This document discusses the importance of maintaining normal tooth form and occlusion when performing restorations. It covers the key aspects of tooth contour, contact areas, embrasures, and occlusal anatomy. Abnormalities in any of these areas can lead to issues like food impaction, periodontal disease, tooth mobility, and wear. When restoring teeth, it is essential to replicate the proper relationships between contacts, embrasures, cusps and ridges to allow for efficient mastication and minimize pathological changes.

2. College of Dentistry
Operative Dentistry I
Tooth Histology, Form & Occlusion:Tooth Histology, Form & Occlusion:
Operative Considerations -2-Operative Considerations -2-
Dr. Hazem El Ajrami

3. • Tooth form and occlusion:
Thorough knowledge of normal tooth form
and occlusion is essential to establish properly
functioning restorations.
• The form of teeth refers to:
Their contour.
Their contact and embrasures.
Their occlusal and incisal anatomy.

4. • Maintaining normal tooth form and occlusion
serves the following functions:
Ensures efficient mastication and function.
Important in esthetics and good physical
appearance.
Assists in speech and proper phonetics.
Protection and maintenance of supporting
tissues.

5. I. Tooth Contour:
It refers to the convexity of the facial and
lingual surfaces of teeth. This degree of
convexity offers protection and stimulation to
the gingival tissues and underlying structures
during mastication.
• Normal tooth contour:
Location:
 In anterior teeth: at the cervical 1/3 of the
facial and lingual surfaces.
 In posterior teeth: at the cervical 1/3 of the
buccal surface and at the middle 1/3 of lingual
surface.

7. Tooth contours; (A): over-contouring, (B): under-
contouring and (C): normal contour of the buccal
surface

8. • Function:
It serves to deflect the food only to the
extent that it stimulates (by gentle massaging)
rather than irritate the gingiva and
periodontium.

9. • Abnormal tooth contour:
If the curvature is too convex (over-contouring),
it will deflect food away from the gingival
tissues depriving the gingiva and periodontium
from natural massaging action of food. This will
increase the susceptibility of periodontal disease
and increase plaque retention.
While with an abnormally flat surface (under-
contouring), the food will be impinged directly
onto the gum margins leading to trauma to the
attachment apparatus causing gingival and
periodontal affection.

10. II. Tooth proximal contact area:
It denotes the area of proximal height of
contour of the mesial or distal surfaces of a
tooth that contacts its adjacent tooth in the
same arch. Upon tooth eruption, there is
initially a contact point. The contact point
becomes an area because of wear of one
proximal surface against another during
physiologic tooth movements.

12. • Normal tooth contact:
 Location:
A. In anterior teeth: bucca-lingually it is
slightly inclined to labial surface, while
inciso-gingivally at the incisal 1/3.
B. In posterior teeth: bucca-lingually it is
inclined to the buccal surface. Occluso-
gingivally; it lies near the junction of
occlusal and middle 1/3 or in the middle 1/3.

13. Bucco-lingual location of contact area:
in upper teeth (A),lower teeth (B).

14. Inciso- or occluso-gingival location of contact area:
in upper teeth (C) and in lower teeth (D)

15. • Function:
Promote healthy interdental papillae.
Stabilizes and maintains the integrity of the
dental arches.
Establishes proper esthetic appearance.

16. Inter-dental PapillaeInter-dental Papillae

18. • Abnormal tooth contact:
An open or faulty contact leads to food
impaction and retention which is objectionable
by its physical presence and by production of
bad odor. In addition, it increases the
susceptibility to periodontal disease and caries.
Faulty location or size of contact area leads to
absence of spillways for food during mastication.
This will lead to periodontal disease as well as
concentration of stresses and fracture of
restoration especially at the marginal ridge.
An open contact may lead to drifting of teeth.

20. • Embrasures:
Embrasures are V-shaped spaces that originate
at the proximal contact areas between adjacent
teeth and are named for the direction toward
which they radiate. There are 4 embrasures;
facial, lingual, incisal or occlusal and gingival
embrasure.

23. • Location and function:
The embrasures are correlated to the contact
size and position. For example, buccal
inclination of the contact area in lower posterior
teeth renders the lingual embrasure wider than
the buccal one. This allows food to be displaced
more lingually, so that the tongue can easily
return the food to the occlusal surface during
mastication.

