Occlusion part 1

2. DEFINITION
OCCLUSION is the contact relationship
of the upper and lower teeth during
various activities of the mandible
(mastication, swallowing and speech) in
functional and non functional positions.

3. WHY DO WE STUDY
OCCLUSION?!

4. 1) Helps in the treatment
of malocclusion and
temporomandibular joint
problems.
2) Proper construction of
dentures and dental
restorations (crowns,
bridges)
3) Alignment of dentition is
important in masticatory
function.

5. We have 2 terms to
differentiate between
Centric Occlusion Centric relation

6. CENTRIC OCCLUSION
•The relation of the upper and lower teeth when
they are in maximum intercuspation.
•It is a tooth to tooth relation irrespective of
condylar position.

7. CENTRIC RELATION
• Is the position of the mandible
in which the condyles are
resting in the uppermost
unstrained position in the
glenoid fossa and related
anteriorly to the distal slope of
the articular eminence.
• It is a bone to bone relation.

8. DEVELOPMENT OF OCCLUSION
Development of permanent occlusion should begin with
the occlusion of deciduous teeth.
Role of deciduous teeth :
1- Aid in development and growth of muscles of
mastication
2- Maintenance of space for proper eruption of
permanent teeth
3- Lack of space due to immature loss of deciduous is a
big factor in malocclusion

10. DECIDUOUS TEETH
Sequence of eruption in
deciduous teeth
A-B-D-C-E

11. PERMANENT TEETH
Sequence of eruption of
maxillary teeth
6-1-2-4-3-5-7-8
6-1-2-4-5-3-7-8
Sequence of eruption of
mandibular teeth
(6-1)-2-3-4-5-7-8
(6-1)-2-4-3-5-7-8
 The sequence of eruption may have some variations
 With teeth in girls erupting an average of 5 months earlier than
boys.

12. 1) Dental arch formation and form.
2) Compensatory curves of dental arches.
3) Angulations of individual teeth in relation to various planes.
4) Functional form of the teeth at their incisal and occlusal thirds.
5) Facial relation of each tooth to its antagonists in centric occlusion.
6) Occlusal contact of all teeth in centric occlusion.
7) Occlusal contact of all teeth during various functional movements.
ITEMS OF OCCLUSION

13. 1.DENTAL ARCH FORM AND FORMATION.
‫الملون‬ ‫الوادي‬-‫طابا‬

14. DENTAL ARCH
FORMATION
•Development of dental arches
passes through 5 phases :
1st phase:
 At 6 years
 1st permanent molars (6) take
place posterior to 2nd deciduous
molars
Help to:
1-increase chewing efficiency
2-Back up the deciduous teeth

15. 2ND PHASE  Central and lateral incisors
erupt lingual to the deciduous
predecessors. (1 & 2)
 Then they attain their position
anteriorly near the midline.

16. 3RD PHASE 4TH PHASE
 1st and 2nd premolars (4 & 5) take
place of deciduous molars anterior
to the first molars.
 This phase is of special significance
because of the larger size of their
predecessors.
 Canine (key-stone) force
itself between 2 and 4.
(wedging effect)
 2nd molar (7) erupts distal to
6 backing it up.

17. 5TH PHASE:
• 3rd molar (8) erupts distal to the 2nd molar (7)
• Dental arches are considered complete without
them.

19.  Interdental spacing between deciduous teeth is normal.
 Primate space: is a space found normally mesial to upper C,
and distal to lower C in deciduous dentition.
These spaces are used to achieve proper molar relationship by
mesial shifting of lower permanent molars in a process known
as
Early mesial shift
C
D

20. EARLY MESIAL SHIFT

21. LEEWAY SPACE
• The erupting premolars are smaller in mesiodistal dimension
than the primary molars.
• The difference in sizes between the premolars and primary
molars as well as the deciduous canines is called “LEEWAY
SPACE”.
CDE
345

22. • [Dec (C) + (D) +(E)] > [perm (3)+ (4)+ (5)]
• The difference between them = average of 4.8 mm
4.8 mm space
gain
The remainder will be
utilized by the perm
mandibular molars to
adjust occlusion
1.6 mm for
alignment of
crowded lower
incisors (Incisal
Liability)

23. Mesial shift of perm molars may correct
an end-to-end molar relationship
(normal for the mixed dentition) into
normal molar relationship in the permanent dentition
Late mesial shift

24. DENTAL ARCH FORM
From the occlusal aspect the outlines of the
dental arch may be elliptical, u shaped, square
or tapered

25. From occlusal aspect the outline of the dental arches
labialy and lingualy conform to parabolic curves (elliptical)
The dental arches have three
overlapping segments:
1. Anterior segment : semicircular line
passing along facial surfaces of anterior teeth
till 4.
2. Middle segment : straight line, include 1st
,2nd premolars, M half of 1st molar.
3. Posterior segment : straight line parallel
to the median plane including distobuccal half of
1st molar, 2nd and 3rd molars.

26. • Outline of the maxillary arch > mandibular arch
• So, maxillary teeth overhang the mandibular teeth when the
teeth are in centric occlusion so this permits:
overbite overjet

27. overjet
• horizontal relation of the upper teeth to the lower teeth in
centric occlusion
• (To remember: jets fly horizontally)
overbite
• vertical relation of the upper teeth to the lower teeth in
centric occlusion
Deep bite
Open bite
Edge to
edge
Cross bite

28. Importance of overjet and overbite
Prevent soft tissue biting
guide the mandible through various
lateral and protrusive movements

29. 1) Dental arch formation and form.
2) Compensatory curves of dental arches.
3) Angulations of individual teeth in relation to various planes.
4) Functional form of the teeth at their incisal and occlusal thirds.
5) Facial relation of each tooth to its antagonists in centric occlusion.
6) Occlusal contact of all teeth in centric occlusion.
7) Occlusal contact of all teeth during various functional movements.
ITEMS OF OCCLUSION

30. 2. Compensatory curvatures of the dental arches
‫الجمال‬ ‫وادي‬

31. 2. Compensatory curvatures of the dental arches

32. 1. CURVE OF SPEE
• Seen within the sagittal
planes
when arches are observed from
a point opposite 6.
• Incisal ridges of the anterior
teeth and the buccal cusps of
the posterior teeth follow a
curve which end at the anterior
surface of the condyle.

