Occlusion in FPD.ppt

CONCEPTS OF OCCLUSION IN
FIXED PARTIAL DENTURES
DR SHRIMANT RAMAN
DEPARTMENT OF
PROSTHODONTICS

 Introduction
 Requirements of occlusal contacts relationship
 Centric relation
 Mandibular movements
 Border movements
 Functional movements
 Optimum occlusion
 Diagnosis
 Intraoral examination
 Radiographic examination
 Mounted cast examination
 Planning of occlusion
 Interferences
 Pathologic occlusion
 Treatment
 Conclusion
 References

Introduction
 The reason for replacement of natural
teeth is not only to aid in mastication,
but for various functions like the
maintenance of proper support for the
oro-facial musculature, esthetic
appearance, proper speech production,
prevention of teeth migration,
maintenance of the morphologic facial
height and prevention of TMJ
dysfunction syndromes

Occlusion:-
 “Is a static relationship between
the incising or masticating surfaces
of maxillary or mandibular teeth or
tooth analogue”
GPT 8th ed.

Requirements of occlusal
contact relationships
 It should be within the adaptive
capacity of the patient
 To restore and maintain the health
& function of the stomatognathic
system
 Simultaneous bilateral contact of
opposing posterior teeth must
occur in centric occlusion

 Some criteria established by
OKESON for optimum occlusion are
1. In closure, the condyles are in the most
supero–anterior position against the
discs of the posterior slopes of the
articular eminences
2. The posterior teeth are in solid and
even contact and the anterior teeth are
in slightly lighter contact.
3. Occlusal forces are directed in the long
axes of the teeth

4. In lateral excursions, working side
contacts (preferably on canines)
disocclude (or) separate the non-
working teeth instantly
5. In protrusive excursions, anterior
tooth contacts will disocclude the
posterior teeth
6. In an upright posture, posterior
teeth contact more heavily than
do anterior teeth

Centric Relation
 Definition: The maxillo-mandibular
relationship in which condyles articulate
with the thinnest avascular portion of
their respective disc with the complex in
the anterior - superior position against the
shape of the articular eminencies. This
position is independent of tooth contact.
This position is clinically disernible when
the mandible is directed superior &
anteriorly. It is restricted to a purely
rotatory movement about the transverse
horizontal axis. GPT 8th ed.

Intercuspal position
 Definition: It is the complete
intercuspation of opposing teeth
independent of condylar position
GPT 8th ed.

 Centric relation is considered a
learnable, repeatable and recordable
reference position
 If the intercuspal position coincides
with the centric relation position –
restorative treatment is often
straightforward
 When they do not coincide – it is
necessary to determine whether
corrective occlusal therapy is needed
before restorative treatment

Mandibular movements
 These complex 3 dimensional
mandibular movement can be broken
down into two basic components:
 Translation – when
all points within a
body have identical
motion and
 Rotation – when the
body is turning about
an axis

 In addition, Mandibular movement
can be easily understood when the
components are describe as:
Horizontal axis
 This movement occurs
in the sagittal plane. It
occurs when the mandible
makes a rotational opening
and closing movement from
centric relation around the
transverse horizontal axis

Vertical axis
 This movement occurs in the
horizontal plane. It occurs when
the mandible makes lateral
excursion. The center for this
rotation is a vertical axis extending
through the working-side condyle

Sagittal axis
 This movement occurs in the
frontal plane. It occurs when the
mandible makes lateral excursion. The
condyle on the side opposite from the
direction of movement travels forward
and downward producing a downward
arc rotating about an anteroposterior
or sagittal axis passing through the
other condyle

Lateral side shift
 When mandible makes a
lateral excursion, the condyle
on the working side will shift
laterally and slightly posteriorly. The angle
formed in the horizontal plane between the
pathway of the non-working condyle,
mandibular lateral translation and the
sagittal plane is called Bennett angle.
 The lateral side shift is also called as Bennett
side shift or progressive side shift.

