Occulasl consideration for implant supported prostehsis

INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com

OCCLUSAL
CONSIDERATIONS
FOR IMPLANT
SUPPORTED
PROSTHESISwww.indiandentalacademy.com

INTRODUCTION

The clinical success and longevity of endosteal dental
implants as load-bearing abutments are controlled largely by the
mechanical setting in which they function. The treatment plan is
responsible for the design, number and position of the implants.
After achievement of rigid fixation, proper crestal bone contour,
gingival health, mechanical stress, and/or strain beyond the physical
limits of hard tissues have been suggested as the primary cause of
initial bone loss around implants. After successful surgical and
prosthetic rehabilitation with a passive prosthesis, such noxious
stresses and loads applied to the implant and surrounding tissues
result primarily from occlusal contacts. Complications (prosthetic
and/or bony support) reported in follow-up studies underline
occlusion as a determining factor for success or failure.

The choice of an occlusal scheme for implant-supported
prostheses is broad and often controversial. Almost all concepts are
based on those developed with natural teeth and are transposed to
implant support systems with almost no modification. No controlled
clinical studies have been published comparing the various implant
occlusal theories.
RISK FACTORS - Implant prostheses with extended
cantilevers have been successful, however, biomechanical factors
clearly demonstrate an increased risk.
Biomechanical parameters are excellent indicators of the
increased risk because they are objective and can be measured. One
can determine which condition presents greater risk, and by how
much the risk is increased. Hence the occlusal concepts developed in
this seminar stem from biomechanical risk factors.

The prosthodontist has specific responsibilities to minimize
overload to the bone-to-implant interface. These include a proper
diagnosis leading to a treatment plan providing adequate support,
based on the patient’s individual force factors, a passive prosthesis of
adequate retention and form and progressive loading to improve the
amount and density of the adjacent bone and further reduce the risk
of stress beyond physiologic limits. The final element is the
development of an occlusal scheme that minimizes risk factors and
allows the restoration to function in harmony with the rest of the
stomatognathic system.

TERMINOLOGY
(GPT 1999)

Anterior protected articulation
A form of mutually protected articulation in which the vertical
and horizontal overlap of the anterior teeth disengage the posterior
teeth in all mandibular excursive movements.
Balanced articulation
The bilateral, simultaneous, anterior, and posterior occlusal
contact of teeth in centric and eccentric positions
Canine protected articulation
A form of mutually protected articulation in which the vertical
and horizontal overlap of the canine teeth disengage the posterior teeth
in the excursive movements of the mandible.
Implant Prosthodontics
The phase of Prosthodontics concerning the replacement of
missing teeth and / or associated structures by restorations that are
attached to dental implants.

Lingualized occlusion
First described by S. Howard Payne, DDS, in 1941, this form
of denture occlusion articulates the maxillary lingual cusps with the
mandibular occlusal surfaces in centric working and nonworking
mandibular positions. The term is attributed to Earl Pound.
Payne SH. A posterior set up to meet individual requirements.
Dent. 1941; 47:20-2.
Pound E. Utilizing speech to simplify a personalized denture
service. J. Prosthet Dent. 1970;24:585-600.
Linguocclusion
An occlusion in which a tooth or group of teeth is located
lingual to its normal position.

Mutually protected articulation
An occlusal scheme in which the posterior teeth prevent
excessive contact of the anterior teeth in maximum intercuspation,
and the anterior teeth disengage the posterior teeth in all mandibular
excursive movements.
Occlusion (1645)
1: The act or process of closure or of bring closed or shut off
2 : the static relationship between the incising or masticating surfaces
of the maxillary or mandibular teeth or tooth analogues
Spherical form of occlusion
An arrangement of teeth that places their occlusal surfaces on
the surfaces of an imaginary sphere (usually 8 inches in diameter)
with its center above the level of the teeth (GPT-4).

IMPLANT PROTECTIVE OCCLUSION (IPO)

A proper occlusal scheme is a primary requisite for long-term
survival, especially when parafunction or marginal foundations are
present. A poor occlusal scheme both increases the magnitude of
loads and intensifies mechanical stresses (and strain) at the crest of
the bone. Implant Protective Occlusion (IPO) was previously known
as medial positioned-lingualized occlusion. This occlusal concept
refers to an occlusal plane that is often unique and specifically
designed for the restoration of endosteal implant, providing an
environment for improved clinical longevity of both implant and
prosthesis.

OCCLUSAL CONSIDERATIONS

Natural Tooth vs. Implant Mobility:
In comparison to an implant, the support system of a natural tooth is
designed to reduce the forces distributed at the crestal bone. The fibrous
tissue interface (periodontal ligament) surrounding natural teeth acts as a
viscoelastic “shock absorber”, serving to both decrease the magnitude of
stress to the bone at the crest, as well as extend the time in which the load is
dissipated.
The presence of a periodontal membrane around natural teeth
significantly reduces the amount of stress transmitted to the bone,
especially at the crestal region. Compared
with a tooth the direct bone interface with an
implant is not as resilient, so the energy
imparted by an occlusal force is not partially
dissipated (the displacement of the
periodontal membrane dissipates energy), but
rather transmits a higher intensity to the
contiguous bone. An analogy of this is hitting
a nail with a steel hammer compared with a
rubber hammer.

The mobility of a natural tooth can increase with occlusal
trauma. This movement dissipates stresses and strains otherwise
imposed on the adjacent bone interface or the prosthetic components.
After the occlusal trauma is eliminated, the tooth can return to its
original condition with respect to the magnitude of movement. Mobility
of an implant can also develop under occlusal trauma. However, after
the offending element is eliminated, an implant rarely returns to its
original rigid condition. Instead, its health is compromised, and failure
is usually eminent.
The width of almost every natural tooth is greater than the width
of the implant used to replace the tooth. The greater the width of a
transosteal structure (tooth or implant), the lesser magnitude of stress
transmitted to the surrounding bone. The cross-section shape of the
natural tooth at the crest is biomechanically optimized to resist lateral
(buccolingual) loads because of the tooth’s bending fracture resistance
(moment of inertia) and the direction of occlusal forces. Implants are
almost all round in cross-section, which is less effective in resisting
lateral bending loads and consequent stress concentration in the crestal
region in the jaws.

