic cleaning action with

the aid of an abrasive aqueous slurry (silicon carbide particles, 40–50 mm

average grain size).

Thirty sound human teeth, stored in a 0.6% NaCl solution, were

randomly divided into two groups. Group 1: two Class V cavities

(buccal and lingual) were made on each tooth by the means of the

Durr Vectorw system. Group 2 (control group): two Class V cavities

(buccal and lingual) were made on each tooth by the help of diamond

burs. The occlusal boundaries of the cavities were located in the

enamel tissue while the gingival ones were located in dentin. The total

number of specimens was 60 (sixty). After a 10 s acid etching (37%

phosphoric acid) and the placing of two layers of an ‘one bottle’

adhesive system (Scotchbond 1e, 3M, 3M Inc., St Paul, MN, USA),

the samples were restored using three different composite products:

Filtek Z250e (3M), Filtek A110e (3M) and Filtek Flowe (3M).

Following the ISO/TR 11405:1994, the specimens were stored in

water (24 h), then thermocycled (500 cycles, 5–50 8C, 30 s dwell

time), and immersed (24 h at room temperature) in a 2% methylene

blue aqueous solution. Finally, they were rinsed and sectioned in a

bucco-lingual direction at three different locations and the tooth/-

restoration interfaces were evaluated at 32X. The extention of the

microleakage was recorded as a percentage of the total length of the

boundaries.

All the specimens showed no microleakage at the occlusal boundaries

while the Anova test of the scores at the gingival contours showed a highly

significant statistical difference (P , 0,001) between the two groups. There

is no statistically significant difference with regard to the behavior of the

composite products used.

The preliminary in vitro experience revealed that the micro-invasive

cavity preparation by Durr Vectorw is effective in preforming tissue

surfaces available to an adhesive system interaction in comparison with the

usage of a standard diamond bur technique. This result seems to be justified

by the eventually more marked roughness of the treated substrates and the

consequent increase of the total surface available for adhesion, resulting

from the ‘alternative’ treatment. Following the ISO/TR 11405:1994, our

preliminary study has to be considered a laboratory screening research that

should encourage more significant in vivo studies.

Gingival Microleakage is reported in the following table as the

average values (and the standard error of the mean).

Material Durr Vectorw Diamond Burs

A 110 7.2 (6.61) 15.1 (6.88)

Z 250 4.8 (6.52) 14.2 (7.31)

FLOW 8.2 (7.77) 16.8 (6.01)

44. Effect of light curing time on the effectiveness of composite

polymerization; J. Portugalp, M.F. Bernardo, C. Pereira, J. Ortet,

J. Leitao (University of Lisbon, Lisbon, Portugal)

Composite manufacturers generally recommend a minimum 40 s

light curing time to achieve adequate polymerization in 2 mm

increments. For some recent composites, shorter curing times are

being recommended by the manufacturers. Shorter curing times may

have a negative influence on polymerization effectiveness. Several

methods for measuring polymerization effectiveness have been

described. Microhardness determination is a simple, indirect method

to assess the effectiveness of composite polymerization.

Objective. The objective of this study was to compare the

polymerization effectiveness, using the traditional 40 s curing time

and the smaller curing time recommended by some manufacturers, in

three different micro-hybrid composites.

Materials and methods. Silicone molds were used to form thirty

composite slabs with 2 mm of thickness. The composites used were Filtek

Z250 (3M Dental Products), Synergy Duo Shade (Coltene/Whaledent) and

Esthet-X (Dentsply/Caulk). All the specimens had equivalent shades and were

polymerized with a 3M Curing Light 3000XL (600 mW/cm2). For each

composite, half of the specimens were light cured for the time recommended

by their manufacturers (Filtek Z250—20 s; Synergy Duo Shade—30 s;

Esthet-X—20 s) and for 40 s. Six groups with five specimens each were

created. Microhardness (VHN) was determined immediately after light curing

with a Shimadzu Microhardness Tester, on the top and bottom surfaces of the

composite slabs. In each surface three measurements were made and their

mean was used to express the individual sample surface hardness. The

hardness ratio (HR) was calculated using the following formula: HR ¼ VHN

of bottom surface/VHN of top surface. The ideal HR should be equal to 1, as

the hardness of the bottom surface should be similar to that of the top surface, it

has been suggested that an effective polymerization is achieved with a HR

equal or superior to 0.8.

Statistical analysis of the results was performed using ANOVA and

Student’s t-test.

Results. Mean HR for each group is presented in the following table

(Means sharing equal superscript letters are not significantly different):

Light Curing Time Synergy

duo shade

Esthet-X Filtek Z250

Recommended

by manufacturer

0.86 a c 0.88 a b 0.93 b

40 seconds 0.87 c 0.98 d 0.97 d

Statistical analysis showed that both the time of exposure to light and

the composite used have a significant ( p , 0.001) influence on the HR.

Interaction between the two factors was found ( p , 0.05).

Conclusions. Using manufacturers recommended curing times pro-

duced an effective polymerization (HR $ 0.8) for all composites tested at

2 mm depths. Increasing the curing time to 40 s resulted in higher HR for all

composites, except for Synergy Duo Shade.

45. Experimental and numerical analysis of the acting loads on fiber-

reinforced composite resin; N. Borgarelli, G. Rappellip, L. Scalise, A.