BORDER MOVEMENTS
 Mandibular movements are
limited by the
temporomandibular joints
and ligaments, the
neuromuscular system, and
the teeth.
 Posselt was the first to
describe the extremes of
mandibular movement, which
he called border movements

Mandibular incisors
track along the
lingual
concavity of the
maxillary anterior
teeth
Edge-to-edge
position
Incisors move
superiorly until
posterior
tooth contact
recurs
Most protrusive
mandibular
position
1
2
3&4
5

Posterior and Anterior
Determinants
 The characteristics of mandibular
movement are established posteriorly
by the morphology of the temporo-
mandibular joints and anteriorly by
the relationship of the anterior teeth

Posterior Determinants
1. Shape of the articular eminences,
2. Anatomy of the medial walls of the mandibular
fossae
3. Configuration of the mandibular condylar
processes
 These cannot be controlled nor is it
possible to influence the neuromuscular
responses of the patient
 It is done by indirect means only
 Through changes in the configuration of the
contacting teeth or by the provision of an
occlusal appliance

Condylar guidance angle:-
1, Flat
2, Average
3, Steep
Anatomy of the medial walls of
the mandibular fossae:-
1, Greater than average
2, Average
3, Minimal sideshift

Anterior Determinants
 Vertical and horizontal overlaps and the
 Maxillary lingual concavities of the anterior
teeth
 These can be altered by restorative and
orthodontic treatment
 If greater vertical overlap
 Increased vertical mandibular opening during
the early phase of protrusive movement and
 Creates a more vertical pathway at the end of
the chewing stroke
 Increased horizontal overlap allows a more
horizontal jaw movement

FUNCTIONAL MOVEMENTS
 Most functional movement of the
mandible (as occurs during mastication and speech)
takes place inside the physiologic limits
established by the:
 Teeth,
 Temperomandibular joints,
 Muscles and ligaments of mastication;
 therefore, these movements are rarely
coincident with border movements

Chewing
 When incising food, adults open their mouth
a comfortable distance and move the
mandible forward until they incise, with the
anterior teeth meeting approximately edge
to edge
 The food bolus is then transported to the
center of the mouth as the mandible returns
to its starting position, with the incisal
edges of the mandibular anterior teeth
tracking along the lingual concavities of the
maxillary anterior teeth

 The mouth then opens slightly, the
tongue pushes the food onto the occlusal
table, and after moving sideways, the
mandible closes into the food until the
guiding teeth (typically the canines) contact
 The cycle is completed as the mandible
returns to its starting position
 This pattern repeats itself until the food
bolus become small enough to be
swallowed

Phonetics
 The teeth, tongue, lips, floor of the mouth,
and soft palate form the resonance
chamber that affects pronunciation.
 During speech, the teeth are generally not
in contact, although the anterior teeth may
come very close together during "C,“ "CH,"
"S," and "Z" sounds, forming the "speaking
space.“

 When pronouncing the "F," the inner
vermilion border of the lower lip traps air
against the incisal edges of the maxillary
incisors.
 Phonetics is a useful diagnostic guide
for tooth position during fixed
prosthodontic treatment

PARAFUNCTIONAL
MOVEMENTS
 Parafunctional movements of the mandible
may be described as sustained activities
that occur beyond the normal functions of
mastication, swallowing, and speech
 There are many forms of parafunctional
activities, including
 Bruxism,
 Clenching,
 Nail biting, and
 Pencil chewing
 Typically, parafunction is manifested by
long periods of increased muscle
contraction and hyperactivity

 Over a protracted period this can result in
 Excessive wear,
 Widening of the PDL,
 Mobility,
 Migration, or
 Fracture of the teeth
 Muscle dysfunction may also occur such
as:-
 Myospasms,
 Myositis,
 Myalgia, and
 Referred pain (headaches) from trigger point
tenderness

Bruxism
 Sustained grinding, rubbing together, or
gnashing of the teeth with greater-than-
normal chewing force is known as
bruxism.
 This activity may be diurnal, nocturnal,
or both
 Although bruxism is initiated on a
subconscious level, nocturnal bruxism is
potentially more harmful because the
patient is not aware of it while sleeping.
Therefore, it can be difficult to detect
 The etiology of bruxism is often unclear.

 Some theories relate bruxism to
malocclusion, neuromuscular
disturbances, responses to emotional
distress, or a combination of these
factors
 Altered mastication has been
observed in subjects who brux and
may be due to an attempt to avoid
premature occlusal contacts
(occlusal interferences).

Clenching
 Clenching is defined as forceful clamping
together of the jaws in a static
relationship
 The pressure thus created can be
maintained over a considerable time with
short periods of relaxation in between
 Etiology can be associated with:-
 Stress,
 Anger,
 Physical exertion, or
 Intense concentration on a given task,
rather than an occlusal disorder

 As opposed to bruxism, clenching does
not necessarily result in damage to the
teeth because the concentration of
pressure is directed more or less through
the long axes of the posterior teeth
without the involvement of detrimental
lateral forces.
 Abfractions-cervical defects at the CEJ
may result from sustained clenching.

