rationale

1. Rationale
And biomechanics
GOOD MORNING
Rationale
And biomechanics

4. SCIENTIFIC RATIONALE AND
BIOMECHANICS IN IMPLANTS
Dr Deepa P M

5. CONTENTS
 Introduction
 Definition
 Types of biomechanics
 Role of biomechanics
 Elements of biomechanical properties
 Loads applied to dental implants
 Forces acting on dental implants
 Stresses acting on dental implants force delivery and failure
mechanisms
 Force delivery and failure mechanism
 Clinical moment arms and crestal bone loss
 Conclusion
 References
 Introduction
 Definition
 Types of biomechanics
 Role of biomechanics
 Elements of biomechanical properties
 Loads applied to dental implants
 Forces acting on dental implants
 Stresses acting on dental implants force delivery and failure
mechanisms
 Force delivery and failure mechanism
 Clinical moment arms and crestal bone loss
 Conclusion
 References

6. INTRODUCTION
 Primary functional design objective is to
dissipate and distribute biomechanical
loads…
 A scientific rationale of dental implant design
may evaluate these designs…
 This seminar will build on and apply basic
biomechanics…
 Primary functional design objective is to
dissipate and distribute biomechanical
loads…
 A scientific rationale of dental implant design
may evaluate these designs…
 This seminar will build on and apply basic
biomechanics…

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

8. TYPES OF BIOMECHANICS
 Reactive Biomechanics:
is the interaction of isolated biomechanical factors
which when combined, produce a cumulative effect.

9. TYPES OF BIOMECHANICS
 Therapeutic Biomechanics
is the clinical process of altering each biomechanical
factor to reduce the cumulative response causing implant
overload.
 Therapeutic Biomechanics
is the clinical process of altering each biomechanical
factor to reduce the cumulative response causing implant
overload.

10. TERMINOLOGIES
 MASS: is the degree of gravitational
attraction the body of matter experiences.
 FORCE ( F) = ma; m = mass and
a= acceleration.
 WEIGHT: is the gravitational force acting on
an object at a specified location.
 MASS: is the degree of gravitational
attraction the body of matter experiences.
 FORCE ( F) = ma; m = mass and
a= acceleration.
 WEIGHT: is the gravitational force acting on
an object at a specified location.

11. TERMINOLOGIES
 STRESS: = F/A, F= force andA = Area.
 STRAIN: is defined as the change in length
divided by the original length.
 MODULUS OF ELASTICITY : stress/ strain
 STRESS: = F/A, F= force andA = Area.
 STRAIN: is defined as the change in length
divided by the original length.
 MODULUS OF ELASTICITY : stress/ strain

12. TERMINOLOGIES
 ELASTIC LIMIT : the maximum stress a material
can withstand before it becomes plastically
deformed.
 YIELD STRENGTH: the stress required to
produce a given amount of plastic deformation
 ULTIMATETENSILE STRENGTH: is the measure
of stress required to fracture a material.
 ELASTIC LIMIT : the maximum stress a material
can withstand before it becomes plastically
deformed.
 YIELD STRENGTH: the stress required to
produce a given amount of plastic deformation
 ULTIMATETENSILE STRENGTH: is the measure
of stress required to fracture a material.

13. LOADS APPLIED TO DENTAL IMPLANTS
 Occlusal loads
 Passive mechanical loads
 Perioral forces
 Non passive prostheses
 Occlusal loads
 Passive mechanical loads
 Perioral forces
 Non passive prostheses

14. CLINICAL LOADING AXES
 A force applied to a
dental implant rarely
is directed absolutely
longitudinally along a
single axis.
 Three clinical loading
axes exist:
1. Mesiodistal
2. Faciolingual
3. Occlusal.
 A force applied to a
dental implant rarely
is directed absolutely
longitudinally along a
single axis.
 Three clinical loading
axes exist:
1. Mesiodistal
2. Faciolingual
3. Occlusal.

15. COMPONENTS OF FORCES
 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.
 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.

