This document discusses the ideal anatomical contacts between the maxillary and mandibular teeth in a Class I occlusion. It explains that the mandibular teeth contacts are positioned one half cusp mesial to their maxillary counterparts. The specific cusp contacts between opposing teeth are described for each tooth group. Guidelines are provided for identifying the tooth and cusp represented by black dots on diagrams. Horizontal determinants of occlusion including ridge and groove direction, balancing and working side interferences, and the effect of distance from the condyles are also outlined.

1. Introduction to
Occlusion
Ideal Anatomical
Contacts
B. Cleghorn DMD MSc
Associate Professor
Dalhousie University

2. Which cusp of which
tooth is represented by
the black dot (red
arrow)?
Theblack dots
22 black dots
represent MI
represent 36
contacts contact
areas of in a
Class I occlusion
of mandibular
teeth with teeth
in the maxillary
arch

3. Guidelines for Learning Ideal Contacts
Maxillary third
molar
Maxillary second
molar
Mandibular Maxillary first
molar The DB (distobuccal)
third molar
cusps of the
Mandibular
mandibular molars
second molar
contact the central pit
Mandibular
or fossa of their
first molar
maxillary counterparts

4. Guidelines for Learning Ideal Contacts
Maxillary third
molar
Maxillary second
molar
Maxillary first
molar The MB (mesiobuccal)
Mandibular
cusps of the
third molar
mandibular molars
Mandibular contact the MMR of
second molar their maxillary
Mandibular counterparts and the
first molar DMR of the tooth
mesial to that

5. Guidelines for Learning Ideal Contacts
Maxillary
The B (buccal) cusps
second
of the mandibular
premolar
premolars contact the
Maxillary MMR of their maxillary
first counterparts and the
Mandibular premolar DMR of the tooth
second premolar mesial to that
Mandibular
first premolar

6. Guidelines for Learning Ideal Contacts
The cusp tip of the
mandibular canines
Maxillary contacts the MMR of
canine their maxillary
counterparts and the
DMR of the tooth
mesial to that
(maxillary lateral
Mandibular
incisor)
canine

7. Guidelines for Learning Ideal Contacts
The incisal ridges of
the mandibular
lateral incisors
contact the MMR of
Maxillary lateral their maxillary
incisor counterparts and the
Maxillary DMR of the tooth
central incisor mesial to that
(maxillary central
incisor)
The incisal ridges of
Mandibular the mandibular
lateral central incisors
incisor contact the MMR of
their maxillary
Mandibular central
counterparts
incisor

8. 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

9. 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

10. Determinants of
Occlusion
Horizontal
Determinants
Ridge and Groove
Direction
B. Cleghorn DMD MSc
Associate Professor
Dalhousie University

12. Working

13. Balancing
Working
Working

14. Protrusion

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Balancing
Working

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Balancing
Working

19. Protrusion
QuickTime™ and a
Animation decompressor
are needed to see this picture.

21. Determinants of
Occlusion
Horizontal
Determinants
Ridge and Groove
Direction
Balancing Side
Interferences
B. Cleghorn DMD MSc
Associate Professor
Dalhousie University

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Balancing
Working

23. Frontal View Balancing
side
Interference
•Inner inclines
of maxillary MLi
cusp (CHC)
•Inner inclines
of mandibular
DB cusp (CHC)
Balancing
Working

24. Determinants of
Occlusion
Horizontal
Determinants
Ridge and Groove
Direction
Working Side
Interferences
B. Cleghorn DMD MSc
Associate Professor
Dalhousie University

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Animation decompressor
are needed to see this picture.
Balancing
Working

26. Frontal View Working side
Interference
•Inner inclines
of maxillary and
mandibular
cusps ( Non-
CHC cusps)
•Outer inclines
of maxillary and
mandibular
cusps (CHC
cusps)
Balancing
Working

27. Determinants of
Occlusion
Horizontal
Determinants
Ridge and Groove
Direction
Distance from the
Condyles
B. Cleghorn DMD MSc
Associate Professor
Dalhousie University

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Balancing
Working

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Balancing
Working

32. Protrusion
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33. The angle
between the
working and
idling grooves
becomes
greater the
further the
tooth is from
the condyles