 Also, the increased load may result
in damage to the periodontium,
temporomandibular joints, and
muscles of mastication
 As with bruxism, clenching can be
difficult to diagnose

Optimum Occlusion
 In an ideal occlusal arrangement, the
load exerted on the dentition should be
distributed optimally. Occlusal contact
has been shown to influence muscle
activity during mastication.
 Horizontal forces on any teeth should be
avoided or at least minimized, and
loading should be predominantly parallel
to the long axes of the teeth.

 This is facilitated when the tips of
the centric cusps are located
centrally over the roots and when
loading of the teeth occurs in the
fossae of the occlusal surfaces
rather than on the marginal ridges.
 Horizontal forces are also minimized
if posterior tooth contact during
excursive movements is avoided

 The chewing and grinding action of the
teeth is enhanced if opposing cusps on the
laterotrusive side interdigitate at the end of
the chewing stroke
 The mutually protected occlusal scheme
probably meets this criterion better than
the other occlusal arrangements. The
features of a mutually protected occlusion
are as follows:-
1. Uniform contact of all teeth when the
mandibular condylar processes are in their most
superior position
2.Stable posterior tooth contacts with vertically
directed resultant forces

3. Centric relation coincident with maximum
intercuspation (CR = MI)
4. No contact of posterior teeth in lateral or
protrusive movements
5. Anterior tooth contacts harmonizing with
functional jaw movements
 In achieving these criteria, it is assumed
that (1) a full complement of teeth
exists, (2) the supporting tissues are
healthy, (3) there is no cross bite, and (4)
the occlusion is Angle Class I

Rationale
 It might seem illogical to load the single-
rooted anterior teeth as opposed to the
multirooted posterior teeth during
chewing.
 However, the canines and incisors have a
distinct mechanical advantage over the
posterior teeth: the effectiveness of the
force exerted by the muscles of
mastication is notably less when the
loading contact occurs farther anteriorly

 The farther anteriorly initial tooth-to-
tooth contact occurs (i.e., the longer the lever arm),
the less effective will be the forces
exerted by the musculature and the
smaller the load to which the teeth are
subjected

 The canine-with its long root, significant
amount of periodontal surface area, and
strategic position in the dental arch-is
well adapted to guiding excursive
movements
 The elimination of posterior contacts
during excursions reduces the amount
of lateral force
 Therefore, molars and premolars in
group function are subjected to greater
horizontal and potentially more
pathologic force than the same teeth in a
mutually protected occlusion

Diagnosis
 This is necessary to determine the
basis for patient’s treatment.
Information about the existing
occlusal scheme can be derived
from 3 sources:
 Intra-oral examination
 Radiographic survey
 Evaluation of mounted diagnostic
casts

1. Intra oral examination
 This examination is done to reveal
signs and symptoms of occlusal
pathosis, if present
 In case occlusal pathosis is present,
they will be found during
 Testing the teeth for the presence or
absence of mobility
 Severe dental attrition
 Charting of periodontal pockets
 Determination of defective occlusal
contacts from CR to CO

2. Radiographic Survey
 A radiograph is a 2 dimensional
representation of a 3 dimensional
object.
 Therefore, a complete radiographic
survey can’t be used exclusively to
arrive upon a diagnosis. Yet, there
are certain radiographic signs that
are indicative of pathologic changes
that may have been caused by the
occlusion

 Radiographic signs of occlusal
pathosis are:
 Widening of the PDL space
 Angular bony defects
 Changes in lamina dura
 Thickening
 Thinning
 These radiographic findings have to
be correlated with clinical evidence
found during the time of patient
examination

3. Examination of the mounted
diagnostic casts
 The relationships between the jaws
and teeth that can be visualized from
the mounted diagnostic casts must
be identified before treatment
planning. This knowledge is
necessary for 3 reasons:-
1. Identification of existing initial tooth
contacts and the analysis of factors
that may contribute to any existing
pathosis or may cause damage to a
future planned occlusion.