The elastic modulus of a tooth is closer to bone than any of the
currently available dental implant biomaterials. The greater the
flexibility difference between two materials (metal and bone or tooth
and bone), the greater the potential relative motion generated between
the two surfaces at the transosteal region. Hence under similar
mechanical loading conditions, implants generate greater stresses and
strains at the crest of bone compared with a tooth.
The precursor signs of occlusal trauma on natural teeth are
usually reversible and include hyperemia and occlusal or cold
sensitivity. Condition often results with the patient seeking
professional treatment to reduce the sensitivity, usually by occlusal
adjustment and a reduction in force magnitude. If the patient does not
have an occlusal adjustment, the tooth often further increases in
mobility to dissipate the occlusal forces. If the patient still fails to seek
professional treatment for the increased mobility, the tooth may
orthodontically migrate away from the cause of the occlusal stress.
Even excess tongue or oral habits can cause tooth migration away
from the causative element.www.indiandentalacademy.com

The initial reversible signs and symptoms of trauma on
natural teeth do not occur with endosteal implants. The magnitude of
stress may cause bone microfractures, place the surrounding bone in
the pathologic loading zone causing bone loss, and lead to the
mechanical failure of prosthetic or implant components. Unlike the
reversible signs and symptoms exhibited by natural teeth, implant
bone loss or unsecured restorations most often occur without any
warning signs. Implant occlusal sensitivity is uncommon and
signifies more advanced complications. The loss of crestal bone
around the implant is not reversible without surgical intervention and
results in a decreased implant support and increased sulcus depth
around the abutment. As a result, unless the density of bone
increases or the amount or duration of force decreases, the condition
is likely to progress and even accelerate until implant loss. In
addition, implants cannot move orthodontically away from the
offending force.

The tooth can show clinical signs of increased stress such as
enamel wear facets, stress lines, lines of Luder (in amalgam fillings),
cervical abfraction, and pits on the cusps of teeth. An implant crown
rarely shows clinical signs other than fatigue fracture. As a result,
fewer diagnostic signs are present to warn the prosthodontist to reduce
the stress on the support system.

When teeth oppose each other, an interference perception is
approximately 20m. An implant opposing a natural tooth has an
interference perception of 48m, therefore more than twice as poor.
An implant opposing implant has an interference perception of 64m,
and when a tooth opposes an implant overdenture the awareness is
108m (5 times poorer than teeth opposing each other). As a result,
premature occlusal contacts on teeth are usually associated with a
modification of arc of closure and with a decreased force, before
centric occlusion or full interdigitation. In addition, the mandible may
close in a different position to avoid the premature contact and result
in centric occlusion different from centric relation occlusion.
Unfortunately, because of the decreased occlusal awareness of
implants, the premature contact does not trigger such as an adaptation.
In addition, premature contacts are often on smaller areas of load and
therefore result in greater stress (S=F/A). They are most often on
inclines of posterior teeth, which also generates an angled load of
greater stress to the implant bone interface.www.indiandentalacademy.com

Implants and teeth also have different proprioceptive
information relayed by both entities. Teeth deliver a rapid, sharp pain
sensation under high pressure that triggers a protective mechanism. On
the other hand, implants deliver a slow, dull pain that triggers a
delayed reaction, if any.
Clinical evidence of occlusal trauma on teeth includes an
overall increase in the periodontal membrane thickness and an
increased radiopacity and thickness of the cribriform plate around the
tooth, observed on radiographs and not just localized at the crest.
There are no generalized radiographic signs around an implant under
excess occlusal force, except at the crestal region, which demonstrates
bone loss but may be misdiagnosed as periimplant disease from
bacteria.

The tooth slowly erupts into occlusion and is present in the mouth
from childhood. The surrounding bone has developed in response to the
biomechanical loads. The permanent teeth are gradually introduced, while
others are present. Hence periodontal tissues have had time to organize in
order to sustain increasing loads, including those brought to bear by an
attached prosthesis. The only progressive bone loading around an implant
is performed by the prosthodontist, and in a much more rapid and intense
fashion.
A lateral force on a natural tooth is rapidly dissipated away from
the crest of bone toward the apex of the tooth. The healthy, natural tooth
moves almost immediately 56 to 108m and pivots two-thirds turn toward
the tapered apex with a lateral load. This action minimizes crestal loads to
the bone. An implant does not exhibit a primary immediate movement, but
a secondary movement 10 to 50m under similar lateral loads. In addition,
it does not pivot (as a tooth) toward the apex but instead concentrates
greater forces at he crest of surrounding bone. Therefore if an initial
angled load of equal magnitude and direction is placed on both an implant
and a natural tooth, the implant sustains a higher proportion of the load
that is not dissipated to the surrounding structures.

The natural tooth, with its modulus of elasticity similar to
bone, periodontal ligament, and unique cross-sections and dimensions
constitutes a near perfect optimization system to handle stress. In fact,
the stress is handled so well, bacteria-related disease is the weak link.
An implant handles stress so poorly (capturing the stress at the crest
of the ridge), has an elastic modulus 5 to 10 times that of bone, and is
unable to increase mobility without failure that stress is the weakest
link in the system. As a result, ways to decrease stress are a constant
concern to minimize the risk of implants complications.

Occlusion on Natural Teeth and Implants:
There has been an ongoing controversy regarding whether a
rigidly fixated implant may remain successful when splinted to natural
teeth. Because the implant has no periodontal membrane, concerns
center around the potential for the “nonmobile” implant to bear the
total load of the prosthesis when joined to the “mobile” natural tooth.
The actual mobility of potential natural abutments may influence the
treatment more than any other factor. In the implant tooth fixed
prosthesis, four important components may contribute movement to
the system, the implant, bone, tooth, and prosthesis.
The sudden, initial tooth movement ranges from 8 to 28m in a
vertical direction under a 3 to 5 lb load, depending on the size,
number, and geometry of the roots and the time elapsed since the last
load application. Once the initial tooth movement occurs, the
secondary tooth movement reflects the property of the surrounding
bone and is very similar to the bone implant movement. The axial
movement of an implant has no initial, sudden movement and ranges
from 3 to 5 m with little correlation to the implant body length.www.indiandentalacademy.com

When teeth oppose each other, the combined intrusive
movements of the contacting elements may be 56m (28m + 28m).
When a tooth opposes an implant, the combined intrusive movement is
33m (28m + 5m). When implant prostheses oppose each other, the
biomechanical mismatch between teeth in the rest of the mouth and
implants increase. The total combined movement may be 10m,
compared with 56m in the rest of the mouth, and contrary to the teeth
that move immediately, even with light loads, the implants only move
this amount under a heavy occlusal load. A lighter load may generate a
total implant movement of less than 3m.

For difference in vertical movement of teeth and implants in
the same arch, the existing occlusion is evaluated before implant
reconstruction. Occlusal prematurities are ideally eliminated on teeth
before implant reconstruction. Thin articulating paper (less than 25m
thickness) is then used for the initial implant occlusal adjustment in
centric relation occlusion under a light tapping force. The implant
prosthesis should barely contact, and the adjacent teeth should exhibit
greater initial contacts. Only axial occlusal contacts should be present
on the implant crown. Once the equilibration with a light bite force is
completed, a heavier centric relation occlusal force is applied. The
contacts should remain axial over the implant body and may be of
similar intensity on the implant crown and the adjacent teeth under
greater bite force to allow all elements to react similar to the occlusal
load. Hence to harmonize the occlusal forces between implants and
teeth, a heavy bite force occlusal adjustment is used because it
depresses the natural teeth, positioning them closer to the depressed
implant position and equally sharing the load.www.indiandentalacademy.com

If healthy anterior teeth and/or natural canines are present, the
occlusion allows those teeth to distribute horizontal loads in
excursions, while the posterior teeth disocclude during excursions.
Anterior, compared with posterior bite force measurements and
electromyographic studies provide evidence that the stomatognathic
system elicits significantly less force when the posterior segments are
not in contact. As a result, all lateral excursions of IPO opposing
fixed prostheses or natural teeth should disocclude the posterior
components. The resultant lateral forces are thus distributed only to
the anterior segments of the jaws, resulting in a decrease in overall
occlusal force magnitude because of diminished muscle firing and
recruitment.
This occlusal scheme should be followed whether or not
anterior implants are in the arch. However, if anterior implants must
disocclude the posterior teeth in excursion, two or more implants
splinted together should help dissipate the lateral forces.