33. 2. CURVE OF WILSON
Seen in the coronal plane.
The occlusal surfaces of posterior teeth conform to a curved plane.
The crowns of mandibular posterior teeth must incline to the lingual while the
crowns of maxillary posterior teeth must incline toward the buccal.
Gets deeper posteriorly so that molars inclination is greater than that of the
premolar .

34.  Seen in coronal and sagittal planes.
 Combination of curve of spee and the curve of wilson.
 Concave for mandibular arch
 Convex for maxillary arch.
 In centric occlusion form a segment of a sphere of 4 inches radius with
the center of the sphere at the glabella
3. CURVE (SPHERE) OF MONSON

35. 4. BONWILL TRIANGLE
The mandibular dental arch adapts
itself to an equilateral triangle of 4
inches length.
 Apex at the mesial
contact area of the lower central
incisors
 angles of the base at
the centers of each condyle

36. IMPORTANCE OF COMPENSATORY CURVES:
1) Help to achieve occlusal balance during
mastication by simultaneous contact at more
than one point.
2) Guidance for the mandible movement to
complement the path of condyles for balance of
the mandible.

37. 1) Dental arch formation and form.
2) Compensatory curves of dental arches.
3) Angulations of individual teeth in relation to various planes.
4) Functional form of the teeth at their incisal and occlusal thirds.
5) Facial relation of each tooth to its antagonists in centric occlusion.
6) Occlusal contact of all teeth in centric occlusion.
7) Occlusal contact of all teeth during various functional movements.
ITEMS OF OCCLUSION

38. 3. Angulations of individual teeth in relation to
various planes.

39. 3. Angulations of individual teeth in relation to various planes.
1-Angulation is described MD and BL.
2-Angulations are described in terms of root inclination
so the crown is inclined to the opposite direction.
3-Importance: Proper occlusal function ( each tooth
must be placed at the angle that best withstand forces
during function )

40. Facio-lingual axial inclination

41. Faciolingual axial inclinations
All teeth lingually inclined EXCEPT
lower 5 slightly
inclined buccally
Lower molars moderately to greatly

42. Mesio-distal axial inclination

43. Mesiodistal Axial
inclinations
All teeth distally inclined
EXCEPT
Incisors nearly straight or slightly mesially inclined
Maxillary molars mesially inclined

44. 1) Dental arch formation and form.
2) Compensatory curves of dental arches.
3) Angulations of individual teeth in relation to various planes.
4) Functional form of the teeth at their incisal and occlusal thirds.
5) Facial relation of each tooth to its antagonists in centric occlusion.
6) Occlusal contact of all teeth in centric occlusion.
7) Occlusal contact of all teeth during various functional movements.
ITEMS OF OCCLUSION

45. Functional form of
the teeth at their
incisal and occlusal
thirds
‫البيضاء‬ ‫الصحراء‬-‫الفرافر‬‫ة‬

46. Functional form of the teeth at their incisal and
occlusal thirds
 Incisal and occlusal thirds of teeth crowns present
or
convex concave
surfaces at all contacting occlusal areas.
 NO FLAT PLANES on the incisal or occlusal surface of
any of the teeth unless they are created by wear or
accident.
Cusps and incisal ridges act as cutting blades when they
come to contact in centric occlusion

47. • When curved surfaces of different planes come into contact they
touch at circumscribed points or areas
spaces appear all around this point
=
SPILLWAYS or ESCAPEMENT SPACES

48. Their location and form differ when occlusal relation is
changed.
They are
LESS in centric occlusion LARGE in lateral and protrusive
relations

49. 1) Dental arch formation and form.
2) Compensatory curves of dental arches.
3) Angulations of individual teeth in relation to various planes.
4) Functional form of the teeth at their incisal and occlusal thirds.
5) Facial relation of each tooth to its antagonists in centric occlusion.
6) Occlusal contact of all teeth in centric occlusion.
7) Occlusal contact of all teeth during various functional movements.
ITEMS OF OCCLUSION

50. 5. Facial relation of each tooth in one
arch to its antagonist in centric
occlusion.
‫الكريستال‬ ‫جبل‬-‫الفرافرة‬

51. Facial relations of each tooth in one arch to its
antagonist in the opposing arch in centric occlusion.
In centric occlusion, each tooth occludes with TWO TEETH in
the opposing arch, except :
1) mandibular central incisors 1
2) maxillary third molars 8

52. Importance:
1. Distribute occlusal forces to several teeth.
2. Reduce the chances of over eruption of the teeth of the
opposing arch and the mesial migration of the teeth in the
same arch.

53. Enumerate the items of occlusion studied so far???
1) Dental arch formation and form.
2) Compensatory curves of dental arches.
3) Angulations of individual teeth in relation to various planes.
4) Functional form of the teeth at their incisal and occlusal
thirds.
5) Facial relation of each tooth to its antagonists in centric
occlusion.

54. To be continued…….
‫المنصورة‬-‫النيل‬ ‫عروس‬