Biomechanics/ dental implant courses

BIOMECHANICAL CONSIDERATIONS IN
IMPLANT DENTISTRY
INDIAN DENTAL ACADEMY
Leader in Continuing Dental Education
www.indiandentalacademy.com

CONTENTS
• Introduction
• Definition
• Types of biomechanics
• Importance in field of dental
implants
• Methods to analyze and
visualize stresses in bone
• Biomechanics of natural teeth
• Elements of mechanical
properties
• Force delivery and failure
mechanism
• Clinical moment arms and
crestal bone loss
• Bone as reactive recipient
material
• The bone repair mechanism
• Endosseous implant
• Biomechanical problems of
implant-supported prostheses
• Effects on treatment planning
• Summary and conclusion

Biomechanics is one of the most important
considerations affecting the design of framework for
an implant –borne prosthesis. In general, the forces
that participate in both the masticatory process and
parafunction must be considered in the design of the
prosthesis. These considerations act as determining
factors of the device’s success or failure.
INTRODUCTION

WHAT ARE BIOMECHANICS?
Biomechanics is the scientific study of the load-force
relationships of a biomaterial in the oral cavity.
(Ralph Mc Kinney).
GPT-8
It is the relationship between the biologic behavior of
oral structures and the physical influence of a dental
restoration.

TYPES OF BIOMECHANICS
TWO TYPES:-
1) Reactive Biomechanics:
is the interaction of isolated biomechanical factors which
when combined, produce an accumulative effect.
2) Therapeutic Biomechanics
is the clinical process of altering each biomechanical
factor to reduce the cumulative response causing implant
overload.

IMPORTANCE IN THE FIELD OF DENTAL IMPLANTS:
• First, to know the loading (bite forces) exerted on the
prosthesis.
• Secondly, to know the distribution of the applied forces to
the implants and teeth supporting the prosthesis.
• Thirdly, the force on each implant must be delivered safely
to the bony tissues which in turn depend on the shape and
size of the implant.
In all these, the aim of biomechanical analysis is to foresee
failure of any part of the system, including the prosthesis,
the supporting implants and the biological tissues.

METHODS TO ANALYZE AND VISUALIZE STRESSES IN BONE
Stress analysis can be performed:-
• Experimentally e.g. Stress-optical examination
• Theoretically & mathematically with computer simulation
e.g. Finite-element method
Stress-optical examination
Implant to be analyzed is embedded in synthetic resin and
stresses induced by loading are made visible by polarized light.
Disadvantages are:-
1. Not possible in inhomogeneous structure of bone
2. Limited optical resolution

Finite-element method
• The structures to be examined are subdivided into a finite
number of elements of similar size that can be connected with
each other at corner points, i.e. nodes.
• The displacements and stresses at each node caused by loading
can be calculated with a computer program.
Advantages are:-
1. Allows inclusion of various materials with differing material
properties. Most importantly, the inhomogeneous structure of
bone, i.e. the subdivision into cortical and cancellous bone, can
be taken into consideration.
2. Allows three-dimensional visualization of the calculated
displacement and stresses.

BIOMECHANICS OF NATURAL TEETH
The tooth is suspended syndesmotically within the alveolar bone
by dentoalveolar bundles of collagen fibers. Because of its
elasticity there is measurable horizontal, vertical, and rotational
tooth mobility.
Basically, tooth movement can be subdivided into two phases:-
1. Desmodontal phase:-
referred to as the first stage of movement, taking place when a
load of up to 100 N acts on the tooth. During this phase, the tooth
moves slightly within the socket. Some periodontal fiber bundles
are stretched, while others are relaxed. However, the alveolar
process does not undergo marked deformation.

2. Periodontal phase:-
commences at loads exceeding 500 N. After the
desmodontal phase has passed and the periodontal fiber
bundles have been stretched to their full length, these strong
forces cause deformation of the entire alveolar process, which
subsequently offers more resistance to further tooth
deflection.
The degree of tooth deflection may vary from one individual
to another and ranges between 10 and 50 µm.

