Occlusion

OCCLUSION Dental Anatomy Dent 201 Summer semester 2005/2006

Occlusion Definition   

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The act of closure or being closed A static morphological tooth contact relationship Includes all factors concerned with the development and stability of the masticatory system and the use of teeth in oral motor behavior Includes the integrated system of functional units involving teeth, joints and muscles of the head and neck

Concepts of occlusion Balanced occlusion   

Bilateral contacts in all functional excursions Prevent tipping of the denture bases Not necessarily existing in natural dentition because each tooth is a separate unit

Intercuspal position Centric occlusion Concepts developed in relation to orthodontics, complete dentures and full mouth rehabilitation 

None are completely applicable to natural dentition

Overview of primary occlusion Each tooth occludes with 2 teeth of the opposing jaw Exceptions  

Mandibular central incisor Maxillary second molar

Occlusion is supported and made more efficient after eruption of first permanent molars Interdental spacing is important for future sufficiency of space in permanent teeth Probability of crowding in permanent teeth is related to the amount of interdental spacing in primary dentition

Primary molar relationship Terminal plane relationship 

Flush  

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Distal step 

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56% - Class I Angle’s molar relationship 44% - Class II Angle’s molar relationship Class II Angle’s molar relationship

Mesial step  

A greater probability for Class I Angle’s molar relationship A lesser probability for Class III Angle’s molar relationship

Primary molar relationship Factors influencing the effect of terminal plane relationship on Angle’s molar relationship   

Differential growth of the jaw Forward growth of the mandible Sufficient Leeway space to accommodate a mesial shift of the permanent molars

• Leeway space is the amount of space gained by

the difference in the mesiodistal diameter between deciduous molars and premolars

Permanent occlusion Anteroposterior relationship Incisors: Class I, II, III  Canine: Class I, II, III  Molars: Angle’s Class I, II, III 

Faciolingual relationship Premolars  Molars 

Incisal relationship Class I Class II Class III Overjet Reverse   overjet Overbite

 Canine relationship Class I Class II Class III

Molar Occlusal relationship Angle’s Class I Angle’s Class II Angle’s Class III

Arch Occlusal relationship

Curves of occlusion Curve of Spee Curve of Wilson Sphere of Monson

Inclination & angulation of the roots of the teeth Mandibular arch is wider than maxillary arch Each tooth must be placed at the angle that best withstands the

Antagonists With the exception of mandibular incisors and maxillary third molars, each tooth contacts two antagonist teeth in the opposing arch Loss of one tooth keeps the adjacent tooth in contact with opposing antagonist Mesial or distal drifting into the space disturbs occlusal contact with antagonist teeth

Centric stops Lingual cusp tips of maxillary posterior make contact with opposing fossae and marginal ridges of mandibular posterior teeth Buccal cusp tips of mandibular posterior make contact with opposing fossae and marginal ridges of maxillary posterior teeth Lingual cusps of maxillary posterior teeth and buccal cusps of mandibular posterior teeth are called “supporting cusps” Areas of occlusal contact that a supporting cusp make with opposing teeth in centric occlusion are “centric stops” The tip of that cusp is also a centric stop Knowledge of centric stops are important in restorative dentistry

Movements away from centric occlusion Lateral   

Working side Non-working side In complete dentures  

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Balancing side Non-balancing side

Movement in TMJ Tooth guidance  

Group function Canine guidance

Protrusive 

Incisal guidance

Retrusive 

The most retrusive position is the centric occlusion in complete dentures