mechanical properties of ceramics - eth - nonmet - nonmetallic
TRANSCRIPT
Materials Science & Technology
Materials Science II - 2010, Ceramic Materials, Chapter 6, Part 5
Mechanical Properties of Ceramicsor
Mechanical Beha ior of Brittle MaterialsMechanical Behavior of Brittle Materials
Jakob Kübler Empa, Science & Technology
& Prof. L.J. Gauckler ETH Zürich, Materials Department
Lab for High Performance Ceramics Überlandstrasse 129, CH-8600 Dübendorf
+41-44-823 [email protected]
1Kübler Empa-HPC, ETHZ MW-II Ceramics-6.5, 2010
What you already know and understand!
Repetition learning targets part 4
• Ceramic materials are susceptible to thermal shock,
they fail if exposed to too fast temperature changes (ΔT/Δ t) and locally to too
What you already know and understand!
they fail if exposed to too fast temperature changes (ΔT/Δ t) and locally to too large temperature gradients (ΔT/ Δ x).
• Small component = small σthermal // Large component = large σthermal
• Low CTE, high KIc, and low E = high RS (= 1st thermal shock parameter)2nd thermal shock parameter → constant heat transfer3rd thermal shock parameter → surface heated by constant rate3 thermal shock parameter → surface heated by constant rate
• Slow Crack Growth (scg): time dependent failure → limited life time
• Crack velocity is influence by humidity → brake up of bonds at crack tip y y y p pe.g. in soda-lime glass by water (Si-O-Si- +H2O → -SiOH + -SiOH).
• SCG parameters can be measured in accordance to state of load(static dynamic cyclic or a combination thereof)(static, dynamic, cyclic, or a combination thereof).
• Correlation between largest failure relevant defect, failure strength and lifetime.
• Link between strength probability of failure and lifetime:
2Kübler Empa-HPC, ETHZ MW-II Ceramics-6.5, 2010
• Link between strength, probability of failure and lifetime: Strength-Probability-Time diagram
Repetition learning targets part 4
• Creep: Boundary (diffusion) or lattice (dislocation) mechanism
• Diffusional creep: Free surfaces and grain boundaries work as source and assembly pointFree surfaces and grain boundaries work as source and assembly point for voids and atoms. Voids diffuse from surfaces under tension to surfaces under compression and matter flows in reverse direction.
Grain boundary sliding:• Grain boundary sliding: Structure elongates by shifting & twisting of grains
• Stages of creep: - primary- secondary (steady state) - tertiary
• Creep should be measured in tensionand not in bending.
St i t i i i ith• Stain rate is increasing with - increasing load & temperature and - decreasing grain size.
3Kübler Empa-HPC, ETHZ MW-II Ceramics-6.5, 2010
Aim of chapter & Learning targets 1 Introduction “Why mechanical testing ”1. Introduction2. Stresses at a crack tip3. Griffith law4 K and K
part
1C
rack
tip
lear
ning
ta
rget
s 1Why mechanical testing …”
“Higher than you’d assume …”“Conditions for failure …”
“Stress intensit & critical stress intensit ”4. KI and KIc
5. R-curve6 P ti
Crt
2ng
th
t“Stress intensity & critical stress intensity …”
ning
et
s 2
“Improving toughness …”“K i h t ”6. Properties
7. Strength
8 St ti ti
par
Stre
ns
lear
nta
rge“Knowing what you measure …”
“Just a value …”
8. Statistic9. Proof testing10. Fractographypa
rt 3
Stat
istic
s
lear
ning
ta
rget
s 3“Weibull, a name you’ll never should forget …”
“Make it or …”“Reading fracture surfaces …”
11. Thermal shock12. Slow crack growth