Calculations of the stress distribution around natural teeth
have shown that physiologic stresses result in a relatively
even stress distribution.
The exception is in the cervical region of the tooth, where
horizontal loading with transfer of the compressive forces into
the periodontium results in moderately high tensile stresses,
and the lamina dura is affected by axial compressive
stresses because of bending of the alveolar bone.

• Mass, is the degree of gravitational attraction the body of
matter experiences.
• Force was described by Newton.
Newton's second law, states that the acceleration of a body is
inversely proportional to its mass and directly proportional to
the force that caused the acceleration.
A α f m Therefore, F = ma
• Weight is the gravitational force acting on an object at a
Specified location.
Weight and Force therefore can be expressed by the same
units, newtons (N) or pound force (Ibf)
ELEMENTS OF MECHANICAL PROPERTIES

FORCES
• Forces may be described by magnitude, duration,
direction, type, and magnification factors.
• Forces acting on dental implants are referred to as vector
quantities; that is, they possess both magnitude and
direction.
A force applied to a dental implant is rarely directed
absolutely longitudinally along a single axis.
In fact, forces are three dimensional with components
directed along one or more of the three clinical coordinatethree clinical coordinate
axesaxes i.e. :-

Components of Forces (Vector Resolution)
A single occlusal contact most commonly result in a three-
dimensional occlusal force. The process by which three-
dimensional forces are broken down into their component parts is
referred to as vector resolution
Types of Forces
Forces may be described as :-
1. Compressive forces attempt to push masses toward each other.
2. Tensile forces pull objects apart.
3. Shear forces on implants cause sliding forces.

• Compressive forces tend to maintain the integrity of a bone-
to-implant interface, whereas tensile and shear forces tend
to disrupt such an interface.
• Shear forces are most destructive to implants and bone
when compared with other load modalities.
• Compressive forces, in general, are best accommodated by
the complete implant-prosthesis system.

The implant body design transmits the occlusal load to the
bone. Threaded or finned dental implants impart a
combination of all three force types at the interface under
the action of a single occlusal load.
Cylindrical implants are at highest risk for harmful shear
loads under an occlusal load directed along the long axis of
the implant body. As a result, cylinder implants require a
coating to manage the shear stress at the interface through
a more uniform bone attachment along the implant length.
Compressive forces should typically be dominant in implantCompressive forces should typically be dominant in implant
prosthetic occlusion.prosthetic occlusion.

STRESS
The manner in which a force is distributed over a surface is
referred to as mechanical stress. Thus stress is defined by the
familiar relation:
Stress = F/A
The internal stresses that develop in an implant system and
surrounding biologic tissues have a significant influence on the
long-term longevity of the implants in vivo.
As a general rule of thumb, a goal of treatment planning should
be to both minimize and evenly distribute mechanical stress in the
implant system and the contiguous bone.

The magnitude of stress is dependent on two variables:-
1. force magnitude and
2. cross-sectional area over which the force is dissipated.
Force magnitude
• rarely be completely controlled by a dental practitioner.
• The magnitude of the force may be decreased by reducing the
significant "magnifiers of force“ :- cantilever length, offset loads,
and crown height.
Night guards to decrease nocturnal parafunction, occlusal
materials that decrease impact force, and overdentures rather
than fixed prosthesis so they may be removed at night are
further examples of force reduction strategies.

Functional cross-sectional area is defined as that surface
that participates significantly in load bearing and stress
dissipation.
It may be optimized by :-
(1) Increasing the number of implants for a given edentulous
site, and
(2) Selecting an implant geometry that has been carefully
designed to maximize functional cross-sectional area.

DEFORMATION AND STRAIN
Strain is defined as the change in length divided by the original
length.
For tension and compression, strain expresses a lengthening and a
shortening of the body respectively. In shear, the shape change is
expressed in terms of a change in angle of one part of the body
relative to the other.
The deformation and strain characteristics of the materials used in
implant dentistry may influence interfacial tissues, and clinical
longevity.
Elongation (deformation) of biomaterials used for dental implants
range from 0% for aluminum oxide (Al2O3) to up to 55% for
annealed 316-L stainless steel.