Putignano (Universita degli Studi di Ancona, Ancona, Italy)

The main objective of this research is to develop a reliable numerical

model, based on a finite element code in a position to being able to offer an

effective appraisal of loads and deformations on dental prosthesis structures,

when static and dynamic solicitations are present simulating the masticatory

act. In particular, we want to estimate the present characteristics and types of

solicitation on fiber-reinforced composite inlay fixed partial dentures and on

the abutments of the bridge. The surface of a molar and of a premolar have been

reconstructed using a non contact 3D acquisition system. The system is based

on the use of a laser triangulation sensor and generates the grid of points

representing the two teeth surfaces. These clouds of points have been imported

into the finite element model and is used as the geometry of the objects under

simulation. Experimental tests on the composite materials have been carried

out for the determination of their proprieties. Experimental tests have been

conducted for the validation of the finite element model. Compression tests on

in vitro structures have been carried out. Good agreement between the

numerical model and the experimental data have been obtained.

46. Interface amalgam-tooth. Study with six different adhesive systems;

F. Ricciardip, M. Grande, L. Cianconi (University of Rome Tor

Vergata, Italy)

The purpose of this study was to evaluate the morphological relation

existing among amalgam, bonding agents and dental structures.

Ninety-six class V cavities were restored using six different adhesive

systems (Pro-bond, Scotchbond, Amalgambond plus, Amalgambond


plus þ HPA, All-bond 2, One Step þ Resinomer) and two cavity

varnishes (Copalite, Tubulitec liner), under a dispersed phase and

spherical amalgam. The restored teeth were fixed on a stub and cut

longitudinally towards buccal–lingual direction in two halves by a

diamond saw. This histological technique does not require dehydration

and embedding of the sample. A clear difference between primer and

bonding was allowed by a simple staining technique.

The specimens were observed with a cofocal microscope and under

SEM. All the adhesive systems, with the exception for Amalgambond,

showed a non-homogeneous distribution pattern along the cavity walls. At

the adhesive agent/amalgam interface, Dispersalloy produced a waver

adhesion surface and 2 mm gaps were seldom observed when the adhesive

systems were used. Amalgambond performed no gaps and the best seal of

the tubules. The cavity varnishes instead showed significant detachments

and gaps 10–20 mm large. The study itself demonstrated that the better

interlock between adhesive agent and amalgam is obtained when the

bonding agent is more flowable and the condensation strength is direct and

appropriate.

47. Flexural strength of indirect composites and porcelains; R.P.

Rusinp, R.F. Murphy, P. Baker, M.E. Cavaleri (3M ESPE Dental, St

Paul, MN)

A new composite block material is now available for dental

CAD/CAM. The objective of this study was to compare the flexural

strength of CAD/CAM milled and conventionally fabricated indirect

materials. Surface flaws from machining or finishing can weaken

materials, particularly ceramics. Thus, it is critical to prepare these

materials for strength measurement in the same way as they are used

clinically. 2.5 £ 1.5 £ 12 mm3 bars were milled on a Sironae

CERECe two system from block materials, or molded and cured

from composite pastes; stored 1 d in deionized water at 37 8C; then

broken in a three-point bending fixture. The flexural strengths were:

CEREC-milled Vitae Mark II 118 ^ 15; CEREC-milled Ivoclare

ProCADe 118 ^ 11; 3Me Z100 Restorative 118 ^ 23; Kerre XRV

Lab 99 ^ 16; Jeneric/Pentrone Sculpturee 93 ^ 16; Kulzere Art-

glasse 96 ^ 13; Kerre Belleglasse HP 133 ^ 22; CEREC-milled

3Me Paradigme MZ100 Block for CERECw 146 ^ 15. The data

were analyzed via one-way ANOVA and compared with Tukey’s T-

test ( p , 0.05). The flexural strength of MZ100 is statistically higher

than Mark II, ProCAD, XRV Lab, Sculpture, Artglass, and Z100

Restorative; MZ100 is similar to Belleglass HP.

48. Influence of illuminants on color parameters of enamel shades of

Enamel Plus HFO and Miris composite resins; J.P. Salomona,b,p, J.N.

Monnetc, L. Lapeyred, M. Degrangea, J. Dejoub (aParis V; bFacultes

d’Odontologie de Marseille; cI.U.T de Nımes, France; dMontpellier)

This study investigated the influence of different illuminants on the

color parameters of the incisal shades of two composite resins: ENAMEL

PLUS HFO-MICERIUM- shades Intensiv Milk, White-IM-, IW-, Generic

Enamel 1,2,3-GE1, GE2, GE3-, Opalescent Amber, Blue, Grey,White-OA,

OB, OG, OW- and MIRIS-COLTENE-WHALEDENT-shades Enamel

White Regular-EWR-, Enamel White Bleach-EWB-, Enamel Neutral

Regular-ENR-, Enamel Neutral Translucent-ENT-, Enamel Ivory Regular-

EIR-, Enamel Ivory Translucent-EIT-, Blue-B. Five 1 mm thick samples

were lighted-cured during 80 s (40 s on each side) and stored 24 h at 37 8C.

Five color parameters—L p, a p, b p, whitness index WI BERGER-,

yellowness index YI D1925—were measured with a spectro-colorimeter

(458/0) using 12 different illuminants: A, C, D50, D55, D65, D75, F2, F6,

F7, F8, F10, F11. The comparison of the delta E values between the 12

illuminants showed that the higher values of delta E are the following:

HFOIM:1,03 (between D55 and F6 illuminants), HFOIG:1,02(D75/F6),H-

FOGE1:1,96(D75/A),HFOGE2:1, 56(D75/A),HFOGE3:1,04(D75/A),

HFOOA:5,03(F7/A),HFOOB:2,53(D75/F11),HFOOG:2,76(D75/A),H-

FOOW:1, 57(D75/A), EWR:1,45(D75/A),EWB:1,07(D75/A),ENR:2,

61(F7/A),ENT:3,19(D75/A),EIR:3,29(D75/A),EIT:3,76 (D75/A),B:4,

07(D75/A). These results may explain the difference of colorimetric

perception by the human eye in different illumination conditions.

