ASTRA TECH AB
Biomechanical aspects
of implant design
www.indiandentalacademy.com
INDIAN DENTAL ACADEMY
Leader in continui...
ASTRA TECH AB
Retention elements
at the neck
Micro thread
TiOblast™
Conical Seal Design™
Standard thread
www.indiandentala...
ASTRA TECH AB
Two different
approaches
to dental implant design• A biological approach
– tissue acceptance is
focused
• A ...
ASTRA TECH AB
Dental implants
• Tiny structures
• Subject to considerable
loads
www.indiandentalacademy.com
ASTRA TECH AB
The development of dental implants
has been characterized by a
biological approach
www.indiandentalacademy.c...
ASTRA TECH AB
Longer fixtures score better
than shorter ones
(Quirynen et al, Clin Oral Impl Res 1992)
Higher success rate...
ASTRA TECH AB
Cortical bone
Cancellous
bone
The nineteen sixties
Soft tissue capsule
Marginal bone resorption
Linkow & Che...
ASTRA TECH AB
19 implants in maxillary (most)
and mandibular positions
Reference point
Marginal bone level without retenti...
ASTRA TECH AB
Marginal bone resorption
Al -Sayyed et al, Clin
Oral Impl Res, 1994
Conclusion: Marginal bone resorption cau...
ASTRA TECH AB
A mechanical versus a biological
perspective
• There is no clash of interests
between the two perspectives
•...
ASTRA TECH AB
Wolff’s law
Wolff, J. (1892) Das Gesetz der
Transformation der Knochen
A bone ..... develops the
structure m...
ASTRA TECH AB
Regulation of bone cell activity
Systemic hormones
– Parathyroid hormone
– Calcitonin
– Thyroxin
– Glucocort...
ASTRA TECH AB
Bone
stress
Subnormal stress
Bone resorption
Normal stress – steady state
Higher stress than normal but
with...
ASTRA TECH AB
Marginal bone resorption
Al -Sayyed et al, Clin
Oral Impl Res, 1994
Conclusion: Marginal bone resorption cau...
ASTRA TECH AB
Retention elements
at the neck
Micro thread
TiOblast™
Conical Seal Design™
Standard thread
www.indiandentala...
ASTRA TECH AB
1000 N
Cortical
bone
Cancellous
bone
1000 N
Maximum interfacial shear stresses
Varying wall
thickness
Varyin...
ASTRA TECH AB
Smooth neck: Interfacial
conditions
Cancellous
bone
Cortical
bone
Smooth neck
- Compressive stresses resiste...
ASTRA TECH AB
Neck with retention elements:
Interfacial conditions
Cancellous
bone
Cortical
bone
Neck with retention eleme...
ASTRA TECH AB
85.0 MPa
78.9 – “ –
72.9 – “ –
66.8 – “ –
60.7 – “ –
54.6 – “ –
48.6 – “ –
42.5 – “ –
36.4 – “ –
30.4 – “ –
...
ASTRA TECH AB
Maximum interfacial shear stress (MPa)
Wall thick- Interlocking all the way up Smooth neck (2 mm
ness Uni-co...
ASTRA TECH AB
Conclusion
Retention elements at the neck
bring about
• a decrease in the peak
interfacial
shear stress
• a ...
ASTRA TECH AB
19 single tooth implants in
maxillary (most) and
mandibular positions
Reference point
Marginal bone level wi...
ASTRA TECH AB
Baseline
mesial
Baseline
distal
1-year
mesial
1-year
distal
2-year
mesial
2-year
distal
Means for
14 subject...
ASTRA TECH AB
Baseline 1-year 2-year
Mesial Distal Mesial Distal Mesial Distal
Quirynen et al. 1992:
means of 10 implants
...
ASTRA TECH AB
Retention elements
at the neck
Micro thread
TiOblast™
Conical Seal Design™
Standard thread
www.indiandentala...
ASTRA TECH AB
Flat top
versus
Conical Seal
Design
www.indiandentalacademy.com
ASTRA TECH AB
Stoiber, B. (1988) Thesis
Mailath et al (1989) Zeitschr Stomatol
Stoiber (1988) and Mailath et al. (1989)
ar...
ASTRA TECH AB
Stoiber, B. (1988) Thesis
Mailath et al (1989) Zeitschr Stomatol
Stoiber (1988) and Mailath et al. (1989)
ar...