Related to deformation is the concept of strain—a parameter
believed to be a key mediator of bone activity.
All materials (both biologic and nonbiologic) are characterized
by a maximum elongation possible before permanent
deformation or fracture results.

STRESS-STRAIN CHARACTERISTICS:
A relationship is needed between the applied force (and stress)
and the subsequent deformation (and strain).
If any elastic body is experimentally subjected to an applied load,
a load-vs.-deformation curve may be generated.
If the load values are divided by the surface area over which they
act and the change in the length by the original length, a classic
engineering stress-strain curve is produced.

Such a curve provides for the prediction of how much strain will be
experienced in a given material under an applied load.
The slope of the linear (elastic) portion of this curve is referred to
as the modulus of elasticity (E), and its value is indicative of the
stiffness of the material under study.
The closer the modulus of elasticity of the implant resembles that of
the biologic tissues, the less the likelihood of relative motion at the
tissue-to-implant interface.
Once a particular implant system (i.e., a specific biomaterial) is
selected, the only way to control the strain is to control the applied
stress or change the density of bone around the implant.

The greater the magnitude of stress applied, the greater the
difference in strain between implant material and bone.

• When two bodies collide in a very small interval of time (fractions
of a second), relatively large forces develop. Such a collision is
described as impact.
• In dental implant systems subjected to occlusal impact loads,
deformation may occur in the prosthetic
restoration, in the implant itself, or in the interfacial tissue.
• The higher the impact load, the greater the risk of implant and
bridge failure and bone fracture.
• Rigidly fixed implants generates a higher impact force than a
natural tooth with its periodontal ligament.
Various methods have been proposed to address the issue of
reducing implant loads.
IMPACT LOADS

Skalak suggested the use of acrylic teeth in conjunction with
osteointegrated fixtures
Weiss has proposed that a fibrous tissue-to-implant interface
provides for physiologic shock absorption in the same manner as by
a functioning periodontal ligament.
one implant design has attempted to incorporate shock absorption
capability in the design itself, by the use of an "intramobile element"
of lower stiffness compared with the rest of the implant.
Misch advocates an acrylic provisional restoration with a progressive
occlusal loading to improve the bone-to-implant interface before the
final restoration, occlusal design, and masticatory loads are
distributed to the system.

FORCE DELIVERY AND FAILURE MECHANISMS
The manner in which forces are applied to implant
restorations dictates the likelihood of system failure.
If a force is applied some distance away from a weak link in
an implant or prosthesis, bending or torsional failure may
result from moment loads.

The moment of a force about a point tends to produce
rotation or bending about that point.
The moment is a vector quantity.
Moment Loads = force magnitude X moment armMoment Loads = force magnitude X moment arm
This imposed moment load is also referred to as a torque or
torsional load and may be quite destructive with respect to
implant systems.
Moment Loads

Proper restorative design must necessarily include
consideration of both forces and the moment loads caused by
those forces.
100 N

"Clinical Moment Arms" and Crestal Bone Loss
A total of six moments (rotations) may develop about the
three clinical coordinate axes.
faciolingual plane

Such moment loads induce microrotations and stress
concentrations at the crest of the alveolar ridge at the
implant-to-tissue interface, which leads to crestal bone loss.
Three "clinical moment arms" exist in implant dentistry:-
1. Occlusal height,
2. Cantilever length, and
3. Occlusal width.
Minimization of each of these moment arms is necessary to
prevent unretained restorations, fracture of components,
crestal bone loss, and/or complete implant system failure.

Occlusal Height Moment Arm
Occlusal height serves as the moment arm for force
components directed along the faciolingual axis as well as
along the mesiodistal axis.

Moment of a force along the vertical axis is not affected by the
occlusal height because there is no effective moment arm.
Offset occlusal contacts or lateral loads, however, will
introduce significant moment arms.