16. COMPONENTS OF FORCES contd..
•Compressive forces
attempt to push masses
toward each other.
Compressive forces tend to
maintain the integrity of a
bone-to-implant interface
•Tensile forces pull objects
apart.
•Shear forces on implants
cause sliding forces.
•Compressive forces
attempt to push masses
toward each other.
Compressive forces tend to
maintain the integrity of a
bone-to-implant interface
•Tensile forces pull objects
apart.
•Shear forces on implants
cause sliding forces.

17. FORCE
Forces acting on dental implants are referred to as vector
quantities.
Force may be described by:
1. Magnitude
2. Duration
3. Direction
4. Type
5. Magnification factors
6. Position in the arch
7. Nature of opposing teeth.
Forces acting on dental implants are referred to as vector
quantities.
Force may be described by:
1. Magnitude
2. Duration
3. Direction
4. Type
5. Magnification factors
6. Position in the arch
7. Nature of opposing teeth.

18. MAGNITUDE
 Greater the force applied greater will the stresses
developed around the implant.
 Parafunctional habits - the magnitude of force greatly
increases……
 normal bite force 23-30 psi
 Maximum bite force 50-500 psi
 Parafunction - increases upto 4-7 times about 990 psi.
 Greater the force applied greater will the stresses
developed around the implant.
 Parafunctional habits - the magnitude of force greatly
increases……
 normal bite force 23-30 psi
 Maximum bite force 50-500 psi
 Parafunction - increases upto 4-7 times about 990 psi.

19. DIRECTION
 Implant and the surrounding bone can best withstand forces
directed along the long axis of the implant…..
 Maxillary anterior implants are rarely placed along the
direction of occlusal forces.
 Mandibular molars are placed with a lingual inclination of the
implant body…..
 Implant and the surrounding bone can best withstand forces
directed along the long axis of the implant…..
 Maxillary anterior implants are rarely placed along the
direction of occlusal forces.
 Mandibular molars are placed with a lingual inclination of the
implant body…..

20. DIRECTION contd
On centric vertical contact
Angle load Axial load
tensile & shear stress compressive stress
Misch 1994
30% offset load - Decreases compressive strength -11%
On centric vertical contact
Angle load Axial load
tensile & shear stress compressive stress
Misch 1994
30% offset load - Decreases compressive strength -11%

21. TYPE
Cowin 1989
Bone - Strongest - Compression
- 30% weaker - tension
- 65% weakest – shear
Compressive force - Maintain integrity
Tensile and shear - Disrupts integrity

22. DURATION
Mastication - 9mins/day with 20 to 30 psi
Swallowing - 20mins/day with 3 to 5 psi
 The perioral muscles also apply a constant yet
light horizontal force on the teeth and implants.
 Parafunctional habits significantly increase the
duration of these loads.
Mastication - 9mins/day with 20 to 30 psi
Swallowing - 20mins/day with 3 to 5 psi
 The perioral muscles also apply a constant yet
light horizontal force on the teeth and implants.
 Parafunctional habits significantly increase the
duration of these loads.

23.  The failure of the prosthesis can result from a
phenomenon called as creep.
 Due to increase in the function of time for a
constant load fatigue fracture occurs in the
implant components.
DURATION contd…
 The failure of the prosthesis can result from a
phenomenon called as creep.
 Due to increase in the function of time for a
constant load fatigue fracture occurs in the
implant components.

24. FORCE MAGNIFIERS
 The magnitude of the force may be decreased by
reducing the significant magnifiers of force:-
 CANTILEVER LENGTH
 OFFSET LOADS
 CROWN HEIGHT
 The magnitude of the force may be decreased by
reducing the significant magnifiers of force:-
 CANTILEVER LENGTH
 OFFSET LOADS
 CROWN HEIGHT

25. POSITION IN THE ARCH
 Maximum biting force occurs in the molar region and
decreases anteriorly.
 molar region 127-250 psi
 canine region 47-100 psi
 Biting force anterior region 30-50 psi
 In natural dentition anterior teeth are shorter and
posterior teeth are longer and broader in size…………..
 Maximum biting force occurs in the molar region and
decreases anteriorly.
 molar region 127-250 psi
 canine region 47-100 psi
 Biting force anterior region 30-50 psi
 In natural dentition anterior teeth are shorter and
posterior teeth are longer and broader in size…………..

