LABORATORY OF BIOLOGICAL STRUCTURE MECHANICS
www.labsmech.polimi.it
INSTITUTE OF HIGH PERFORMANCE COMPUTING - Singapore
Meditech Meeting on:
“Innovations in Materials and Manufacturing of Dental Devices”
Cardiff MediCentre, 29th March 2007
Thermal-mechanical reliability of Ti/HAp-based endosseous dental implant in severe conditions of Bruxism
Giuseppe Cevola
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Giuseppe Cevola 29/03/07
Outline
• Introduction
• 3D FEM Modelling
mandibular bone
FGMs (Functionally Graded Materials) endosseous dental implant
• Mechanical loading conditions
occlusive loading
bruxism loading
• FGMs composition’s parametric studying
• Thermal-mechanical Studying & Bruxism conditions
• Conclusions and future developments
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Giuseppe Cevola 29/03/07
Bruxism is a disorder of the masticatory
system characterized by teeth grinding
and clenching
Bruxism is considered
• aetiological factor for temporomandibular disorders (TMD)• tooth wear (attrition)• loss of periodontal support • failure of dental restorations
Introduction
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Giuseppe Cevola 29/03/07
Introduction
The most common current dental implants are:
ENDOSSEOUS Sub-PERIOSTEAL
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Giuseppe Cevola 29/03/07
Endosseous dental implant performance requirements:
• biocompatibility: osteointegration
• thermal/mechanical reliability: residual stress due to
production (Hot Isostatic Pressing, Spark Sintering)
Introduction
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Giuseppe Cevola 29/03/07
The success of the endosseous dental implant integration is due to:• Lack of clinical signs and symptoms of pathology• Lack of mobility
• Radiographically stable interface
Introduction
Adaptive capacity: load-bearing biological structures that bond with bone
• Dynamic Modeling process
• Remodeling process
Clark M. Stanford
Biomechanical and functional behavior of implants
Adv Dent Res 13:88-92, June, 1999
Radiographically stable interface
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Giuseppe Cevola 29/03/07
Used Materials
Groundbreaking dental implants are designed using Functionally
Graded Materials (FGM’s) made of Ti/HAp – Graduality along vertical
direction:
• Titanium and its alloys• Bioceramics : Hydroxyapatite (HAp) as coating, Zirconia
• Titanium: upper part (occlusive loading)• HAp: lower part (bone contact)
Introduction
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Giuseppe Cevola 29/03/07
Outline
• Introduction
• 3D FEM Modelling
mandibular bone
FGMs (Functionally Graded Materials) endosseous dental implant
• Mechanical loading conditions
occlusive loading
bruxism loading
• FGMs composition’s parametric studying
• Thermal-mechanical studying & Bruxism conditions
• Conclusions and future developments
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Giuseppe Cevola 29/03/07
3D FEM models
Mandibular bone segment (35.25 mm) FGM’s endosseous dental implant
(first lower molar)
obtained by
Computed Tomography (CT) images
of Human mandibular bone
Computed Tomography (CT) images
of Titanium dental implant (Bioform®)
Modelling
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Giuseppe Cevola 29/03/07
Mandible Computed Tomography image
Modelling
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Giuseppe Cevola 29/03/07
Modelling
Completed Model
The materials are supposed
isotropic with linear-elastic
behaviour Toparli M, Sasaki S. Finite element analysis of the temperature and thermal stress in a postrestored tooth.
J Oral Rehabil 2003;30:921–926.
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Giuseppe Cevola 29/03/07
Implant mechanical performances are evaluated by means peri-implant-bone stresses:• von Mises stress• First principal stress• Third principal stress
Higher peri-implant tensile and compressive stresses would imply:• implant-bone bond failure• bone absorption
Modelling
Buccal-Lingual
section
Mesial-Distal
section
S.C.Huang, C.F.Tsai
Finite element analysis of a dental implant
Biomedical Engineering-Applications, Basis & communications
Vol.15 No.2 April 2003
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Giuseppe Cevola 29/03/07
Outline
• Introduction
• 3D FEM Modelling
mandibular bone
FGMs (Functionally Graded Materials) endosseous dental implant
• Mechanical loading conditions
occlusive loading
bruxism loading
• FGMs composition’s parametric studying
• Thermal-mechanical Studying & Bruxism conditions
• Conclusions and future developments
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Giuseppe Cevola 29/03/07
TWENTY-SECOND BIENNIAL MEETING
7–10 June 2001, Lugano, Switzerland
Journal of Oral Rehabilitation 2002 29; 872–889 Upper and lower dental appliances containing miniaturestrain-gauge transducers.