• Large moments may develop from vertical axis force
components in cantilever extensions or offset loads from
rigidly fixed implants.
• A lingual force component may also induce a twisting
moment about the implant neck axis if applied through a
cantilever length.
Cantilever length moment arm

• An implant with a cantilevers extending1 cm, 2 cm, and 3 cm
has significant ranges of moment loads.
• A 100-N force applied directly over the implant does not
induce a moment load or torque because no rotational forces
are applied through an offset distance.
• This same 100-N force applied 1 cm from the implant results
in a 100 N-cm moment load.
• Similarly, if the load is applied 2 cm from the implant, a 200
N-cm torque is applied to the implant-bone region, and 3 cm
results in a 300 N-cm moment load.
• (Implant abutments are typically tightened with less than
30 N-cm of torque).

The distance from the center of the most anterior implant to the
distal of each posterior implant is called the anteroposterior (AP)
distance.
The greater the A - P distance, the smaller the resultant load on
the implant system from cantilevered forces, because of the
stabilizing effect of the anteroposterior distance.
According to Misch, the amount of stress applied to system is
determined by the length of the distal cantilever.
Nobel Biocare prosthetic protocol uses four to six anterior
implants placed in front of the mental foramen or maxillary sinus
and uses a full-arch fixed prosthesis with cantilevered segments.

Replacement of maxillary anterior
teeth in a tapered arch form requires
more posterior implants than in a
square arch form, with less offset
loading of mandibular teeth.
A tapered arch form permits greater
cantilever length than a square arch
form in mandibular anterior region.

• The most ideal biomechanical arch form depends on the
restorative situation:-
• Tapering arch form is favorable for anterior implants with
posterior cantilevers.
• Square arch form is preferred when canine and posterior
implants are used to support anterior cantilevers in either arch.
• Ovoid arch form has qualities of both tapered and square arches.
• Clinical experiences suggest that the distal cantilever should not
extend 2.5 times the A-P distance under ideal conditions.
• Patients with severe bruxism should not be restored with any
cantilevers.

Occlusal Width Moment Arm
Wide occlusal tables increase the moment arm for any offset
occlusal loads.
Faciolingual tipping (rotation) can be significantly reduced by
narrowing the occlusal tables and/or adjusting the occlusion
to provide more centric contacts.
It can be summarized that a destructive cycle can develop with
moment loads and result in crestal bone loss. Unless the bone
increases in density and strength , the cycle continues
towards implant failure if the biomechanical environment is
not corrected.

BONE AS REACTIVE RECIPIENT MATERIAL
Meier (1887) assumed that the trajectories within cancellous bone
show the same direction as in the femur head. Wolff (1892) gave
more clarity to Meier hypothesis and established it as law of nature.
Roux (1895) suggested that natural tissues are capable of adapting
to changing loading conditions because of a cellular regulation
process. Depending on the magnitude of loading ,bone tissue cells
either respond by bone formation or bone resorption.
Later, Wolff’s hypothesis and Roux’s principle merged into one
concept as Wolff’s Law.
Today, practically all load related changes in the bone structure areToday, practically all load related changes in the bone structure are
grouped together under termgrouped together under term remodelingremodeling and are associated withand are associated with
Wolff’s Law.Wolff’s Law.

THE BONE REPAIR MECHANISM
Pauwels hypothesis (1960) is based on the observation that bone
responds to physiologically relevant long-term loading by increasing
bone formation.
If bone remains unloaded for the same period of time it will undergo
resorption.
If a physiologically relevant force acts on the bone, bone tries tobone tries to
reduce strainreduce strain by bone apposition or reduction and by changing its
cross section and stiffness.
This is done by :-
• Bone formation or resorption at surface [external or surface
remodeling]
• Altering the bone mineral content [internal remodeling]

As long as the mechanical stimulus remains within a certain
physiologic limit, the system will maintain balance between
bone resorption and new bone growth.
Stress of 2.48x10N/mm² --- will cause increase in bone growth.
Stress ranging 2.5x10 to 6.9x10N/mm2
– will lead to reduction
of bone growth.
Stress exceeding 6.9x10N/mm² -- will cause cell destruction.

