Occlusion – Basic concepts presentation

this presentation gives a brief overview about the basic concepts of occlusion

1. OCCLUSION –
BASIC
CONCEPTS
Dr. Ridhi Kothari Tyagi

2. OCCLUSION
•Angle defined it as the normal relation of the occlusal inclined planes
of the teeth when the jaws are closed.
•According to Glossary of Orthodontic terms-Occlusion:
The relationship of the maxillary & mandibular teeth, as they are
brought into functional contact.
•According to Glossary of prosthodontic terms-Occlusion:
The Static relationship between the incising or masticating surfaces
of the maxillary or mandibular teeth or teeth analogues

3. Occlusion has
•Static aspect : refers to form, alignment, and articulation of
teeth within and between the arches and their relationship
to their supporting structures.
•Dynamic aspect : refers to the functions of the
stomatognathic system as a whole comprising of teeth,
supporting structures, TMJ, nerves and muscles.

4. Important terms
•Ideal occlusion : a preconcieved theoretical concept of occlusal
structural and functional relationships that include idealized
principles and characteristics that an occlusion should have.
•Physiologic occlusion : it refers to an occlusion that deviates in
one or more ways from ideal yet it is well adapted to that
particular environment, is esthetic and shows no pathologic
manifestation or dysfunction.
•Functional occlusion : occlusion in which balanced and equal
contacts are maintained throughout the entire arch during all
excursions of the mandible.

5. •Therapeutic occlusion : an occlusion that has been
modified by therapeutic modalities in order to change a
non-physiologic occlusion to one that is atleast physiologic
if not ideal.
•Traumatic occlusion : is an abnormal occlusal stress which
is capable of producing or has produced an injury to the
periodontium.
•Trauma from occlusion : defined as periodontal tissue
injury caused by occlusal forces, through abnormal
occlusal contacts.

6. Types Of Cusps
1) Centric holding cusps
They occlude in to the central fossae and marginal ridges of
opposing teeth.They are also called the stamp cusps.eg. Max.
lingual and mand buccal.
2) Non-supporting cusps
They contact and guide the mandible during lateral
excursions and shear food during mastication.They are also
called shearing or guiding cusps.eg. Max. buccal and mand.
lingual

7. Teeth arrangement
•Cusp to embrasure / Marginal ridge
occlusion: Occlusion of one
supporting cusps into a fossa and
the occlusion of another cusp of the
same tooth into the embrasure area
of two opposing teeth. This is a tooth-
to-two-teeth relation.
•Cusp to fossa occlusion : Supporting
cusp occluding into fossa. This
produces an interdigitation of the
cusps and fossa of one teeth with the
fossa of only one opposing tooth.
This is tooth-to-one-tooth relation.

8. Imaginary occlusal planes and
curves
•Curve of Spee
•Curve of Wilson
•Curve of Monson

9. An imaginary anteroposterior line from the cusp tips of the
canine extending to the buccal cusps of the posterior teeth
◦An excessively concave curve of Spee and mandibular
core line restrict the occlusal surface available for
maxillary teeth.
◦A flat to slightly concave curve of Spee and mandibular
core line bare the proper occlusal surface for optimal
occlusion.
◦A convex curve of Spee and mandibular core line bare
excessive portions of the occlusal surface.
Curve of Spee

10. It is a curve that contacts the
buccal and lingual cusps tips
of the mandibular posterior
teeth.
It helps in two ways
◦Teeth aligned parallel to
direction of medial
pterygoid for optimum
resistance to masticatory
forces.
◦The elevated buccal cusps
prevent food from going
past the occlusal table.
Curve of Wilson

11. Curve of Monson
•It is obtained by extension of the curve of spee and curve of
Wilson to all cusps and incisal edges
• According to G.S.Monson, who introduced this concept in 1920
• All cusps & incisal edges in a natural dentition are tangent to a
surface of a sphere, approximately 4 inches (10.2cm) in radius,
with its center in the area of the glabella

12. Classification of occlusion
•Based on Mandibular Position
•CENTRIC RELATION
Centric relation is the relation of the mandible to the
maxilla when the mandibular condyles are in the most
superior and retruded position in their glenoid fossa
with the articular disc properly interposed.

13. CENTRIC OCCLUSION
Centric occlusion is that position of the
mandibular condyle when the teeth are in
maximum intercuspation. Centric occlusion is also
called intercuspal position or convenience
occlusion.
• Centric relation and centric occlusion should
coincide in order to have perfect harmony
between the teeth, the temperomandibular joint
and the neuromuscular system.

14. CENTRIC CONTACTS
They are areas of the teeth
that contact the opposing
teeth.

Centric contacts have been
classified into
- posterior centric contacts
and
- anterior centric contacts.