26. NATURE OF OPPOSING TEETH
 Natural teeth offer greater loads than dentures.
 The force depends upon
-location
-condition of the muscles
-joint
 Natural teeth offer greater loads than dentures.
 The force depends upon
-location
-condition of the muscles
-joint

27. STRESS
 The manner in which a force is distributed over a surface
is referred to as mechanical stress.
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.
 The manner in which a force is distributed over a surface
is referred to as mechanical stress.
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.

28. 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“ :-
1. cantilever length,
2. offset loads, and
3. crown height.
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“ :-
1. cantilever length,
2. offset loads, and
3. crown height.

29. FORCE MAGNITUDE
 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.
 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.

30. FUNCTIONAL CROSS-SECTIONAL AREA
 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.
 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.

31. DEFORMATION AND STRAIN
STRAIN
TENSION COMPRESSION
 In shear, the shape change is expressed in terms
of a change in angle of one part of the body
relative to the other.
LENGTHENING SHORTENING

32. STRESS-STRAIN CHARACTERISTICS
 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.
 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.

33. STRESS-STRAIN CHARACTERISTICS contd
 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.
 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.

34. STRESS-STRAIN CHARACTERISTICS contd
 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.

35. STRESS-STRAIN CHARACTERISTICS contd
 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 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.

36. IMPACT LOADS
• 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
1. the prosthetic restoration,
2. in the implant itself, or
3. in the interfacial tissue.
• 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
1. the prosthetic restoration,
2. in the implant itself, or
3. in the interfacial tissue.

37. IMPACT LOADS contd
• 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.
• 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.

38. IMPACT LOADS contd
 Skalak suggested the use of acrylic teeth in conjunction with
osteointegrated fixtures. (JPD ; June 1983, vol 49)
 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.
 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.
 Skalak suggested the use of acrylic teeth in conjunction with
osteointegrated fixtures. (JPD ; June 1983, vol 49)
 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.
 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.

39. •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.
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.

40. The moment of a force about a point tends to produce
rotation or bending about that point.
The moment is a vector quantity.
MomentMoment LoadsLoads == forceforce magnitudemagnitude XX momentmoment armarm
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
The moment of a force about a point tends to produce
rotation or bending about that point.
The moment is a vector quantity.
MomentMoment LoadsLoads == forceforce magnitudemagnitude XX momentmoment armarm
This imposed moment load is also referred to as a torque or
torsional load and may be quite destructive with respect to
implant systems.

41. 100 N
Proper restorative design must necessarily include consideration
of both forces and the moment loads caused by those forces.

42. CLINICAL MOMENTARMS AND CRESTAL BONE LOSS
A total of six moments (rotations) may develop about the three
clinical coordinate axes.
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.

43. Three "clinical moment arms" exist in implant dentistry:-
1. Occlusal height,
2. Cantilever length, and
3. Occlusal width.

44. Occlusal height serves as the moment arm for force components
directed along the faciolingual axis as well as along the mesiodistal
axis.
OCCLUSAL HEIGHT MOMENT ARM

45. 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.
More
crown
height
Further
increase in
crown
height
OCCLUSAL HEIGHT MOMENT ARM
More
crown
height
Vertical
cantilever
More
stress at
the crestal
areas
Bone
resorption
Further
increase in
crown
height

46. • 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
• 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.

48. • 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).
• 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).

49. A - P DISTANCE
 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.
 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.

50. Maxillary anterior teeth in a tapered
arch form requires more posterior
implants than in a square arch form,
A - P DISTANCE
A tapered arch form permits greater
cantilever length than a square arch
form in mandibular anterior region.