To prevent bone resorption caused by biomechanical
factors,forces should be as even as possible and not
exceeding a maximum value of 2.5x10 N/mm².
The balance can be regulated by both hormonal and
mechanical factors. Several theories concern the effect of
mechanical loads and repair mechanisms.

ENDOSSEOUS IMPLANT (OPEN IMPLANT SYSTEM)
• The biomechanical conditions around an implant
differ fundamentally from those around natural teeth.
• While natural teeth are anchored within the socket by
the fibers of the periodontal membrane, implants may
show either direct bone bonding or connective tissue
encapsulation.

Direct bone bonding
• Can be achieved if implant is allowed to heal into bone in
the absence of loading and new bone is oppositioned onto
the implant surface.
• Ankylotic-healing can be considered as one of the most
important aspects of the force transfer mechanisms in
osseointegrated implants because it prevents relative
movement of implant and bone.
• Close apposition of bone to the implant can even be
observed in microasperities at the Angstrom level.

Connective tissue encapsulation
• occurs if the implant is loaded
immediately after having been placed.
• Following long periods of function, the
bone around endosseous implants can
undergo resorption observed as funnel-
shaped local areas of cortical bone
reduction at the site where the implant
enters bone.
• Aside from inflammatory causes, bone
resorption is mainly due to biomechanical
factors.

Will the use of "isoelastic" implants result in more favorable
stress conditions in bone than those observed when relatively
stiff, conventional dental implants are used?
Soltesz and Siegele (1982) as well as Moilgth et al (1989) have
shown that :-
• The global stress pattern remains the same when the material
properties of an implant are changed.
• Most stress values only show minor changes, except for the
site where the implant enters bone.
• The values obtained from implants made of bonelike
substances are more than twice as high as those calculated for
implants made of stiffer materials.
Impact of implant stiffness on stress distribution

All in all, the use of isoelastic implants cannot be
recommended.
On the contrary, implants should be as stiff as possible from
the biomechanical standpoint, and should have modulus of
elasticity of atleast 100,000N/mm². The stiffness of an implant
can also be increased by choosing an implant of larger
diameter.
If the diameter is increased by 30%, implant stiffness will be
five times higher, and the stresses around the implant neck
are thus reduced.

Impact of implant shape on stress distribution
The stress conditions around an implant can also be improved by
selecting an appropriate implant shape.
Endosteal dental implant designs may be generally considered as
blade or root form.
The neck design in either implant system (i.e. root form & blade
form) is particularly important in the consideration of implant
geometry because the physiologic load is transmitted
through the neck region to the implant body and the
surrounding tissues.
As the cross-sectional area of the neck decreases, the stress levels
in the neck and the surrounding tissues increases.
( stress= force/area.)

The implant body must exhibit a macrogeometry suitable for
force transfer to the surrounding tissues as well as for
implantation into a bony site of a particular anatomic size.
When viewed from the broad end, blade implants show a
relatively favorable stress pattern, when viewed from the front,
they exhibit an extremely unfavorable stress pattern,
particularly with regard to horizontal forces.

Because force transfer into bone should be as even as possible,
implants showing rotational symmetry can be considered more
favorable from the biomechanical point of view. However, this
imposes size constraints on the geometry of the implantation
site.
Blade implants are designed to serve in those bony sites which
are too narrow to accommodate root form implants. However ,
they have reduced cross-sectional area available to resist axial
loads as compared to root form implants.

Perforations or "vents" in the body of an endosteal dental
implant provide a means for bone in growth into the device
with resultant stabilization of the implant within the tissues. In
blade form implants, vents also serve to increase the amount
of cross-sectional area available to resist axial loads.