24. • In addition, the contact areas are located
progressively lower cervically from anterior to
posterior teeth. Thus, larger occlusal
embrasures result posteriorly. When
embrasures are given proper form, the
supporting tissues receive adequate stimulation
from food during mastication.

25. • Abnormal embrasure form:
Narrow embrasure (wide contact) will create
additional stresses on the teeth and the
supporting structure. Meanwhile, the food will
be deflected away from the gingival leading to
its atrophy.
Large embrasure (narrow contact) will
provide little protection to the supporting
structures as the food is forced by the
opposing cusp interproximally leading to
gingival inflammation and recession.

26. Narrow contact area (y) leading to large
embrasure (x)

27. III. Occlusal anatomy:
The posterior teeth are provided with
various anatomic markings on their
occlusal surfaces to serve many functions.
These anatomic markings are the cusps,
ridges , fossae and grooves.

28. • Location and functions of anatomic markings:
Cusps: cusps that contact the opposing teeth
along the central fossa in centric occlusion are
termed supporting (centric, holding) cusps and
those that overlap the opposing teeth during
centric occlusion are termed non-supporting (non-
centric, non-holding) cusps. In normal occlusion,
the maxillary teeth overlap the mandibular teeth.
In lower teeth, the buccal cusps are the supporting
cusps and the lingual are the non-supporting
cusps in centric occlusion. While in upper teeth,
the palatal cusps are supporting and the buccal are
non-supporting cusps.

30. Ridges: marginal ridges are elevated rounded
ridges located on the mesial and distal edges of
the occlusal surface of the tooth. Oblique ridge is
characteristic for maxillary molars while
transverse ridge is characteristic for lower first
premolar.
Fossae: are depressions between the cusps. Non-
coalesced enamel in a fossa is termed a pit.
Grooves: cusps are separated by distinct
developmental grooves and sometimes have
additional supplemental grooves on the cusp
inclines. Non-coalesced enamel in a groove is
termed a fissure.

31. Oblique ridge
Transverse ridge

34. • Two types of fissures exist:
I. Most of the teeth have normal fissure
shape; in cross section they V-shaped,
having a wide opening followed by a
narrow cleft. The carious lesion usually
starts as an enamel lesion on both sides of
the entrance of the fissure which is visible
and accessible to diagnose.

35. II. Atypical fissure pattern (10%) with a narrow
opening and a bulbous widening at the base.
These fissures are regarded as caries risk,
because a lesion can start at the base as well as
at the entrance to the fissure. It is difficult to
diagnose.

36. Normal fissure shapeNormal fissure shapeAtypical fissure shapeAtypical fissure shape

37. Atypical fissure pattern

38. • These anatomic markings should have definite
form, size, location and relation to each other
in order to perform their function properly. In
normal occlusal relationships forces of stable
vertical centric closure should be directed
along the long axes of teeth.

39. Normal occlusal relationship

40. • Functions of anatomic markings:
Mastication of food.
Stabilization of the jaws in different
positions.
Maintenance of the inter-arch relationship.

41. • Improper restoration of anatomic markings:
A. Adaptive changes: where efficiency of
mastication is affected but there is a
physiologic adaptation to the new
circumstances, for example: development of
light wear facets within the physiologic
adaptation range.

42. B. Pathologic changes: If abnormalities are
beyond the adaptive power of the tissues,
pathologic changes might occur such as:
1) Development of abnormal chewing habits
and abnormal jaw movements.
2) Development of tooth mobility.
3) Tooth wear.
4) Affection of supporting structures and
development of periodontal diseases.
5) Tempro-mandibular joint disturbances.

43. • Clinical considerations during restoration:
I. In anterior teeth:
 In incisors, incisal edges should be
restored to proper labio-lingual thickness
designed to cut or incise food.
 In cuspids, the cusp tip should be restored
with correct mesial and distal slopes
designed for tearing of food.

44. II. In posterior teeth:
 The correct relationships of contacts,
embrasures, cusps and marginal ridges of
adjacent and opposing teeth provide for the
escape of food from the occlusal surface
during mastication.

45.  The occlusal anatomy should be properly
carved:
 Cusps and opposing grooves act as mortar
and pestle for crushing food.
 Mesial and distal triangular fossae define the
marginal ridges and sharpen occlusal
contacts.
 Supplemental grooves widen the pathways for
opposing cusps movement.

46. Thank You