51. • 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.
A - P DISTANCE
• 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.

52. BIOMECAHNICAL CONSIDERATIONS IN
OSSEOINTEGRATED PROSTHESES-
Richard Skalak JPD 1983
 Cantilevered ends of a
fixed partial denture
increases the loading
on the first screw
nearest the
cantilevered end.
 Moderate overhangs
may be tolerated if
fixtures are
sufficiently strong.
 Cantilevered ends of a
fixed partial denture
increases the loading
on the first screw
nearest the
cantilevered end.
 Moderate overhangs
may be tolerated if
fixtures are
sufficiently strong.

53. 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.
 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.

54. BONE RESPONSE TO MECHANICAL LOAD
 Bone responds to number of factors including
systemic and mechanical forces.
 Cortical and trabecular bone are modified by
modelling and remodelling…. Controlled by
mechanical environment of strain.
 Bone responds to number of factors including
systemic and mechanical forces.
 Cortical and trabecular bone are modified by
modelling and remodelling…. Controlled by
mechanical environment of strain.

55. FROST ZONES OF MICRO STRAIN

56.  Pathologic overload zone and acute disease
window are the two extremes of the strain
conditions.
 Each of these conditions result in less bone.
 Higher BRR ……. Increased woven bone
formation.
 Mild overload zone…. Higher BRR…..
Increases woven bone formation.
FROST ZONES OF MICRO STRAIN
 Pathologic overload zone and acute disease
window are the two extremes of the strain
conditions.
 Each of these conditions result in less bone.
 Higher BRR ……. Increased woven bone
formation.
 Mild overload zone…. Higher BRR…..
Increases woven bone formation.

57.  The adapted window zone is most likely to be
organized, highly mineralized, lamellar bone.
 It is the ideal strain condition next to a dental
implant,
FROST ZONES OF MICRO STRAIN
 The adapted window zone is most likely to be
organized, highly mineralized, lamellar bone.
 It is the ideal strain condition next to a dental
implant,

58. FATIGUE FAILURE
FATIGUE FRACTURE: Continuous forces on a
certain material, results in internal deformation
which after a certain amount results in
permanent deformation or fracture.
 Biomaterial
 Force factor
 Number of cycles
 Geometry
FATIGUE FRACTURE: Continuous forces on a
certain material, results in internal deformation
which after a certain amount results in
permanent deformation or fracture.
 Biomaterial
 Force factor
 Number of cycles
 Geometry

59. Biomaterial
Stress level below which an implant biomaterial can be
loaded indefinitely is referred as endurance limit.
Ti alloy exhibits high endurance limit compared with
pureTi.
Number of cycles
Loading cycles should be reduced.
Eliminate parafunctional habits.
 Reduce occlusal contacts.
FATIGUE FRACTURE
Biomaterial
Stress level below which an implant biomaterial can be
loaded indefinitely is referred as endurance limit.
Ti alloy exhibits high endurance limit compared with
pureTi.
Number of cycles
Loading cycles should be reduced.
Eliminate parafunctional habits.
 Reduce occlusal contacts.

60. Implant geometry
 should resist bending & torsional load .
 Related to metal thickness.
 2 times thicker in wall thickness – 16 times
stronger.
Force magnitude
Arch position( higher in posterior & anterior)
Eliminate torque
Increase in surface area
FATIGUE FRACTURE
Implant geometry
 should resist bending & torsional load .
 Related to metal thickness.
 2 times thicker in wall thickness – 16 times
stronger.
Force magnitude
Arch position( higher in posterior & anterior)
Eliminate torque
Increase in surface area

61. MOMENT OF INERTIA
 MOMENT OF INERTIA (RADIUS)4
 Important property of cylindrical implant design
because of its importance in the analysis of bending
and torsion.
 Bending stress and likelihood of bending
fracture decreases with increasing moment of
inertia.
 MOMENT OF INERTIA (RADIUS)4
 Important property of cylindrical implant design
because of its importance in the analysis of bending
and torsion.
 Bending stress and likelihood of bending
fracture decreases with increasing moment of
inertia.