Impact of implant surface on stress distribution
Osteolytic loosening of an implant may result from selection of a
biomechanically unfavorable implant shape.
Because endosseous implants lack the natural attachment to bone,
this missing periodontal function must be compensated for by
minimization of the specific surface pressure (snowshoe principle).
This means that implant surface used for force transfer should be as
large as possible.
To minimize the compressive forces, the implant surface can be
enlarged by:-
•Applying threads
•Plasma flame spray coating
•Surface roughening
•Acid etching

Another factor that influences the size of the surface area is
the length of the implant.
Albrektsson et al (1983) revealed a clear correlation between
the length of an implant and implant prognosis. Implants with
a length of less than 10mm showed a markedly worse
prognosis than did implants whose length exceeded 10 mm.
This may be due to the fact that short implants have a
considerably smaller surface area and are affected by
markedly higher moments.

BIOMECHANICAL PROBLEMS OF IMPLANT-SUPPORTED
PROSTHESES
Connecting implants with natural teeth
In a combined tooth-implant prosthesis, force distribution
depends on whether, the main load is borne by the tooth or
the implant .
• If the superconstruction above the implant is affected by
vertical loads, load transfer will take place almost
exclusively via implant, the natural tooth only being used
minimally as support.

Use of an implant with an integrated elastic layer, i.e. an
intramobile element can reduce the stresses.
From the prosthodontic point of view, whenever possible
avoid a rigid connection between implant and tooth and use
purely implant-supported superconstructions instead.
• lf the same vertical load acts on the portion of the prosthesis
above the tooth, the load distribution will differ from the one
previously described. In this case, the prosthesis acts as a
lever arm. The tooth is affected both by vertical force and
torque and can slightly sink into the socket .

Purely implant-supported prostheses
Implant-supported prostheses seem to involve fewer
biomechanical problems. However, there are many
aspects that need to be clarified, because:
1. The prosthesis must follow the arched shape of the
mandible.
2. The implants cannot be considered an ideal rigid system.
3. The mandible undergoes functional deformation.

One of the most common indication for implant treatment is the
atrophic edentulous mandible. Aside from the widely used bar-joint
dentures, fixed implant-supported prostheses with a posterior
cantilever are gaining increasing importance.
The number of implants to be placed can be calculated from the
space available between the two mental foramina and the distance
between the implants postulated by Branemark et al (1985).
Because the mean distance between the two mental foramina is 47
mm and the distance from the center of one implant to that of the
adjacent implant should be 7 mm, up to six implants can be placed.

The author's (Mailath-Pokorny/Solar) own finite-element
analyses have shown that :-
1. The maximum shear stress and moments can be observed
in the implant closest to the site of force impact and the
effects on all other implants can even be ignored.
2. When the distribution and density of stress on a prosthesis
supported by four implants are compared with those
supported by six implants, the additional procedures needed
for placement of the two additional implant do not seem to
be justified.

3. Prolongation of the cantilever by more than two times the
width of a premolar tooth results in unfavorable loading
condition because of lever arm effect. It seems to be
sensible to use cantilever prostheses whose free end is
not longer than two times the width of a premolar tooth.
4. Also, the use of six implants would not improve the
unfavorable loading conditions caused by a long cantilever.

EFFECTS ON TREATMENT PLANNING
1) The most common complications in implant dentistry, once
the prosthesis is delivered are, bone loss, fracture of
occlusal materials or implant components, and unretained
restorations.
These problems are primarily related to increases in stress.
Therefore once the sources of additional force are identified
on the implant system, the treatment plan is altered to lower
their negative impact on the implant, bone, and final
restoration.

2) Stress can be reduced by using Additional implants, rather
than only an increase in implant width or height. This will:-
• decrease the number of pontics and the associated
mechanics and strains on the prosthesis.
• dissipate stresses more effectively to the bone structure,
especially in crestal region.
• retention of the final prosthesis or superstructure is further
improved.
• The amount of bone in contact with the implant is also
increased as a multiple of the number of implants.
• Also, Increase in implant width is preferable to length as
lesser stresses transmitted to crestal bone.