2. Occlusal plane and occlusal contacts study
to facilitate and aid in designing the
occlusal scheme of the FPD
3. In order to plan for an occlusal scheme, the
dentist has to first decide whether changes
have to be made in respect to:-
 Character of the opposing dentition
 Location and amount of tooth contact
 Plane of occlusion
 The position in which the occlusion must be
established (CR or CO)
 Type and number of lateral tooth contacts that
occur during eccentric mandibular movements.

Factors to be studied on the
mounted diagnostic casts
A. Centric relation, centric occlusion and
initial tooth contacts
 CR is an anatomic position i.e. more
specifically a neuromuscular position
 It is a position dictated by the muscles
attached to the mandible and articular
disc and ligaments and not dictated by
tooth position
 Since it is a position controlled by the
NM system, it can vary slightly from day
to day and different times of the day

 CO is a tooth position. It is the
position of the maxilla in relation
to the mandible when the teeth are
in maximum inter-cuspation. CO
changes through attrition, tooth
migration, tooth loss though it does
so very slowly

 Only when casts are mounted in CR,
the occlusal information of the
patient can be portrayed in three
dimensions. The information is in
regard to:
 Initial tooth contact
 Subsequent tooth position
 This must then be correlated with
that from radiographic and intra-oral
examination so that the patient’s
adaptive ability can be assessed.

 The areas to be observed specifically are
 Interference from CR to CO caused by
deflective tooth contacts.
 Magnitude and direction of the interference
from CR to CO.
 Knowing the difference that exits
between CR and CO will help future
planning for any occlusal adjustment
necessary to achieve harmonious and
simultaneous contact during function

B. Plane of occlusion
 The plane of occlusion of the natural
dentition can be visualized as an
imaginary curved plane that connects the
incisal edges of the anterior teeth with
cusp tips of the posterior teeth. This
antero-posterior and mesio-distal curved
plane is important functionally as it
allows the mandibular teeth to be cradled
within the confines of the maxillary
dental arch. It aids in protecting the soft
tissues from injury and in stabilizing the
mandible during final closure to CO

 Disruption of this can occur due to
supraeruption of tooth due to the
missing antagonist tooth. This
results in an indentation of the
occlusal plane, such that during
protrusion movement of the
mandible this extruded tooth will
contact the proximal surface of the
tooth bonding the indentation
resulting in a deflection downwards.
This leads to increase stresses to
tooth, bone and musculature

 When this exceeds the patient’s
adaptive capacity, it leads to:
 Increase tooth wear
 Changes of lamina dura
 Increase tooth mobility
 TMJ dysfunction
 This problem can be due to one
single tooth extrusion or the entire
segment of an arch.

C. Anterior and posterior
determinants of occlusion
 The anatomic determinants of
mandibular movements i.e. anterior
guidance and condylar guidance
have a strong influence on the
occlusal surface morphology of the
teeth being restored.

(i) Condylar Guidance / Posterior
determinant
 Condylar guidance that has an impact on
the occlusal surface of posterior teeth is
the protrusive condylar path inclination
and mandibular lateral translation
 The inclination of the condylar path during
protrusive movement can vary from steep
to shallow in different patients. If the
protrusive inclination is steep, the cusp
height may be longer. However, if the
inclination is shallow, the cusp height must
be shorter

 Immediate mandibular lateral
translation is the lateral shift
during lateral movement. If
immediate lateral translation is
great, then the cusp height must be
shorter. With minimal immediate
translation, the cusp height may be
made longer.

(ii) Anterior Guidance / Anterior
Determinant
 The track of the incisal edges from
maximum intercuspation to edge-edge
occlusion is termed as the protrusive
incisal path. The angle formed by the
protrusive incisal path and the
horizontal reference plane is the
protrusive incisal path inclination
(Ranges 50º – 70º). In healthy dentition,
the anterior guidance is approximately
5º-10º steeper than the condylar path in
the sagittal plane

 Therefore when the mandible moves
protrusively, the anterior teeth guide the
mandible downward to create disocclusion
or separation between the maxillary and
mandibular posterior teeth. This should
also occur during lateral mandibular
excursions
 The mandibular incisal edges should
contact the maxillary lingual surface at the
transition. Anterior guidance which is the
combination of the vertical and horizontal
overlap of anterior teeth also governs the
occlusal surface morphology of the
posterior teeth

 Greater the vertical overlap, longer
the posterior cuspal height and vice
versa
 Greater the horizontal overlap, less
cuspal height needed and vice versa

D. Compensating curves in prosthesis
Vs the curve of Spee and Wilson in
natural teeth
 The antero-posterior and
mediolateral compensating curves
generated in prosthesis has to
follow the already existing curves of
spee and curves of Wilson present
in the natural dentition. If the
curves are shallow, then a shallow
curve should be generated

 But it should be kept in mind that the
anterior guidance and posterior guidance
are the physiologic limits or border
movements of mandibular function. Any
factors that will create a steeper
guidance than those dictated by border
movements should be considered
pathologic interferences. The dentist
must work within these limits to develop
an individual occlusal scheme for each
patient’s particular needs that will
preserve the remaining dentition.