49. Microleakage around a low-shrinkage composite (InTen-S)

cured with a high-performance light (ASTRALIS 10);

A. Santinip, E Milia. (Edinburgh, UK and University of Sassari,

Sardinia, Italy)

The purpose of the study was to compare microleakage around the low-

shrinkage composite (InTen-S; Ivoclar) cured with the high-performance

light (ASTRALIS 10:Ivoclar) using a bonding agent (Excite; Ivoclar) with a

combination of controls as listed below.

Method and materials. Class V cavities were cut in 18 intact

human teeth. One half of each cavity was in enamel, one half in

cementum/dentine. The teeth were randomly assigned to three groups

ðn ¼ 12Þ: Group 1. Excite, InTen-S, ASTRALIS 10: Group 2. Excite,

InTen-S, Prismetics Lite2 (DeTrey) Group 3. Prime & Bond NT

(DeTrey), Spectrum (DeTrey), Prismetics Lite2; Excite was cured

with ASTRALIS 10 on low setting (700 mV/cm2) for 10 s. InTen-S &

Spectrum were applied in 2.0 mm increments. InTen-S was cured for

10 seconds with ASTRALIS 10 at .1250 mV/cm2 in Group 1 and for

20 s with the Prismetics Lite2 at 400 mV/cm2 in Group 2. In Group 3,

Prime & Bond NT and Spectrum were cured strictly in accordance

with the manufacturer’s instructions. Root apices were sealed with

acrylic resin and the teeth covered with two layers of nail varnish

except for an area of 1 mm around the cavity. The specimens were

stored in water for 6 days and then thermocycled 5000 times between

water baths held at 5 and 55 8C for 10 s at each temperature. The

transport time between baths was 10 s. After thermocycling the

samples were immersed in 5% Procion Brilliant Red buffered to pH 7

at 37 8C for 24 h and rinsed in distilled water for 15 min. A bucco-

lingual cut was made with a diamond disc through each cavity

creating two surfaces along which dye penetration could be measured.

The extent of microleakage was evaluated at £ 10 magnification

using the following criteria.

0 ¼ no leakage;

1 ¼ penetration to 1/3 cavity depth,

2 ¼ penetration to 2/3 cavity depth,

3 ¼ penetration to full cavity depth,

4 ¼ penetration onto axial wall.

The data was analyzed using Kruskal–Wallis non-parametric analysis

of variance test and Dunn’s multiple comparison test.

Results. There was no microleakage around any restorations at the

Enamel margins.

Gingival margins results:

Comparison Mean rank difference Mean rank difference Mean rank difference P value

Test Group 1. vs. Test Group 2. 25.875 ns P . 0.05

Test Group 1. vs Test Group 3. 29.50 Significant * significant * P , 0.05

Test Group 2. vs. Test Group 3. 23.625 ns ns P . 0.05


Group1. (Excite/InTenS/ASTRALIS10) Group3. (P&B.NT/Spectrum/-

Prismatics Lite2)

The results suggest that the low-shrinkage material cured with the high

performance light allows the placement of restorations in less time with

reduced microleakage and therefore offers significant clinical advantages.

50. In vitro erosion of dental luting cements by acidic beverages as a

function of the marginal gap; P. Scheutzelp, D. Lohmann (Department

of Prosthodontics, University of Munster, Germany)

As dissolution and disintegration of dental luting cements may result in

recurrent caries and loosening of the fixed restoration, one of the most

important properties of dental luting agents is their resistance to

environmental factors. In most international standards the values of

solubility and disintegration of dental luting agents are measured in water

and lactic acid solutions. However, these measurements may bear only little

relationship to the nature of in vivo erosion processes by different dietary

acids. Thus, the present study was conducted to investigate the solubility of

different types of dental luting agents immersed in commonly used acidic

beverages as it relates to the size of the cement gap.

The following luting agents were tested: zinc phosphate cements

(Harvard Zement w, Fixodont w), zinc oxide-eugenol cement (Opotow

Trial Zement w), zinc polycaboxylate cement (Carboxylatzement w),

glass ionomer (Aqua Meron w, Ketac Cem w), compomere (Dyract

Cem w), composite (Duo Cement w, Dual Zement w) and resin cements

(F21 w). Using acid-resistant Plexiglasw plates, standardized test

specimens with cement-filled gaps measuring 50, 100, 200, 250 and

300 mm in width were produced. The amount of substance lost at the

cement surface after 3- or 6 h immersion of test pieces in lemon,

orange and apple juice, Coca Cola w, Isostar w, mineral water, white

wine, and buttermilk was quantified profilometrically. In addition to

profilometric analysis, micromorphological surface changes were

assessed qualitatively by scanning electron microscopy.

Clear-cut differences were recorded between the different groups of

luting agents in their susceptibility to erosion. For example, the zinc

polycaboxylate and the zinc phosphate cements (mean erosion depth after

6 h: 2.5–2460 and 1.5–1400 mm, respectively) were eroded distinctly

more strongly under the same conditions than the glass ionomer cements

and the ZOE cement (mean erosion depth after 6 h: 3.0–570 and 5.0–

65 mm, respectively). The least substance loss was recorded in the

composite and the compomere luting agents (mean erosion depth after

6 h: 0–40 mm). Apart from the resin cement, which was not eluated but

rose out of the gap, the erosion depth of all luting agents, especially in case

of compomere and composite cements, underwent a marked increase with

an increasing width of the cement gap (rp ¼ 0:4–0:6; p , 0.001). The

erosion depth of the water-soluble cements was moreover closely correlated

with the acid content of the respective solution (multiple regression

analysis: rp ¼ 0:88–0:98=R2 ¼ 0:78–0:96; p , 0.001). A comparison of

the different beverages revealed clear-cut differences in their capacity to

erode the luting agents tested.

