Occlusion and malocclusion

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Occlusion and malocclusion

عاشجم مـناد جهاد .أ

عاشجمـناد جهاد . د 19 / 2020/12

Ass. prof. Munad Jihad AL Duliamy

Types of dentition

Primary dentition

Mixed dentition

Permanent Dentition

2020/12 / 19

Ass. prof. Munad Jihad AL Duliamy

OcclusionIN PERMANENT DENTITIONAndrews in 1970 put forward the keys to normal occlusion.Andrews’ six keys to normal occlusion are as

follows:I. Molar interarch relationshipII. Mesiodistal crown angulationIII. Labiolingual crown inclinationIV. Absence of rotationV. Tight contactsVI. Curve of Spee

مـناد جهاد عاشج. د2018/11/18 19 / 2020/12

OcclusionAndrews’ six keys to normal occlusion

I. Molar interarch relationship

Mesiobuccal cusp of maxillary first molar rests in the mesiobuccal groove ofmandibular first molar.Distal surface of the distobuccal cusp of maxillary first molar should occlude withmesial surface of the mesiobuccal cusp of mandibular second molar. Mesiolingual cusp of the maxillary first molar should occlude in the central fossa of mandibular first molar.

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Andrews’ six keys II. Mesiodistal crown angulation (tip)

Crown angulations (tip) The gingival portion of the long axis of each crown should be distal to the incisal portion, this is known as crown angulation. Measured by the inclination of long axis of the crown to a line perpendicular to the occlusal plane.

M

مـناد جهاد عاشج. د2018/11/18

Andrews’ six keys III. Labiolingual crown inclination

Crown inclination (torque) The buccolingual inclination of the long axis of the crown and not the long axis of the entire tooth is known as crown inclination. Negative crown inclination or lingual crown inclination occurs in the maxillary and mandibular posteriors, whereas positive or labial inclination is seen in maxillary incisors.


Andrews’ six keys IV. Absence of rotation

• Rotation • Arch should be devoid of any rotated tooth. A rotated molar

occupies more mesiodistal space, creating a situation unreceptive to normal occlusion while a rotated incisor occupies less space.

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Andrews’ six keys V. Tight contacts

Interproximal contact Proximal contacts should be tight and no spacing should be present.

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Andrews’ six keys VI. Curve of Spee

Deep curve of Spee results in crowding. Flat curve of Spee is most receptive for normalocclusion. Reverse curve of Spee results in spacing.

Curve of Spee: A normal occlusion plane according toAndrews should be flat, with the curve of Spee not exceeding1.5 mm.

Normal occlusionAngle’s concept



Edward H. Angle in his 50s, as the proprietor of the Angle School of OrthodontiaNormal occlusionAngle’s concept


Angle’s concept of normal occlusion is based on: I. key of occlusion andII. line of occlusion.

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Normal occlusionAngle’s concept


i. Key of occlusionAngle considered maxillary first molar as the key of occlusion, as it is most constant in its position and this is related to key ridge position.According to Angle the mesiobuccal cusp of upper firstmolar rests in the mesiobuccal groove of mandibular firstmolar in normal occlusion, i.e. class I molar relation


The line of occlusion is a smooth curve passing through the central fossa of each uppermolar and across the cingulum of the upper canine and incisor teeth. The same line runsalong the buccal cusps and incisal edges of the lower teeth, thus specifying the occlusalas well as interarch relationships once the molar position is established.

According to Angle, in normal occlusion full complement of teeth should be present. Lines of occlusion are intact in both maxillary and mandibular arches, and molars in class I relation.

line of occlusion.

malocclusion


Skeletal

Munad . AL Duliamy

Dental

Classification of malocclusionDENTAL


Classification has traditionally been an important tool in diagnosis and treatment planning

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Classification of malocclusion


Angle described seven malpositions of individual teeth: (1) buccal or labial, (2) lingual, (3) mesial, (4) distal, (5) torso (rotated), (6) infra (not erupted sufficiently to reach the occlusal plane), and (7) supra (erupted through and beyond the occlusal plane). These individual tooth malpositions can be used to describe a malocclusion more fully.

malpositions of individual

Permanent DentitionClassification of malocclusion


The Angle classification system for malocclusions proposed by Angle is widely used and serves as an excellent means of general description that has facilitated the communication about different malocclusions within the professionThe system basically describes anteroposterior relationships of the permanent first molars and canines.

Angle’s classificationDivisions and subdivisions

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Angle described three classes of malocclusion, based on the occlusal relationships of the first molars of occlusion

Normal occluion

Class I: Normal relationship of the molars, but line of occlusion incorrect

because of malposed teeth, rotations, or other causes •

Class II: Lower molar distally positioned relative to upper molar, line of

occlusion not specified

Class III: Lower molar mesially positioned relative to upper molar, line of

occlusion not specified

Note that the Angle classification has four classes: normal occlusion, Class I

malocclusion, Class II malocclusion, and Class III malocclusion (see Fig)

Angle’s classification

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Munad . AL Duliamy

Normal occlusion and malocclusion classes as specified by Angle


Normal occlusion and Class I malocclusion share the same molar relationship but differ in the arrangement of the teeth relative to the line of occlusion. The line of occlusion may or may not be correct in Class II and Class III malocclusion.