ASTRA TECH AB
85.0 MPa
78.9 – “ –
72.9 – “ –
66.8 – “ –
60.7 – “ –
54.6 – “ –
48.6 – “ –
42.5 – “ –
36.4 – “ –
30.4 – “ –
...
ASTRA TECH AB
Flat Top Design
1000 N
Assumption: Interlocking
all the way up
www.indiandentalacademy.com
ASTRA TECH AB
Flat Top Design
1000 N
100.0 MPa
92.7
85.7
78.6
71.4
64.3
57.1
50.0
42.9
35.7
28.6
21.4
14.3
7.1
0
Interfaci...
ASTRA TECH AB
1000 N
Conical Seal Design
www.indiandentalacademy.com
ASTRA TECH AB
1000 N
100.0 MPa
92.7
85.7
78.6
71.4
64.3
57.1
50.0
42.9
35.7
28.6
21.4
14.3
7.1
0
Conical Seal Design
Inte...
ASTRA TECH AB
Flat Top Design
• High stress peak - 100.4 MPa
• Unfavourable location of
stress peak
Conical Seal Design
•...
ASTRA TECH AB
Baseline 1-year 2-year
Mesial Distal Mesial Distal Mesial Distal
Quirynen et al. 1992:
means of 10 implants
...
ASTRA TECH AB
Retention elements
at the neck
Micro thread
TiOblast™
Conical Seal Design™
Standard thread
www.indiandentala...
ASTRA TECH AB
A rough surface brings
about interlocking
www.indiandentalacademy.com
ASTRA TECH AB
The mechanism of
interlocking
Implant Bone
Fracture plane
www.indiandentalacademy.com
ASTRA TECH AB
Which are the characteristics
of a good surface roughness?
Implant Bone
Fracture plane
www.indiandentalacade...
ASTRA TECH AB
A mathematical model for
prediction of the interfacial
shear strength of a rough
bone implant surface
www.in...
ASTRA TECH AB
A rough surface is
conceptualized
as consisting of pits of
different
sizes, different shapes and
different d...
ASTRA TECH AB
The interfacial
tissue
Implant Bone
Normal bone
Reduced content of collage
and/or mineral
Much reduced conte...
ASTRA TECH AB
Normal bone
Reduced content of collagen
and/or mineral
Much reduced content of
collagen and/or mineral
0 < x...
ASTRA TECH AB
The retention strength of a
bone plug
Bone of full strength
Reduced strength
Much reduced strength
The fract...
ASTRA TECH AB
= interfacial shear strength
= pit effectivity factor
= pit density factor
= shear strength of normal bonetb...
ASTRA TECH AB
= interfacial shear strength
= pit effectivity factor
= pit density factor
= shear strength of normal bonetb...
ASTRA TECH AB
The pit effectivity factor – definition
Imaginary caseReal case
Fr
D
Fi
= Fifpe Fr /
Fr
Fi
x
dx
F= t (x) 2...
ASTRA TECH AB
Pit effectivity factor: Effect of
pit size
0
0,1
0,2
0,3
0,4
0,5
0,6
0,7
0,8
0,9
1
1
L
2
L
5
L
10
L
20
L
40
...
ASTRA TECH AB
Implant
Fracture surface
Bone of full strength
Reduced strength
Much reduced strength
Pit effectivity factor...
ASTRA TECH AB
0
0,1
0,2
0,3
0,4
0,5
0,6
0,7
0,8
0,9
1
1 L 2.5 L 5 L 10 L 25 L
Diameter
(0.4m) (1m) (2m) (5m) (10m)
Assumpt...
ASTRA TECH AB
Pit effectivity factor: Effect of pit s
D
www.indiandentalacademy.com
ASTRA TECH AB
Surface area
Assumption: L = 0.4m
Pit effectivity
factor = fpe fpd btit
Pit effectivity factor: Effect of pi...
ASTRA TECH AB
Surface area
Assumption: L = 0.4m
Pit effectivity
factor = fpe fpd btit
Pit effectivity factor: Effect of pi...
ASTRA TECH AB
A high value of the pit
effectivity factor requires:
• A certain size of the pits
• A favourable shape of th...
ASTRA TECH AB
= interfacial shear strength
= pit effectivity factor
= pit density factor
= shear strength of normal bonetb...