15. Posterior centric contacts
The posterior centric contacts consist of the facial range of
contacts and the lingual range of contacts.
Facial range of posterior centric contacts involve the
mandibular facial cusp tips contacting the central fossae
and mesial marginal ridges of the opposing maxillary teeth.
Lingual range of posterior centric contacts involve the
maxillary lingual cusp tips contacting the central fossae
and distal marginal ridges of the opposing mandibular
teeth.

16. Anterior centric contacts
Anterior teeth have only one range of centric contacts and are
in line with the facial range of posterior centric contacts.
Posterior centric contacts result in axially directed forces as
convex cusp tips occlude on an opposing tooth area that is
perpendicular to the force.
These contacts that occur on inclines are called poded centric
contacts.
If the contact occurs on two inclines, the contact is termed bi-
poded contact.
on three inclines; tri-poded contacts.
on four inclines; quadra-poded contacts.

17. ECCENTRIC OCCLUSION
Eccentric occlusion refers to contact of teeth that occurs
during movement of the mandible.
- Eccentric occlusion can be of two types:
1.Functional occlusion
2.Non-functional occlusion

Functional occlusion
Functional occlusion (also called working side occlusion)
refers to tooth contacts that occur in the segment of the
arch towards which the mandible moves.

- Functional occlusion can be of two types :
a. Lateral functional occlusion
b. Protrusive functional occlusion

18. Lateral functional occlusion:
It includes tooth contacts that occur on canines and
posterior teeth on the side towards which the mandible
moves.
- The lateral functional occlusion can be of two types :
1. Canine guided occlusion:
2. Grouped lateral occlusion

19. Canine guided occlusion:
During lateral mandibular movement, the opposing upper &
lower canines of the working side contact thereby causing
disclusion of all posterior teeth on the working &, balancing
sides.

Canine guided occlusion is usually seen in young individuals
with unworn dentition.
In a canine guided occlusion, the mandibular canine cusp tip
tracks from the centric contact point at the mesial marginal
ridge towards the cusp tip of the maxillary canine.

20. Grouped lateral occlusion :
In addition to canine guidance, certain other posterior teeth
on the working side also contact during lateral movement of
the mandible.
 Such a type of contact during lateral movement is called
grouped lateral occlusion.
Protrusive functional occlusion:
It includes eccentric contacts that occur when the mandible
moves forward.
Ideally the six mandibular anterior teeth contact along the
lingual inclines of the maxillary anterior teeth while the
posteriors disocclude.

21. Non-functional occlusion

They are tooth contacts that occur in the segment
away from which the mandible moves.
For example if the mandible is moved to the left side,
contacts occur on the right side of the arch.

22. Disclusion
•It is used to describe separation of non-functional
posterior teeth during eccentric motions of the jaw.
•Brought by :
•Condylar guidance
•Incisal guidance

23. SIX KEYS TO NORMAL OCCLUSION
Given by Lawrence F Andrews in 1972.

.
The six keys are :
1.Molar interarch relationship.
2.Mesiodistal crown angulation.
3.Crown inclination.
4.Absence of Rotations.
5.Tight contacts.
6.Occlusal plane

24. Molar interarch relationship ;
The distal surface of the distobuccal cusp of the upper
first permanent molar contacts & occludes with the
mesial surface of the mesiobuccal cusp of the lower
second molar.
The mesiobuccal cusp of the upper first permanent
molar lies within the groove between the mesial &
middle cusps of the lower first permanent molar
The mesio-lingual cusp of the upper first molar seats
in the central fossa of the lower first molar.

25. 1. Improper molar relationship. 2. Improved molar relationship.
3. More improved molar relationship. 4. Proper molar relationship

26. Mesiodistal crown angulation
The gingival portion of the long axis of each crown is
distal to the incisal portion, varying with the individual
tooth type.

27. Crown angulation (tip) – long axis of crown
measured from line 90 degree to occlusal
plane

28. Crown inclination( labiolingual/ buccolingual inclination)
•It is determined from a mesial or distal view.
•The long axis of the crowns of the maxillary & mandibular
incisors are labially inclined to a degree sufficient to resist
overeruption of their antagonists.

29. Crown inclination is determined by the resulting angle between a
line 90 degrees to the occlusal plane and a line tangent to the
middle of the labial or buccal clinical crown.

30. In the case of the maxillary canines & posterior teeth a lingual
crown inclination exists, which is relatively constant & similar
from the canines through the second premolars, & is slightly
more pronounced in the molars.
The mandibular posterior teeth have a similar lingual crown
inclination that increases progressively from the canines through
the second molars.

31. Absence of Rotations :
The normal occlusion should be free of undesirable rotations.
Tight contacts :
No interdental spaces exist, but rather tight contacts between
the teeth.
Occlusal plane :
The plane of occlusion is either flat or a mild curve of spee is
present.
Intercuspation of teeth is best when the plane of occlusion is
relatively flat.

32. Conclusion
•The study of occlusion is an important aspect of
dentistry and a thorough knowledge of the same helps
in creating a well balanced stomatognathic system.