OCCLUSION, MALOCCLUSION AND ITS CLASSIFICATION

DR. GOLAM SOROARFCPS TRAINEE, DDCH

IntroductionThe study of occlusion involves the entire stomatognathic system, the understanding of the inter relationship between the teeth, periodontal tissues, bones, joints, muscles, and nervous system during the full range of mandibular movements as well as the normal functional movements.The study of occlusion is essential for the proper undertsnding and for achieving the objectives of orthodontic treatment.

Definitions Occlusion: Occlusion may be defined as

the contact relationship between maxillary and mandibular teeth in function and parafunction.

Normal occlusion: The ward “Normal” simply implies a situation commonly found in the absence of disease.

Normal occlusion usually involves occlusal contact, alignment of teeth, overjet, overbite, arrangement and relationship of teeth to osseous structure.

Cont… Ideal occlusion: The structural and

functional relationship of maxilla and mandible that include idealized principles and characteristics that an occlusion should have.

Balanced occlusion: An occlusion in which balanced and equal contacts are maintained throughout the entire arch during all excursions of the mandible.

Cont… Functional occlusion: It is defined as an

arrangement of teeth, which will provide the highest efficacy during all the excursive movements of the mandible, which are necessary during function.

Physiological occlusion: An occlusion which has no signs of occlusion related pathosis.

It may not be an ideal occlusion.

Cont… Traumatic occlusion: It is an abnormal

occlusal relation that is capable of producing or has produced an injury to the periodontium.

Theraputic occlusion: An occlusion that has been modified by appropriate therapeutic modalities in order to change a non-physiological occlusion to that is at least physiologic if not ideal.

Cont… Centric relation: It may be defined

as the relation between maxilla and mandible in which the mandibular condyles are in the most superior and retruded position in their glenoid fossa with the articular discs properly interposed.

Cont… Centric occlusion: The occlusion in

which maxillary and mandibular teeth are in maximum intercuspal contact with the centric relation of the mandible.

Eccentric relation: Other than centric relation is called eccentric relation. It may be lateral, protruded or retruded occlusion.

Cont… Canine guided or protected

occlusion: During lateral movement of mandible, the opposing upper and lower canines of the working side comes in contact resulting in disocclusion of all posterior teeth.

This type of occlusion is seen in young adults with unworn dentition.

Cont… Mutually protected occlusion: The

occlusion in which the posterior teeth prevent excessive contact of the anterior teeth in maximum intercuspation and the anterior teeth disengage the posterior teeth in all mandibular excursive movements.

Cont… Group function occlusion: It may be

defined as the multiple contact relationship between the maxillary and mandibular teeth, in lateral movements of the working side; where by simultaneous contacts of several teeth is achieved and they act as a group to distribute occlusal forces

Andrew’s six keys to normal occlusion.

Key 1: Molar realtion- The mesio-buccal cusp of maxillary 1st permanent molar should occlude in the anterior buccal groove of mandibular 1st permanent molar.

Cont… Key 2: Crown

angulation- The gingival part of the long axis of the crown must be distal to the occlusal part.

Cont… Key 3: Crown

inclination- The crowns of the maxillary incisors are so placed that the incisal portion of the labial surface is labial to the gingival portion of the clinical crown. In all other crowns, the occlusal portion of the labial or bucccal surface is lingual to the gingival portion.

Cont… Key 4: Absence of rotation- All

teeth must be free from any undesirable rotations.

Key 5: Tight contacts- All teeth must have tight contact points.

Key 6: Flat curve of spee- Curve of spee should flat.

Compensatory curvatures

Curve of spee: It refers to the antero-posterior corvature of the occlusal surfaces, beginning at the lower cuspid and following cusp tip of the bicuspids and molars continuing as an arc through the condyle. If the curve is extended it forms a circle of about 4 inches diameter.

Compensatory curvatures It is measured from the most

prominent cusp of the lower 2nd molar to the lower central incisor. More than 1.5 mm deep curvature in not acceptable.

Compensatory curvatures Curve of wilson: If a line

is drawn from the buccal cusp tip to the lingual cusp tips of mandibular posterior teeth and extended to the opposite side, it forms another curvature, which is termed as curve of wilson

This is due to inward inclination of the posterior teeth.

Compensatory curvatures Curve of monson: ?????????

Malocclusion and It’s ClassificationMalocclusion may be defined as appreciable deviations from the ideal that may be considered aesthetically or functionally.

Classification of malocclusion is the description of dentofacial deviations according to a common characteristic or norm

Types of MalocclusionIntra arch MalocclusionInter arch MalocclusionSkeletal Malocclusion

Intra-arch malocclusion Includes individual tooth position,

variations and malocclusions affecting a group of teeth within an arch.

Inclinations- mesial,distal,lingual

and buccal Displacements- mesial,

distal,lingual and buccal.

Infra occlusion Supra occlusion Rotations Transposition

Intra Arch Malocclusion

Intra Arch Malocclusion

Inter-arch malocclusion Malrelation of dental arches to one

another upon skeletal bony basis that may themselves be normally related.