ASTRA TECH AB
D k D
Pit density factor ( ) - definitionfpd
Pit density factor : The share of the surface area
which is occ...
ASTRA TECH AB
0
0,1
0,2
0,3
0,4
0,5
0,6
0,7
0,8
0,9
1
k
0 0.1 0.2 0.4 0.6 0.8 1 2
Pit density factor: half
spherical pits
...
ASTRA TECH AB
Conclusio
ns
= fpe fpd btit
The pits should have
- a certain size
- a favourable shape
The pits should be
ve...
ASTRA TECH AB
Surface
Structure
– Machined
• Small pit
size
• Low pit
density
www.indiandentalacademy.com
ASTRA TECH AB
• A patented process
• Roughens the titanium surface
• by means of blasting
• with grains of titanium dioxid...
ASTRA TECH AB
TiOblast
TM
www.indiandentalacademy.com
ASTRA TECH AB
Surface
Roughness
Machined TiOblast
TM
www.indiandentalacademy.com
ASTRA TECH AB
Animal no TiOblast Machined
screw screw
1 >150 64
2 150 62
3 >150 57
4 120 46
Gotfredsen et al, Clin Oral Im...
ASTRA TECH AB
Removal torque
(Dogs, 12 weeks, Ncm)
Animal no TiOblast Machined
cylinder cylinder
1 120 34
2 1 28 42
3 91 3...
ASTRA TECH AB
The implant surface
Machined or TiOblast
Baseline 1-year 2-year
Mesial Distal Mesial Distal Mesial Distal
Q...
ASTRA TECH AB
Retention elements
at the neck
Micro thread
TiOblast™
Conical Seal Design™
Standard thread
www.indiandentala...
ASTRA TECH AB
Bone
stress
Subnormal stress
Bone resorption
Normal stress – steady state
Higher stress than normal but
with...
ASTRA TECH AB
D k v c
0.1
0.2
0.3
0.4
0.1
0.2
0.4
0.6
0.8
1
0
10
20
30
40
50
60
0
0.2
0.4
0.8
1.6
Infinitely long and
infi...
ASTRA TECH AB
-0.73
-0.38
-0.04
0.31
0.66
1.01
1.35
1.70
2.05
2.40
Maximum tensile stress: 2.40 MPa
www.indiandentalacadem...
ASTRA TECH AB
D=0.3mm; no straight part
Maximum tensile stress in the bone (MPa
Colour code:
Prohibited area due to
high c...
ASTRA TECH AB
2.21 MPa
2.30 MPa
2.35 MPa
2.44 MPa
Maximum tensile stress in the bone (MPa)
www.indiandentalacademy.com
ASTRA TECH AB
Conclusions
• The profile of the thread is important
• A micro-thread can be as effective
as a thread of big...
ASTRA TECH AB
The implant neck
Smooth or provided with a micro-thread
Baseline 1-year 2-year
Mesial Distal Mesial Distal M...
ASTRA TECH AB
Retention elements
at the neck
Micro thread
TiOblast™
Conical Seal Design™
Standard thread
www.indiandentala...
ASTRA TECH AB
Retention elements at the implant neck;
Conical Seal Design; TiOblast; micro-thread
Baseline 1-year 2-yea...
ASTRA TECH AB
Thank you
For more details please visit
www.indiandentalacademy.com
www.indiandentalacademy.com
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Biomech aspects implants /certified fixed orthodontic courses by Indian dental academy

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The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and offering a wide range of dental certified courses in different formats.

