what is the Dental Occlusion

1. By
Prof. Mohamad Helal
Head of Oral Biology
Department

2. Occlusion
Def.
Contact relationship of the upper and
lower teeth during various activities of
the mandible (mastication, swallowing
and speech) .

3. Centric occlusion
•The relation of the upper and lower teeth
when they are in maximum intercuspation
during swallowing and the terminal position
of the masticatory stroke.

5. Centric relation
•Is a position of the
mandibule in which the
condyles are resting in
the most retrusive
unstrained position in
the glenoid fossa and
related anteriorly to the
distal slope of the articular
eminence.

6. Why we study the occlusion?
The study of occlusion helps in the
treatment of malocclusion,
Temporomandibular Joint problems,
in proper construction of dentures and
other dental restorations (e.g., crown and
bridge, etc…).

7. To study the occlusion it must be include the following
items:
1. Dental arch formation.
2. Compensatory curves of dental arches.
3. Compensatory curves of individual teeth.
4. Angulations of individual teeth in relation to various planes.
5. Functional form of the teeth at their incisal and occlusal thirds.
6. Facial relation of each tooth in one arch to its antagonist in
centric occlusion.
7. Occlusal contact and intercuspation of all teeth of one arch with
those in the opposing arch in centric occlusion.
8. Occlusal contact and interaction of all teeth during various
functional movements.

8. 1. Dental arch formation:
Outline of the maxillary arch is larger
than mandibular arch
• So, maxillary teeth overhang the
mandibular teeth when the teeth are in
centric occlusion
•Permits overbite and overjet relation
ship

9. Overbite: vertical relation of the upper
teeth to the lower teeth in centric
occlusion .
(increase efficiency of ant. teeth in biting
Over jet: horizontal relation of the
upper teeth to the lower teeth in centric
occlusion .
(increase duration of occlusal contact in
protrusive and lateral movements in incision
and mastication )
Importance:
•Prevent soft tissue biting
•Guide the mandible through
various lateral movement

10. Overbite enables the disclusion of the
posterior teeth during food incision and
increases the efficiency of the anterior teeth
in biting well.
Overjet increases duration of occlusal
contact in protrusive and lateral movements
in incising and mastication.

11.  From occlusal aspect the outline following
labial and lingual surfaces confirmed to a
parabolic curves.
• the dental arches have three segments:
1. Anterior segment : semicircular line
passing along facial surfaces of anterior
teeth.
2. Middle segment : straight line
continuous with semicircular segment ,
include 1st , 2nd , M half of 1st molar.
3. Posterior segment : straight line which
is parallel to the median plane e including
distobuccal half of 1st molar, B of 2nd
and 3rd molars.

12. Phases in development of dental arches :
1st phase: 6
•6 years
• 1st permanent molar take place post. to 2nd
deciduous molar
•Due to jaw growth Lead to :
• 1- increase chewing efficiency
2- Serve to back up the deciduous teeth
Mandibular one erupt firstly and max. one to
established occlusion
•1st permanent molar corner stone
2nd phase: 1,2
•Central and lateral lingual to the deciduous
predecessors.

13. 3rd phase: 4,5
•1st and 2nd premolar take place of
deciduous molar.
•Primate space the size of premolars
are smaller than the larger teeth they replace.
(Leeway space)
4th phase: 3,7
The canines (Keystones) and 2nd molars emerge. The
forcing of the canine bet. Incisors & 1st premolars in both
jaw with backing effect of 2nd molar
5th phase: 8
•3rd molar distal to the 2nd molar.

14. 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 called
“Leeway space’.

15. The average mesiodistal size of the deciduous
molars in that area is 47mm, which when
compared with the premolars dimension of
42.2 mm, indicates an average gain of 4.8 mm
in available space.
The leeway space must be utilized for
alignment of the lower incisors as these teeth
erupt with an average of 1.6 mm of crowding.
The remainder of the space will be utilized by
the mandibular molar.

16. This movement of the mandibular molars
may correct an end-to-end molar relationship
(normal for the mixed dentition) into a
normal molar relationship in the permanent
dentition, i.e., the mesiolingual cusp of the
maxillary first molar occludes in the central
fossa of the mandibular molar. This
relationship is discussed later on.

17. 2- Compensatory Curvatures of the dental
arches (Curved Occlusal Planes):
The significant of these curve as guidance
for mandible Movement to complement the
condyle paths and
for balance of mandible

18. •Curve of Spee
• Sagittal planes.
• Incisal Ridges of the anterior teeth and the B cusps of the
posterior teeth follow a curve which end at the anterior surface of
the condyle.
• when the arches were observed from a point opposite 6.

19. Curve of Wilson
• 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.
• Deeper posteriorly molars inclination is greater than
that of the premolar .

20. Curve of Monson
• Combination of curve of Spee and the curve of Wilson.
• coronal and sagittal planes.
• concave for the mandibular arch and convex for the maxillary
arch.
• in centric occlusion form a segment of a sphere of 4 inches
radius with the center of the sphere at the glabella

21. Bonwill Triangle
• Describe the mandible and found
that 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

22. Importance of compensatory
curves:
Guidance for the mandible movement to
complement the path of condyles for
balance of the mandible.

23. 3- Compensating curvatures of individual teeth :
 long axis of post. Teeth are not
To a horizontal plane but show axial
curvature
 importance :
1- stability of teeth to resist force
of mastication .
7, 8 distally inclined to
prevent any distal drift of the posterior teeth.
7,8 mesially inclined to
strike the maxillary molar

24. 3. Compensating curvatures of the
individual teeth:
When we observed the
dissected human jaw with
their roots exposed prove
that the long axis of
posterior teeth are not
perpendicular to a
horizontal plane but show
axial curvature. This
curvature is essential for
stability of teeth in the
dental arches to resist
forces of mastication.

25. •The maxillary 2nd &3rd
molars have distal
inclination to prevent
any distal drift of
posterior teeth while
mandibular 2nd & 3rd
molarare inclined
mesially to strike the
maxillary molars with a
mesial direction of
force

26. 4- Angulations of individual teeth in
relation to various planes
The inclination of a
tooth from a vertical
axis in mesiodistal
and faciolingual
directions
1- upper anterior: FL
inclined lingual
MD 1&2 inclined
slightly mesial but
canine toward distal

27. Def . Inclination of the tooth from a vertical axis in a MD
and FL direction.
(Considered root inclination so the crown inclined in
opposite direction ).
importance: Proper occlusal function ( each tooth must be
placed at the angle that best withstand forces during function )

28. 2-Maxillary premolars
are slight lingual in
FL, Distal in MD
3-Maxillary Molars
roots have lingual
inclination with distal
inclination

29. 4-Mandibular
anterior have
greet lingual root
inclination in FL. In
MD incisors are
nearly straight or
minor root
inclination while
canine has distal
root inclination

30. 5- Mandibular premolars
In MD have distal
inclination but in FL 1st
premolar incline
lingually. But 2nd
premolars is offset
buccally
6-Mandibular molars
moderate to great
buccal and distal toot
angulations

31. Frontal view of the angulation of mandibular teeth:

32. Frontal view of the angulation of maxillary teeth:

33. Sagittal view of the angulation of
maxillary & mandibular teeth:

34. FL angulations
All teeth
have
lingual
root
inclination
except the
2nd PM and
mandibular
M have
buccal
root
inclination

35. MD angulations
All teeth have
distally root
inclination except
the upper
incisors teeth
have slight
mesially root
inclination and
the lower
incisors have
slight mesial or
straight .