Occlusion in FPD
Learning objective
• By the end of this session, the students should know about the
difference in concepts of complete denture occlusion and fixed partial
denture occlusion.
Introduction
• Occlusion is the integrated relationship of the tooth periodontium;
TMJ and neuromusculature, 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.
Introduction
DEFINITION:
• The act (or) process of closure (or) of being closed (or) shut off.
• The static relationship between the incising or masticating surfaces of
maxillary or mandibular teeth or tooth (GPT-7)
Centric Relation-
A maxillomandibular relationship in which
the condyles articulate with the thinnest
avascular portion of their respective disks
with the complex in the anterior-superior
position against the slopes of the articular
eminences, independent of tooth
contacts.
Centric Relation
This position is clinically
discernable when the
mandible is directed
superiorly and anteriorly
and restricted to a purely
rotary movement about a
transverse horizontal
axis.
Maximum Intercuspation
Maximum occlusal inter-arch
contact irrespective of condylar
position. This type of contact may
or may not occur on the path of the
centric relation closure. When
centric occlusion does not occur in
the centric relation contact position,
the external pterygoid plays an
active role in positioning the
condyle for clenching. Syn: Acquired
Centric, Habitual Centric,
Intercuspation Position.
Centric Occlusion
The occlusion with
opposing teeth
when the
mandible is in
centric relation.
May or may not
coincide with MI.
Various concepts of occlusion
• BILATERAL BALANCED OCCLUSION:
This requires having a maximum no. Of teeth in contact in maximum
intercuspation and all excursive positions in complete denture
fabrication this tooth arrangement helps maintain denture stability;
because non-working contact prevents the denture form being
dislodge.
• If the bilateral balanced occlusion applied to the FPD it is proved to be
extremely difficult to accomplish.
• In addition high rates of failure resulted. An increased rate of
occlusal wear; increased or accelerated periodontal breakdown and
Neuro muscular disturbances were observed.
Unilaterally Balanced Articulation
In lateral excursions, the posterior
teeth on the working side contact
as a group simultaneously with
contact on the anterior guidance.
The effect is to distribute lateral
forces to multiple teeth rather
than a single cuspid or other
weakened anterior guiding teeth.
The more teeth that bear the
stress, the less stress any one
tooth must bear. Group function
with progressive disclusion is
useful when anterior teeth are
weak or non-functional. Syn:
Group Function Articulation.
Mutually Protected Articulation
An occlusal arrangement in which
the posterior teeth contact in
maximum intercuspation, but not
in lateral or protrusive movements.
The anterior teeth protect the
posteriors during eccentric
contacts. The posterior teeth
protect the anterior teeth in MI.
Often, the cuspids are the only
teeth contacting in lateral
movement and the incisors the
only teeth contacting in protrusive
movement. Syn: Anterior
Protected Occlusion, Posterior
Disclusion.
SALIENTS FEATURES OF MUTUALLY PROTECTED OCCLUSION
• Uniform contact of all teeth around the arch when the mandibular
condylar processes are in their most posterior position.
• Stable posterior tooth 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 harmonising with function jaw movements.
Advocated by Stuart and
Stallard in early 1960’s.
LONG CENTRIC:
• As the concept of long centric is evolved it was suggested that allowing
some freedom of movement in A-P direction.
• It is important for the posterior teeth to be in harmonial gliding contact
when mandible translates from centric relation toward to make anterior tooth
contact.
• At the given V-D the long centric ranges from 0.5-1.5mm. It also necessitates a
greater horizontal space between maxillary and mandibular anterior teeth (deep
lingual concavity) allowing horizontal movement before posterior disocclusion.
CONCLUSION
Take home message
• Different concepts of occlusion and advantages and disadvantages of
each.
LAQS AND SAQS
• LAQ
• IDEAL OCCLUSION
• SAQ
• WHAT IS BALANCED OCCLUSION