E. Inter-Ridge Space
 Often the maxillo-mandibular space
is very greatly reduced, due to
natural teeth opposing residual
ridges extrude.
 The extruded teeth needs to be
evaluated, if minimal
“odontoplasty” will bring back the
tooth into plane of occlusion or will
it require endodontic therapy
followed by the restoration of a FPD

Planning the occlusion
 Historically, the study of occlusion has
undergone an evolution of concepts.
These can be broadly categorized as
bilaterally balanced, unilaterally
balanced, and mutually protected.
 Current emphasis in teaching fixed
prosthodontics and restorative dentistry
has been on the concept of mutual
protection

Bilateral Balanced Occlusion
 having a maximum
number of teeth in
contact in maximum
intercuspation
and all excursive positions
 It helps in complete denture fabrication
helps in maintaining denture stability due to
the nonworking side contact prevents the
denture from being dislodged

 However, as the principles of bilateral
balance were applied to the natural
dentition and in fixed prosthodontics, it
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 neuromuscular
disturbances were commonly observed
 Thus the concept of a unilaterally
balanced occlusion (group function)
evolved

 In a unilaterally balanced articulation,
excursive contact occurs between all
opposing posterior teeth on the
laterotrusive (working) side only. And not
on the mediotrusive (nonworking) side
 Thus, in this occlusal arrangement the load
is distributed among the periodontal
support of all posterior teeth on the
working side
 This can be advantageous if, for instance,
the periodontal support of the canine is
compromised
 In the protrusive movement, no posterior
tooth contact occurs
Unilateral balanced occlusion / group
function

Long Centric
 As the concept of unilateral
balance evolved, it was suggested
that allowing some freedom of
movement in an anteroposterior
direction is advantageous. This
concept is known as long centric
 Schuyler was one of the first to advocate
such an occlusal arrangement
 He thought that it was important for the
posterior teeth to be in harmonious
gliding contact when the mandible
translates from centric relation forward
to make anterior tooth contact

 Others have advocated long centric
because centric relation only rarely
coincides with the maximum
intercuspation position in healthy natural
dentitions
 However, its length is arbitrary ranging
from 0.5 to 1.5 mm
 This theory presupposes that the condyles
can translate horizontally in the fossae
before beginning to move downward.
 It also necessitates a greater horizontal
space between the maxillary and
mandibular anterior teeth (deeper lingual
concavity), allowing horizontal movement
before posterior disocclusion

Mutually protected occlusion /
organic / canine guided occlusion
 During the early 1960s, an occlusal scheme
called mutually protected occlusion was
advocated by Stuart and Stallard, based on
earlier work by D'Amico
 In this arrangement, centric relation
coincides with the maximum
intercuspation position
 Anterior maxillary & mandibular teeth,
together guide excursive movements of the
mandible, and no posterior occlusal
contacts occur during any lateral or
protrusive excursions

 In a mutually protected occlusion,
the posterior teeth come into
contact only at the very end of
each chewing stroke, minimizing
horizontal loading on the teeth
 Concurrently, the posterior teeth
act as stops for vertical closure
when the mandible returns to its
maximum intercuspation position

Interferences
 When the teeth are not in harmony with the
joints and the mandibular movements,
interference is said to exist
 Interferences are undesirable occlusal
contacts that may produce mandibular
deviation during closure to maximum
intercuspation or may hinder smooth
passage to and from the intercuspal position
 4 types of interferences:-
 Centric interference
 Working interference
 Non-working interference
 Protrusive interference

(i) Centric interference
 Premature contact that occurs when
the mandible closes with the
condyles in their optimum position
in the glenoid fossae
 Causes deflection of the mandible in
a posterior, anterior and/or lateral
direction.
 Interference occurs between the
mesial inclines of maxillary teeth and
distal inclines of mandibular teeth.