62. GOOD MORNING

63. SCIENTIFIC RATIONALE
 The biomechanical principles are related to
implant design in order to decrease the more
common complications observed in implant
dentistry.
 A scientific rationale of dental implant design
may evaluate these designs as to the efficacy
of their biomechanical load management
 The biomechanical principles are related to
implant design in order to decrease the more
common complications observed in implant
dentistry.
 A scientific rationale of dental implant design
may evaluate these designs as to the efficacy
of their biomechanical load management

64. IMPLANT
DESIGN
Macroscopic
body design
Microscopic
body design
Macroscopic
body design
Early loading
and mature
loading periods
Microscopic
body design
Initial implant
healing and initial
loading period

65. Biomechanical
load
management
Character of
force applied
Functional
surface area

66. FORCE TYPE AND INFLUENCE ON
IMPLANT BODY DESIGN
• Bone is strongest
Compressive
• 35% weaker
Tensile
• 65% weaker
Shear

67. IMPLANT MACRO GEOMETRY
 Smooth sided cylindrical implants
– subjected to shear forces
 Smooth sided tapered implants –
places compressive load at interfac
 Tapered threaded implants-
compressive load to bone
 Greater the taper – greater the
compressive load delivery
 Smooth sided cylindrical implants
– subjected to shear forces
 Smooth sided tapered implants –
places compressive load at interfac
 Tapered threaded implants-
compressive load to bone
 Greater the taper – greater the
compressive load delivery

68. Watzeck et al-histologic and
histomorphometric analysis after 18 months
of occlusal loading in baboons
 Bone trabeculae pattern and the higher BIC
resulted in superior support system for
threaded implants than smooth cylinder
implants.
 Bone trabeculae pattern and the higher BIC
resulted in superior support system for
threaded implants than smooth cylinder
implants.

69. Bolind et al- compared cylinder implants
with threaded implants from functioning
prosthesis
 Greater BIC was found in threaded implant
 Greater marginal bone loss was observed
around cylinder implants.
 Cylinder implants had roughened surface
condition but still bone loss was observed.
 Hence implant body design is more important
than surface condition.
 Greater BIC was found in threaded implant
 Greater marginal bone loss was observed
around cylinder implants.
 Cylinder implants had roughened surface
condition but still bone loss was observed.
 Hence implant body design is more important
than surface condition.

70. FORCE DIRECTION AND INFLUENCE
ON IMPLANT BODY DESIGN
 Bone is weaker when loaded under an angled
load.
 A 300 angled load increases overall stress by
50%.
 Implant body long axis should be
perpendicular curve of wilson and Spee to
apply long axis load.
 Bone is weaker when loaded under an angled
load.
 A 300 angled load increases overall stress by
50%.
 Implant body long axis should be
perpendicular curve of wilson and Spee to
apply long axis load.

71. FUNCTIONAL V/S THEORETICAL
SURFACE AREA
 Plasma spray coating provide 600% more of
TSA.
 Bone cell does not receive a transfer of
mechanical stress from this feature.
 The amount of actual BIC that can be used for
compressive loading < 30% ofTSA.
 length or diameter of implant FSA
 Plasma spray coating provide 600% more of
TSA.
 Bone cell does not receive a transfer of
mechanical stress from this feature.
 The amount of actual BIC that can be used for
compressive loading < 30% ofTSA.
 length or diameter of implant FSA

72. IMPLANT LENGTH
 Increase in length –Bi cortical stabilization
 Maximum stress generated by lateral load
can be dissipated by implants in the range of
10-15mm
 Softer the bone –greater length or width
 Sinus grafting & nerve re-positioning to place
greater implant length
 Albrektsson et al (1983)
 Increase in length –Bi cortical stabilization
 Maximum stress generated by lateral load
can be dissipated by implants in the range of
10-15mm
 Softer the bone –greater length or width
 Sinus grafting & nerve re-positioning to place
greater implant length
 Albrektsson et al (1983)