S4 Te
mp
ing
ts 4
“Temperature, time and geometry …” “After several years …”
13. SPT diagrams14. Creep15. Failure maps
part
Tim
e&T
lear
nita
rget“Combining strength, lifetime & statistics …”
“Temperature makes it move …”“Finding your way …”
4Kübler Empa-HPC, ETHZ MW-II Ceramics-6.5, 2010
part 5 - Case Study: Lifetime of All-Ceramic Dental Bridges
AcknowledgementsThis lecture is based on / a compilation of• A.R. Studart, F. Filser, P. Kocher, H. Lüthy, L.J. Gauckler
dental materials 23 (2007) 115-123 and dental materials 23 (2007) 177-185dental materials 23 (2007) 115 123 and dental materials 23 (2007) 177 185• A.R. Studart, F. Filser, P. Kocher, L.J. Gauckler
dental materials 23 (2007) 106-114 and Biomaterials 28 (2007) 2695-2705• I Sailer A Fehér F Filser L J Gauckler H Lüthy Ch H F Hämmerle• I. Sailer, A. Fehér, F. Filser, L.J. Gauckler, H. Lüthy, Ch.H. F. Hämmerle
The International Journal of Prosthodontics, 20 (2007) 151-156• presentation Lifetime of All-Ceramic Dental Bridges @ ETH Materials Day
2005 F Filser2005, F. Filser• presentation Load Bearing Capacity and Reliability of All-Ceramic Four-Unit
Posterior Bridges @ CICC-4 (2005), F. Filser• lecture Lifetime Prediction of Dental Ceramics under Cyclic Fatigue @ ETHZ-
Special thanks go to
• lecture Lifetime Prediction of Dental Ceramics under Cyclic Fatigue @ ETHZ-MW-II-2007, F. Filser
p g• University of Zürich, Center for Dental & Oral Medicine
M. Schumacher, O. Loeffel, C. Löscher • Degudent, Dentsply Ceramco, Ivoclar and VITA Zahnfabrik for supporting
5Kübler Empa-HPC, ETHZ MW-II Ceramics-6.5, 2010
g , p y , pp gthose studies.
OutlineOutline• Introduction
- Dental bridges in time- Why ceramics- Mechanical short & longtime properties Ai & Obj ti f t d- Aim & Objectives of study
• Production process, various
Experimental & Results• Experimental & Results - Mechanical short-time properties- Lifetime prediction
influence of water- influence of water - subcritical crack growth & fatigue
• Lifetime diagrams
• Summary, Conclusion & Outlook
6Kübler Empa-HPC, ETHZ MW-II Ceramics-6.5, 2010
D t l b id i ti
Introduction
Dental bridges in time
Etruscanprosthesis
Metal-porcelainbridge
All-ceramicbridge
200 BC 1960s 1999
Filser , PhD thesis, ETHZ
7Kübler Empa-HPC, ETHZ MW-II Ceramics-6.5, 2010
Crown (frame & veneer)
AbutmentAbutmentScrew
Jaw-bone
Implant
8Kübler Empa-HPC, ETHZ MW-II Ceramics-6.5, 2010
http://bpi-implants.com
Introduction
Ch i ll i t• Chemically inert
• Low allergenic potential
• Pink esthetic of gums - Biocompatibility - Low deposition of plaque p p q
• White esthetic of tooth - natural look
i it ti f t
Metallic framework
- imitation of nature- translucent
CeramicCeramicframework
Why ceramics ?5-unit Bridge in the Molar Region
9Kübler Empa-HPC, ETHZ MW-II Ceramics-6.5, 2010
5-unit Bridge in the Molar Regionafter3 years in service (2002)
(Courtesyof A. Fehérand I. Sailer, University of Zurich)
Introduction
AB tiAB ti
Filser et al.PhD thesis
ETHZ (2001)
typical failure situation
11 22 33
AB cross sectionAB cross section ETHZ (2001)
11 22 33
800 N 80 k
A B High strength
800 N = 80 kg
1 2 3
High-strength materials are
i d !
Ch i fCh i f
2 3 required !
h “f l l d” 800 N 900 N 250 N /
10Kübler Empa-HPC, ETHZ MW-II Ceramics-6.5, 2010
Chewing forcesChewing forces The “failure load” was set to 800 N, 900 N or 250 N / teeth depending on the time in the long-time research
project a specific part has been conducted.