(ii) Working interference
 Occurs when there is contact between
the maxillary and mandibular posterior
teeth on the same side as the direction
in which the mandible has moved and
should be heavy enough to disocclude
anterior teeth
(iii) Non-working interference
 Is an occlusal contact between maxillary
and mandibular teeth on the side of the
arches opposite to the direction in
which the mandible moves in a lateral
excursion.
 It is destructive in nature

(iv) Protrusive interference
 Occurs when distal facing inclines of
maxillary posterior teeth contacts the
mesial facing inclines of mandibular
posterior teeth during a protrusive
movement
 Causes destructive forces
 These interferences may lead to
pathologic occlusion

Pathologic Occlusion
 A pathologic occlusion is defined as
the one in which sufficient
disharmony exists between teeth
and the TMJ’s to result in
symptoms that requires
intervention

Signs and Symptoms
(i) Teeth
 May exhibit hyper mobility, open contacts or
abnormal wear like fracture or chipping of
incisal edges
(ii) Periodontium
 Chronic periodontal disease.
 Widened PDL space (radiographically).
 Tooth movement
(iii) Musculature
 Chronic muscle fatigue leading to muscle
spasm and pain
 Restricted opening or trismus
 Myositis
(iv) TMJ’s
 Pain, clicking or popping in the TMJ’s

Treatment
 Includes certain objectives. They are
 To direct the occlusal forces along the
long axes of the teeth
 To attain simultaneous contact of all teeth
in CR
 To eliminate any occlusal contact on
inclined planes to enhance the positional
stability of the teeth
 To have CR coincident with the
intercuspal position
 To arrive at the occlusal scheme selected
for the patient (e.g. Group function or mutually protected
occlusion)

 In the short term,
these objectives
can be
accomplished
with a removable
occlusal device
fabricated from
clear acrylic resin
that overlays the
occlusal surfaces
of one arch

 On a more permanent basis, this
can be accomplished through
 Selective occlusal reshaping,
 Tooth movement,
 The placement of restorations, or
 Combination of these

 Definitive occlusal treatment involves
accurate manipulation of the mandible,
particularly in centric relation. Because
the patient may resist such
manipulation as a result of protective
muscular reflexes, some type of
deprogramming device may be needed
(e.g., an occlusal device)

OCCLUSAL DEVICE THERAPY
 Occlusal devices (sometimes referred
to as occlusal splints, occlusal
appliances, or orthotics) are
extensively used in the management of
TM disorders and bruxism.
 In controlled clinical trials, they have
effectively controlled myofascial pain.

 However, no clear hypothesis about the
mechanism of action has been proved, and
none of the various hypotheses
 repositioning of condyle and/or the articular
disk,
 reduction in masticatory muscle activity,
 modification of "harmful" oral behavior, and
 changes in the patient's occlusion
has been consistently supported by
scientific studies
 Occlusal devices are particularly helpful in
determining whether a proposed change in a
patient's occlusal scheme will be tolerated.

 If a patient responds favorably to
an occlusal device, the response to
restorative treatment should be
positive as well.
 Thus, occlusal device therapy can
serve as an important diagnostic
procedure before initiation of fixed
prosthodontic treatment.

Fabrication of Device:
 There are several satisfactory methods
for making an occlusal device
 One made from heat-polymerized acrylic
resin will have the advantage of
durability, but autopolymerizing resin
used alone or in conjunction with a
vacuum-formed matrix can serve equally
well

Direct Procedure Using
a Vacuum-Formed Matrix
1. Adapt a sheet of clear thermoplastic
resin to a diagnostic cast using a
vacuum-forming machine
 Block excessive undercuts
 Trim the excess resin
 On the facial surfaces, the device must be
kept well clear of the gingival margins

2. then check for fit and stability
 Add a small amount of
autopolymerizing acrylic resin in the
incisal region
 Guide the mandible into CR to make
shallow indentations in the resin

3. Add more resin to the incisor and canine
regions and guide the patient to retrusive,
protrusive, and lateral closures in the soft
resin
4. Adjust the resin to give smooth, even
contacts during protrusive and lateral
excursions as well as a definite occlusal
stop for each incisor in centric relation
 Confine protrusive contacts to the incisors
 lateral contacts to the laterotrusive canines
 All posterior contacts should be relieved at
this stage.

