Occlusion part/ orthodontic continuing education

OCCLUSION (PART III)
INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com

Contents
 Introduction
 Posterior controlling factors
 Anterior controlling factors
 Understanding the controlling
factors

Vertical determinants of occlusal
morphology (on cusp height)
Horizontal determinants of
occlusal morphology (on ridge and
groove direction)
Summary
References

Introduction
 The occlusal anatomy of the teeth must
function in harmony with the structures
controlling the movement patterns of the
mandible.
 To maintain harmony of the occlusal
condition, the posterior teeth must pass
close to but must not contact their
opposing teeth during mandibular
movement

Posterior controlling factors

The angle at which the condyle moves
away from horizontal reference plane is
referred to as the condylar guidance
angle.
Two TMJ’s –posterior controlling
factors
Fixed factors

Anterior controlling factors
Vertical overlap and horizontal overlap
Variable factor (altered by dental
procedures)

Understanding the controlling factors
If the criteria for optimum functional
occlusion has to be fulfilled, the
morphologic characteristics of each
posterior tooth must be in harmony with
those of its opposing tooth or teeth during
all eccentric mandibular movements.
The relationship of a posterior tooth to the
controlling factors influences the precise
movement of that tooth.

Therefore, the significance of the
anterior and condylar guidances lies in
how they influence posterior tooth
shape.

Occlusal surface of the posterior teeth can be
affected in 2 manners
1. Height
2. Width
 Factors that influence the heights of cusps
and depths of fossae are the vertical
determinants of the occlusal morphology
 Factors that influence the direction of ridges
and grooves on the occlusal surfaces are
considered the horizontal determinants of
the occlusal morphology www.indiandentalacademy.com

Vertical determinants of occlusal
morphology (on cusp height)
a) Effect of condylar guidance
b) Effect of anterior guidance
c) Effect of plane of occlusion
d) Effect of curve of Spee
e) Effect of mandibular lateral
translation movement www.indiandentalacademy.com

a) Effect of condylar guidance

b) Effect of anterior guidance
It is a function of the relationship
between the maxillary & mandibular
anterior teeth.
Anterior guidance = Overjet X
overbite

c) Effect of plane of occlusion
It is an imaginary line extending from
cusp tip of mandibular canine to
distobuccal cusp of lower second molar
Relationship of this plane to the angle
of articular eminence influences the
steepness of the cusps.

As the plane of occlusion becomes
more nearly parallel to the angle of the
articular eminence, the posterior cusps
must be made shorter.

d) Effect of curve of Spee
3 components affecting the cusp
height are:
a) Length of the radius of the curve
b) Degree of curvature of the curve of
Spee
c) Orientation of curve of Spee

Length of the radius of the curve

Degree of curvature of the curve of
Spee

Orientation of curve of Spee

e) Effect of mandibular lateral
translation movement
Bennett movement- A bodily side shift
of the mandible that occurs during
lateral movements.

The degree of medial movement of
orbiting condyle depends on two
factors :
a.Morphology of medial wall of the
fossa.
b.Inner horizontal portion of the
Temporomandibular ligament
(which attaches to the lateral pole
of the rotating condyle)

Lateral translation movement has 3
attributes
1. Amount
2. Direction
3. Timing
 Amount and Timing are dependent on
medial wall of fossa and TM ligament.
 Direction depends on the direction
taken by the rotating condyle.www.indiandentalacademy.com

Effect of amount of lateral translation
movement on cusp height
Greater the amount of lateral translation
movement, shorter is the posterior cusp

Effect of the direction of lateral
translation movement on cusp height
Determined by the morphology and
ligamentous attachments of the TMJ
undergoing rotation.
The movement occurs within a 60
degree cone whose apex is located at
the axis of rotation.

Effect of timing of lateral translation
movement on cusp height
Dependent on the medial wall of fossa
and TM ligament.
Immediate side shift – when the lateral
translation movement occurs early
Progressive side shift – if movement
occurs in conjunction with an eccentric
movement

Horizontal determinants of occlusal
morphology
Influences the direction of ridges and
grooves on the occlusal surfaces
Each centric cusp tip generates both
laterotrusive and mediotrusive pathways
across its opposing tooth
Each pathway represents a portion of
the arc formed by the cusp rotating
around the rotating condyle www.indiandentalacademy.com

Horizontal determinants of occlusal
morphology (on ridge and groove
direction)
a) Effect of distance from rotating condyle
b) Effect of distance from mid-Sagittal plane
c) Effect of distance from rotating condyle and
from mid-Sagittal plane
d) Effect of mandibular lateral translation
movement
e) Effect of inter-condylar distance

a)Effect of distance from rotating
condyle
Greater the distance – wider the angle

b) Effect of distance from mid-
Sagittal plane
More the distance – wider the angle

c) Effect of distance from rotating
condyle and from mid-Sagittal plane
 The combination of the two positional
relationships is what determines the exact
pathways of the centric cusp tips
 Because of the curvature of the dental arch;
as the distance of tooth from rotating condyle
increases – distance from midsagittal plane
decreases, but distance from rotating
condyles increases FASTER than decrease
in distance from midsagittal plane.

Therefore, the teeth toward the
anterior region (e.g. premolars) have
larger angles than posterior teeth
(e.g. molars).

d) Effect of mandibular lateral
translation movement
 influences the directions of ridges
and grooves
Movement depends on 2 factors:
1. Amount
2. Direction

Effect of amount of lateral
translation movement on ridge and
groove direction

Effect of direction of lateral
translation movement on ridge and
groove direction

e) Effect of inter-condylar distance
 As inter condylar distance increases –
distance between the condyle and the
tooth increases – wider angles
(in a given arch configuration)
 As inter condylar distance increases – the
tooth is placed nearer the mid-sagittal
plane relative to the rotating condyle-
midsagittal plane distance – decrease in
the angle generated

Increase in inter-condylar distance – decrease in
angle between mediotrusive and laterotrusive
pathways

Summary
Vertical determinants of occlusal
morphology (on cusp height and
fossa depth)
Horizontal determinants of
occlusal morphology (on ridge and
groove direction)

Factor Condition Effect
Condylar
guidance
Steeper Taller
Anterior
guidance
More overbite
More Overjet
Taller
Shorter
Plane of
occlusion
More parallel Shorter
Curve of
Spee
More acute Shorter
Lateral
translation
Greater movement
More superior
Greater immediate shift
Shorter
Shorter
Shorter

Factor Condition Effect
Distance from
rotating condyle
Greater Wider the angle
Distance from
midsagittal plane
Greater Wider the angle
Lateral translation Greater Wider the angle
Intercondylar
distance
Greater Smaller the angle

References
 Occlusion series in BDJ, 2001;191:6-
7
 Okeson JP. Management of
Temporomandibular Disorders and
Occlusion, ed. 4th
, 1998; Mosby
 Ash MM and Ramfjord S. Occlusion,
ed. 4th
, 1966; WB Saunders Company,
Michigan

Santos JD. Occlusion Principles and
Concepts, ed. 2nd
, 1999; Ishiyaku
EuroAmerica, Inc. U.S.A.
 Shillingburg HT. Fundamentals of
Fixed Prosthodontics, ed.3rd
,
1997;Quintessence

Thank you
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Occlusion part/ orthodontic continuing education

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