BIOMECHANICAL CONSIDERATIONS IN IMPLANT DENTISTRY

Dr. Niyati SinghMDS IIIrd year

UNDER THE GUIDANCE OFDR. AJAY SINGH Presented by

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.

BIOMECHANICS OF NATURAL TEETH

The tooth is suspended 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 coordinate three 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 .

2. Tensile forces

3. Shear 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 implant Compressive 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 STRAINStrain is defined as the change in length divided by the original length.

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.

• 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 prostheticrestoration, 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,

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 producerotation 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

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 distributionThe 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 transmittedthrough the neck region to the implant body and thesurrounding 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 distributionOsteolytic 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.

Proper restorative design must necessarily include

consideration of both forces and the moment loads caused by

those forces.

100 N

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.

"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 MATERIALMeier (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 are Today, practically all load related changes in the bone structure are

grouped together under termgrouped together under term remodeling remodeling and are associated with and 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 appositioned 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 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.

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 mainly related to increase 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, 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