When anterior implants and teeth are not connected - The
initial lateral movement of healthy anterior teeth ranges from 68 to
108m before secondary tooth movement. Anterior implant
movements are not immediate and range from 10 to 50m. Because of
the greater discrepancies in lateral movement, the occlusal adjustment
in this direction is more critical to implant success and survival. Light
force and thin articulating paper(20m) are first used to ensure that no
implant crown contact occurs during the initial occlusal or lateral
movement of the teeth. A heavier force during centric occlusion and
excursions is then used to develop similar occlusal contacts on both
anterior implants and natural teeth.

Unlike teeth, implants do not extrude, rotate, or migrate under
occlusal forces. Natural teeth exhibit mesial drift and slight changes
in occlusal position do occur over time. The proposed occlusal
adjustment does not encourage additional tooth movement because
regular occlusal contacts occur. The teeth opposing implants are not
taken out of occlusion. Brief occlusal contacts on a daily basis
maintain the tooth in its original position (similar to the rest of the
mouth). In addition, because most teeth occlude with two teeth, the
opposing teeth positions are even more likely to remain the same.
No occlusal scheme will prevent mesial drift and minor tooth
movement from occurring. An integral part of the IPO philosophy is
the regular evaluation and control of occlusal contacts at each
regularly scheduled hygiene appointment. This permits the correction
of minor variations occurring during long-term function and also
helps prevent porcelain fracture and other stress-related
complications on the remainder of the natural teeth.

For implants joined to natural teeth a similar scenario is used
for the occlusal equilibration. A light force and thin articulating paper
are used, and the implant crown exhibits minimum contact compared
with the natural abutment crown. A gradient of force is designed on
the pontics. A heavy bite force is then used to establish equal occlusal
contacts for all abutments and the entire prosthesis, whether implant
or natural.

Implant Orientation and Influence of Load Direction:
Forces acting on dental implants are referred to as vectors (defined
in both magnitude and direction). Occlusal forces are typically three-
dimensional, with components directed along one or more of the clinical
coordinate axes.

Implants are designed for a long axis load to the implant
body. Stress contours were primarily concentrated at the transosteal
(crestal) region. An axial load over the long axis of an implant body
generates a greater proportion of compressive stress than tension or
shear forces.
Any load that is applied at an angle may be separated into
normal (compressive and tensile) and shear forces. The greater the
angle of loads to the implant long axis, the greater the compressive,
tensile and shear stresses. When FEA evaluates the direction of the
force changed to a more angled or horizontal load, the magnitude of
the stress is increased by 3 times or more. In addition, rather than a
compressive type of force primarily, greater tensile and shear forces
are also demonstrated and increase more than 10 times compared
with the amount found with an axial force. These stress contours
resemble the pattern of early crestal bone loss on implants.

BONE MECHANICS AND OCCLUSION

The effect of offset or angled loads to bone is further
exacerbated because of the anisotropy of cortical bone. Anisotropy
refers to the character of bone, whereby its mechanical properties,
including ultimate strength, depend on the direction in which the bone
is loaded. Cortical bone of human long bones has been reported as
strongest in compression, 30% weaker in tension, and 65% weaker in
shear. Therefore IPO attempts to eliminate or reduce all shear loads to
the implant to bone interface.

A force applied at a 30-degree angle decreased the bone
strength limits by 10% under compression and 25% with tension. A
60-degree force reduced the strength 30% under compression and
55% under tension. Therefore not only does the crestal bone load
increase around the implant with angled forces, but the amount of
stress the bone may withstand is also decreased. The greater the angle
of load, the lower the ultimate strength.

The primary component of the occlusal force should therefore
be directed along the long axis of the implant body, not on an angle or
following an angled abutment post. Angled abutments are used only
to improve the path of insertion of the prosthesis or the final esthetic
result. The angled abutment, which is loaded along the abutment axis,
will transmit a significant moment load to both the implant crestal
region and abutment screw, proportional to its angle of inclination. In
addition, the angled implant often requires an angled abutment.
Angled abutments are fabricated in two pieces and are weaker in
design than a one-piece post. Furthermore, a larger transverse load
component develops at the crest as a result of angled loads. An angled
load to the implant long axis increases the compressive forces at the
crest of the ridge on the opposite side of the implant in which the
force is directed, increasing the tension component of force along the
same side. The greater the angle of force to the long axis of the
implant body, the greater the potentially damaging load at the crest of
the bone. www.indiandentalacademy.com

Hence the angled load increases the amount of crestal stresses
around the implant body, transforms a greater percentage of the force to
tensile and shear force, and reduces bone strength in compression and
tension. In contrast, the surrounding implant body stress magnitude is
least and the strength of bone is greatest under a load axial to the
implant body.
Premature occlusal contacts result in localized lateral loading of
the opposing contacting crowns. Because the surface area of a
premature contact is small, the magnitude of stress in the bone increases
proportionately (i.e., stress=force/area). All the occlusal force is applied
to one region rather than being shared by several abutments and/or
teeth. In addition, the premature contact is most often on an inclined
plane, therefore creating a greater horizontal component to the load and
increasing compressive and tensile crestal stresses. Therefore occlusal
evaluation and adjustment in partially edentulous implant patients are
more important than in the natural dentition because the premature
contacts can result in more damaging consequences on implants
compared with teeth.

The elimination of premature contacts is more important than
in natural teeth because the implant is less mobile and often cannot
effectively dissipate the forces. In addition, the teeth benefit from a
greater occlusal awareness (proprioception) or oral tactile function
than implants.
Once the natural teeth are removed, the bone remodels to the
height at or below the lowest level of the lateral cortical plates.
Hence the implant crown height is often greater than the original
natural anatomic crown, even in Division A bone. Crown height,
with a lateral load, is a magnifier of stress to an implant to bone
interface. The greater the crown height, the greater the resulting
crestal moment with any lateral component of force that develops as
a consequence of an angled load. Angled abutments loaded in the
direction of the abutment with an increase in crown height are
subject to even greater crestal moment loads because of both the
lateral load and the increased lever effect from the crown height.

In the anterior maxilla, labial concavities may require that the
implant be angled away from the labial bone and the abutment toward the
facial crown contour. These implant bodies are more frequently loaded at an
angle, and an angled prosthetic abutment is required. As a result, larger
diameter implants or a greater number of implants are indicated to minimize
the crestal bone stress on each abutment. IPO aims at reducing the force of
occlusal contacts, increasing implant number, and/or increasing implant
diameter for implants subjected to angled loads or with an increased crown
height or on the cantilever portion of a prosthesis.

