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CLINICAL
BIOMECHANICS
IN
IMPLANT
DENTISTRY
INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalaca...
INTRODUCTION
www.indiandentalacademy.com
living
MECHANICSBIO
www.indiandentalacademy.com
Loads applied to dental implant
 Occlusal loads,
 Passive mechanical loads,
 Low horizontal perioral forces,
 Mechanic...
www.indiandentalacademy.com
www.indiandentalacademy.com
force
Compressive
Tensile
Sliding
compressive
www.indiandentalacademy.com
www.indiandentalacademy.com
stress
force
area
No of implant
Implant geomatrywww.indiandentalacademy.com
Deformation and strain-
Load application may induce deformation of
both implant and surrounding tissues.
Biological tissue...
It is more important to decrease stress in
softer bone because of greater elastic
difference and lower ultimate strength.
...
IMPACT LOAD
When two bodies collide in a very small
interval of time, relatively large reaction forces
develop.
Such colli...
Impact loads can be decreased by-
- Using acrylic teeth – Skalak (JPD 1983 : 49;
843-49).
- Weiss advocated fibrous tissue...
Misch advocates acrylic provisional with
progressive occlusal loading to improve
Bone-Implant interface before final
resto...
FORCE DELIVARY AND FAILURE MECHANISM
Moment loads
Moment of force about a point tends to
produce rotation or bending about...
www.indiandentalacademy.com
Clinical moment arms and crestal bone
loss
Six moments may develop about the 3
clinical coordinate axes .
Such loads induc...
Three clinical moment arms exist in implant
dentistry, minimization of each is necessary to
prevent failure.
www.indianden...
www.indiandentalacademy.com
Occlusal height moment arm
Acts as a moment arm for a force components
directed along faciolingual and mesiodistal axis
ww...
Cantilever length moment arm
Large moments from vertical axis force
component is seen in prosthetic
environments designed ...
www.indiandentalacademy.com
Occlusal width moment arm
Wide occlusal tables increase moment
arm for any offset occlusal loads
Faciolingual rotation can...
Scientific rationale for dental implant design
Biomechanical load management Is
dependent on two factors:
- Character of t...
Character of forces applied to dental
implants
Forces applied to dental implants may be
characterized in terms of five dis...
Force magnitude
Physiologic constraints on design:
- After sustained period of edentulism……
- Careful treatment planning &...
Clinical implant design failures related to
choice of biomaterial and force magnitude.
www.indiandentalacademy.com
Force duration
Physiologic constraints on design-
-Ideally the forces duration while eating and
swallowing is ≈ 30 min ∕ d...
stress
Endurance limit
cycles
FAILURE
www.indiandentalacademy.com
How the implant and abutment resists,
fracture from bending forces -----
www.indiandentalacademy.com
Force type
Physiological constraints on design :
- Bone is strongest in compressive > tensile >
shear
- Endosteal implants...
Influence on Implant body design :
- As angulation of load increases stress around
the implant Increases particularly in t...
www.indiandentalacademy.com
Force magnification
Extreme angulation and parafunctional habits
exceed the capability of the dental implant
design to wit...
Surface area
Anatomical constraints on surface area
optimization-
Bone vol : external architecture of bone
- Width is grea...
- Therefore implant width may increase as
amount of force magnification increases from
anterior to posterior region.
- On ...
Bone quality : internal architecture of bone
- four distinctly different bone density
classifications exist within the max...
Functional surface area forces vs. Total
surface area-
For a given bone vol, implant surface area
must be optimized for fu...
Functional thread surface area: portion of
the thread that participates in compressive
load transmission under the action ...
Since most stress to the I-B interface Is in the
crestal 1/2 of the implant, the crestal zone is
most important to distrib...
Implant macro geometry
Smooth sided cylindric implants provide
surgical ease however B-I interface is
subjected to signifi...
Threaded implants with circular cross section
provide ease of surgical placement and allow
for >FSA optimization to transf...
