Tooth form and occlusion are important factors in restoring teeth. The restoration should mimic the original tooth anatomy to restore efficient chewing, aesthetics, speech, and protect tissues. Correct tooth contours, marginal ridges, embrasures, and proximal contacts are important for function and self-cleaning. Cavity preparation should consider the structure of enamel and dentin to avoid enamel fracture or sensitivity. Ideal occlusion involves cusp-fossa relationships between opposing teeth and aligned dental arches with correct intercuspation.

1. Tooth form & Occlusion

2.
Tooth form and occlusion
Importance
Determine:
- Restoration of teeth: Generally, the
restoration should mimic the original tooth
anatomy to restore
1. efficient mastication,
2. esthetics,
3. speech and
4. protection of investing tissues

3. Agenda
Physiology of tooth form
How the structure of enamel
and dentin influence cavity
design?
Features of an ideal
occlusion
Factors of occlusion
affecting restorative
dentistry

4. Physiology of tooth form
Contact area
Marginal ridge
Embrasure

5. Normal periodontium
• Restoration margin should be placed
supragingivally to preserve the gingival health

6. Tooth contours
• Definition: convexity of axial surfaces of teeth
• Function:
Protection of supporting tissues
Stimulation of gingiva during mastication

7.
Tooth contours
Over-contour
- Food deflect during
mastication with less
stimulation of gingiva.
- Food retention under
overcontour with consequent
caries or gingivitis
Under-contour
- Direct impact of
food on supporting
tissues causing
trauma to them.
Normal

8. Height of epithelial attachment
• The epithelial attachment seals the soft tissue to
the tooth.
• It could be injured during
- Careless probing during examination.
- Improper tooth preparation techniques.
• Care should be taken during tooth preparation
to avoid injury to periodontal attachment.

9. Marginal ridges
• In restorative dentistry,
marginal ridges should be
restored in two planes;
buccolingually and cervico
occlusally
• Adjacent marginal ridges
should be restored at the same
height.

10. Embrasure
• The correct relationship of embrasures, cusp
to sulci, marginal ridge and grooves of
adjacent and opposite teeth provide for the
escape of food from occlusal surfaces during
mastication.
• Correct embrasure form and size is important
for self cleaning action.

11. Proximal contact
Definition: height of contour of
the proximal surface of tooth
that touches its adjacent tooth in
the same arch
Location:
- Incisal 1/3 of incisors
- Premolars and molars: Junction
of occlusal and middle 1/3

12. How the structure of enamel and
dentin influence tooth preparation?
• Enamel
- Enamel is brittle and when not
supported by sound dentin
[undermined enamel], it is liable to
fracture and should be removed.

13. How the structure of enamel and
dentin influence cavity design?
• Dentin
-Dentin is sensitive at dentino- enamel junction due to
branching of dentinal tubules at that region.
-Obstruction of dentinal tubules and precipitation of
minerals by aging or due to subjection to irritation reduce
dentin sensitivity.
- Cavity floor should be o.20.5 mm beyond sensitive
DEJ for non adhesive
restoration..

14. Occlusion
• Definition
Occlusion means the contact of teeth in
opposing dental arches when the jaws are
closed (static occlusal relationships) and
during various jaw movements (dynamic
occlusal relationships)

15. Occlusion
• Definition
Centric relation is the relation between
mandible and maxilla where the condyle in
the rear most, upper and mid most position in
the glenoid fossa.

16. Occlusion
Definition
• Maximum intercuspation is the maximum
occlusal intercuspation irrespective of condylar
position.
• Complete intercuspation is seen when the
intercuspal position and retruded position are
coincident during mandibular closure.
• Occlusal contacts that prevents this are called
premature contacts

17. Angle’s classification for interarch
relationship
- Class I: most common
[maxillary mesiofacial cusp
located in the mesiofacial
developmental groove of the
mandibular first molar]
- Class II: posterior
positioning of mandible to
maxilla.
- Class III: anterior
positioning of mandible to
maxilla.

18. Mandibular movement
Rotational movement around the horizontal axis.

19. Mandibular movement
Forward movement of the mandible
[protrusion]

20. Mandibular movement
Side to side movement
[lateral excursions]
Working
side
Balancing
side

21. Features of an ideal occlusion

22. Inter-arch tooth relationship
• The contact relationship is either
1- Surface contact [anterior]
2- Cusp to fossa apposition
[posterior teeth].
Supporting
cusp

24. Cusp to fossa relationship [cusp to
marginal ridge]
• Supporting
cusps are
mandibular
buccal cusps
and maxillary
palatal cusps

25. Cusp to fossa relationship
• Non
Supporting
cusps are
mandibular
lingual cusps
and maxillary
buccal cusps

26. Patient with cusp to fossa contact

27. Alignment of teeth
and Dental arches
• In both jaws, cusps are
aligned in parabolic
curves.
• In normal condition,
maxillary jaw overlap
mandibular jaw.

28. References
Chapter 4; physiology of
tooth form
Chapter 2; clinical significance of
dental anatomy, histology,
physiology and occlusion