Sagittal plane malocclusions Vertical plane malocclusions Transverse plane malocclusions

Sagittal plane malocclusions Pre-normal occlusion

Mandibular arch anteriorly placed in centric occlusion.

Post-normal occlusionMandibular arch posteriorly placed in centric occlusion.

Vertical plane malocclusions Deep bite

Excessive vertical overlap between maxillary and mandibular anteriors.

Open biteNo vertical overlap.- Anterior region- Posterior region

Transverse plane malocclusions

Includes various types of cross bites.

Poterior cross biteAnterior cross bite

Skeletal malocclusion Includes defects in underlying skeletal

structure. Due to abnormalities in maxilla or mandible in

size, position or relationship between jaws. Sagittal abnormalities

Prognathism Retrognathism Combinations

Transverse abnormalities Narrowing and widening of jaws causes crossbites

Vertical abnormalities Variation affects lower facial height.

Systems of Classification of Malocclusion 1. Angle’s classification2. Dewey’s modification of Angle’s

classification 3. Lischer’s modification of Angle’s

classification 4. Bennet’s classification 5. Simon’s classification 6. Ackermann-Profitt classification 7. Incisor classification

Angle’s classification It was introduced by Edward Angle in 1899. Based on mesiodistal relationship of teeth, dental

arches and jaws. Maxillary 1st molar is taken as key to occlusion.Three classes : Class I Class II

Class II division I Class II division II Class II subdivision

Class II division I subdivision Class II division II subdivision

Class III True Class III Pseudo Class III Class III subdivision

Class I Normal inter-arch molar relation The anterior buccal grove of mandibular 1st

permanent molar occlude with the anterior buccal cusp of the maxillary 1st permanent molar.

Dental irregularities Crowding Spacing Rotations Missing teeth

Normal skeletal retaionships. Normal muscle function. Includes bimaxillary proclination – normal Class I

molar relationship but the dentitions of both arches are forwardly placed in relation to the facial profile.

Class-I Malocclusion

Class II The lower arch occlude at least half a

cusp distal than normal in relation to the upper arch.

Class II division I Characterized by proclined upper

incisors,therefore, increased overjet. Lip trap and abnormal muscle activity

like hypotonic upper lip or hypertonic mentalis and buccinator may be associated.

Class II division II Characterized by lingually inclined

upper central incisors and labially tipped upper lateral incisors overlapping the centrals.

Class II subdivision Class II molar relation exist on one

side and Class I molar relation on the other side. Class II division I subdivision Class II division II subdivision

Division 1

Class-ІІ Malocclusion

Division 2

Class III The lower dental arch occlude at least half a

cusp mesial than normal in relation to the upper dental arch.

True Class III Pseudo Class III Class III subdivision

True Class III – Skeletal Class III malocclusion of genetic origin. Characterized by -

Excessively large mandible Forwardly placed mandible Maxilla is smaller than normal Combinations

Pseudo Class III – Produced by forward movement of mandible during jaw closure Also called postural/habitual Class III Due to

Occlusal prematurities Premature loss of posterior deciduous.

Class III subdivision – Class III molar relation on one side and Class I on the other.

Class-III Malocclusion

Advantages of Angle’s Classification First comprehensive classification. Most widely accepted. Simple Easy to use Conveys precisely the relationship

of mandibular teeth with the maxillary 1st permanent molar.

Drawbacks of Angle’s Classification Considers malocclusion only in the

anteroposterior plane and not in transverse/ vertical planes.

Considered 1st permanent molar as fixed points in the skull, not found to be so.

Cannot be applied if 1st permanent molar is missing or to deciduous dentition.

Doesn’t distinguish between skeletal/dental malocclusion.

Doesn’t highlight etiology.

Dewey’s modification of Angle’s classificationAngle’s Class I Type I – Class I with crowded anteriors. Type II – Class I with protrusive maxillary

incisors. Type III – Class I with anterior cross bite. Type IV – Class I with posterior cross bite. Type V – Mesially drifted permanent

molars due to early extraction of deciduous.

Incisor classification Class I Class II

Division I Division II

Class III

Class II div 1

Class I Class II div 2

Class III

Class I Mandibular incisor edges occlude with

or lie immediately below the cingulum plateau of the maxillary central incisors.

Class II Mandibular incisor edges lie posterior

to the cingulum plateau of the maxillary central incisors.

Division I Division II

Division I Maxillary central incisors are proclined or of

average inclination and there is an increased overjet.

Division IIMaxillary central incisors are retroclined; the overjet is normally decreased, but maybe increased.

Class III Mandibular incisor edges lie anterior to the

cingulum plateau of the upper central incisors; the overjet is decreased or reversed.

Incisor Classification

Class-I Class-II Class-III

Conclusion Normal alignment of teeth not only

contributes to the oral health but also goes a long way in the overall well-being and personality. Correct tooth position is an important factor for esthetics, function and for overall preservation of dental health. So malocclusion should be considered as a factor that may affect a person’s physical and mental health as well as his social status.