OCCLUSAL SCHEMES
A primary goal of an occlusal scheme is to maintain the
occlusal load that has been transferred to the implant body within the
physiologic limits of each patient. These limits are not identical for all
patients or restorations. The forces generated by a patient are
influenced by parafunction, masticatory dynamics, tongue size,
implant arch position and location, and implant arch form and crown
height. The prosthodontist can best address these force factors by
selecting the proper implant size, number, and position, using stress-
relieving elements, increasing bone density by progressive loading
and selecting the appropriate occlusal scheme.

CLASSIFICATION OF OSSEOINTEGRATED
PROSTHESIS

Hobo et al
1. Fully bone anchored bridge
2. Overdenture
3. Freestanding bridges
a. Kennedy class I
b. Kennedy class II
c. Kennedy class III
d. Kennedy class IV
4. Bridge connected to the natural teeth.
5. Single tooth replacement.www.indiandentalacademy.com

Misch C.E et al
TYPE DEFINITION
FP-1 Fixed prosthesis, replaces only the crown, looks
like a natural tooth
FP-2 Fixed prosthesis, replaces the crown and a portion
of the root, crown contour appears normal in the
occlusal half is elongated or hypercontoured in the
gingival half
FP-3 Fixed prosthesis, replacing missing crowns and
gingival colour and a portion of the edentulous site,
prosthesis must often use denture teeth and acrylic
gingiva, but may be porcelain to metal
RP-4 Removable prosthesis, overdenture supported
completely by implant
RP-5 Removable prosthesis, overdenture supported by
both soft tissue and implants

IMPLANT PROTECTIVE OCCLUSION(IPO)

When teeth are present, the maxillary dentate posterior ridge is
positioned slightly more facial than its mandibular counterpart. Once
the maxillary teeth are lost, the edentulous ridge resorbs in a medial
direction as it evolves from Division A to B, Division B to C, and
Division C to D. As a result, the maxillary permucosal implant site
gradually shifts toward the midline as the ridge resorbs.
As a result of ridge resorption in
width the maxillary posterior implant
permucosal site may even be lingual to the
opposing natural mandibular tooth. The
posterior mandible also resorbs lingually as
the bone resorbs from Division A to B. As a
consequence, endosteal implants are also
more lingual than their natural tooth
predecessors.

Occlusal Table Width:
A wide occlusal table favors offset contacts during mastication
or parafunction. Narrower implant bodies are even more vulnerable to
occlusal table width and offset loads. Wider root form implants can
accept a broader range of vertical occlusal contacts while still
transmitting lesser forces at the permucosal site under offset loads.
Therefore in IPO the width of the occlusal table is directly related to
the width of the implant body.
During mastication, the amount of force used to penetrate the
food bolus is also related to occlusal table width. For example, less
force is required to cut a piece of meat with a sharp knife (narrow
occlusal table), than with a dull knife (wider occlusal table). The
greater surface area requires greater force to achieve a similar result.
Hence the wider the occlusal table, the greater the force developed by
the biologic system to penetrate the bolus of food.

The posterior narrow occlusal table also facilitates daily home
care. The laboratory technician often attempts to fabricate occlusal
facial and lingual contours similar to that of natural teeth. This often
results in ridge laps or porcelain extension at the facial gingival margin
of the implant, to create an occlusal table approximately 8 to 10 mm
wide. As a result, home care in the sulcular region of the implant is
impaired by the overcontoured crown design. On the contrary, a narrow
occlusal table combined with a reduced buccal contour (in the posterior
mandible) permits easier sulcular oral hygiene in manner similar to a
tooth and improves axial loading.

The narrower occlusal contour also reduces the risk of
porcelain fracture. A facial profile similar to a natural tooth on the
smaller diameter implant results in cantilevered restorative materials.
The facial porcelain is most often not supported by a metal
substructure because the gingival region of the crown is also
porcelain. As a result, shear forces result on the buccal cusp on the
mandibular crown or lingual cusps in the maxillary crown, and are
more likely to increase the risk of porcelain fracture.
Restorations mimicking the occlusal anatomy of natural teeth
often result in offset loads (increased stress), complicated home care
and increased risk of porcelain fracture. As a result, in nonesthetic
regions of the mouth, the occlusal table should be reduced in width
compared with natural teeth.

DIVISION OF AVAILABLE BONE:A,B,C&D
(MISCH)

CROWN CONTOUR

Division A Bone
The primary component of the occlusal force is evaluated during
the treatment-planning phase. In an edentulous ridge with abundant
height and width and little resorption, the implant may be placed in a
more ideal position for occlusion and esthetics.
Offset loads are used to describe cantilevered buccal or lingual
occlusal contacts, not directed along the long axis of the implant body.
When offset loads are generated at an angle, the distance between the
offset contact and the long axis acts as a moment arm that magnifies
the effect of the lateral force.

The most common implant placement corresponds to a central
position in the residual ridge. The implant osteotomy begins in the center
of the crest and is gradually increased to the optimal width indicated in
relation to the recipient bone. Facial concavities are avoided, and the
thinner facial cortical bone is protected, to limit surgical complications
such as labial dehiscence. As a consequence, whether in the maxilla or
the mandible, the implant is frequently placed under the central fossa
region of the former natural tooth.
To load the implant body in an
axial direction, the primary occlusal
contact should therefore be the central
fossa region in Division A bone. Thus
for maxillary implant opposing
mandibular natural teeth, the
mandibular buccal cusp acts as the
primary tooth contact.

Because bone loss occurs at the expense of the facial plate, a
modified buccal contour anatomy may need to be generated in Division
A or B mandibles. The occlusal table width is reduced to favor an axial
load on the implant in nonesthetic regions. The Division A mandibular
implant is placed under the central fossa region of the natural tooth.
When opposing a natural maxillary molar, the primary contacting cusp
becomes the maxillary lingual cusp opposing the mandibular implant
crown, with the mandibular buccal cusp of decreased height and width
over the implant body. Hence all contacts are situated medially
compared with those on natural teeth.
The lingual contour of the mandibular
implant crown is similar to the original natural
dentition in position, complete with horizontal
overlap to the maxillary lingual cusp to
prevent tongue biting during function. There
is no occlusal contact on the lingual cusp, so
offset loads during parafunction are
eliminated. www.indiandentalacademy.com

The posterior maxillary crown is reduced only from the lingual
aspect, compared with a natural maxillary molar, to reduce the occlusal table
width. such a reduction increases the lingual overjet when the teeth are in
occlusion. Narrower opposing mandibular occlusal tables are desirable to
direct occlusal forces over the maxillary implant body. As a result, when
opposing maxillary implants, the buccal cusps of natural mandibular teeth
(or crowns on implants) should be recontoured to minimize offset loads in
centric relation occlusion. The maxillary buccal cusp may then be retained
for esthetics, but the functional occlusal table is reduced.
When esthetics are not a concern the distal one half of the first
molar and / or the entire second molar is often restored in cross bite to
improve the direction of forces. In the posterior esthetic regions of the
maxilla with facial bone resorption and / or lingually placed implants, a
wider occlusal table is required to project the facial contours for ideal
esthetics. Bone grafting to increase bone width may be required in these
esthetics zones, so a larger diameter implant may be placed that permits
restorations of the buccal contours with maintenance of cervical contours
with emergence profiles, which permit proper hygiene of the sulcular
regions. www.indiandentalacademy.com

