This document discusses concepts of occlusion including definitions of normal, ideal, physiologic, and pathologic occlusion. It describes static and dynamic occlusion as well as supporting and non-supporting cusps. Compensatory curves including the curves of Spee, Wilson, and Monson are explained. Posterior and anterior centric contacts, the plane of occlusion, centric relation, and centric occlusion are defined. The importance of understanding centric relation for orthodontic diagnosis and treatment planning is highlighted.

1. DR DURGA PRASAD
Professor, Dept Of
Orthodontics.
Navodaya Dental College,
Raichur.
CONCEPT OF OCCLUSION

2. INTRODUCTION
 The study of occlusion is important aspect of
dentistry. The study & practice of dentistry
should be based on strong foundation of
knowledge of occlusion.
 The orthodontist should know what constitutes
normal occlusion in order to be able to
recognize abnormal occlusion.

3. OCCLUSION
 OCCLUSION : by dictionary definition refers
to the act of closure or being closed.
 OCCLUSION : The relationship of maxillary
and mandibular teeth when they are in
functional contact during activity of the
mandible
- Dorland’s Medical Dictionary

4. OCCLUSION
 According to Angle – occlusion is the
normal relation of the occlusal inclined
planes of the teeth when jaws are closed.
 According to Bishara – occlusion is the
way the maxillary and mandibular teeth
articulate.

5. OCCLUSION
 In modern dentistry – the word occlusion
has a static, morphological, tooth contact
connotation.
 Occlusion also has a functional implication
that involves the teeth and other parts of
masticatory system in various movement
situations.

6. NORMAL OCCLUSION
 Normal implies a situation commonly found
in absence of disease, and normal values in
a biological system are given within an
adaptive physiological range.

7. NORMAL OCCLUSION
 Normal occlusion therefore should imply
more than a range of anatomically
acceptable values, it should also indicate
physiological adaptability and the absence of
recognizable pathological manifestation.

8. IDEAL OCCLUSION
 The concept of ideal or optimal occlusion
refers both to an aesthetic and physiologic
ideal.
 It includes functional harmony, stability of
masticatory system & Neuromuscular
harmony

9. PHYSOLOGIC OCCLUSION
 The occlusion that shows no signs of
occlusion related pathosis.
 It may not be an ideal occlusion but it is
devoid of any pathological manifestations in
the surrounding tissues.

10. PATHOLOGIC OCCLUSION
 If the form & function are not in harmony &
the physiologic adaptive mechanism is weak,
one or more of its components can show
break down & exhibit Pathologic occlusion.

11. PATHOLOGIC OCCLUSION
 Evidences of pathologic occlusion:
- attrition of teeth
- occlusal trauma
- muscular spasm
- TMJ disorders

12. FUNCTIONAL OCCLUSION
 It is defined as an arrangement of teeth
which will provide the highest efficiency
during all the excursive movements of the
mandible which are necessary during
function.

13. STATIC & DYNAMIC OCCLUSION
‘Static’ refers to the form, alignment and
articulation of the teeth within and between the
arches, and the relationship of the teeth to their
supporting structure.
‘Dynamic’ refers to the function of the
stomatognathic system as a whole comprising
teeth, supporting structure, temporomandibular
joint & neuromuscular system.

14. TRAUMATIC OCCLUSION
 An occlusion judged to be causative factors
in the formation of traumatic lesions or
disturbances in the orofacial complex.

15. THERAPEUTIC OCCLUSION
 It is a treated occlusion employed to
counteract structural interrelationship related
to traumatic occlusion.

16. SUPPORTING CUSP:
- facial cusp of mandibular & palatal cusp of
maxillary posteriors
- also known as Stamp cusps
- occluded with central fossa & marginal
ridges of opposing teeth.

17. NON-SUPPORTING CUSP
- maxillary buccal & mandibular lingual cusp
- Shearing or Guiding cusps
- contact & guide the mandible during lateral
excursions & shear food during mastication

18. DYNAMIC OCCLUSION
 The 13 muscle attachment to the mandible in
addition to articular capsule and tendon
provide a high degree of stability of position
that occlusal equilibration and full mouth
reconstruction can’t change permanently

19. DYNAMIC OCCLUSION
 The teeth are in occlusal contact only 2 to
6% of the time.
 94% of the time, they are apart.
 The largest segment of time is in postural
rest position determined by musculature.