Implant width
Over the years implants have gradually
Increased in width
Scientific principle being > the width greater
the...
Crestal bone anatomy limits implants to <
5.5mm except in limited situations
Thus implant design innovations in crestal
re...
Thread geometry
FSA for unit length of the implant may be
modified by varying three geometric
parameters of implant
- Thre...
Thread pitch is defined as the distance
measured parallel with its axis between
adjacent thread forms ( for V type threads...
www.indiandentalacademy.com
Thread shape:
• V shaped
• Square
• Buttress
- Dental implant applications dictates the
need for a thread shape optimized ...
www.indiandentalacademy.com
The square thread provides an optimum
surface area for intrusive & compressive load
transmission
Shear loading most detrim...
Thread depth : refers to the distance between
the major and minor diameter of the thread
It may be varied for the length o...
www.indiandentalacademy.com
Implant length
As length of the implant increases so does the
overall total surface area
Once I-B interface is formed exce...
Nerve repositioning is cited as an acceptable
clinical treatment to facilitate longer implants
in the posterior mandible
M...
Crest module configuration
Crest module of implant body is the
transosteal region from implant body and is
characterized a...
www.indiandentalacademy.com
www.indiandentalacademy.com
Angulated crest module > 20° with surface
texture that increases bone contact causes
slightly beneficial cumbersome stress...
Apical design considerations
Most root form implants are circular in cross
section
Around cross section does not resist sh...
www.indiandentalacademy.com
Another anti - rotational feature flat sides or
gross along the body or apical the region of
the implant body
When bone gr...
Surface coatings
Titanium plasma spray ( TPS )
- Implant body may be covered with a porous
coating , two materials commonl...
- There is 600% increase in total surface area
- FSA increases by 25 to 30% which is
significant
- Improved initial fixati...
Advantages of surface coatings:
- Increased surface area
- Increased roughness for initial stabilization
- Stronger B-I in...
Disadvantages of surface coatings :
- Coatings may be damaged when being
inserted in dense bone
- Increased surface roughn...
Contemporary implant dentistry – Carl E. Misch , 2nd
edition
Dental materials – Philips 11th
edition
Fundamentals of impla...
For more details please visit
www.indiandentalacademy.com
www.indiandentalacademy.com
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Biomechanics/ orthodontics australia

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implants,Orthodontics,Endodontics,Cosmetic Dentistry, Prosthetic

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Biomechanics/ orthodontics australia

  1. 1. www.indiandentalacademy.com
  2. 2. CLINICAL BIOMECHANICS IN IMPLANT DENTISTRY INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com www.indiandentalacademy.com
  3. 3. INTRODUCTION www.indiandentalacademy.com
  4. 4. living MECHANICSBIO www.indiandentalacademy.com
  5. 5. Loads applied to dental implant  Occlusal loads,  Passive mechanical loads,  Low horizontal perioral forces,  Mechanical loads from nonpassive prosthesis. www.indiandentalacademy.com
  6. 6. www.indiandentalacademy.com
  7. 7. www.indiandentalacademy.com
  8. 8. force Compressive Tensile Sliding compressive www.indiandentalacademy.com
  9. 9. www.indiandentalacademy.com
  10. 10. stress force area No of implant Implant geomatrywww.indiandentalacademy.com
  11. 11. Deformation and strain- Load application may induce deformation of both implant and surrounding tissues. Biological tissue interprets deformation and it’s manifestations and responds with remodeling. Stress and strain relationship-The closer the modulus of elasticity of the implant to the bone, less the likelihood of relative motion at the tissue to implant interface. www.indiandentalacademy.com
  12. 12. It is more important to decrease stress in softer bone because of greater elastic difference and lower ultimate strength. www.indiandentalacademy.com
  13. 13. IMPACT LOAD When two bodies collide in a very small interval of time, relatively large reaction forces develop. Such collisions are called impacts. Example : occlusal loads. Cause deformation of implants and surrounding tissue. www.indiandentalacademy.com