Introduction
30
40
mpl
es
Ceramic30
40
mpl
es
Ceramic30
40
mpl
es
Ceramic
20
30
f fai
led
sam Ceramic
Metal
20
30
f fai
led
sam Ceramic
Metal
20
30
f fai
led
sam Ceramic
MetalMechanical strength of
10
Num
ber o
f
10
Num
ber o
f
10
Num
ber o
fgceramics and metals
100100
0
68 74 80 86 92 98 104
110
116
122
Strength (MPa)
0
68 74 80 86 92 98 104
110
116
122
Strength (MPa)
0
68 74 80 86 92 98 104
110
116
122
Strength (MPa)
metals
80
100
ure
(%) Ceramic
Metal80
100
ure
(%) Ceramic
Metal
Strength (MPa)Strength (MPa)Strength (MPa)
40
60
bilit
y of
failu Improved
ceramic
40
60
bilit
y of
failu Improved
ceramic Strength ofStrength oftraditional ceramicstraditional ceramicshad to be improved !had to be improved !
Improved ceramic
0
20
Prob
ab
0
20
Prob
ab had to be improved !had to be improved !
11Kübler Empa-HPC, ETHZ MW-II Ceramics-6.5, 2010
060 80 100 120
Strength (MPa)
060 80 100 120
Strength (MPa)
Fatigue and subcritical crack growthIntroduction
Cyclic stresses Water+Mastication:
80
100
e (%
)
80
100
e (%
)
80
100
e (%
)
80
100
e (%
)
80
100
e (%
)
80
100
e (%
)
80
100
e (%
)
80
100
e (%
)
80
100
e (%
)
80
100
e (%
)
80
100
(%)
80
100
(%)
80
100
(%)
80
100
(%)
80
100
e (%
)
80
100
e (%
)
80
100
e (%
)
80
100
e (%
)
80
100
e (%
)
80
100
e (%
)Stress onthe bridge
40
60
ty o
f fai
lure
40
60
ty o
f fai
lure
40
60
ty o
f fai
lure
40
60
ty o
f fai
lure
40
60
ty o
f fai
lure
40
60
ty o
f fai
lure
40
60
ty o
f fai
lure
40
60
ty o
f fai
lure
40
60
ty o
f fai
lure
40
60
ty o
f fai
lure
40
60
ty o
f fai
lure
40
60
ty o
f fai
lure
40
60
ty o
f fai
lure
40
60
ty o
f fai
lure
40
60
ty o
f fai
lure
40
60
ty o
f fai
lure
40
60
ty o
f fai
lure
40
60
ty o
f fai
lure
40
60
ty o
f fai
lure
40
60
ty o
f fai
lure
20
40
Pro
babi
lit
Improvedceramic
20
40
Pro
babi
lit
Improvedceramic
20
40
Pro
babi
lit
Improvedceramic
20
40
Pro
babi
lit
Improvedceramic
20
40
Pro
babi
lit
Improvedceramic
20
40
Pro
babi
lit
Improvedceramic
20
40
Pro
babi
lit
Improvedceramic
20
40
Pro
babi
lit
Improvedceramic
20
40
Pro
babi
lit
Improvedceramic
20
40
Pro
babi
lit
Improvedceramic
20
40
Pro
babi
lit
20
40
Pro
babi
lit
20
40
Pro
babi
lit
20
40
Pro
babi
lit
20
40
Pro
babi
lit
20
40
Pro
babi
lit
20
40
Pro
babi
lit
20
40
Pro
babi
lit
20
40
Pro
babi
lit
20
40
Pro
babi
lit
060 80 100 120
Stress (MPa)
060 80 100 120
Stress (MPa)
060 80 100 120
Stress (MPa)
060 80 100 120
Stress (MPa)
060 80 100 120
Stress (MPa)
060 80 100 120
Stress (MPa)
060 80 100 120
Stress (MPa)
060 80 100 120
Stress (MPa)
060 80 100 120
Stress (MPa)
060 80 100 120
Stress (MPa)
01.E+00 1.E+10
Time
01.E+00 1.E+10
Time
01.E+00 1.E+10
Time
01.E+00 1.E+10
Time
01.E+00 1.E+10
Time
01.E+00 1.E+10
Time
01.E+00 1.E+10
Time
01.E+00 1.E+10
Time
01.E+00 1.E+10
Time
01.E+00 1.E+10
Time300 400 500 600
FatigueFatigue mechanismsmechanisms decreasedecrease thethe strengthstrength overover time !time !