Posterior implants opposing each other attempt to axially load
both entities. The facial cusp of the maxillary crown is required for
esthetics. The other contours of the opposing crowns are reduced in
width to minimize the occlusal table width and axially load the
implants.
WHENEVER POSSIBLE THE PORTIONS OF AN IMPLANT
CROWN THAT ARE NOT SUPPORTED BY AN AXIALLY
POSITIONED IMPLANT SHOULD BE RECONTOURED SO
THEY DO NOT RECEIVE OCCLUSAL LOADS.
ALTERNATIVELY, SEVERAL ADDITIONAL IMPLANTS
SHOULD BE USED TO DISSIPATE THE FORCE.

DIVISION B BONE
Division B bone has maxillary and mandibular implants positioned
under the lingual cusp when compared with the original natural tooth
position. As a result, mandibular crowns require even more reduced buccal
contours to avoid offset occlusal contacts. The primary contact of occlusion
on an opposing natural posterior maxillary tooth is the lingual cusp, which
is reshaped to axially load the implant.

The buccal cusp of the mandibular implant crown is located
near the original central fossa of the natural tooth. The medially
positioned Division B mandibular implant crown may have a central
fossa, but it is more lingual than the original position. The lingual
contour of the crown is similar to that of the original natural tooth and
has an overjet with the opposing natural tooth to prevent biting the
tongue during function. The mandibular posterior implant may, on
occasion, be angled medially because of the sub mandibular fossa.
As a result, an angled abutment
and a lingual straight emergence crown
profile to minimize the lingual volume of
the restoration are indicated.
Augmentation of the mandibular
Division B ridge is often required when
stress factors are moderate to improve
the implant position and prosthetic
guidelines. www.indiandentalacademy.com

A Division B maxillary implant is often placed under the palatal cusp
region of the original natural tooth. The maxillary occlusal table cannot
always be reduced from the facial aspect for esthetic reasons; therefore the
buccal cusp is offset facially but left completely out of occlusion (as with
natural teeth) in centric relation occlusion and during all mandibular
excursions. The buccal cusp of the opposing natural tooth is recontoured in
width and height to reduce offset loads to the opposing crown on the
maxillary implant. The primary
occlusal contact is centric relation
occlusion is the maxillary palatal
cusp over the implant body and
the central fossa region of the
mandibular natural tooth. Bone
augmentation for larger implant
width is more indicated in the
maxilla because of the less dense
bone and the prosthetic needs to
replace an esthetic buccal crown
contour.

When Division B
implants are placed in both
arches, the maxillary and
mandibular prostheses are
similar to that described in the
previous scenario. However,
it is usually not possible to
load both arches with an axial
load, so the weakest implant
in bone density, width, or
prosthesis type (fixed vs.
removable) determines the
axial load, because it is the
most vulnerable arch.

When further resorption occurs and the ridge evolves into
Division C or D, the maxillary palatal cusp becomes the
primary contact area, situated directly over the implant body.
Hence the occlusal contacts differ from those of a natural tooth
and may even be positioned more medial than the natural palatal
cusp when the implant is placed in Division C or D bone.

Influence of Surface Area:
An important parameter in IPO is the adequate surface area to
sustain the load transmitted to the prosthesis. It is important to
remember that mechanical stress, in its simplest form, can be defined as
the force magnitude divided by the cross sectional area over which that
force is applied.
When implants of decreased surface area are subject to angled
or increased loads, the magnified stress and strain magnitudes in the
interfacial tissues can be minimized by placing an additional implant in
the region of concern.
Thus when narrow diameter implants are used in regions that
receive greater forces, additional splinted implants are even more
indicated to compensate for their narrow design and to help decrease
and distribute the load over a broader region. When forces are
increased in magnitude, direction or duration (e.g., parafunction), ridge
augmentation maybe required to improve implant placement, reduce
crown height, and increase implant width and number to compensate
for the increased loads.

Maxillary Root surface area
(mm2)
CENTRAL 204
LATERAL 179
CANINE 273
FIRST
PREMOLAR
234
SECOND
PREMOLAR
220
FIRST MOLAR 433
SECOND
MOLAR
431
Mandibular Root surface area
(mm2)
CENTRAL 154
LATERAL 168
CANINE 268
FIRST
PREMOLAR
180
SECOND
PREMOLAR
207
FIRST MOLAR 431
SECOND
MOLAR
426

Radius (mm) Length (mm) Surface Area (mm2)
1.75 10
12
14
110
132
154
2.00 10
12
14
126
151
176
2.25 10
12
14
141
169
197
2.50 10
12
14
157
188
220
2.75 10
12
14
172
207
242
3.00 10
12
14
188
226
264www.indiandentalacademy.com

The prosthesis type may also be modified from a fixed
restoration (FP-1 to FP-3) to a removable prosthesis (RP-4). This is
most effective when nocturnal parafunction is present because the
restorations may then be removed while sleeping. In addition, stress
relieving elements may be included in the removable restoration, and
additional support may be gained from the soft tissue (RP-5
restorations).
Wider diameter root form implants have a greater area of bone
contact at the crest than narrow implants (resulting from their
increased circumferential bone contact areas). As a result, for a given
occlusal load, the mechanical stress at the crest is reduced with wider
implants compared with narrow ones.
Natural teeth follow similar principles of diameter and surface
area as just described. The anterior region of the mouth is
characterized by reduced bite force compared with the posterior
region. Consequently, the anterior tooth cross section is smaller, and
the surface area is reduced compared with the greater diameter and
surface area of posterior teeth.

Design to the Weakest Arch:
Any complex engineering structure will typically fail at its
“Weakest link”, and dental implant structures are no exception.
The amount of force distributed to a system can be reduced by
stress relieving components that may dramatically reduce impact loads
to the implant support. The soft tissue of a traditional completely
removable prosthesis opposing implant prosthesis is displaced more
than 2 mm and is an efficient stress reducer. Lateral loads do not result
with as great a crestal load to the implants because the opposing
prosthesis is not rigid.
The most common implant treatment, which includes a
traditional soft tissue supported complete denture, is a maxillary denture
opposing a mandibular implant supported restoration. The occlusal
scheme for this condition raises the posterior occlusal plane, uses a
medial positioned lingualized occlusion, and has a bilateral balanced
scheme. Whether the mandibular restoration is FP-1, FP-2, FP-3, RP-4,
or RP-5, the maxillary denture follows these guidelines.www.indiandentalacademy.com

The mandibular implant supported restoration may exert
greater force on the premaxilla than a mandibular denture and cause
accelerated bone loss. Therefore modification of the occlusal scheme
aims at protecting the premaxilla under a maxillary denture by the
total elimination of anterior contacts with the mandibular anterior
teeth in centric occlusal relation.
Reduced occlusal forces with an absence of lateral contacts in
excursions are recommended on posterior cantilevers or anterior
offset pontics whenever possible. This minimizes the moment forces
on the abutments.
It is better for mandibular cantilever pontics to oppose
maxillary implants than the reverse situation.