As the glass ionomer, compomere and composite luting cements are

distinctly more resistant to acidic beverages than zinc phosphate cements,

they should be given preference in the dentition damaged by or susceptible

to erosion. However, since the erosion depth especially for compomere and

composite cements were correlated with cement gap size, even in the case

of those largely erosion-resistant cements, every effort should be made to

optimize the marginal fit of fixed restorations and minimize the marginal

gap. The marked material loss of the zinc polycaboxylate cement tested

confirms previous observations which suggested that this type of cement

should be used with caution for long-term luting of fixed restorations.

51. Fluoride-release and secondary caries inhibition by new fluoride-

releasing restorative materials; H. Sonodap, S. Phanthavong,

M. Okuda, Y. Sasafuchi, Y. Kitasako, T. Nikaido, M. Otsuki, J. Tagami

(Tokyo Medical and Dental University, Tokyo, Japan)

This study evaluated the fluoride-releasing properties of a light-cured

one-step bonding resin (Reactmer Bond, Shofu) in vitro and also estimated

the effects of fluoride-releasing restorative materials (Reactmer Bond and

Reactmer Paste, Shofu) on the inhibition of artificial secondary caries

around restorations in monkey teeth in vivo. These materials, Reactmer

Bond and Reactmer Paste, are called ‘GIOMER’ system. GIOMER

comprises pre-reacted glass-ionomer filler (PRG, Ikemura et al., 2000), and

it is a new hybridization of glass-ionomer and composite resin.

Disk-shaped specimens of Reactmer Bond with a diameter of 3.0 mm and

a height of 0.36 mm were prepared. The amount of fluoride released from the

specimens in distilled water was measured up to 3 months (n ¼ 5 for each

group).

One box-shaped cavity (approximately 3 mm long, 4 mm wide, and

1.5 mm deep) was prepared on a buccal root dentin surface restored with

Reactmer. At 7, 30, and 90 days after operation, the teeth were removed

from the experimental animals and the roots were obtained by separating

them from the crown segments (n ¼ 4 for each group). Extracted bovine

roots were used as a control. Two box-shaped cavities on each bovine root

surface were prepared and filled with a bonding system without fluoride-

releasing (Clearfil Liner Bond 2V, Kuraray)/a resin composite without

fluoride-releasing (Clearfil AP-X, Kuraray) ðn ¼ 12Þ: The bovine roots

were then stored for one week in water. All restored roots were stored in

demineralizing solution (pH 4.5) for 3.5 days at 37 8C. A cut through the

center of each restoration was made parallel to the long axis of the root, and

the cut surfaces were polished and observed using a confocal laser scanning

microscope (CLSM, Okuda et al.,2000). Data were analyzed by one-way

ANOVA, Fisher’s PLSD Test at the 95% level of confidence.

Cumulative amounts of fluoride and the widths of the inhibition zone

are summarized in the table. Reactmer created a thick inhibition zone in the

artificial lesion along the restoration–dentin interface. The widths of the

inhibition zones were not significantly different among all groups

( p . 0.05). Inhibition zones were not observed adjacent to LB2V/AP-X

specimens. These results indicated that the fluoride-releasing restorative

materials have the potential to inhibit secondary caries formation around

restorations.

52. Post-operative symptoms after single-visit endodontic retreatment

of periapical lesions; G. Gambarini, L. Testarellip, G. Pongione, C. Di

Paolo, G. Floridi, E. Tucci, R. Pippi, L. Gallottini, M. De Luca

(University of Rome “La Sapienza” Dental School)

Several studies reported the efficacy of laser in disinfecting a contaminated

root canal and consequently reduce post-operative symptoms. The aim of the

present clinical investigation was to determine whether Nd/YAG laser therapy

has a beneficial effect on post-operative pain after single-visit non-surgical

endodontic retreatment of periapical lesions. Thirty retreatment cases

(infected teeth with periapical lesions) were selected and divided into two

homogeneous groups. All teeth (Groups A and B) were prepared using a

crown-down nickel–titanium rotary preparation, irrigated with 5.25% sodium

hypochlorite (Niclor, Ogna, Milan) and, after shaping procedures were

7 days 30 days 90 days

Cumulative amounts of fluoride (mean(SD) ppm) 0.07(0.004) 0.14(0.01) 0.21(0.02)

Widths of the inhibition zone (mean(SD) mm) 26(6) 32(11) 38(18)


completed, irrigated using ultrasonic irrigation for 2 min. Teeth of Group B

(laser) patients were then irradiated with Nd/YAG laser for 20 s. All canals

were obturated in the same visit with warm guttapercha and sealer. Occurrence

of pain was recorded 7 days after treatment. Data were collected and

statistically analyzed using the Mann–Whitney Wilconxon test. Pain ratings

were: Group A: 0. None 3 (20%), 1. Mild 4 (27%), 2. Moderate 6 (40%), 3.

Severe 2 (13%); Mean 2.2. Group B: 0. None 7 (46%), 1. Mild 4 (27%), 2.

Moderate 4 (27%), 3. Severe 0 (00%); Mean 1.2 Mean values showed that pain

intensity difference was significantly less ( p , 0.05) in the laser treated group

(B) than in the control (A) group. These findings suggest that the clinical

application of Nd/YAG laser migth be advantageous in reducing post-

operative pain following endodontic retreatment of periapical lesions.