Indian dental academy provides dental crown & Bridge,rotary endodontics,fixed orthodontics,
Dental implants courses.for details pls visit www.indiandentalacademy.com ,or call
0091-9248678078

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Biomech aspects implants /certified fixed orthodontic courses by Indian dental academy

  1. 1. ASTRA TECH AB Biomechanical aspects of implant design www.indiandentalacademy.com INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com
  2. 2. ASTRA TECH AB Retention elements at the neck Micro thread TiOblast™ Conical Seal Design™ Standard thread www.indiandentalacademy.com
  3. 3. ASTRA TECH AB Two different approaches to dental implant design• A biological approach – tissue acceptance is focused • A biomechanical approach – the loads are focused www.indiandentalacademy.com
  4. 4. ASTRA TECH AB Dental implants • Tiny structures • Subject to considerable loads www.indiandentalacademy.com
  5. 5. ASTRA TECH AB The development of dental implants has been characterized by a biological approach www.indiandentalacademy.com
  6. 6. ASTRA TECH AB Longer fixtures score better than shorter ones (Quirynen et al, Clin Oral Impl Res 1992) Higher success rate in the lower jaw than in the upper jaw Better bone quality in the lower jaw than in the upper jaw Overloading a main factor behind fixture loss www.indiandentalacademy.com
  7. 7. ASTRA TECH AB Cortical bone Cancellous bone The nineteen sixties Soft tissue capsule Marginal bone resorption Linkow & Cherchève, 1970, taught that dental implants should ha smooth endoosseous neck porti www.indiandentalacademy.com
  8. 8. ASTRA TECH AB 19 implants in maxillary (most) and mandibular positions Reference point Marginal bone level without retention elements at the neck Machined surface Baseline 1 year 2 years -2.2 -3.4 -3.6 Engquist, B. et al. Clin Oral Impl Res, 1995: 6: 238-245. m m www.indiandentalacademy.com
  9. 9. ASTRA TECH AB Marginal bone resorption Al -Sayyed et al, Clin Oral Impl Res, 1994 Conclusion: Marginal bone resorption caused by disuse atrophy – no load transfer Astudy on dog 0.75mm 1.8mm Machined Rough www.indiandentalacademy.com
  10. 10. ASTRA TECH AB A mechanical versus a biological perspective • There is no clash of interests between the two perspectives • The principle of adaptive bone modeling and remodeling (Wolff’s law) constitutes the link between them www.indiandentalacademy.com
  11. 11. ASTRA TECH AB Wolff’s law Wolff, J. (1892) Das Gesetz der Transformation der Knochen A bone ..... develops the structure most suited to resist the forces acting upon it. www.indiandentalacademy.com
  12. 12. ASTRA TECH AB Regulation of bone cell activity Systemic hormones – Parathyroid hormone – Calcitonin – Thyroxin – Glucocorticoids – Estrogens Osteoblast Osteoclast Nutrition Mechanical stimulation – Stress / strain Cytokines – Insulin-like growth factors 1 and – Bone morphogenic proteins – Interleukin 1 and 6 – Colony stimulating factors – Transforming growth factor-ß – Platelet derived growth factors Prostaglandins – Prostaglandin E2 Genome www.indiandentalacademy.com
  13. 13. ASTRA TECH AB Bone stress Subnormal stress Bone resorption Normal stress – steady state Higher stress than normal but within physiological limits Bone formation Stress above physiological limits Bone loss – disuse atrophy Conclusion: Advanced mathematical stress analysis should be used in the design of dental implants •High stress peaks should be avoided •Regions of low stresses should be avoided Consequences of Wolff´s law www.indiandentalacademy.com
  14. 14. ASTRA TECH AB Marginal bone resorption Al -Sayyed et al, Clin Oral Impl Res, 1994 Conclusion: Marginal bone resorption caused by disuse atrophy – no load transfer Astudy on dog Machined Rough 0.75mm 1.8mm www.indiandentalacademy.com