Full – Arch fixed prostheses
(FP-1 to RP-4)
Fixed prostheses on natural teeth opposing FP-1 to RP-4
implant restorations should follow mutually protected occlusal schemes
whenever possible. In protrusion, there should be total absence of
posterior contacts, especially for cantilevered posterior units. The
masticatory force generated during lateral excursions is decreased in
absence of posterior contacts. This assists in reducing the noxious
effect of lateral forces on the anterior implants. Two or more implants
should share any lateral force, and lateral excursions should occur as
far forward as is practical and include the canine.
Minimal occlusal contact in the cantilevered regions and the
total absence of posterior lateral contacts during excursions are
indicated when opposing the natural dentition or a fixed restorations.
Seven to eight implants to support a complete implant
prosthesis in two separate units are suggested in the mandible for a
fixed restoration opposing a fixed prosthesis or natural teeth with
inadequate to severe stress factors.

In the edentulous maxilla, flexure of the bone is not a
concern. A full arch prosthesis may be fabricated in one section.
Eight to ten maxillary implants most often are required for a
twelve unit fixed prosthesis opposing a fixed dentition on teeth and /
or implants with moderate to severe stress factors. Posterior implants
are more critical in the maxilla, in order to eliminate cantilevers and
increase the anteroposterior implant distance, which further
decreases stress to the maxillary anterior implants.

Fully bone anchored bridge
Mandibular edentulous case
for fully bone anchored
bridge
•Recommended to have a mutually
protected occlusion.
•In centric it is necessary to have 30m
clearance at the anterior region
•disocclusion should be employed.
•To avoid localization of stresses
anterior group function should be
employed.
•The anterior guidance should be made
slightly flatter than natural teeth to
avoid over stresses on the fixtures.

Kennedy Class I
OCCLUSION FOR FREESTANDING
BRIDGES
o Clearance of the anterior teeth
should be smaller than the
natural teeth.
o Amount of disocclusion
required is same as natural teeth
since the anterior guidance is
provided by the remaining
anterior natural teeth.
Protrusive : 1.1mm
Non working side : 1.0 mm
Working Side : 0.5 mm

Kennedy Class II
•In centric the posterior
osseointegrated bridge should
have 30m open contacts, while
anterior teeth also should have 30
m open contacts and begin to
contact under strong bite pressure.
•Amount of disocclusion required
is same as natural teeth since the
anterior guidance is provided by
the remaining anterior natural
teeth.
Protrusive : 1.1mm
Non working side : 1.0mm

Kennedy Class III
 Vertical dimension is maintained
by remaining natural teeth
 The osseointegrated bridge should
contact only under strong pressure.
 Amount of disocclusion required
is same as natural teeth since the
anterior guidance is provided by the
remaining anterior natural teeth.
Protrusive : 1.1mm
Non working side : 1.0 mm

Kennedy Class IV
 To minimize horizontal loads
group function occlusion is
recommended.
 During lateral movement
posterior teeth on working side can
bear the horizontal load while non
working side can be discluded.
Anterior guidance should be flatter than natural dentition
to minimize load induced on the fixture during protrusive
movement.
Amount of disclussion suggested is as follows
Protrusive : 0.8 mm
Non- working side : 0.4 mm
Working side : 0.0 mmwww.indiandentalacademy.com

IMPLANT AND SOFT TISSUE SUPPORTED OVERDENTURE
(RP-5)
Anterior Tooth Position
Centric stops or pressure from the tongue and muscle positions
usually prevent continued extrusion of anterior natural teeth. maxillary
anterior prosthetic teeth are positioned forward of the anterior
supporting bone to satisfy phonetic and esthetic requirements. Moment
forces result from contact with the anterior teeth, which may cause
instability of the maxillary prosthesis. Therefore the maxillary denture
usually does not have anterior incisal centric stops. This helps protect
the premaxilla from excess forces in centric occlusion relation and
initial excursions of the mandible, as the premaxilla is vulnerable to
resorption from external stresses.

Posterior Tooth Position
The maxillary edentulous posterior ridge resorbs in a medial directions
it transforms from Division A to B, Division B to C, and Division C to D.
therefore the maxillary denture tooth gradually becomes more cantilevered off
the bone support, even when positioned in the same spatial location. The
mandibular edentulous posterior ridge also resorbs in a medial redirection as it
transforms from Division A to B, but then resorbs laterally from Division B to
C, and more lateral as it resorbs from Division C to D. In complete dentures,
the position of the mandibular posterior teeth is often determined first. Bone
support concepts of occlusion often position the mandibular teeth
perpendicular to the edentulous ridge. This positions the central fossa of the
posterior mandibular teeth more medial than that of their natural predecessors
in Division B, but more facial in Division C, and very facial in Division D
compared with the natural tooth placement.
The maxillary teeth are then situated farther facially than the original
teeth, if a normal cusp fossa relation is maintained. Consequently, maxillary
denture teeth are always placed lateral to the resorbing bony support, and the
condition is compounded in cases of advanced atrophy (Division C or D
bone). www.indiandentalacademy.com

The basic, concept of lingualized occlusion was first introduced
by Gysi. Later Payne suggested the maxillary buccal cusps of posterior
teeth should be reduced, so only the lingual cusps would be in contact.
Pound discussed a similar concept, but reduced the buccal cusp of the
mandible and introduced the term “lingualized” occlusion. Pound also
placed the lingual cusp of the mandibular posterior teeth between lines
drawn from the canine to each side of the retromolar pad. Consistent in
the Philosophy of Payne and Pound, was the belief that the palatal cusp
should be the only area of maxillary
tooth contact. These occlusal schemes
were designed to narrow the occlusal
table and improve mastication, reduce
forces to the underlying bone, and help
stabilize a lower denture. The
techniques of Payne and Pound may be
modified further to a medial positioned
lingualized occlusion, proposed by
Misch. www.indiandentalacademy.com

Medial Positioned Lingualized occlusion : Laboratory steps
1. Mount the upper cast using a face bow record. Mount the lower
cast using the centric relation record. Set the horizontal condylar
guidance according to the protrusive record.
2. Set the maxillary and mandibular anterior teeth for esthetics,
phonetics, and lip support.
3. Cut back the posterior flange of the lower record base to expose
the retromolar pad. Outline the retromolar pad in pencil. Draw a
line from the lingual border of the pad to the mesial aspect cuspid.
The central fossa of mandibular posterior teeth will be set along
this line.