Normal bilateral occlusive loading:
Molar region : 400-650 N
Premolar region : 222-445 N
Canine region : 133-334 N
Incisive region : 89-111 N
K.J. Anusavice, Phillips Science of Dental Materials,
W.B.Saunders Co., New York, (1996)
Molar region unilateral occlusive loading :
30% smaller than one obtained during
bilateral loading
Mechanical loading conditions:Experimental data
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Giuseppe Cevola 29/03/07
First lower molar
Bruxist bilateral clenching loading
molar region : 790 N
transversal force: 50 N
Journal of Oral Rehabilitation 2001 28; 485-491
K. Nishigawa Department of Fixed Prosthodontics, The University of Tokushima
School of Dentistry, Tokushima, Japan
Mechanical loading conditions:Experimental data
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Giuseppe Cevola 29/03/07
Outline
• Introduction
• 3D FEM Modelling
mandibular bone
FGMs (Functionally Graded Materials) endosseous dental implant
• Mechanical loading conditions
occlusive loading
bruxism loading
• FGMs composition’s parametric studying
• Thermal-mechanical Studying & Bruxism conditions
• Conclusions and future developments
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m
h H
zHV
ht VV 1
Exponential law between composition and longitudinal coordinate
h = hydroxyapatite
t = titanium
FGMs composition’s parametric studying
HA Volumetric Fraction along the FGM Dental Implant
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 1 2 3 4 5 6 7 8 9 10 11 12 13
FGM Dental Implant Lenght [mm]
HA
Vo
lum
etr
ic F
rac
tio
n
m=0.1m=0.2m=0.5m=1m=2m=5m=10
Increasing value of Ti along the implant lenght
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Giuseppe Cevola 29/03/07
Outline
• Introduction
• 3D FEM Modelling
mandibular bone
FGMs (Functionally Graded Materials) endosseous dental implant
• Mechanical loading conditions
occlusive loading
bruxism loading
• FGMs composition’s parametric studying
• Thermal-mechanical Studying & Bruxism conditions
• Conclusions and future developments
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Giuseppe Cevola 29/03/07
Thermal-mechanical Studying
Changing temperature implant performances: ΔT = 0°CVon Mises, Mesial/Distal Section, DT=0
0.5
1.5
2.5
3.5
4.5
5.5
6.5
100500 100550 100600 100650
Nodes along M/D section
Vo
n M
ises
Str
ess
[MP
a]
Von Mises, Buccal Lingual Section, DT=0
0.5
1.5
2.5
3.5
4.5
5.5
6.5
100100 100120 100140 100160 100180 100200
Nodes along B/L section
Vo
n M
ises
Str
ess
[MP
a]
First Principal Stress, Mesial/Distal Section, DT=0
-3.5
-3
-2.5
-2
-1.5
-1
-0.5
0
0.5
1
100500 100520 100540 100560 100580 100600 100620 100640 100660
Nodes along M/D section
Firs
t Pri
ncip
al S
tres
s [M
Pa]
m=0.1 m=0.2 m=0.5 m=1 m=2 m=5 m=10 Ti
First Principal Stress, Buccal/Lingual section, DT=0
-3.5
-3
-2.5
-2
-1.5
-1
-0.5
0
0.5
1
1.5
100100 100120 100140 100160 100180 100200
Nodes along B/L section
Fis
rst
Pri
nc
ipa
l S
tre
ss
[Mp
a]
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Giuseppe Cevola 29/03/07
Thermal-mechanical Studying
Third Principal Stress, Mesial/Distal Section, DT=0
-9
-8
-7
-6
-5
-4
-3
-2
-1
0
100500 100550 100600 100650
Nodes along M/D section
Th
ird
Pri
nc
ipal
Str
ess
[M
Pa
]
Third Principal Stress, Buccal/Lingual section, DT=0
-9
-8
-7
-6
-5
-4
-3
-2
-1
0
100100 100120 100140 100160 100180 100200
Nodes along B/L sectionT
hir
d P
rin
cip
al S
tres
s [M
Pa]
m=0.1 m=0.2 m=0.5 m=1 m=2 m=5 m=10 Ti
Changing temperature implant performances: ΔT = 0°C
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Giuseppe Cevola 29/03/07
Thermal-mechanical Studying
Von Mises Stress, Buccal/Lingual Section, Occlusal Loading
1
2
3
4
5
6
7
8
9
10
100100 100110 100120 100130 100140 100150 100160 100170 100180 100190 100200
Nodes along B/L section
Vo
n M
ise
s S
tre
ss
[M
Pa
]
m_5_-20
m_5_+20
m_5_0
Von Mises Stress, Buccal Lingual Section, Occlusal Loading
1.5
2.5
3.5
4.5
5.5
6.5
7.5
8.5
9.5
100100 100110 100120 100130 100140 100150 100160 100170 100180 100190 100200
Nodes along B/L section
Vo
n M
ises
Str
ess
[MP
a]
m_2_+20
m_2_0
m_2_-20
Von Mises Stress, Buccal/Lingual Section, Occlusal Loading
1
2
3
4
5
6
7
8
100100 100110 100120 100130 100140 100150 100160 100170 100180 100190 100200
Nodes along B/L section
Vo
n M
ise
s S
tre
ss
[M
Pa
]
m_0.5_-20
m_0.5_0
m_0.5_+20