53. Role of composite materials to prevent enamel marginal

demineralization; L. Savarinoa, A. Saponara Teutonicob,p, L. Breschib,

M. Visentina, C. Prati b (aIstituti Ortopedici Rizzoli, Bologna;bUniversity of Bologna, Italy)

New composite restorative materials have been recently developed to

prevent secondary caries formations and to reduce the risks for marginal

alterations. Several investigations demonstrated that marginal enamel surfaces

are highly affected by gaps and fractures caused by polymerization shrinkage

stress of composite materials. These gaps may increase the depth and the

extent of enamel demineralization and the consequent enamel caries. The

purpose of this study was to evaluate the role of composite and fluoride

releasing-materials to prevent demineralization after immersion in cariogenic

solution, in an attempt to evaluate their role in preventing secondary caries

formation. Twelve class V restorations were placed in vitro in human extracted

third molars and immersed in demineralizing solution to simulate the

formation of secondary caries and its effect on marginal integrity of composite

restorations. Scotchbond 1 plus Z 250, Scotchbond 1 plus F 2000, SE Bond

plus APX, ABF plus APX, and Fuji IX were used in the study. All restorations

were made by one operator. Each sample was stored in demineralizing solution

(lactic acid, pH 4.5) at 378 for 4 days. The cariogenic solution was changed

three times a day. Enamel marginal demineralization was firstly inspected

under optical microscope ( £ 60 magnifications). Microhardness evaluations

were performed with a Leica VMHT 30A microindenter device working at 50

gr for 15 s and with indentations at 20 mm. Results (mean(SD); n ¼ ; ANOVA

plus t test for paired data)

Conclusions. Exposed enamel was affected by demineralizing-cario-

genic procedures. However, enamel close to restoration margins frequently

showed the highest rate of demineralization, as demonstrated by the lowest

rate of microhardness number.

The materials which claimed fluoride release did not prevent any type of

enamel marginal alteration. The study demonstrated that exposed marginal

enamel shows the highest rate of demineralization and for this reason it may

be rapidly affected by secondary caries formation.

54. Resin bond strength and micromorphology of human teeth prepared

with an erbium/YAG laser; C.P. Trajtenberga,b,p, P.N.R. Pereiraa,b, J.M.

Powersa,b (aUniversity of Texas-Houston Dental Branch; bUniversity of

North Carolina at Chapel Hill, School of Dentistry)

The Er/YAG laser (2940 nm) used for cavity preparation offers advantages

over the rotary instrumentation such as selective caries removal, surface

etching and no need for anesthesia. There are limited data on how these effects

influence bond strength of restorative materials. The purpose of this study was

to determine the effect of two different surface treatments and 3 conditioners

on the bond strength of composite to enamel and dentin. Forty-eight, caries-

free third molars were used. Dentin specimens (D) were sectioned at the

occlusal surface 2 mm from the highest pulp horn. Enamel specimens (E) were

sectioned mesio-distally. Surfaces were polished and treated either with

carbide bur (B, Brasseler, USA) or an Er: YAG Laser (L, DeLight Laser

System, Continuum Biomedical). Laser energy settings for enamel and dentin

were 260 mJ/25 Hz and 160 mJ/10 Hz, respectively. Three different con-

ditions: acid-etch/bonding agent (ASM, Scotchbond Multipurpose, 3M

ESPE); same bonding agent without etching (SM), and an experimental

self-etching primer (SEP, EXL 547, 3M ESPE) were used. Resin composite

(Filtek Z250, 3M ESPE) was used to create composite build-ups. After storage

for 48 h at 37 8C and 100% RH, specimens were prepared in an hourglass

shape for microtensile bond test (ca. 1 mm) and debonded in tension at a

crosshead speed of 0.5 mm/min. Failure modes were classified using SEM into

three types: type 1, complete adhesive failure between bonding resin and

dentin/enamel; type 2, partial adhesive failure between bonding resin and

dentin/enamel, and partial cohesive in bonding resin; type 3, cohesive failure

within bonding resin. Means, standard deviations and failure modes by type

with percentages are listed. Data were analyzed with ANOVA ( p , 0.05).

Morphology of surface treatments were analyzed with SEM.

Scheffe’s intervals ( p , 0.05) for comparison among treatments,

conditioners and tooth substrates were 1.7, 2.7 and 1.7 MPa, respectively.

BD/ASM group had the highest bond strength. LE and LD resulted in the

highest bond strengths when used with ASM. Bur exhibited higher bond

strengths than laser with the use of SEP. Laser showed higher bond strengths

than bur with the use of SM. Most laser-treated groups exhibited a type two-

failure mode with the exception of LE/SM that was a type 1. BE and BD/SM

exhibited a 100% type 1. The remaining bur-cut groups exhibited a type 2

except BD/ASM that showed type 3. SEM analysis of laser-treated enamel and

dentin showed absence of the smear layer when compared to untreated control

surfaces. Laser-treated enamel resulted in a retentive pattern similar to acid-

etched enamel. Micromorphology of laser-treated dentin revealed a good

Material Groups

(N ¼ 8)

Marginal Enamel

Vickers Number

Exposed Enamel

Vickers Number

Protected Enamel

Vickers Number

ABF Bond þ APX 243.8(37.4) P , 0.001 325.5(54.4) 573.0(88.1)

Fuji IX 179.0(64.8) P , 0.001 272.9(101.2) 407.1(98.7)

F 2000 139.5(69.1) P , 0.001 227.9(108.5) 379.0(54.5)

Tensile bond strength (MPa) Predominant failure type and (%)

LE LD BE BD LE LD BE BD

SM 16.7 (5.8) n ¼ 15 9.1 (5.7) n ¼ 19 0a* n ¼ 20 0a n ¼ 20 1(77) 2(79) 1(100) 1(100)

