Fundamentals of occlusion/cosmetic dentistry courses

INDIAN DENTAL ACADEMY
Leader in continuing Dental Education
www.indiandentalacademy.com

CONTENTS
 INTRODUCTION
 DEFINITION
 TMJ
 CENTRIC RELATION
 MANDIBULAR MOVEMENTS
 DETERMINENTS OF OCCLUSION
 OCCLUSAL INTERFERENCES
 NORMAL V/S PATHOLOGIC OCCLUSION
 VARIOUS OCCLUSAL CONCEPTS
 CONCLUSION
 BIBLIOGRAPHY

INTRODUCTION
 Unfortunately the occlusion of teeth is
frequently overlooked or taken for granted in
providing restorative dental treatment for
patients. This may be due in part to the fact
that the symptoms of occlusal disease are
often hidden from the practitioner not
trained to recognize them or to appreciate
their significance..

 The long term successful restorations are
dependent upon the maintenance of occlusal
harmony. The minimal expectation of the
competent practitioner is the ability to
diagnose and treat simple occlusal
disharmonies. Practitioners must be able to
produce restorations that will avoid the
creation of iatrogenic occlusal disease

DEFINITION:
 The static relationship between the incising
or masticating surfaces of maxillary or
mandibular teeth or tooth (GPT-7)

ANATOMY OF
TEMPOROMANDIBULAR JOINT

Collateral ligament
•They function to restrict
the movement of the disc
away from the condyle.
•They allow the disc to
move passively with the
condyle as it glides
anteriorly and posteriorly

Capsular ligament
The capsular ligament acts
to resist any medial, lateral
or inferior forces that tend
to separate or dislocate the
articular surfaces
A significant function of
the capsular ligament is to
encompass the joint, thus
retaining the synovial fluid

Temporomandibular ligament
•Consists of 1) outer oblique
portion. 2) inner horizontal
portion
•The oblique portion prevents
excessive dropping of the
condyle, therefore limiting the
mouth opening.
•The inner horizontal portion
limits the posterior movement
of the condyle.

Accessory ligaments

CENTRIC RELATION
The maxillomandibular relationship in which
the condyles articulate with the thinnest
avascular portion of their respective discs with
the complex in the anterior-superior position
against the shapes of the articular eminences.
This position is independent of tooth contact.
This position is clinically discernible when the
mandible is directed superiorly and anteriorly. It
is restricted to a purely rotary movement about
the transverse horizontal axis.

 CHIN POINT GUIDANCE:
 DAWSON’S BILATERAL MANIPULATION:
 TONGUE TO PALATE

MANDIBULAR MOVEMENTS

SAGITTAL PLANE
In sagittal plane, the
mandible is capable of
purely rotational movements,
as well as translation
rotation occurs around the
terminal hinge axis.

Rotational
translatory

HORIZONTAL PLANE:

FRONTAL PLANE:
The lateral movement in the
frontal plane, the non-working
condyle moves downward and
medially.
While the working condyle
rotates around the sagittal axis
perpendicualr to this
plane.This may be lateral and
upward.

Transverse hinge axis
A purely hinge movement occurs as a
result of the condyles rotating in the
lower compartments of the TMJ
within a 10- 13 degree arc, which
creates 20- 25 mm separation of the
anterior teeth
This phenomenon was the basis for
the terminal hinge axis theory in
early 1920’s by McCollum

BENNETT MOVEMENT
In this type of movement, the
condyle on the non-working side
will arc forward and medially.
Meanwhile, the condyle on the
working side will shift laterally
usually posteriorly.
The bodily shift of the mandible
in the direction of the working
side was first described by
Bennett.

BENNETT ANGLE

 86% of condyle had immediate or early
lateral translation.
 Lundeen and Wirth used mechanical
apparatus, showed a median dimension to be
approximately 1.0mm to max of 3mm.
 Hobo and Mochizuki used electronic
measuring device found 0.4mm to 2.6mm of
immediate lateral translation.

 Progressive side shift or bennett side shift.
 Lundeen and Wirth found slight variation in
the direction of progressive lateral translation
or bennett angle with a mean value of 7.5
degree.
 Hobo and Mochizuki foung a much greater
variation ranging from1.5 to 36 degree with a
mean value of 12.8degree.