Munad . AL Duliamy

Angle’s classification

Molar’s classification=modificationof

Angle’s clasification


Canine’s classification


Class I: mesial incline of the upper canine overlaps thedistal slope of the lower canine (The maxillary canineoccludes between the mandibular canine and 1stpremolar).

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Class II: Distal slope of the maxillary canine occludes or contacts the mesial slope of the lower canine.



Class III: The mandibular canine is displaced anterior to the maxillary canine with no overlapping



incisor’s classification


Class I: When the mandibular incisor edges lie or are below the cingulum plateau of the maxillary incisor (BSI, 1983), the overjet is 2-4 mm.

BSI: British Standards Institute

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Class II: When the mandibular incisors edges lie posterior to the cingulum plateau of the maxillary incisors (BSI, 1983). It could be:

Class II/1: Proclined maxillary incisors with overjet more than 4 mm.

Class II/2a: Retroclined maxillary centrals and proclined laterals, or both central and lateral incisors are retroclined with normal or reduced overjet.

Class II/2b: Retroclined maxillary centrals andproclined laterals, or both centraland lateral incisors are retroclined

but with increased overjet.



Class III: When the mandibular incisors edges lie anterior to the cingulum

plateau of the maxillary incisors (BSI, 1983).

Class III type 1: Positive overjet but less than 2 mm.

Class III type 2: Edge to edge incisors relationship.

Class III type 3a: Negative overjet.

Class III type 3b: Negative overjet but patient can

make edge to edge (pseudo Class III).

It is believed that incisor classification could

also be used for esthetic considerations.


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Flush terminal (FT): Present when the distal surfaces of the upper and lowersecond primary molars were in the same vertical plane when thejaws were in centric occlusion.

Occlusion PRIMARY DENTITION

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Occlusion PRIMARY DENTITION

Distal step (DS): Recorded when the distal surfaces of the lower primary second molar present in posterior relationship to the distal surface of the upper second molars when the jaws were in centric occlusion.


OcclusionPRIMARY DENTITION

Mesial step (MS): It was listed as present when the jaws were in centric occlusionand if the distal surfaces of the lower primary second molar occurred in anterior

relationship to the distal surface of the upper second molars

OcclusionPRIMARY DENTITION


A normal relationship of the primary molar teeth is the flush terminal plane relationship .

The primary dentition equivalent of Angle’s Class II is the distal step. A mesial step relationship corresponds to Angle’s Class I.

An equivalent of Class III is not often seen in the primary dentition because of the normal pattern of craniofacial growth in which the mandible lags behind the maxilla.


Proffit et al, 2019

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Classification of malocclusionSKELTAL




The ideal relationships of the facial and dental components can be represented as shown in (A). Cephalometric analysis can distinguish and clarify the differing dental and skeletal contributions to malocclusions that present identical dental relationships. A Class II division 1 malocclusion, for example, could be produced by (B) protrusion of the maxillary teeth although the jaw relationship was normal,(C) mandibular deficiency with the teeth of both arches normally related to the jaw,



(D) downward and backward rotation of the mandible produced by excessive vertical growth of the maxilla. A Class III malocclusion could be produced by (E) true mandibular prognathism with a normal maxilla, (F) maxillary anteroposteriorand vertical deficiencies that make a normal-size mandible look prominent because the maxillary vertical deficiency allowed it to rotate up and forward, or any other combination of maxillary deficiency and mandibular excess.

Aims of Orthodontic treatment


The Development of OrthodonticsCrowded, irregular, and protruding teethhave been a problem for someindividuals since antiquity, and attemptsto correct this disorder go back at least to1000 BC

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The objectives of orthodontic treatment


The objectives of orthodontic treatment are summarized by Jackson into:

i. Functional efficiency

ii. Structural balance

iii. Aesthetic harmony

Munad . AL Duliamy(Fig. 1) Jackson’s triad

the fowllowing three objectives put together are popularly known as Jackson’s triad (Fig. 1)

i. Establishing functional efficiency: Correction of malocclusion eliminates all the unfavorable sequelae of malocclusion and thereby restores the functional efficiency of the masticatory apparatus.

ii. Restoring structural balance Achieving structural balance between the hard and soft tissues maintains stability of the corrected malocclusion.

Failure to achieve structural balance will lead to relapse or loss of correction achieved.

iii. Aesthetic harmony: The prime objective of orthodontic treatment is the improvement of the facial aesthetics and is the single most common reason for the patients to approach an orthodontist.

The objectives of orthodontic treatment


Imbalanced oral environment

Restoring structural balance

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Limitations of orthodontic treatment

Patient Compliance

periodontal disease

Presence of Heavily restored teeth

Presence of crowns and bridges

Systemic diseases, Bone, blood, endocrine disorders and drug presecriotinsmoking and poor oral hygiene

There is several limiting factors for orthodontic treatment below are the main

Occlusion and malocclusion

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