  14. 14. Impact loads can be decreased by- - Using acrylic teeth – Skalak (JPD 1983 : 49; 843-49). - Weiss advocated fibrous tissue to implant interface for shock absorption. - Use of intramobile element to lower the stiffness than rest of the implant. www.indiandentalacademy.com
  15. 15. Misch advocates acrylic provisional with progressive occlusal loading to improve Bone-Implant interface before final restoration. www.indiandentalacademy.com
  16. 16. FORCE DELIVARY AND FAILURE MECHANISM Moment loads Moment of force about a point tends to produce rotation or bending about that point. M = Force x perpendicular distance , from the point of interest. Also called torque or torsional load. www.indiandentalacademy.com
  17. 17. www.indiandentalacademy.com
  18. 18. Clinical moment arms and crestal bone loss Six moments may develop about the 3 clinical coordinate axes . Such loads induce microrotation and stress concentration at the crest of alveolar ridge – implant – bone interface and leads to crestal bone loss www.indiandentalacademy.com
  19. 19. Three clinical moment arms exist in implant dentistry, minimization of each is necessary to prevent failure. www.indiandentalacademy.com
  20. 20. www.indiandentalacademy.com
  21. 21. Occlusal height moment arm Acts as a moment arm for a force components directed along faciolingual and mesiodistal axis www.indiandentalacademy.com
  22. 22. Cantilever length moment arm Large moments from vertical axis force component is seen in prosthetic environments designed with cantilevered extensions or offset loads from rigid implants Distal cantilever should not extend 2.5 x the A-P distance under ideal conditions www.indiandentalacademy.com
  23. 23. www.indiandentalacademy.com
  24. 24. Occlusal width moment arm Wide occlusal tables increase moment arm for any offset occlusal loads Faciolingual rotation can be reduced by narrow occlusal tables and adjusting occlusion to provide more centric contact www.indiandentalacademy.com
  25. 25. Scientific rationale for dental implant design Biomechanical load management Is dependent on two factors: - Character of the applied force - Functional surface area over which the load is dissipated www.indiandentalacademy.com
  26. 26. Character of forces applied to dental implants Forces applied to dental implants may be characterized in terms of five distinct factors, namely: - Magnitude - Duration - Type - Direction - Magnification www.indiandentalacademy.com
  27. 27. Force magnitude Physiologic constraints on design: - After sustained period of edentulism…… - Careful treatment planning & appropriate implant design selection. Influence on biomaterial selection: - Many biocompatible materials unable to sustain the magnitude of parafunctional loads imposed on dental implant. www.indiandentalacademy.com
  28. 28. Clinical implant design failures related to choice of biomaterial and force magnitude. www.indiandentalacademy.com
  29. 29. Force duration Physiologic constraints on design- -Ideally the forces duration while eating and swallowing is ≈ 30 min ∕ day. -Bruxers and other parafunctional habit pt. Influence on implant body design- - Materials that are subjected to repetitive loads are at greater risk of fatigue failure. www.indiandentalacademy.com
  30. 30. stress Endurance limit cycles FAILURE www.indiandentalacademy.com
  31. 31. How the implant and abutment resists, fracture from bending forces ----- www.indiandentalacademy.com
  32. 32. Force type Physiological constraints on design : - Bone is strongest in compressive > tensile > shear - Endosteal implants load bone - implant interface in pure shear, unless surface features are incorporated in design to transform shear loads to more resistant force types www.indiandentalacademy.com
  33. 33. Influence on Implant body design : - As angulation of load increases stress around the implant Increases particularly in the vulnerable crestal region - As a result all implants are designed for placement perpendicular to the occlusal plane - The face of thread or plateau can change the direction of load from prosthesis to abutment connection, to a different force direction at the bone www.indiandentalacademy.com
  34. 34. www.indiandentalacademy.com
  35. 35. Force magnification Extreme angulation and parafunctional habits exceed the capability of the dental implant design to withstand physiological load Cantilever crown heights are levers and force magnifiers Careful treatment planning and multiple implants are indicated in case of force magnification www.indiandentalacademy.com