Von Mises Stress, Buccal/Lingual Section, Occlusal Loading
0
1
2
3
4
5
6
7
8
100100 100110 100120 100130 100140 100150 100160 100170 100180 100190 100200
Nodes along B/L section
Vo
n M
ise
s S
tre
ss
[M
Pa
] m_0.2_+20
m_0.2_0
m_0.2_-20
Changing temperature implant performances: ΔT= + 20°C and -20°C
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Giuseppe Cevola 29/03/07
Thermal-mechanical Studying
First Principal Stress, Buccal/Lingual Section, Occlusal Loading
-3.00E+00
-2.00E+00
-1.00E+00
0.00E+00
1.00E+00
2.00E+00
3.00E+00
4.00E+00
5.00E+00
100100 100110 100120 100130 100140 100150 100160 100170 100180 100190 100200
Nodes along B/L section
Fir
st
Pri
nc
ipa
l Str
es
s [
MP
a]
m_5_-20
m_5_+20
m_5_0
Fisrt Principal Stress, Buccal Lingual Section, Occlusal Loading
-3.50E+00
-2.50E+00
-1.50E+00
-5.00E-01
5.00E-01
1.50E+00
2.50E+00
3.50E+00
4.50E+00
100100 100120 100140 100160 100180 100200
Nodes along B/L section
Fir
st P
rin
cip
al S
tres
s [M
Pa]
m_2_-20
m_2_0
m_+20
First Pricipal Stress, Buccal/Lingual Section, Occlusal Loading
-3.5
-2.5
-1.5
-0.5
0.5
1.5
2.5
3.5
100100 100110 100120 100130 100140 100150 100160 100170 100180 100190 100200
Nodes along B/L section
Fir
st
Pri
nc
ipa
l Str
es
s [
MP
a] m_0.5_+20
m_0.5_0
m_0.5_-20
First Principal Stress, Buccal/Lingual Section, Occlusal Loading
-4
-3
-2
-1
0
1
2
3
4
100100 100120 100140 100160 100180 100200
Nodes along B/L section
Fir
st P
rin
cip
al S
tres
s [M
Pa]
m_0.2_+20
m_0.2_0
m_0.2_-20
Changing temperature implant performances: ΔT= + 20°C and -20°C
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Giuseppe Cevola 29/03/07
Thermal-mechanical Studying
Von Mises Stress, Implant Buccal/Lingual section, Bruxism
3
8
13
18
23
28
33
38
100100 100110 100120 100130 100140 100150 100160 100170 100180 100190 100200
Nodes along B/L section
Von
Mis
es S
tres
s [M
Pa]
m=0.2
m=0.5
m=2
Ti
Third Principal Stress, Implant Buccal/Lingual Section, Bruxism
-55
-45
-35
-25
-15
-5
100100 100110 100120 100130 100140 100150 100160 100170 100180 100190 100200
Nodes along B/L section
Thir
d Pr
inci
pal S
tres
s [M
Pa]
m=0.2
m=0.5
m=2
Ti
First Principal Stress, Implant Buccal/LingualSection, Bruxism
-18
-13
-8
-3
2
7
100100 100120 100140 100160 100180 100200
Nodes along B/L section
Fir
st P
rin
cip
al S
tres
s [M
Pa]
m=0.2
m=0.5
m=2
Ti
Bruxism Conditions: Clenching load & grinding force
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Giuseppe Cevola 29/03/07
Outline
• Introduction
• 3D FEM Modelling
mandibular bone
FGMs (Functionally Graded Materials) endosseous dental implant
• Mechanical loading conditions
occlusive loading
bruxism loading
• FGMs composition’s parametric studying
• Thermal-mechanical Studying & Bruxism conditions
• Conclusions and future developments
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Giuseppe Cevola 29/03/07
Conclusions and future developments
So far
m = 2 composition withstands the highest von Mises and first principal
stresses in all the implants, with temperature reduction of 20°C
In progress
On the basis of provided experimental data (K. NISHIGAWA School of Dentistry, Tokushima, Japan ) the bruxism behaviour is in progress
Future works
Would be desirable to carry-out fatigue analysis for the implant-bone bond
The residual stresses due to the technological processes can neglect the
hosting oral changing temperature effect?
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Giuseppe Cevola 29/03/07
Acknowledgment
• Dr. WANG Fang, PhD. Institute of High Performance Computing Singapore,
External Advisor
• Prof. Estevam Barbosa de Las Casas, Universidade Federal de Minas Gerais,
Belo Horizonte, BRASIL
• Prof. K. Nishigawa, School of Dentistry, Tokushima, Japan
• Prof. F. Lobbezoo, Department of Oral function, Academic Centre for Dentistry
Amsterdam (ACTA), Amsterdam, The Netherlands
Are gratefully acknowledged for their assistance and contributions
• Prof. Roberto Contro, Prof. of Biomechanics, Politecnico di Milano, Italy
• Prof. Pasquale Vena, Assoc. of Biomechanics, Politecnico di Milano, Italy
• Dr. Dario Gastaldi, PhD. of Material Engineering, Politecnico di Milano, Italy
Are also acknowledged for their kind assistance and useful discussions
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Giuseppe Cevola 29/03/07
Thank you!
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