73. IMPLANT WIDTH
 Increase in implant width –
increases functional surface area
of implant
 Increase in 1mm width – increase
in 33% of functional surface area
 Wider diameter implants reduce
the likelihood of component
fracture in dental implants
(Steven Boggan et al; JPD 1999)
 Increase in implant width –
increases functional surface area
of implant
 Increase in 1mm width – increase
in 33% of functional surface area
 Wider diameter implants reduce
the likelihood of component
fracture in dental implants
(Steven Boggan et al; JPD 1999)

74. IMPACT OF IMPLANT SHAPE ON
STRESS DISTRIBUTION
 Endosteal dental implant designs may be generally
considered as blade or root form.
 When viewed from the broad end, blade implants
show a relatively favorable stress pattern,
 when viewed from the front….extremely
unfavorable stress pattern…..horizontal forces.
 Endosteal dental implant designs may be generally
considered as blade or root form.
 When viewed from the broad end, blade implants
show a relatively favorable stress pattern,
 when viewed from the front….extremely
unfavorable stress pattern…..horizontal forces.

76. IMPACT OF IMPLANT SHAPE ON STRESS
DISTRIBUTION
 Blade implants are designed to serve in those bony sites
which are too narrow to accommodate root form
implants.
 They have reduced cross-sectional area available to resist
axial loads as compared to root form implants.
 Perforations or "vents" serve to increase the amount of
cross-sectional area available to resist axial loads.
 Blade implants are designed to serve in those bony sites
which are too narrow to accommodate root form
implants.
 They have reduced cross-sectional area available to resist
axial loads as compared to root form implants.
 Perforations or "vents" serve to increase the amount of
cross-sectional area available to resist axial loads.

77. THREAD GEOMETRY
 Maximize initial contact.
 Enhance surface area
 Facilitate dissipation of loads at the bone
implant interface.
 FSA can be modified by varying three thread
parameters:Thread pitch, thread shape and
thread depth
 Maximize initial contact.
 Enhance surface area
 Facilitate dissipation of loads at the bone
implant interface.
 FSA can be modified by varying three thread
parameters:Thread pitch, thread shape and
thread depth

78. THREAD PITCH
•Chun et al, Evaluation of design
parameters of osseointegrated
dental implants using FEA
J Oral Rehab 2002; 29:565-574
•Maximum effective stress
decreased with decrease in screw
pitch.
•
•Changing screw pitch was an more
effective way than changing
implant length in reducing the
stresses.
•Chun et al, Evaluation of design
parameters of osseointegrated
dental implants using FEA
J Oral Rehab 2002; 29:565-574
•Maximum effective stress
decreased with decrease in screw
pitch.
•
•Changing screw pitch was an more
effective way than changing
implant length in reducing the
stresses.

79. LIANG KONG, ELECTION OF THE IMPLANT THREAD PITCH FOR
OPTIMAL BIOMECHANICAL PROPERTIES: A THREE-
DIMENSIONAL FINITE ELEMENT ANALYSIS,
 Effects of the implant thread pitch on the maximum
stresses were evaluated in jaw bones and implant–
abutment complex by a finite element method.
 The thread pitch ranged from 0.5 mm to 1.6 mm.
 When thread pitch exceeded 0.8 mm, minimum stresses
were obtained.
 Cancellous bone was more sensitive to thread pitch than
cortical bone did.
ClinOral Implants 2010 Feb;21(2):129-36
 Effects of the implant thread pitch on the maximum
stresses were evaluated in jaw bones and implant–
abutment complex by a finite element method.
 The thread pitch ranged from 0.5 mm to 1.6 mm.
 When thread pitch exceeded 0.8 mm, minimum stresses
were obtained.
 Cancellous bone was more sensitive to thread pitch than
cortical bone did.

80. IMPLANT THREAD SHAPE
 v shaped reverse buttress square threads

 v shaped reverse buttress square threads

Kim et al.They evaluated an implant with the same number and
depth of threads with different thread shapes.TheV-shape and
reverse buttress had similar values.
The square thread had less stress in compressive and more
importantly shear forces.