  36. 36. Surface area Anatomical constraints on surface area optimization- Bone vol : external architecture of bone - Width is greater in the posterior region - In general 6 to 8mm bone is available in the anterior region and 4mm implant is used - 7mm width is available in the posterior region and 5mm implant is used www.indiandentalacademy.com
  37. 37. - Therefore implant width may increase as amount of force magnification increases from anterior to posterior region. - On the contrary bone height usually decreases from anterior mandible, compared with the anterior maxilla, the posterior mandible, to the least in the edentulous posterior maxilla - Hence as occlusal force increases bone height and vol decreases www.indiandentalacademy.com
  38. 38. Bone quality : internal architecture of bone - four distinctly different bone density classifications exist within the max and mand - Greater failure rate has been documented in porous bone compared with dense bone - Additional implants or implants with greater surface area have to be used in porous bone www.indiandentalacademy.com
  39. 39. Functional surface area forces vs. Total surface area- For a given bone vol, implant surface area must be optimized for functional loads FSA: defined as the area that actively serves to dissipate compressive and tensile non shear loads through the I-B interface and provides initial stability of the implant following its surgical placement www.indiandentalacademy.com
  40. 40. Functional thread surface area: portion of the thread that participates in compressive load transmission under the action of a axial or near axial occlusal load Total surface area : may Include a passive area that does not participate in load transfer Example : plasma spray coatings have 600% more TSA but less than 30% is actually exposed to the bone www.indiandentalacademy.com
  41. 41. Since most stress to the I-B interface Is in the crestal 1/2 of the implant, the crestal zone is most important to distribute stresses appropriately Design variables in SA optimization Implant macrogeometry Implant width Thread geometry Implant length Crest module configuration Apical design considerationswww.indiandentalacademy.com
  42. 42. Implant macro geometry Smooth sided cylindric implants provide surgical ease however B-I interface is subjected to significantly large shear conditions Smooth sided , tapered implants allows for a component of compressive load to be delivered to bone B-I interface depending on the degree of taper www.indiandentalacademy.com
  43. 43. Threaded implants with circular cross section provide ease of surgical placement and allow for >FSA optimization to transfer compressive forces to the B-I interface Also gives initial rigid fixation to limit micro movement during healing Smooth sided cylinder depends on coating our micro structure for load transmission to bone www.indiandentalacademy.com
  44. 44. Implant width Over the years implants have gradually Increased in width Scientific principle being > the width greater the surface area 4mm implants have 33% > SA than 3mm implants Largest the width better the emergence profile of the crownwww.indiandentalacademy.com
  45. 45. Crestal bone anatomy limits implants to < 5.5mm except in limited situations Thus implant design innovations in crestal region are required to provide increase in FSA in this vulnerable region www.indiandentalacademy.com
  46. 46. Thread geometry FSA for unit length of the implant may be modified by varying three geometric parameters of implant - Thread pitch - Thread shape - Thread depth www.indiandentalacademy.com
  47. 47. Thread pitch is defined as the distance measured parallel with its axis between adjacent thread forms ( for V type threads ), for the number of threads per unit length in the same axial plane and on the same side of the axis Smaller / finer pitch : more threads on the Implant body for given unit length and thus greater surface area per unit length www.indiandentalacademy.com
  48. 48. www.indiandentalacademy.com
  49. 49. Thread shape: • V shaped • Square • Buttress - Dental implant applications dictates the need for a thread shape optimized for a long-term function ( load transmission ) under occlusal intrusive ( opposite of pull out ) load directions www.indiandentalacademy.com
  50. 50. www.indiandentalacademy.com
  51. 51. The square thread provides an optimum surface area for intrusive & compressive load transmission Shear loading most detrimental to bone Shear force on V thread face its ten times greater than on square thread Buttress has similar shear component as V under occlusal load www.indiandentalacademy.com