  15. 15. ASTRA TECH AB Retention elements at the neck Micro thread TiOblast™ Conical Seal Design™ Standard thread www.indiandentalacademy.com
  16. 16. ASTRA TECH AB 1000 N Cortical bone Cancellous bone 1000 N Maximum interfacial shear stresses Varying wall thickness Varying implant length The finite element method Smooth neck Neck with retention elements www.indiandentalacademy.com
  17. 17. ASTRA TECH AB Smooth neck: Interfacial conditions Cancellous bone Cortical bone Smooth neck - Compressive stresses resisted - Tensile stresses not resisted - Interfacial shear stresses not resisted Stresses resisted Stresses not resisted www.indiandentalacademy.com
  18. 18. ASTRA TECH AB Neck with retention elements: Interfacial conditions Cancellous bone Cortical bone Neck with retention elements - Compressive stresses resisted - Tensile stresses not resisted - Interfacial shear stresses resisted Stresses resisted Stresses not resisted www.indiandentalacademy.com
  19. 19. ASTRA TECH AB 85.0 MPa 78.9 – “ – 72.9 – “ – 66.8 – “ – 60.7 – “ – 54.6 – “ – 48.6 – “ – 42.5 – “ – 36.4 – “ – 30.4 – “ – 24.3 – “ – 18.2 – “ – 12.1 – “ – 6.1 – “ – 0.0 – “ –Cortical bone Cancellous bone 1000 N 1000 N Smooth neck Retention ele- ments at the neck Maximum interfacial shear stress Wall thickness: 0.6 mm Bi-cortical fixation www.indiandentalacademy.com
  20. 20. ASTRA TECH AB Maximum interfacial shear stress (MPa) Wall thick- Interlocking all the way up Smooth neck (2 mm ness Uni-cortical Bi-cortical Uni-cortical Bi-cortical fixation fixation fixation fixation 0.3 mm 37.7 34.9 110.1 92.3 0.4 -"- 35.9 32.5 105.8 86.6 0.5 -"- 34.7 30.8 103.2 83.0 0.6 -"- 34.0 29.6 101.3 80.6 0.7 -"- 33.4 28.6 78.8 0.8 -"- 33.3 27.9 99.0 77.5 Increasingaxial stiffness 100.0 Maximum interfacial shear stress www.indiandentalacademy.com
  21. 21. ASTRA TECH AB Conclusion Retention elements at the neck bring about • a decrease in the peak interfacial shear stress • a beneficial mechanical stimulation of the marginal bone www.indiandentalacademy.com
  22. 22. ASTRA TECH AB 19 single tooth implants in maxillary (most) and mandibular positions Reference point Marginal bone level without retention elements at the neck Machined surface Baseline 1 year 2 years -2.2 -3.4 -3.6 Engquist, B. et al. Clin Oral Impl Res, 1995: 6: 238-245. m m www.indiandentalacademy.com
  23. 23. ASTRA TECH AB Baseline mesial Baseline distal 1-year mesial 1-year distal 2-year mesial 2-year distal Means for 14 subjects Means for 12 subjects -0.48 -0.46 -0.38 -0.53 -0.4 -0.34 -0.33 -0.43 -0.27 -0.45 Zero: Bone level coincident with the top of the implant or corona Minus sign: Bone level in mm apical to the implant margin Legend Palmer RM et al. Clin Oral Impl Res: 1997: 8: 173-179. Single tooth Maxillary anterior positions Marginal bone level with retention elements at the neck www.indiandentalacademy.com
  24. 24. ASTRA TECH AB Baseline 1-year 2-year Mesial Distal Mesial Distal Mesial Distal Quirynen et al. 1992: means of 10 implants -0.9 -3.3 -3.8 Engquist et al. 1995: means of 19 implants -2.2 -3.4 -3.6 Palmer et al. 1997: means of 12 implants -0.4 -0.34 -0.33 -0.43 -0.27 -0.45 Recon- struction In partial and full prosthesis Single tooth Single tooth The implant neck - smooth or provided with retention elements Clinical results www.indiandentalacademy.com
  25. 25. ASTRA TECH AB Retention elements at the neck Micro thread TiOblast™ Conical Seal Design™ Standard thread www.indiandentalacademy.com
  26. 26. ASTRA TECH AB Flat top versus Conical Seal Design www.indiandentalacademy.com