4. Using a flat plane or 10 degree mold, set the mandibular posterior
teeth in a compensating curve. The curve should have both a
mediolateral and anteroposterior dimension that progressively
develops as the teeth are set posteriorly. The curve starts with the
first premolar and becomes more accentuated in the molar region
(closer to the condyle) (i.e., first premolar 0 to 5 degrees, second
premolar 5 to 10 degrees, first molar 15 to 20 degrees, second
molar 20 to 25 degrees). The anteroposterior angle of the curve
is the second molar region and should ideally approximate the
horizontal condylar guidance (i.e., 20 to 25 degrees).
5. Drop the incisal pin of the articulator 1 to 2 mm.
6. Using a 30 to 33 degree mold, set the maxillary posterior teeth
with the buccal cusp tilted out facially. The lingual cusp should
contact the central groove of the mandibular teeth (this will be the
only tooth contact point). There should be no contact between the
mandibular buccal cusp and the opposing maxillary tooth.

7. Return the incisal pin to the original position (up 1 to 2 mm).
8. Using articulating paper to check the contacts, grind a small fossa
in the mandibular tooth for the maxillary lingual cusp tip.
Continue to adjust the occlusion until the incisal pin touches the
incisal table. Check for balanced occlusion in excursions.
9. Festoon the set up for the try in appointment.

Overdenture
Maxillary edentulous case for
overdenture
• Recommended occlusion for
overdenture is fully balanced
occlusion with lingualized
occlusion.
• Incase maxillary overdenture is
opposed by a mandibular fully
bone anchored bridge, in centric
a small clearance is
recommended in the anterior
teeth, while posterior contact
simultaneously.
• Disocclusion is not employed
here. www.indiandentalacademy.com

OCCLUSAL MATERIALS

The materials selected for the occlusal surface of the prosthesis
affect the transmission of forces and the maintenance of occlusal
contacts. In addition, occlusal material fracture is one of the most
common complications for restorations on natural teeth or implants.
Therefore it is wise to consider the occlusal material for each
individual restoration. Occlusal materials maybe evaluated by
esthetics, impact force, a static load, chewing efficiency, fracture, wear,
interarch space requirements, and accuracy of castings. The three most
common groups of occlusal material are fixed prostheses on implants
are reviewed with relevance to the previous eight criteria.

Esthetics:
Esthetics is a major concern for patients. The most esthetic
material available today is porcelain. Acrylic is acceptable for esthetics,
and metal is a poor choice of materials when esthetics is the chief
criterion. However, there are many situations in which esthetics is not
an important aspect of the restorations. For example, when a maxillary
second molar is restored, most patients do not expose this area when
smiling or laughing.

Forces:
The materials on the occlusal aspect of the prostheses affect the
transmission of force to the bones. Impact loads give rise to brief episodes of
increases force, primarily related to the speed of closure and the dampening
effect of the occlusal material. The hardness of material is related to its ability
to absorb stress from impact loads. All porcelain occlusal surface exhibits a
hardness 2.5 times greater than that of natural teeth. Acrylic resin has a Knoop
hardness of 17 kg/mm2, and enamel has a 350 kg/mm2 hardness. A composite
resin may exhibit a hardness of 85% that of enamel. Therefore impact loads
are lowest with acrylic, increase with composite and metal occlusals, increase
even more with enamel, and further increase with porcelain. As a
consequence, it has been suggested to use resin because of its dampening
characteristics.
Clenching patients do not have a considerable amount of stress
reduction when acrylic versus porcelain materials are used on the occlusal
surfaces.
Progressive bone loading is performed with acrylic transitional
prostheses. This material may reduce the impact force on the early implant
bone interface. As the bone matures and its density increases, the need for
force reduction decreases.

Chewing efficiency:
Fixed prostheses exhibit an improve efficiency compared with
removable soft tissue borne prostheses, regardless of the occlusal
material.
Acrylic was 30% less efficient than porcelain or metal,
whereas there was no difference between gold and porcelain.

Wear:
The definition of wear is the deterioration, change or loss of a
surface caused by use. The factors affecting the amount of wear include
magnitude, angle, duration, speed, hardness, and surface finish of the
opposing force and surface, together with the lubricant, temperature,
and chemical natural of the surrounding environment. Most occlusal
wear occurs as a result of bruxism. An intuitive feeling is the harder the
occlusal material, the less the wear. However, surface hardness has
been shown to be a poor indicator of wear rate. Acrylic resin wears 7 to
30 times faster when opposing gold, resin, enamel, or polished
porcelain, compared with gold opposing gold, enamel or porcelain.
Gold occlusal surface exhibit less volume loss (sum of loss of opposing
occlusal surfaces) than any other combination of materials. Porcelain
opposing porcelain wears more than porcelain opposing gold or metal.

The wear rate of occlusal materials, especially in the partially
edentulous patient with unrestored teeth, should be similar to enamel.
In this way, occlusal changes will not dramatically change the occlusal
scheme. Lambrechts et al in an in vivo investigation reported vertical
wear of premolar and molar tooth enamel to be 20 to 40 um per year
when opposing the enamel of natural teeth.
In principle, for the partially edentulous patient it would be
better to have more occlusal wear on implants, rather than less,
because the additional forces on the teeth are better tolerated than on
implant prostheses. As a result, total volume wear may favor porcelain
opposing enamel for the implant prosthesis opposing teeth in the
partially edentulous patient and metal opposing enamel in the other
regions of the mouth that require restorations of natural teeth.
The use of gold, regardless of the opposing combination,
always provides the least total volume loss.

Adhesive wear occurs when one hard surface slides over a
surface of lesser hardness. As a result, wear fragments of one
material adhere to the other material. Gold occlusal surfaces are
observed to have gold particles adhered to enamel. This may account
for less total volume loss when opposing other materials.
For full arch implant supported prostheses, the restoring
doctor may consider metal occlusal to minimize wear and prolong
the accuracy of occlusal scheme long term. Porcelain in esthetic
regions opposing gold in the more nonesthetic area or metal occlusal
in both arches when parafunction or marginal interarch space is
present are the material most often selected as implant occlusal
materials.

Materials fracture:
Materials fracture is one of the more common factors that lead
to refabrication of a prosthesis. Porcelain, acrylic and composite
fractures occur under excessive loads or even with a lesser load of
longer duration, angulation, or frequency. Acrylic or composite
materials fracture more easily. The compressive strength of acrylic
resin is 11,000 psi, compared with 40,000 psi for enamel. Composite
resin is 3 times stronger than acrylic.
Porcelain opposing porcelain is not suggested with extreme
parafunction, because it may fracture more often than porcelain
opposing metal. Metal occlusals do not easily fracture, provide good
wear resistance, and have minimum impact load compared with
porcelain.

Accuracy:
Metal shrinkage is 10 times less than porcelain or acrylic and
therefore permits the fabrication of a more passive casting. When
accuracy of the casting is paramount, as with screw retained
restorations, the occlusal material may make a significant difference.
This is most important in regions of long spans and / or with a large
volume of materials.
Interarch space:
Acrylic restorations receive their strength from bulk and
therefore require greater interarch space. Metal occlusals require the
least amount of space. In addition, when increased retention of a
cement retained prosthesis is required, a high abutment and greater
retention may be accomplished with a metal occlusal. Porcelain is
intermediate in the interarch space requirement.www.indiandentalacademy.com

Therefore when all seven criteria are evaluated, metal is
an excellent occlusal material, with improved properties in
accuracy, wear, fracture resistance, abutment retention, and good
qualities for impact or static force. Esthetics is best satisfied with
porcelain, which has improved properties compared with acrylic
concerning fractures and retention.