DETERMINANTS OF OCCLUSION
 Posterior determinants
 Anterior determinants
 Neuromuscular system

Posterior determinants
 Rt and lt temporomandibular joints.
 No control over it.
 Condylar path is the basis for the use of
articulator.

Anterior determinants
 Teeth.
 Posterior teeth – vertical stops for closure.
Also guide the mandible to maximum
inercuspation
 Anterior teeth – guide the mandible in lateral
excursive and in protrusive movements.

 Anterior teeth are suited for guidance 1)canines
having longest, strongest roots.
2)the load being reduced by distance from the
fulcrum.
3)the proprioceptive threshold and concomitant
reflexes reducing the load.
 Dentist have direct control over the tooth
determinants by orthodontic movement,
restoration of anterior lingual or posterior
occlusal surfaces, selective grinding.

Neuromuscular system
 The neuromuscular system, through
proprioceptive nerve endings in the
periodontium, muscles and joints monitor the
position of the mandible and its path of
movement.
 Indirect control over it.

Effects of anatomic determinants

Molar disocclusion
 Normal occlusions perform repeated lateral
mandibular movements, they will not trace
the same path on electronic recordings due to
flexible nature of articular disc.
 The measurement deviation averages 0.2mm
in centric relation, 0.3mm in working, and
0.8mm in both protrusive and nonworking
movements

 Therefore one of the treatment goals in
placing occlusal restorations should be to
produce a posterior occlusion with buffer
space that equals or surpasses the deviations
resulting from natural variations found in the
temporomandibular joint.

Condylar guidance
*Protrusive condylar inclination – average 30.4
degree.
- steep
- shallow

Immediate lateral
translation
 Ridge and groove directions are affected by
the condylar path, particularly lateral
translation. The effect was observed on the
occlusal surface of a mandibular molar and
premolar.
 The working path is traced on the mandibular
tooth in lingual direction and nonworking
path is in a distobuccal direction.

 Nearer the tooth is to the working side
condyle anteroposteriorly, the smaller the
angle between the working and nonworking
paths

Anterior guidance
 Protrusive incisal path inclination – 50 to 70
degrees.

FactorFactor ConditionCondition EffectEffect
CondylarCondylar
guidanceguidance
SteeperSteeper TallerTaller
AnteriorAnterior
guidanceguidance
More overbiteMore overbite
More OverjetMore Overjet
TallerTaller
ShorterShorter
Plane ofPlane of
occlusionocclusion
More parallelMore parallel ShorterShorter
Curve ofCurve of
SpeeSpee
More acuteMore acute ShorterShorter
LateralLateral
translationtranslation
Greater movementGreater movement ShorterShorter

Anterior guidanceAnterior guidance
More overbiteMore overbite TallerTaller
More OverjetMore Overjet ShorterShorter

Condylar guidanceCondylar guidance
SteeperSteeper
TallerTaller

Lateral translationLateral translation
Greater movementGreater movement ShorterShorter

FactorFactor ConditionCondition EffectEffect
Distance fromDistance from
rotating condylerotating condyle
GreaterGreater Wider the angleWider the angle
Distance fromDistance from
midsagittal planemidsagittal plane
GreaterGreater Wider the angleWider the angle
Lateral translationLateral translation GreaterGreater Wider the angleWider the angle
IntercondylarIntercondylar
distancedistance
GreaterGreater Smaller the angleSmaller the angle

Occlusal interferences
 Centric
 Working
 Nonworking
 protrusive

Centric interference
• is a premature contact that
occurs when the mandible
closes with the condyles in
their optimum position in
glenoid fossa.
•It will cause deflection of
mandible in a posterior,
anterior and /or lateral
direction.