  27. 27. ASTRA TECH AB Stoiber, B. (1988) Thesis Mailath et al (1989) Zeitschr Stomatol Stoiber (1988) and Mailath et al. (1989) argued for a smooth neck Axial load Horizontal load Stress peak Stress peak Combined horizontal and axial load Stress peak www.indiandentalacademy.com
  28. 28. ASTRA TECH AB Stoiber, B. (1988) Thesis Mailath et al (1989) Zeitschr Stomatol Stoiber (1988) and Mailath et al. (1989) argued for a smooth neck Combined horizontal and axial load Stress peak due to horizontal load Stress peak due axial load Combined horizontal and axial load Stress peak www.indiandentalacademy.com
  29. 29. ASTRA TECH AB 85.0 MPa 78.9 – “ – 72.9 – “ – 66.8 – “ – 60.7 – “ – 54.6 – “ – 48.6 – “ – 42.5 – “ – 36.4 – “ – 30.4 – “ – 24.3 – “ – 18.2 – “ – 12.1 – “ – 6.1 – “ – 0.0 – “ –Cortical bone Cancellous bone 1000 N 1000 N Smooth neck Retention ele- ments at the neck Maximum interfacial shear stress Wall thickness: 0.6 mm Bi-cortical fixation www.indiandentalacademy.com
  30. 30. ASTRA TECH AB Flat Top Design 1000 N Assumption: Interlocking all the way up www.indiandentalacademy.com
  31. 31. ASTRA TECH AB Flat Top Design 1000 N 100.0 MPa 92.7 85.7 78.6 71.4 64.3 57.1 50.0 42.9 35.7 28.6 21.4 14.3 7.1 0 Interfacial shear stress 100.4 MPa www.indiandentalacademy.com
  32. 32. ASTRA TECH AB 1000 N Conical Seal Design www.indiandentalacademy.com
  33. 33. ASTRA TECH AB 1000 N 100.0 MPa 92.7 85.7 78.6 71.4 64.3 57.1 50.0 42.9 35.7 28.6 21.4 14.3 7.1 0 Conical Seal Design Interfacial shear stress 31.6 MPa www.indiandentalacademy.com
  34. 34. ASTRA TECH AB Flat Top Design • High stress peak - 100.4 MPa • Unfavourable location of stress peak Conical Seal Design • Moderate stress peak - 31.6 MPa • Favourable location of stress peak Comparison: Standard load www.indiandentalacademy.com
  35. 35. ASTRA TECH AB Baseline 1-year 2-year Mesial Distal Mesial Distal Mesial Distal Quirynen et al. 1992: means of 10 implants -0.9 -3.3 -3.8 Engquist et al. 1995: means of 19 implants -2.2 -3.4 -3.6 Palmer et al. 1997: means of 12 implants -0.4 -0.34 -0.33 -0.43 -0.27 -0.45 Recon- struction In partial and full prosthesis Single tooth Single tooth The abutment-fixture interface Flat top or Conical Seal Design www.indiandentalacademy.com
  36. 36. ASTRA TECH AB Retention elements at the neck Micro thread TiOblast™ Conical Seal Design™ Standard thread www.indiandentalacademy.com
  37. 37. ASTRA TECH AB A rough surface brings about interlocking www.indiandentalacademy.com
  38. 38. ASTRA TECH AB The mechanism of interlocking Implant Bone Fracture plane www.indiandentalacademy.com
  39. 39. ASTRA TECH AB Which are the characteristics of a good surface roughness? Implant Bone Fracture plane www.indiandentalacademy.com
  40. 40. ASTRA TECH AB A mathematical model for prediction of the interfacial shear strength of a rough bone implant surface www.indiandentalacademy.com
  41. 41. ASTRA TECH AB A rough surface is conceptualized as consisting of pits of different sizes, different shapes and different densities www.indiandentalacademy.com
  42. 42. ASTRA TECH AB The interfacial tissue Implant Bone Normal bone Reduced content of collage and/or mineral Much reduced content of collagen and/or mineral Albrektsson T. et al. 1982, 1985, 1986 Hansson, H.-A. et al. 1983 Johansson, C. et al. 1989, 1990 Sennerby L. et al. 1991, 1992, 1993 www.indiandentalacademy.com
  43. 43. ASTRA TECH AB Normal bone Reduced content of collagen and/or mineral Much reduced content of collagen and/or mineral 0 < x < L t(x) = 0.5(ts + tb) + 0.5  cos(p x/L) (ts - tb) x > L t(x)= tb ts tb Shear strength Implant Bone xL The shear strength function 0.5m www.indiandentalacademy.com
  44. 44. ASTRA TECH AB The retention strength of a bone plug Bone of full strength Reduced strength Much reduced strength The fracture plane www.indiandentalacademy.com