Panoramic radiograph of mandibular fixed prosthesis opposing
natural dentition. Posterior implants are used as abutments rather
than cantilevers to decrease stress on implants and prosthesis. No
second molars are provided to decrease stress.

3) Forces from bruxism are often the most difficult forces to
control. Crestal bone loss, unretained abutments, and fatigue
stress fractures of implants or prostheses are more likely a
result of this condition.
The implant treatment plan is modified primarily in two ways
when implants are inserted in the posterior region.
• Additional implants and occlusal considerations are both
primordial.
• The elimination of posterior lateral occlusal contacts during
excursive movements is recommended when opposing
natural teeth or an implant or tooth supported fixed
prostheses.

• The anterior teeth may be modified to recreate the proper
incisal guidance and avoid posterior interferences during
excursions.
• Use of a night guard is helpful for the bruxism patient with
fixed prostheses.
• Anterior-guided disocclusion of the posterior teeth in
excursions is strongly suggested in the night guard, which
may be designed for the maxilla or mandible.

• A removable partial denture over a healing implant is
especially of concern. These patients often have many
remaining teeth and higher forces are transmitted to the soft
tissue regions that support the restorations. The acrylic
between the soft tissue-borne region and metal substructure is
usually less than 2 mm thick.
• Removing the thin acrylic region over the implant is often not
sufficient. Instead, a 6-mm diameter hole through the metal
substructure should be prepared. In this manner, a bruxing
patient will not load the submerged implant during healing.

4) The time Intervals between prosthodontic restoration
appointments may be increased to provide additional time to
produce load-bearing bone around the implants through
progressive bone-loading techniques.
• Anterior implants submitted to lateral parafunction forces
require further treatment considerations. Additional implants
are indicated, preferably of greater diameter.

• The excursions are canine guided if natural, healthy
canines are present.
• Mutually protected occlusion is developed if the implants are
in the canine position or if this tooth is restored, as a pontic.
• A first premolar may also disocclude the remaining posterior
teeth when the patient is in skeletal Class II or when anterior
implants are small in size or number

5) Prosthesis may be designed to improve the distribution of
stress throughout the implant system.
• Centric vertical contacts should be aligned with the long
axis of the implants whenever possible.
• The posterior occlusal tables may be narrowed to prevent
inadvertent lateral forces, and to leave greater space for
the tongue.
• Enameloplasty of the cusp tips of the opposing natural
teeth is done to improve the direction of vertical forces.

6) A Lateral tongue thrust is most detrimental if horizontal
forces are applied to the implant during the early stages
of interface formation.
Submerged, two-phase, rigid, fixated implants are
indicated.

7) Inadequate bone height for endosteal implants usually
means a higher crown height and extension of the implant
substructure. These permucosal abutment posts are subject
to increased lateral oral forces.
valid treatment alternatives are:-
• Myofunctional therapy and/or autogenous bone grafts to
modify the bone type.
• cantilevered bridges from the anterior teeth or implants.
• conventional removable partial dentures.

SUMMARY AND CONCLUSION
The most common complications in implant-related
reconstruction are related to biomechanical conditions.
The manifestation of biomechanical loads on dental
implants (moments, stress, and strain) controls the long-
term health of the bone-to-implant interface. Knowledge of
basic biomechanical principles is thus required for the
dentist.

• Biomechanics in clinical dentistry -Angelo. A CapitoAngelo. A Capito
• Contemporary implant dentistry - Carl E Misch Ed 2nd.Carl E Misch Ed 2nd.
• Oral rehabilitation with implant supported prostheses-
Vicente jimenez- LopezVicente jimenez- Lopez
• Endosteal Dental Implants -Ralf V McKinney JrRalf V McKinney Jr
• Endosseous implants- Georg WatzekGeorg Watzek
• Dental implant prosthetics - Carl E MischCarl E Misch
REFERENCES

Biomechanics/ dental implant courses

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