5. Repeated protrusive and lateral
movements will overcome most problems
in jaw manipulation
 Occasionally it will be necessary for the
patient to wear the device overnight before
the acquired protective muscle patterns are
overcome
6. Add autopolymerizing acrylic resin to
the posterior region of the device and
guide the patient into centric relation.
Hold CR until the acrylic resin has
polymerized

7. Remove the device and examine the
impressions. Polymerization can be
accelerated by placing the device on the
cast in warm water
8. Place pencil marks in the depressions
formed by the opposing centric cusps. If a
cusp registration is missing, new resin can
be added and the device reseated
9. Remove excess resin and leave only the
pencil marks. All other contacts must be
eliminated if posterior disclusion is to be
achieved

10. Check the device in the mouth for CR
contacts. Relieve heavy contacts by
continued adjustment until each centric
cusp has an even mark.
11. Identify protrusive and lateral
excursions. Adjust excursive contacts as
necessary
12. Smooth and polish the device, again
being careful not to alter the functional
surfaces
13. After a period of satisfactory use, the
device can be duplicated in heat-
polymerized resin using a standard
denture reline technique.

Indirect Procedure Using Autopolymerizing
Acrylic Resin
 Accurately mounted diagnostic
casts are essential for this
procedure
 Particular attention must be given
to occlusal defects or interfering
soft tissue projections on the casts,
which could cause errors during
mounting

1. Be sure that the device is made at
the same vertical dimension of
occlusion as the CR record. This
will reduce mounting errors derived
from using an arbitrary facebow
2. Incisal guidance table initially set
flat
3. Lower the incisal guide pin until
there is approximately 1 mm of
clearance between the
posterior teeth

4. Now reposition the incisal guide
table after
5. Check the clearance between
opposing casts during protrusive
movement of the articulator. Where
this is less than 1 mm, increase it
by tilting the incisal guidance table
6. Raise the platform wings
of the incisal guidance table
so there is at least 1 mm of
clearance in all lateral
excursions

7. Mark the height of contour of each
tooth on the cast and block out
undercuts with wax
8. Form wire clasps to engage facial
undercuts and seal the cast with a
separating medium

9. Fabricate the device
with autopolymerizing
clear acrylic resin
10. While the resin is still soft, close
the articulator into protrusive and
lateral excursions. Add or remove
resin until it is in constant contact
with the anterior teeth when the
incisal guide pin contacts the incisal
guidance table

11. after the polymerization, Refine
the occlusion on the articulator
a. There should be even contact in
centric relation
b. A stop should exist for each anterior
tooth in CR
c. Protrusive contact on the incisors
should be smooth and even
d. There should also be smooth and even
lateral contact on the laterotrusive
(working-side) canines

12. lastly, smooth and polish the
device, taking care not to alter the
functional surfaces
13. At try-in, check for fit and
stability. Also check the occlusal
contacts and adjust as necessary

Indirect Procedure Using Heat
polymerized Acrylic Resin
 A more durable device can be made
with heatpolymerized acrylic resin
 Desired occlusal surface is shaped
in wax on articulated diagnostic
casts, or the direct device made
with a vacuum-formed matrix can
be used as a pattern

 Lastly, flasked and processed in a
manner similar to that for a
complete denture
 Because of processing errors, it is
important to remount the cast and
make necessary adjustments before
finishing and polishing are
completed

FOLLOW-UP
 After delivery to the patient, the
occlusion must be verified and
corrected as necessary
 The patient is instructed to wear
the device 24 hours a day,
removing it only for oral hygiene,
and to return at regular weekly and
biweekly intervals for modification.

 A reduction in discomfort suggests
that definitive occlusal adjustment
or restorative dentistry, or both,
will likely be successful
 If device therapy fails to relieve the
discomfort, further evaluation and
diagnosis of the etiology and
parameters of the chief complaint
should be pursued

Conclusion
Knowing everything about the
occlusion enables the dentist to
provide a fixed partial denture
which helps the patient in restoring
the function and appearance

References
 Herbert.T Shillingburg JR, Sumiya
Hobo: Fundamentals of Fixed
Prosthodontics; 3rd Edition.
 Stephen.F Rosentiel, Martin F. Land,
Junhei Fujimoto: Contemporary Fixed
Prosthodontics; 3rd Edition.
 William F.P Malone, David L Koth:
Tylman’s Theory and Practice of Fixed
Prosthodontics; 8th Edition.

Occlusion in FPD.ppt

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