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

ASTRA TECH AB
Biomechanical aspects
of implant design
www.indiandentalacademy.com
INDIAN DENTAL ACADEMY
Leader in continuing dental education

ASTRA TECH AB
Retention elements
at the neck
Micro thread
TiOblast™
Conical Seal Design™
Standard thread

ASTRA TECH AB
Two different
approaches
to dental implant design• A biological approach
– tissue acceptance is
focused
• A biomechanical approach
– the loads are focused

ASTRA TECH AB
Dental implants
• Tiny structures
• Subject to considerable
loads

ASTRA TECH AB
The development of dental implants
has been characterized by a
biological approach

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

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

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

ASTRA TECH AB
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

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

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.

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

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

ASTRA TECH AB
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

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

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

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

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

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

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

ASTRA TECH AB
19 single tooth implants in
maxillary (most) and
mandibular positions
Reference point
Marginal bone level without retention
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

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

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:
-2.2 -3.4 -3.6
Palmer et al. 1997:
-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

ASTRA TECH AB
Flat top
versus
Conical Seal
Design

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

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

ASTRA TECH AB
Flat Top Design
1000 N
Assumption: Interlocking
all the way up

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

ASTRA TECH AB
1000 N
Conical Seal Design

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
Interfacial shear stress
31.6 MPa

ASTRA TECH AB
Flat Top Design
• High stress peak - 100.4 MPa
• Unfavourable location of
stress peak
• Moderate stress peak - 31.6 MPa
• Favourable location of stress
peak
Comparison: Standard load

ASTRA TECH AB
-0.9 -3.3 -3.8
means of 19 implants -2.2 -3.4 -3.6
Palmer et al. 1997:
-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

ASTRA TECH AB
A rough surface brings
about interlocking

ASTRA TECH AB
The mechanism of
interlocking
Implant Bone
Fracture plane

ASTRA TECH AB
Which are the characteristics
of a good surface roughness?
Implant Bone
Fracture plane

ASTRA TECH AB
A mathematical model for
prediction of the interfacial
shear strength of a rough
bone implant surface

ASTRA TECH AB
A rough surface is
conceptualized
as consisting of pits of
different
sizes, different shapes and
different densities

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

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

ASTRA TECH AB
The retention strength of a
bone plug
Bone of full strength
Reduced strength
Much reduced strength
The fracture plane

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

ASTRA TECH AB
fpd
fpe
= fpe fpd btit
ti
ti
The pit effectivity factor

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

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

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

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)
Pit effectivity
factor = fpe fpd btit
Pit effectivity factor: Effect of pit s

ASTRA TECH AB
D

ASTRA TECH AB
Surface area
Pit effectivity
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

ASTRA TECH AB
Surface area
Pit effectivity
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

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

ASTRA TECH AB
fpd
fpe
= fpe fpd btit
ti
ti
The pit density factor

ASTRA TECH AB
D k D
Pit density factor ( ) - definitionfpd
Pit density factor : The share of the surface area
which is occupied by pits

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

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

ASTRA TECH AB
Surface
Structure
– Machined
• Small pit
size
• Low pit
density

ASTRA TECH AB
• A patented process
• Roughens the titanium surface
• by means of blasting
• with grains of titanium dioxid
• under controlled conditions
TiOblast
TM

ASTRA TECH AB
TiOblast
TM

ASTRA TECH AB
Surface
Roughness
Machined TiOblast
TM

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

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.

ASTRA TECH AB
The implant surface
Machined or TiOblast
-0.9 -3.3 -3.8
-2.2 -3.4 -3.6
Palmer et al. 1997:
-0.4 -0.34 -0.33 -0.43 -0.27 -0.45
Recon-
struction
In partial and
full prosthesis
Single
tooth
Single
tooth

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

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

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

ASTRA TECH AB
2.21 MPa
2.30 MPa
2.35 MPa
2.44 MPa
Maximum tensile stress in the bone (MPa)

ASTRA TECH AB
Conclusions
• The profile of the thread is important
• A micro-thread can be as effective
as a thread of bigger dimensions

ASTRA TECH AB
The implant neck
Smooth or provided with a micro-thread
-0.9 -3.3 -3.8
-2.2 -3.4 -3.6
Palmer et al. 1997:
-0.4 -0.34 -0.33 -0.43 -0.27 -0.45
Recon-
struction
In partial and
full prosthesis
Single
tooth
Single
tooth

ASTRA TECH AB
Retention elements at the implant neck;
Conical Seal Design; TiOblast; micro-thread
-0.9 -3.3 -3.8
-2.2 -3.4 -3.6
Palmer et al. 1997:
-0.4 -0.34 -0.33 -0.43 -0.27 -0.45
Recon-
struction
In partial and
full prosthesis
Single
tooth
Single
tooth

ASTRA TECH AB
Thank you
For more details please visit

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

Recomendados

Recomendados

Mais conteúdo relacionado

Mais procurados

Mais procurados (20)

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

Semelhante a Biomech aspects implants /certified fixed orthodontic courses by Indian dental academy (20)

Mais de Indian dental academy

Mais de Indian dental academy (20)

Último

Último (20)

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