  45. 45. ASTRA TECH AB = interfacial shear strength = pit effectivity factor = pit density factor = shear strength of normal bonetb fpd fpe = fpe fpd btit ti ti Interfacial shear strength www.indiandentalacademy.com
  46. 46. ASTRA TECH AB = interfacial shear strength = pit effectivity factor = pit density factor = shear strength of normal bonetb fpd fpe = fpe fpd btit ti ti The pit effectivity factor www.indiandentalacademy.com
  47. 47. ASTRA TECH AB The pit effectivity factor – definition Imaginary caseReal case Fr D Fi = Fifpe Fr / Fr Fi x dx F= t (x) 2p (D/2-x) dx D x=0 D/2 www.indiandentalacademy.com
  48. 48. ASTRA TECH AB Pit effectivity factor: Effect of pit size 0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1 1 L 2 L 5 L 10 L 20 L 40 L 1 L 2 L 4 L 10 L 20 L 40L Pit diameter (0.4m) (0.8m) (1.6m) (4m) (8m) (16m) Assumption: L = 0.4m Pit effectivity factor = fpe fpd btit D Implant Bone 0.4m www.indiandentalacademy.com
  49. 49. ASTRA TECH AB Implant Fracture surface Bone of full strength Reduced strength Much reduced strength Pit effectivity factor: Effect of pit size = fpe fpd btit L 5L L 1.5L www.indiandentalacademy.com
  50. 50. ASTRA TECH AB 0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1 1 L 2.5 L 5 L 10 L 25 L Diameter (0.4m) (1m) (2m) (5m) (10m) Assumption: L = 0.4m Pit effectivity factor = fpe fpd btit Pit effectivity factor: Effect of pit s www.indiandentalacademy.com
  51. 51. ASTRA TECH AB Pit effectivity factor: Effect of pit s D www.indiandentalacademy.com
  52. 52. ASTRA TECH AB Surface area Assumption: L = 0.4m Pit effectivity factor = fpe fpd btit Pit effectivity factor: Effect of pit s W/H = 1 W/H = 2 W/H =5 W/H =10 W/H =20 0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1 Half spherical pit www.indiandentalacademy.com
  53. 53. ASTRA TECH AB Surface area Assumption: L = 0.4m Pit effectivity factor = fpe fpd btit Pit effectivity factor: Effect of pit 0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1 Half spherical pit = 20 = 40 = 60 = 80 www.indiandentalacademy.com
  54. 54. ASTRA TECH AB A high value of the pit effectivity factor requires: • A certain size of the pits • A favourable shape of the pits. The half spherical and square shapes are the best ones • The pits shall not be too rounded at the edges = fpe fpd btit www.indiandentalacademy.com
  55. 55. ASTRA TECH AB = interfacial shear strength = pit effectivity factor = pit density factor = shear strength of normal bonetb fpd fpe = fpe fpd btit ti ti The pit density factor www.indiandentalacademy.com
  56. 56. ASTRA TECH AB D k D Pit density factor ( ) - definitionfpd Pit density factor : The share of the surface area which is occupied by pits www.indiandentalacademy.com
  57. 57. ASTRA TECH AB 0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1 k 0 0.1 0.2 0.4 0.6 0.8 1 2 Pit density factor: half spherical pits D k DPit density factor Conclusion: The pits should be very densely packed www.indiandentalacademy.com
  58. 58. ASTRA TECH AB Conclusio ns = fpe fpd btit The pits should have - a certain size - a favourable shape The pits should be very densely packed ti www.indiandentalacademy.com
  59. 59. ASTRA TECH AB Surface Structure – Machined • Small pit size • Low pit density www.indiandentalacademy.com
  60. 60. ASTRA TECH AB • A patented process • Roughens the titanium surface • by means of blasting • with grains of titanium dioxid • under controlled conditions TiOblast TM www.indiandentalacademy.com
  61. 61. ASTRA TECH AB TiOblast TM www.indiandentalacademy.com
  62. 62. ASTRA TECH AB Surface Roughness Machined TiOblast TM www.indiandentalacademy.com
  63. 63. ASTRA TECH AB Animal no TiOblast Machined screw screw 1 >150 64 2 150 62 3 >150 57 4 120 46 Gotfredsen et al, Clin Oral Impl Res 1992;3:77-84. Removal torque (Dogs, 12 weeks, Ncm) TM www.indiandentalacademy.com