20. DYNAMIC OCCLUSION
Three components of occlusion can be summed up
as :
1. Occlusal position (or) tooth contact position
- Masticatory habits, tooth inclination and
malposition, shape of teeth, premature
contact,
faulty restoration, tooth loss, the condition of
periodontium affect the occlusal positions
2. Postural resting position
3. TMJ

21. NEUTRAL ZONE
 Dental arches are situated in a space
bounded by the lips & cheeks externally &
tongue internally
 There is equilibrium of muscular forces if the
lip-cheek-tongue system is in balance.

22. NEUTRAL ZONE

23. NEUTRAL ZONE
 Equal forces acting on the teeth from lingual
& facial sides helps the teeth to attain a
position of relative stability.
 An imbalance of the system can unfavorably
influence the position of teeth in the dental
arches.

24. COMPENSATORY CURVES OF DENTAL ARCHES
 Bonwill (1899)
- first to describe the mandible & mandibular
arch as adapting itself in part to an
equilateral triangle.

25. BONWILL’S TRIANGLE

26. COMPENSATORY CURVES OF DENTAL ARCHES
 Curve of Spee
- F. Graf Von Spee of Germany in 1890
 Its an antero-posterior curve extending from
tip of mandibular cuspid & following the
buccal cusp of bicuspid & molar continuing
as arc through condyle.
 It would form a circle of 4” diameter

27. CURVE OF SPEE

28. CURVE OF SPEE
 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.

29. CURVE OF WILSON
 It is a mesiodistal curve that contacts the
buccal and lingual cusps tips of the
mandibular posterior teeth.

30. CURVE OF WILSON

31. CURVE OF WILSON
 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.

32. CURVE OF WILSON

33. CURVE OF MONSON
 Monson (1920)
 Connected curve of Spee & curve of Wilson
to all cusp & incisal edges
 Suggested that mandibular arch adopted
itself to the curved segment of a 4” radius.

34. CENTRIC CONTACTS
 Anterior teeth contacts
 Posterior teeth contacts

35. POSTERIOR CENTRIC CONTACTS
 Facial & lingual range of contacts
- facial range of posterior centric contacts
involve the mandibular facial cusp tips
contacting the central fossa & marginal
ridges of opposing maxillary teeth

36. POSTERIOR CENTRIC CONTACTS
 Lingual range of posterior centric contact
involve the maxillary lingual cusp tips
contacting the central fossa & distal marginal
ridges of the opposing mandibular teeth.

37. ANTERIOR CENTRIC CONTACTS
 Anterior teeth have only one range of centric
contacts & are in line with the facial range
posterior centric contacts.

38. CENTRIC CONTACTS

39. PLANE OF OCCLUSION
 An imaginary surface that is related
anatomically to the cranium & that
theoretically touches the incisal edges of the
incisors & the tips of the occluding surfaces
of posterior teeth.

40. PLANE OF OCCLUSION
 A flat occlusal plane increases the chances
for the other occlusal factors as condylar &
incisal guidance, to disarticulate the posterior
teeth in protrusion & on the non working side.

41. CENTRIC RELATION
 CR may be defined as the relationship of the
mandible to the maxilla when the properly
aligned condyle disk assemblies are in the
most superior position against the eminentia,
irrespective of tooth position or vertical
dimension.

42. CENTRIC OCCLUSION
 CO refers to the relationship of the mandible
to the maxilla when the teeth are in
maximum occlusal contact, irrespective of
the position or alignment of the condyle disk
assemblies.
 Maximum interocclusal position

43.  CR is bilaterally symmetrical, is
physiologically accepted, & serves as a
therapeutic position for occlusal adjustment.
 CR is approximately 1mm distal to CO in 70-
90% of individuals.

44. IMPORTANCE OF CENTRIC RELATION
 In Orthodontics, diagnosis and treatment
planning should be performed by an
evaluation of an malocclusion with the
mandible in centric relation, i.e. the natural
musculoskeletal position of the condyle in
the fossa, in order to obtain the true maxillary
- mandibular skeletal and dental relations in
the three planes of space.

45. IMPORTANCE OF CENTRIC RELATION
 If this is overlooked an incorrect diagnosis
and treatment plan of the actual
malocclusion, along with its unfavorable
consequences, may result.