REVIEW OF LITERATURE
J.B. Brunskin and J.A. Hipp in 1984 studied the in vivo
forces on dental implants. Methods are presented for
measuring vertical force components or bridged titanium
dental implants in dog mandibles. These methods have
included custom made strain gauge transducers, plus
hard wiring and telemetric schemes for data collection.
The essential components of the measurements system
are described, and typical bite force data are illustrated

Rangert et al in 1989 carried out a study on the
forces and moments on Brenamark implants. The
placement of fixture (implants) in relation to the geometry
of a prosthetic restoration has a great influence on the
mechanical loading of the implant. Based on Theoretic
consideration and clinical experiences with the Brenamark
system, this article gives simples guidelines for controlling
these loads. The emphasis is on design rules that can be
used in clinical practice. With the class I lever as a
reference. Various clinical implant prosthesis situations are
discussed and evaluated.

Parker et al in 1991 reviewed the occlusal considerations in restorative
dentistry. The major topics include the assessment and treatment of
occlusal wear, the controversies surrounding treatment position of the
mandibular condyles, occlusal considerations in osseointegrated
prosthesis, the two way relationship between occlusal factors and
temporomandibular disorders, design criteria and longevity studies in
resin bonded, fixed partial denture.
Hobo et al in 1991 presented a case report on occlusion for
osseointegrated prosthesis and concluded that the concept of occlusion
suitable for osseointegrated prosthesis is basically the same as the
gnathological occlusion. However the natural tooth sinks about 30µm
during function, while an osseointegrated bridge which is supporte
only by the bone does not sink. Therefore it is necessary to adjust the
centric contacts of the osseointegrated fixed bridge slightly more open
than the natural teeth. During the eccentric movement, in order to
minimize horizontal loading, the concept of disocclusion is generally
used. www.indiandentalacademy.com

James et al in 1993 discussed the edentulous implants
an emphasized that the occlusal contacts of the final
fixed restoration are affected significantly by implant
position. Lateral occlusal forces, may lead to abutment
screw fracture. They may be due to either excessive
lateral occlusal pressure or a malposed implant that
requires non axial loading during normal function.

C.E. Misch et al in 1994 discussed an implant protected
occlusal on a biomechanical rationale. The clinical
success and longevity of endosteal dental implants are
controlled, in a large part, by the mechanical milieu
within which they function. The occlusion is a critical
component of such a mechanical environment. “Implant
protected occlusion” refer to an occlusal scheme that is
often uniquely specific to the restoration of endosteal
implant prosthesis. Implant orientation and the
influence of load direction, the surface area of implants,
occlusal table width, and protecting the weakest area are
blended together from a biomechanical rationale to
provide support for a specific occlusal philosophy.

Tashkandi et al in 1996 did an analysis of strain at
selected bone sites of a cantilevered implant supported
prosthesis. the results revealed that the maximum strain
occurred at the strain gauge positioned on cortical bone
over the apex of the most distal implant under 10 and 20 lb
loading conditions.
Osamu et al in 2002 did a study on influence of supra
structure materials on strain around an implant under two
loading conditions. The results showed under static and
non impact dynamic loading the three super structure
materials tested (highly filled composite resin, acrylic resin
and gold alloy), had the same influence on the strain
transmitted to the bone simulant that surrounded a single
implant. www.indiandentalacademy.com

Kent et al in 2004 did a photoelectric analysis of the effect
of palatal support on various implant supported overdenture
designs and concluded that at the removal of the palatal
support produces a greater effect and more concentrated
stress difference for maxillary overdenture than difference
between the attachment designs.
With palatal coverage Without palatal coverage

Steven et al in 2004 did a study of stress transfer of four
mandibular implant overdenture cantilevered designs. His
results condluded that under load all prosthetic designs
demonstrated a low stress transfer to the ipsilateral
abutment and to the contralateral side of the arch. The
plunger retained prosthesis retained by two implants
demonstrated a more uniform stress trasnfer to the
ipsilateral terminal abutment than the clip retained
prosthesis retained by three implants and provided more
retention.

Lucie et al in 2004 Did a finite element analysis on the influence of
implant length and diameter on stress distribution. Results showed
an increase in the implant diameter decreased the maximum von
Mises equivalent stress around the implant neck more than an
increase in the implant length, as a result of a more favorable
distribution of the simulated masticatory forces applied in this study.

Osseointegrated supported prosthesis (ISP) have shown high standard
of success. This success rate depends not only on meticulous surgical
protocol but also on understanding concept of occlusion.
Occlusion should be a key factor to overall success rate. The concept
of occlusion suitable for implant supported prosthesis is basically the
same as gnathological occlusion.
In Centric contact of the Osseo integrated crown or fixed prosthesis
should be slightly more open than natural teeth.
In centric Osseo integrated crown or fixed prosthesis should not
contact with opposing teeth under the soft bite pressure (to avoid the
occlusal load on the I.S.P. which leads overload the bone structure)
Under the strong bite pressure Osseo integrated supported prosthesis
should contact after the natural tooth intrudes approximately 30µm.
SUMMARY

• To avoid overloading of the occlusal surface, the I.S.P. should not
have plane-to-plane contact.
• Point contact especially cusp-to-fossa tripodal contact is preferred.
• During eccentric movement, in order to minimize horizontal
movement, the concept of disocclusion is generally recommended.
• Anterior segments of the osseointegrated prosthesis should guide the
mandible to produce posterior disocclusion.
• Canine guided occlusion is not recommend for the Osseo integrated
prosthesis to avoid excessive occlusal forces into the single implant
fixture which is placed in the canine area. Group function is
recommended to distribute the stress over the entire fixture.
• The ideal place to bear the horizontal load is the trapezoid area,
which is surrounded by the osseointegrated fixtures.
• Load transmitted to the fixture is not so destructive when extended
mesially in the anterior region, whereas more destructive when
extended distally.

CONCLUSION
The local occlusal considerations in implant dentistry include
the transosteal forces, bone biomechanics, basic biomechanics,
differences in natural teeth and implants, muscles of mastication and
occlusal force, and bone resorption. The incorporation of all these
factors lead to an occlusal scheme (IPO) discussed in this seminar.
Occlusal schemes consider the weakest component, full or
partial edentulous arches, and posterior or anterior teeth and / or
implants. An IPO is a consistent approach for implant occlusal
schemes.
The material from which the occlusal region are fabricated
may affect implant loading and also affect implant reaction forces to
the opposing arch. These occlusal material also affect wear and
fracture, which affects the occlusal contacts, vertical occlusal
dimension, and esthetics.www.indiandentalacademy.com

References
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