  64. 64. ASTRA TECH AB Removal torque (Dogs, 12 weeks, Ncm) Animal no TiOblast Machined cylinder cylinder 1 120 34 2 1 28 42 3 91 35 4 84 22 TM Gotfredsen et al, Clin Oral Impl Res 1992;3:77-84. www.indiandentalacademy.com
  65. 65. ASTRA TECH AB The implant surface Machined or TiOblast Baseline 1-year 2-year Mesial Distal Mesial Distal Mesial Distal Quirynen et al. 1992: means of 10 implants -0.9 -3.3 -3.8 Engquist et al. 1995: means of 19 implants -2.2 -3.4 -3.6 Palmer et al. 1997: means of 12 implants -0.4 -0.34 -0.33 -0.43 -0.27 -0.45 Recon- struction In partial and full prosthesis Single tooth Single tooth www.indiandentalacademy.com
  66. 66. ASTRA TECH AB Retention elements at the neck Micro thread TiOblast™ Conical Seal Design™ Standard thread www.indiandentalacademy.com
  67. 67. ASTRA TECH AB Bone stress Subnormal stress Bone resorption Normal stress – steady state Higher stress than normal but within physiological limits Bone formation Stress above physiological limits Bone loss – disuse atrophy Conclusion: Advanced mathematical stress analysis should be used in the design of dental implants •High stress peaks should be avoided •Regions of low stresses should be avoided Consequences of Wolff´s law www.indiandentalacademy.com
  68. 68. ASTRA TECH AB D k v c 0.1 0.2 0.3 0.4 0.1 0.2 0.4 0.6 0.8 1 0 10 20 30 40 50 60 0 0.2 0.4 0.8 1.6 Infinitely long and infinitely stiff implant in cortical bone The model L P cxL Bottom radius (Rb) - 0.1 x D Top radius (Rt) - k x D Flank angle (v) D f3.5 mm f 10.5 mm www.indiandentalacademy.com
  69. 69. ASTRA TECH AB -0.73 -0.38 -0.04 0.31 0.66 1.01 1.35 1.70 2.05 2.40 Maximum tensile stress: 2.40 MPa www.indiandentalacademy.com
  70. 70. ASTRA TECH AB D=0.3mm; no straight part Maximum tensile stress in the bone (MPa Colour code: Prohibited area due to high compressive stresse 0 10 20 30 40 50 60 T o p r a d i u sFlank angle 0.1xD 0.2xD 0.4xD 0.6xD 0.8xD D 2.54 2.82 2.78 2.54 2.29 2.30 2.64 2.42 2.43 2.42 2.27 2.04 1.99 2.34 2.11 2.13 2.12 2.04 1.86 1.75 1.98 2.04 1.92 1.95 1.91 1.77 1.65 1.80 1.99 1.88 1.80 1.78 1.70 1.59 1.69 1.93 1.69 1.71 1.65 1.55 1.62 O O O O O O O www.indiandentalacademy.com
  71. 71. ASTRA TECH AB 2.21 MPa 2.30 MPa 2.35 MPa 2.44 MPa Maximum tensile stress in the bone (MPa) www.indiandentalacademy.com
  72. 72. ASTRA TECH AB Conclusions • The profile of the thread is important • A micro-thread can be as effective as a thread of bigger dimensions www.indiandentalacademy.com
  73. 73. ASTRA TECH AB The implant neck Smooth or provided with a micro-thread Baseline 1-year 2-year Mesial Distal Mesial Distal Mesial Distal Quirynen et al. 1992: means of 10 implants -0.9 -3.3 -3.8 Engquist et al. 1995: means of 19 implants -2.2 -3.4 -3.6 Palmer et al. 1997: means of 12 implants -0.4 -0.34 -0.33 -0.43 -0.27 -0.45 Recon- struction In partial and full prosthesis Single tooth Single tooth www.indiandentalacademy.com
  74. 74. ASTRA TECH AB Retention elements at the neck Micro thread TiOblast™ Conical Seal Design™ Standard thread www.indiandentalacademy.com
  75. 75. ASTRA TECH AB Retention elements at the implant neck; Conical Seal Design; TiOblast; micro-thread Baseline 1-year 2-year Mesial Distal Mesial Distal Mesial Distal Quirynen et al. 1992: means of 10 implants -0.9 -3.3 -3.8 Engquist et al. 1995: means of 19 implants -2.2 -3.4 -3.6 Palmer et al. 1997: means of 12 implants -0.4 -0.34 -0.33 -0.43 -0.27 -0.45 Recon- struction In partial and full prosthesis Single tooth Single tooth www.indiandentalacademy.com
  76. 76. ASTRA TECH AB Thank you For more details please visit www.indiandentalacademy.com www.indiandentalacademy.com

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