ASM 25.8 (8.0)b n ¼ 20 21.1 (6.1) n ¼ 20 25.4 (10.3)b n ¼ 19 35.7 (10.2)d n ¼ 20 2(84) 2(63) 2(58) 3(68)

SEP 10.8 (4.7)c n ¼ 20 11.9 (2.8)c n ¼ 20 16.9 (9.3)a n ¼ 12 19.6 (5.5)a n ¼ 17 2(70) 2(53) 2(58) 2(80)pGroups with the same superscript letters are statistically the same ( p , 0.05)


definition of dentinal tubules. At lower energy settings, some smear plugs

remained evident. Bonded interfaces showed continuity of the hybrid layer

with the intertubular dentin when the dentin was acid-etched, and a gap when

the self-etching primer was used. The acid-etch and self-etching primers

allowed good resin tag formation. The resin tags produced by ASM and SEP in

the dentin presented a collar-like formation in the first 5 mm, and lateral

filaments due to the effect of the laser and as a result of resin monomer

penetration. The hybrid layer in the enamel disclosed an intimate adaptation of

the bonding agent with both ASM and SEP. Bonding of laser-treated teeth with

adhesive resin without the application of phosphoric acid was possible due to

the ability of the laser to remove the smear layer, which is usually present on

bur-cut surfaces. Acid-etching the tooth surface treated with either the laser or

bur, prior to the application of bonding resin, is necessary to achieve clinically

acceptable bond strengths. Supported in part by 3M ESPE.

55. National survey of adverse reactions to dental materials in the UK;

R. Van Noortp, A. Scott, J. Grummitt, P. Hatton, W. Egner,

D. Gawkrodger, C. Yeoman (University of Sheffield, UK)

Purpose

Dental treatment involves the use of a wide range of materials, and

they are therefore the most extensively employed biomaterials. Many

of these materials or their components pose a potential occupational

risk, as well as a risk to the patient. While the introduction of new

materials brings great benefits, there is always a risk of an adverse

reaction to one or more components by members of the dental team or

the public. Pre-market biocompatibility testing cannot guarantee

absolute safety, so it is important to identify materials that can

cause an adverse reaction when placed on the open market. The

prevalence of adverse reaction to dental materials and surgical

products among the general population and the dental profession has

not been effectively monitored, and have been reported to be up to 4

and 20%, respectively. It is important to identify the true extent and

severity of these reactions so as to be able to respond appropriately.

The aim of this project is to evaluate adverse reactions to dental

materials in the UK.

Method

A simple reporting form has been designed, and is being circulated to

approximately 23,500 dental practices and 2700 dental laboratories on a

regular basis. It has also been made available on the web (http://www.shef.

ac.uk/~arrp/). Dental professionals are requested to complete a reporting

form whenever an adverse reaction is suspected. An adverse reaction is

described as an unusual or unexpected response to contact with a dental

material. By dental material we mean any material found in the dental

practice or sold for dental purposes, such as restorative materials, rubber

gloves, toothpastes and oral rinses. However, it excludes drugs and local

anaesthetic that should be reported to the Yellow Card Adverse Drug

Reactions Reporting Scheme.

Results

To date the number of adverse reactions reported is 600, consisting of

268 and 329 patients and occupational adverse reactions, respectively. The

results show that the dental material suspected of causing most adverse

reactions in patients is metal, specifically amalgam ðn ¼ 64Þ: These adverse

reactions are seen as intra-oral swelling, tenderness and lichenoid type

lesions. Occupational adverse reactions were predominantly associated

with gloves ðn ¼ 213Þ; causing contact dermatitis, irritation and respiratory

problems to dentists, dental nurses and hygienists in the dental practice. In

contrast dental technicians were seen to experience most adverse reactions

to resin ðn ¼ 23Þ; causing contact dermatitis on the hands and fingers.

Conclusion

The results show that different groups of people are susceptible to

adverse reactions to different materials. This national survey has only just

begun and further work is needed to establish trends in relation to the

adverse reactions and whether or not adverse reactions are increasing or

declining.

Acknowledgement

Funded by the NHS National Programme for Primary Dental Care

Research and Development, reference number RDO/90/40.

56. Color stability of two resin-based composites after water aging;

A. Vichip, E. Bertelli, G. Blasi, M. Ferrari (University of Siena and

University of Genova, Italy)

Objectives. It has been recently suggested that some resin composite

systems, initially developed for indirect technique, can be used also for

direct restorations. As the polymerization method is different, this may

result in a different behavior of the resin system. One of the parameters that

may be affected, it is the intrinsic color shifting with time. The aim of this

study was to test the influence of exposure to water on the color stability of

two different resin-based composites.

Methods. Four comparable Vita shades of two different resin-based

composite systems were selected: Gradia (GC, Tokyo, Japan) and Sinfony

(Espe, Seefeld, Germany). For each product at each shade, three disks were

made, 1 mm in thickness and 15 mm in diameter. For each product, the

polymerization was made with its proprietary polymerization device and

with an office polymerization lamp. The samples were studied with a

spectrophotometer equipped with an integrating sphere. For color

determinations, a 50% gray card was used as background, and the data

were recorded in the CIE L pa pb p system. After the initial measurements,

the samples were stored for 30 days in a 60 8C water bath and then

measured again under same conditions. The color shifts were calculated

using the formula: DE ¼ ½ðL1 2 L2Þ2 þ ða1 2 a2Þ

2 þ ðb1 2 b2Þ2�1=2:

Results. If the standard of DE , 3.3 is taken into consideration as reference

for clinical acceptability both materials showed shade shifts that exceed the

reference value. Gradia showed a lower degree of discoloration, with 50%

of the comparisons within an acceptable shade shift (DE , 3.3) after aging

when polymerized in the laboratory device, and 75% of the comparisons

acceptable when polymerized in the laboratory device. Sinfony showed a

higher degree of discoloration with 25% of the comparison within

acceptable shade shift when polymerized with the halogen lamp and 50%

acceptable when polymerized in the laboratory device. However, the

difference of the DE values between the two products was not statistically

significant ðp ¼ 0:575Þ when evaluated with ANOVA statistical analysis.