81. IMPLANT THREAD SHAPE contd
 V shaped threads convert the primary
compressive forces to the and result in 30 0
angled load
 Square shaped threads are more resistant to a
shear load.

82. THREAD DEPTH
 Greater the thread depth , greater the
surface area of the implant.
Thread depth is most in v shaped threads
As the diameter thread depth also
Thread depth can be modified along with
diameter of implant to theTSA by 150%
for every 1mm in diameter.
 Greater the thread depth , greater the
surface area of the implant.
Thread depth is most in v shaped threads
As the diameter thread depth also
Thread depth can be modified along with
diameter of implant to theTSA by 150%
for every 1mm in diameter.

83.  Should be slightly larger than outer diameter of the implant
1. to completely seal the osteotomy site…
2. Seal provides for greater initial stability
3. Increase FSA thereby reducing stress at the crestal region.
 Height should be sufficient to provide biologic width.
CREST MODULE DESIGN
 Should be slightly larger than outer diameter of the implant
1. to completely seal the osteotomy site…
2. Seal provides for greater initial stability
3. Increase FSA thereby reducing stress at the crestal region.
 Height should be sufficient to provide biologic width.

84. CREST MODULE DESIGN
 Smooth parallel sided crest –shear stress…
 Angled crest module less than 20 degree-
-Increase in bone contact area
-Beneficial compressive load
 Larger diameter than outer thread diameter
-Prevents bacterial ingress
-Initial stability
-Increase in surface area
 Smooth parallel sided crest –shear stress…
 Angled crest module less than 20 degree-
-Increase in bone contact area
-Beneficial compressive load
 Larger diameter than outer thread diameter
-Prevents bacterial ingress
-Initial stability
-Increase in surface area

85. APICAL DESIGN
 Round cross-section do
not resist torsional load
 Incorporation of anti –
rotational feature
- Vent hole- bone grows
into it
- Resist torsion
- Flat sidegroove - bone
grow against it.
- places bone in
compression
 Round cross-section do
not resist torsional load
 Incorporation of anti –
rotational feature
- Vent hole- bone grows
into it
- Resist torsion
- Flat sidegroove - bone
grow against it.
- places bone in
compression

86. IMPLANT BODY BIOMATERIAL
RELATED TO FRACTURE
• Modulus of elasticity optimal
• Ultimate strength not adequate
VITREOUS
CARBON
• Ultimate strength adequate
• Modulus of elasticity 33 times stifferCERAMIC
• Closest approximation of modulus of
elasticity
• Ultimate strength adequate
TITANIUM

87. IMPLANT BODY BIOMATERIAL
RELATED TO FRACTURE contd
Titanium
CP
Titanium
Ti-6Al-4V
alloy
CP
Titanium
Ti-6Al-4V
alloy
•Titanium alloy is 4 times stronger than CP
titanium
•The fatigue strength is also 4 times stronger than
CP titanium

88. IMPLANT COMPONENTS AND THEIR
REACTION TO FORCE
RETENTION SCREWS:
The retention screw loosening may result from the
following factors
-occlusal interferences,
-increased crown height,
-its design
-load on the abutment
-material type.
RETENTION SCREWS:
The retention screw loosening may result from the
following factors
-occlusal interferences,
-increased crown height,
-its design
-load on the abutment
-material type.

89.  Screw loosening can be decreased by a preload with a
torque wrench on the screw.
 Tighten the screw untighten it after few minutes
retighten it to the required force again.
 This causes a deformation at the thread interface which
forms a more secure reunion.
IMPLANT COMPONENTS AND THEIR
REACTION TO FORCE
 Screw loosening can be decreased by a preload with a
torque wrench on the screw.
 Tighten the screw untighten it after few minutes
retighten it to the required force again.
 This causes a deformation at the thread interface which
forms a more secure reunion.

