B. Cleghorn DMD MScAssociate ProfessorDalhousie University

Introduction to Occlusion

Ideal Anatomical Contacts

Which cusp of which tooth is represented by the black dot (red arrow)?

The black dots represent MI contacts in a Class I occlusion

22 black dots represent 36 areas of contact of mandibular teeth with teeth in the maxillary arch

Guidelines for Learning Ideal Contacts

The DB (distobuccal) cusps of the mandibular molars contact the central pit or fossa of their maxillary counterparts

Maxillary third molar

Mandibular third molar

Maxillary second molar

Mandibular second molar

Maxillary first molar

Mandibular first molar

Guidelines for Learning Ideal Contacts

The MB (mesiobuccal) cusps of the mandibular molars contact the MMR of their maxillary counterparts and the DMR of the tooth mesial to that

Maxillary third molar

Mandibular third molar

Maxillary second molar

Mandibular second molar

Maxillary first molar

Mandibular first molar

Guidelines for Learning Ideal Contacts

The B (buccal) cusps of the mandibular premolars contact the MMR of their maxillary counterparts and the DMR of the tooth mesial to that

Maxillary second premolar

Mandibular second premolar

Maxillary first premolar

Mandibular first premolar

Guidelines for Learning Ideal Contacts

The cusp tip of the mandibular canines contacts the MMR of their maxillary counterparts and the DMR of the tooth mesial to that (maxillary lateral incisor)

Maxillary canine

Mandibular canine

Guidelines for Learning Ideal Contacts

The incisal ridges of the mandibular lateral incisors contact the MMR of their maxillary counterparts and the DMR of the tooth mesial to that (maxillary central incisor)

The incisal ridges of the mandibular central incisors contact the MMR of their maxillary counterparts

Maxillary lateral incisor

Mandibular lateral incisor

Maxillary central incisor

Mandibular central incisor

Guidelines • Identify tooth shown• Dot represents cusp of opposing

tooth• Mandibular teeth are 1/2 cusp mesial

to the maxillary counterparts• Contacts same for all mandibular

molars• DB cusp (Md) ->Central Fossa (Mx)• MB cusp (Md)-> MMR & DMR (Mx)

• B cusps and canines (Md) contact MMR & DMR of teeth 1/2 cusp mesial to maxillary counterparts

• Each tooth contacts two teeth• Except maxillary third molars• Except mandibular central

incisors

Which cusp of which tooth is represented by the black dot (red arrow)?

DB cusp of the mandibular left first molar

B cusp of the mandibular right first premolar

B. Cleghorn DMD MScAssociate ProfessorDalhousie University

Determinants of Occlusion

Horizontal DeterminantsRidge and Groove Direction

Working

Working

Balancing

Working

Protrusion

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Balancing

Working

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Balancing

Working

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Protrusion

B. Cleghorn DMD MScAssociate ProfessorDalhousie University

Determinants of Occlusion

Horizontal DeterminantsRidge and Groove DirectionBalancing Side Interferences

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Balancing

Working

Balancing

Working

Balancing sideInterference•Inner inclines of maxillary MLi cusp (CHC) •Inner inclines of mandibular DB cusp (CHC)

Frontal View

B. Cleghorn DMD MScAssociate ProfessorDalhousie University

Determinants of Occlusion

Horizontal DeterminantsRidge and Groove DirectionWorking Side Interferences

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Balancing

Working

Balancing

Working

Working sideInterference•Inner inclines of maxillary and mandibular cusps ( Non- CHC cusps) •Outer inclines of maxillary and mandibular cusps (CHC cusps)

Frontal View

B. Cleghorn DMD MScAssociate ProfessorDalhousie University

Determinants of Occlusion

Horizontal DeterminantsRidge and Groove DirectionDistance from the Condyles

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Balancing

Working

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Balancing

Working

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Protrusion

The angle between the working and idling grooves becomes greater the further the tooth is from the condyles