Working interference
This may occur when there is
contact between maxillary and
mandibular posterior teeth on the
same side of the arches as the
direction in which the mandible has
moved. If the contact is heavy
enough to disocclude anterior teeth,
it is interference

Nonworking interference
• is an occlusal contact
between maxilary and
mandibular teeth on the side
of the arches opposite in
direction in which mandible
has moved in a lateral
excursion
•It is of destructive in nature
•The potential for damaging
the masticatoty apparatus has
been attributed to changes in
mandibular leverage, the
placement of forces outside
the long axis of the the teeth,
and disruption of normal
muscle function

Protrusive interference
Is a premature contact occuring
between mesial aspects of the
mandibular posterior teeth and
distal aspects of maxillary
posterior teeth.
The proximity of the teeth to
the muscles and oblique vector
of forces make contacts
between the opposing posterior
teeth during protrusion more
destructive, as well as interfere
with the patient’s ability to in
incise properly.

NORMAL V/S PATHOLOGIC
OCCLUSION
 10% population with complete harmony
according to old concept
 In majority of population, the maximum
intercuspation causes the mandible to be
deflected away from its optimum position.
 In the absence of symptoms, this is considered
physiologic or normal .
 So in physiologic occlusion teeth will be in the
maximum intercuspation and condyle in the less
optimal position.

 Patient ability to adapt may be influenced by
the effects of psychic stress and emotional
tensions on CNS.
 Lowering the threshold, leads to
parafunctional activity.
 Normal occlusion becomes the pathologic
one.

Okesons criteria for optimal occlusion;
1. In closure, the condyles are in the most
superoanterior position against the discs on
the posterior slopes of the eminences of the
glenoid fossae. The posterior teeth are in
solid and even contact and the anterior
teeth are in slightly lighter contact.
2. Occlusal forces are in the long axes of the
teeth

3. In lateral excursions of the mandible, working
side contacts disocclude or separate the
nonworking teeth instantly.
4. In protrusive excursions, anterior tooth
contacts will disocclude the posterior teeth.
5. In an upright posture, posterior teeth contact
more heavily than do anterior teeth.

Occlusal concepts
 Bilateral balanced occlusion
 Unilateral balanced occlusion
 Mutually protected occlusion

Bilateral balanced
occlusion
 Von spee and Monson
 Very difficult to achieve In case of fpd
High rate of failure.
 Excessive frictional wear.
 Increased periodontal breakdown and
neuromuscular disturbance.

Unilateral balanced
occlusion
 Schuyler
 Distributes the occlusal load on working side
 Prevents the teeth from oblique directed
forces on non-working side.
 Saves centric holding cusps from excessive
wear.
 Maintainance of occlusion.

Group function occlusion

Mutually protected
occlusion
 D’Amico, stuart and stallard.
 Maximum intercuspation coincides with the
optimal condylar position
 All posterior teeth are in contact and forces
directed along the long axes.
 Anterior teeth either lightly contact of very
slight out of contact (25microns)

Salient features of
mutually protected
occlusion Uniform contact of all teeth around the arch ,when the
mandibular condyles are in their most posterior position
 Stable posterior teeth contacts with vertically directed
resultant forces
 Centric relation coincident with maximum intercuspal
position
 No contact of the posterior teeth in lateral or protrusive
movements
 Anterior tooth contacts harmonizing with fuctional jaw
movements.

Canine guided occlusion

 Easy of fabrication and greater tolerance by
the patients.
 Anterior teeth should be periodontally
healthy
 Depends on the orthodontic relation of the
opposing arches.
 Cannot be used in reverse occlusion or cross
bite.

conclusion
 Occlusion is the integrated relationship of the
tooth periodontium, TMJ and neuromusculature,
and not merely the interdigitation of the tooth.
There is a complex interaction of many
components of masticatory system. Changes in
one component affect the entire system. The
dentist who practice restorative dentistry should
appreciate their significance for the long term
successful restorations by maintaining the
occlusal integrity.

Bibliography
 Okeson JP. Management of
Temporomandibular Disorders and Occlusion,
ed. 4th, 1998; Mosby .
 Shillingburg HT. Fundamentals of Fixed
Prosthodontics, ed.3rd.
 Rosenstiel S.F. Contemorary Fixed
Prosthodontics, 3rd edition.
 Glossary of prosthodontics terms – 7th edition,
1999.

Fundamentals of occlusion/cosmetic dentistry courses

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