  52. 52. Thread depth : refers to the distance between the major and minor diameter of the thread It may be varied for the length of the implant to increase FSA in the region of highest stress, example : crestal region Reverse taper leads to a dramatic increase in functional surface area at the crest of the bone where stresses are highest www.indiandentalacademy.com
  53. 53. www.indiandentalacademy.com
  54. 54. Implant length As length of the implant increases so does the overall total surface area Once I-B interface is formed excessively long implants do not receive stress transmission to the apical region and are not needed D3, D4 bone in the posterior region have less available bone height www.indiandentalacademy.com
  55. 55. Nerve repositioning is cited as an acceptable clinical treatment to facilitate longer implants in the posterior mandible Maxillary sinus grafts done for posterior maxilla Longer implants have been suggested to provide greater stability under lateral loading stress generated by lateral load can be dissipated by implant in the range of 10 -15 mm length compared with implant of 20-30 mm length www.indiandentalacademy.com
  56. 56. Crest module configuration Crest module of implant body is the transosteal region from implant body and is characterized as a region of high concentration of mechanical stress Many crest modules have been designed to reduce plaque accumulation once bone loss has occurred However design of crest module contributes to crestal bone losswww.indiandentalacademy.com
  57. 57. www.indiandentalacademy.com
  58. 58. www.indiandentalacademy.com
  59. 59. Angulated crest module > 20° with surface texture that increases bone contact causes slightly beneficial cumbersome stress to adjacent bone and decreased bone loss Crest module should be slightly larger than outer thread diameter Crest module height is often 2 mm A polished collar of minimum height should be designed on the superior portion just below the prosthesis platform (0.5 mm) www.indiandentalacademy.com
  60. 60. Apical design considerations Most root form implants are circular in cross section Around cross section does not resist shear forces As a result anti - rotational feature is incorporated in apical region of implant body www.indiandentalacademy.com
  61. 61. www.indiandentalacademy.com
  62. 62. Another anti - rotational feature flat sides or gross along the body or apical the region of the implant body When bone grows against flat end it is kept under compression with rotational loads , thus apical end must be flat than pointed www.indiandentalacademy.com
  63. 63. Surface coatings Titanium plasma spray ( TPS ) - Implant body may be covered with a porous coating , two materials commonly used for this purpose titanium and hydroxyapatite - Both are plasma sprayed on to implant body - TPS increases B-I surface area and acts similar to three dimensional surface rates may stimulate adhesion osteogenesis www.indiandentalacademy.com
  64. 64. - There is 600% increase in total surface area - FSA increases by 25 to 30% which is significant - Improved initial fixation of implant is seen specially in softer bone Hydroxyapatite coatings : - Similar roughness as TPS and increase FSA - Direct bonding to bone which is of greater strength - Enhanced gap healing in hydroxyapatite coating is seen www.indiandentalacademy.com
  65. 65. Advantages of surface coatings: - Increased surface area - Increased roughness for initial stabilization - Stronger B-I interface Additional advantages of HA over TPS - Faster healing of B-I interface - Increased gap healing between B & HA - Stronger interface than in TPS - Less corrosion of metalwww.indiandentalacademy.com
  66. 66. Disadvantages of surface coatings : - Coatings may be damaged when being inserted in dense bone - Increased surface roughness with the risk of bacterial contamination when present above bone - HA : increased plaque retention when exposed - Increased costs www.indiandentalacademy.com
  67. 67. Contemporary implant dentistry – Carl E. Misch , 2nd edition Dental materials – Philips 11th edition Fundamentals of implant dentistry, Weiss and Weiss Implants in restorative dentistry, Scortsessi Journal of dental education vol 52 no 12 pg 755, 1988 Jpd 1985 : 54; 410-14 Jpd 1983 : 49; 843-49 Atlas of oral imlantology – Crennin www.indiandentalacademy.com
  68. 68. For more details please visit www.indiandentalacademy.com www.indiandentalacademy.com

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