The difference of the DE values between the two methods of polymerization

was also not statistically significant ðp ¼ 0:827Þ: Significance. From this

work it can be concluded that for these two products aging in water leads to

a certain degree of color instability. The different method of polymerization

does not influence the degree of shade shift of the two products when

submitted to water aging.

57. Carbon fiber post/composite core restoration of flared roots:

adaptation of one or more posts; D. Angerame (University of Trieste,

Trieste, Italy)

The aim of this in vitro qualitative study was to evaluate the adaptation

among materials and between materials and dentin in flared roots restored

with carbon fiber post and composite core build-up. A total of 48 human

monorooted premolars were divided into four groups of 12 teeth; their

crowns were sectioned and the root canals were enlarged by a diamond bur

until the dentin walls became very thin. After acid (20 s) and adhesive (self-

curing mode) conditioning (Scotchbond Multipurpose System, 3M) the

canals were completely filled with a self curing composite resin (Ti-Core N,

EDS, USA). A control group (G1) had only the composite resin into the

canal; the second group (G2) was restored with one carbon fiber post (Tech

2000, Isasan, Italy) inserted into the composite before its polymerization;

the third (G3) and fourth (G4) groups were restored by inserting three and

seven posts, respectively. The specimens were aged by thermocycling (150

cycles at 2–4/90–95 8C), nail coated, and immersed in super-saturated


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methylene blue solution (5 min); then they were sectioned and 10 cross-

sections (A) were obtained from each root; the cervical portion of the

specimen was longitudinally sectioned and four mesio-distal sections (B)

were prepared. The sections were observed by a stereomicroscope and the

dye penetration was scored 0–3; defects of adaptation and voids were also

checked. The data were analyzed by Kruskal–Wallis and Mann–Whitney

tests. The adaptation of materials was found very good and the percentage

of sections without dye penetration was high in all groups (A: G1 ¼ 99:17;

G2 ¼ 100; G3 ¼ 98:33; G4 ¼ 97:5; B: G1 ¼ 93:75; G2 ¼ 95:83; G3 ¼

89:58; G4 ¼ 87:5); there was no statistical difference among the groups.

The three variants of the technique can be useful in treating flared roots;

further in vitro investigations are required to understand which of the

variants has the better resistance to load.

58. The influence of the light source on resin composite polymerization;

P. Casconep, L. Di Palma, G. Montanaro, A. Apicella, S. Rengo

(University of Naples “Federico II”, Italy)

The aim of this study was to investigate the difference in kinetics of

composite polymerization using three types of light source. Four different

composites were tested: two traditional composites (Prodigy–Kerr and

Charisma–Kulzer); and two flow composites (Revolution–Kerr and Flow-

line–Kulzer). The composite samples were positioned in the Differential

Scanner Calorimeter cell (DSC 25 by Mettler Instrumente AG) and then light

cured. The DSC is able to record the heat developed during the polymerization

reaction. From the heat reaction it is possible to calculate the relative degree of

polymerization of composite materials. Each material was cured with three

different light sources: six samples were light cured with a halogen light

(Optilux 500-Kerr) at a constant power of 500 mW/cm2 for 60 s; six samples

were light cured with a halogen light (Astralis 10-Ivoclar Vivadent) using soft

start polymerization: in the first 10 s the intensity light increases from 150 to

650 mW/cm2, in the following 10 s the light works in a pulsating mode

between 650 and 1200 mW/cm2; six samples were light cured with a LED light

source (Zap) using a step polymerization technique: 5 s at low intensity

(50 mW/cm2) and then 12 s at high intensity (300 mW/cm2). The specific

reaction heats (J/g) with standard deviations for all tested composite materials

are shown in the following table:

Material Halogen

(Optilux)

reaction heat

(J/g)

LED (Zap)

reaction heat

(J/g)

Halogen

soft start

(Astralis)

reaction heat

(J/g)

Prodigy (Kerr) 30 (3) 32 (1) 32 (4)

Charisma (Kulzer) 29 (4) 29 (1) 30 (1)

Revolution (Kerr) 62 (4) 61 (2) 60 (7)

Flowline (Kulzer) 65 (9) 52 (1) 52 (2)

ANOVA statistical analysis was performed with p , 0.05. The three

different polymerization techniques showed no statistically different

reaction heats for all the tested materials except for the Flowline (Kulzer);

in this case the reaction heat obtained with the polymerization with halogen

light in one step at high power was statistically significantly higher than the

reaction heat obtained with the soft start and the step polymerization.

In conclusion, step and soft start polymerization are not able to cure all

the composite materials with the same conversion obtained with traditional

halogen polymerization.