90. CEMENT: loads over a cement retained prosthesis may cause
disruption of the cement seal causing movement of the
prosthesis.
 These movements can further cause increase in the
direction of offset loads and may be detrimental to the
prosthesis as well as the implant.
BONE -IMPLANT INTERFACE: When the implant receives an
occlusal load there is increase in micro strain next to implant
–bone interface resulting in increase in bone density.
 Therefore increasing the bone implant interface density
reduces the crestal bone loss.
IMPLANT COMPONENTS AND THEIR
REACTION TO FORCE
CEMENT: loads over a cement retained prosthesis may cause
disruption of the cement seal causing movement of the
prosthesis.
 These movements can further cause increase in the
direction of offset loads and may be detrimental to the
prosthesis as well as the implant.
BONE -IMPLANT INTERFACE: When the implant receives an
occlusal load there is increase in micro strain next to implant
–bone interface resulting in increase in bone density.
 Therefore increasing the bone implant interface density
reduces the crestal bone loss.

91. OCCLUSION
 Progressively loaded implants remain stable within the
bone….
 Lamellar bone is highly organized but takes about 1 yr to
mineralize completely after the trauma induced by implant
placement.
 PIERAZZINI: demonstrated the development of denser
trabaculae around progressively loaded implants in animals.
IMPLANT COMPONENTS AND THEIR
REACTION TO FORCE
OCCLUSION
 Progressively loaded implants remain stable within the
bone….
 Lamellar bone is highly organized but takes about 1 yr to
mineralize completely after the trauma induced by implant
placement.
 PIERAZZINI: demonstrated the development of denser
trabaculae around progressively loaded implants in animals.

92. 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
 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.
 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
 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.

93. REFERENCES
 Contemporary implant dentistry - Carl ECarl E MischMisch EdEd
3rd3rd
 Endosteal Dental Implants -RalfV McKinneyRalfV McKinney
 Dental implant prosthetics - Carl ECarl E MischMisch
 Atlas of tooth & implant supported prosthesis-
LawrenceA.Weinberg.
 Phillips Science of Dental Materials 10 th edition.
 Osseointegration and occlusal rehabilitation,
Sumiya Hobo.
 Basic bio-mechanics of dental implants in prosthetic
dentistry J Prosthet Dent 1989; 61:602-609
 Contemporary implant dentistry - Carl ECarl E MischMisch EdEd
3rd3rd
 Endosteal Dental Implants -RalfV McKinneyRalfV McKinney
 Dental implant prosthetics - Carl ECarl E MischMisch
 Atlas of tooth & implant supported prosthesis-
LawrenceA.Weinberg.
 Phillips Science of Dental Materials 10 th edition.
 Osseointegration and occlusal rehabilitation,
Sumiya Hobo.
 Basic bio-mechanics of dental implants in prosthetic
dentistry J Prosthet Dent 1989; 61:602-609

94.  Biomechanical considerations in osseointegrated prostheses,
J Prosthet Dent 1983,49:843-848.
 Influence of hex geometry and prosthetic table width on static
and fatigue strength of dental implants, J Prosthet Dent
1999,82:436-440.
 Chun et al, Evaluation of design parameters of
osseointegrated dental implants using FEA, J Oral Rehab
2002; 29:565-574
 Liang kong, election of the implant thread pitch for optimal
biomechanical properties: a three-dimensional finite element
analysis, Clin Oral Implants 2010 Feb;21(2):129-36
REFERENCES
 Biomechanical considerations in osseointegrated prostheses,
J Prosthet Dent 1983,49:843-848.
 Influence of hex geometry and prosthetic table width on static
and fatigue strength of dental implants, J Prosthet Dent
1999,82:436-440.
 Chun et al, Evaluation of design parameters of
osseointegrated dental implants using FEA, J Oral Rehab
2002; 29:565-574
 Liang kong, election of the implant thread pitch for optimal
biomechanical properties: a three-dimensional finite element
analysis, Clin Oral Implants 2010 Feb;21(2):129-36

95. THANK YOU