59. Wear of posterior composite resins by glass beads abrasion test;

Y. Tanip, K. Kamata, A. Ishikawa (University of East Asia and Nippon

Dental University at Tokyo, Shimonoseki and Tokyo, Japan)

The glass-beads abrasion test reported by Tani et al. (1983) had foreseen

that the coarse-filled composites would be inferior to microfilled

composites in clinical results of wear resistance. The purpose of this

study was undertaken to determine an accurate appraisal of wear resistance

of different types of the composite resins. The composite resins used in this

study consisted of three highly-loaded coarse-filled composites; Clearfil

AP-X (Kuraray), Z250 (3M) and Beautifil (Shofu), two submicrofilled

composites; Palfique Estelite (Tokuyama) and Palfique Toughwell

(Tokuyama), and two microfilled composites; Silux Plus (3M) and Metafil

C (Sun Medical). Five specimens (10 £ 10 £ 1.5 mm3) of each material

were prepared by photo-curing. All specimens were polished with a 1200

grit SiC paper to wear away 200 mm from the surface to be tested. After,

these specimens were kept in a desiccator until they attained a constant

weight, the specific gravity of each material was measured by an electronic

gravity meter. The specimens, fixed in the horizontal drive arm, was

reciprocated with a 400 g load of glass beads at a velocity of 120 strokes per

minute for 10,000 times, which is equivalent to traveling 2000 m. The

degree of wear was measured by weight loss, converted to volume loss with

the specific gravity of each material. Two types of glass beads (Toshiba–

Ballotini) slurries were mixed with 140 g of the surface-treated glass beads

(EGB) to 100 ml water. The other slurry was prepared with the surface-non-

treated glass beads (GB). Both glass beads were 40 mm in diameter. These

were placed in an open-top stainless steel container like a ship. The slurry

was poured into the container. The results of glass bead wear of composite

resins are shown in Table 1.

Data were analyzed by two way ANOVA. It was concluded that the

wear with EGB was much larger than with GB. The microfilled composite

resin showed least wear compared to larger wear of the coarsefilled

composite resins. This result suggests that the filler particle size is relatively

important to wear resistance of the composite resin.

This research was supported in part by the Scientific Research Grant

(B)(1) No. 11470425, Ministry of Education and Science, Japan.

60. Thermal effects on the microstructure of human dentin; Y.K.E.

Ariantop, Na Peng Bo, S.M. Surono Akbar (Graduate Program of

Materials Science, Faculty of Mathematics and Natural Sciences and

Faculty of Dentistry, University of Indonesia, Jakarta, Indonesia)

Human dentin represents a hydrated biological composite structure for

Table 1

Glass bead wear of composite resins (cm2 £ 1023)

Materials Specific gravity Surface treated glass beads (EGB) Surface-untreated glass beads (GB)

Clearfil AP-X 2.03 56.37 (3.23) 22.53 (1.59)

Z250 2.08 61.31 (6.82) 28.63 (5.53)

Beautifil 2.25 71.78 (3.61) 37.48 (2.57)

Palfique Estelite 1.88 34.97 (3.14) 16.11 (2.43)

Palfique Toughwell 2.04 45.12 (1.97) 20.74 (2.88)

Silux Plus 1.60 32.13 (1.90) 15.10 (2.87)

Metafil C 1.47 23.04 (1.69) 7.56 (0.76)


which only limited structure–thermal property relationship are available.

Underlying treated and untreated dentin structural characteristics and

properties are the key considerations for future development of improved

restorative treatment.

The purpose of this study was to investigate the thermal effects on the

microstructure of human dentin by X-ray diffractometry (XRD), differential

scanning calorimetry (DSC), differential thermal analysis (DTA) and

thermogravimetry analysis (TGA).

Dentin samples were taken from sound permanent human third molar

teeth. Discs and powder specimens were heated to different temperatures

from room temperature (RT) to 1000 8C. The heat-energy changes

associated with physical and chemical transformations as a function of

temperature were measured by differential thermal analysis (DTA-50,

Shimadzu Corp., Japan). Dentin disc was placed in an alumina crucible and

heated from room temperature to 900 8C with heating rate of 10 8C/min.

Thermal decomposition behavior of human dentin discs and powder

from RT to 700 8C were determined using Differential Scanning

Calorimetry (DSC-50, Shimadzu Corp, Japan).

The loss of volatile decomposition products were measured by loss of

weight from dentin powder using Thermogravimetry analysis as a function

of temperature (TG-50, Shimadzu Corp, Japan). The heating rate was

10 8C/min from room temperature to 1000 8C.

To identify the structural phase changes, dentin discs were heated in a

Ring furnace at temperature of 150, 600, 750 and 830 8C, respectively. The

normal and heat-treated dentin discs were then examined by X-ray

diffractometry (Philips X-Ray Diffractometer type PW 3710 based with

PC-APD diffraction software) with Co K radiaton, 35 kV, 20 mA and step

scanning type with 1.5 s time/step. The crystallinity of dentin crystals were

calculated after profile fitting ð2u ¼ 288 2 428Þ using reference specimen of

quartz. Peak width (B) was calculated using Full Width at Half Maximum

(FWHM) from peaks of (002), (211) and (112) planes by Warren equation

ðB2 ¼ b2 þ b2Þ and crystallite size by Scherrer equation ðD ¼ kl=b cos uÞ:

The DSC of dentin shows a large endothermic curve at 50–285 8C,

likewise the DTA endothermic peak at 137 8C which represent a material of

less crystallinity and inhomogenous crystals. An exothermic peak was also

shown at 498 8C by DSC. The loss of dentin weight by TG analysis at 35–

330 8C was 8.52% with total weight loss of 21.26% after heated to 900 8C.

The results of XRD revealed that at higher temperature (750 and

830 8C) the amount of diffraction peaks of hydroxyapatite were higher and

more intense with the development of Whitlockite peaks at 2u ¼ 34:72;

36.32; 40.3; 55.48. The crystallite size were also higher showing crystal

growth upon heat-treatment.

It can be concluded that the thermal behavior of human dentin shows

physical and chemical changes with higher temperature, which affect their

microstructure and properties relationship.


Comparative evaluation of 2 resin materials in luting composite inlays

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