12Kübler Empa-HPC, ETHZ MW-II Ceramics-6.5, 2010
FatigueFatigue mechanismsmechanisms decreasedecrease thethe strengthstrength overover time !time !
New materialsIntroduction
New materials10
2 ) AdvancedAdvanced
8P
a m
1/2
ZrOZrO22(Y,Mg(Y,Mg--PSZ) PSZ)
ceramicsceramicsGlassGlass--infiltrated infiltrated porous aluminasporous aluminas
6
KIC
(MP
NanoNano--ZrOZrO22(Y(Y--TZP) TZP) AlAl22OO33--GlassGlass
AlAl22OO33--ZrOZrO22--Glass Glass ((InceramInceram--ZirconiaZirconia))
GlassGlass--ceramicsceramics& reinforced & reinforced porcelainsporcelains
4
ness
, K
AlAl22OO33
((InceramInceram--AluminaAlumina))
ConventionalConventional
pp
2
Toug
hn
22 33Conventional Conventional porcelainsporcelains
MK IIMK II
LiLi22O.2SiOO.2SiO22((Empress 2Empress 2))
Empress 1Empress 1
Dicor MGCDicor MGC
0 200 400 600 800 10000
T
OmegaOmega
Empress 1Empress 1
13Kübler Empa-HPC, ETHZ MW-II Ceramics-6.5, 2010
Strength, σc (MPa)
Aim & OjectivesSystematically evaluate the lifetime under cyclic conditions for selected, representative dental ceramics.
GlassGlass--infiltrated infiltrated porous aluminasporous aluminas
With variables effect of water and effect of coating (porcelain)
Framework:Framework:Framework:Framework:
Establish guidelines for materials selection, fabrication process and bridge design
Framework:Framework:Framework:Framework:Zirconia (Cercon, degudent)Zirconia (Cercon, degudent)
Framework: Framework: Inceram Zirconia (VITA)Inceram Zirconia (VITA)
AlAl22OO33--ZrOZrO22--GlassGlass NanoNano--ZrOZrO2 2 (Y(Y--TZP)TZP)
Framework:Framework:LiSilicate (Ivoclar, Empress II)LiSilicate (Ivoclar, Empress II)
LiLi22O.2SiOO.2SiO22
10 500 nm 2 μm
14Kübler Empa-HPC, ETHZ MW-II Ceramics-6.5, 2010
Veneer: Veneer: Glass ZGlass ZVeneer: Veneer: Glass AGlass A
10μm 500 nm
Veneer: Veneer: ApatiteApatite
2 μm
Empress-2Process
Introduction
Process
Pre-operative view shows the presence of extensive
Teeth are prepared. The four waxed copings are sprued and then investedthe presence of extensive
infiltrated composites.sprued and then invested.
The frameworks after being d i h i
View of the finished frame-k h d l
The crowns and veneer are
15Kübler Empa-HPC, ETHZ MW-II Ceramics-6.5, 2010
pressed in the pressing furnace.
works on the master model. again placed on the master model.
IvoclarVivadent: “i, Vol. 7, Nr. 1, 2005
Introduction Empress-2ProcessProcess
Facial view of the four Labial view of the four Facial view of the four restorations. restorations. restorations following
immediate operative placement
16Kübler Empa-HPC, ETHZ MW-II Ceramics-6.5, 2010IvoclarVivadent: “i, Vol. 7, Nr. 1, 2005
Introduction InCeram-Zirconia (Alumina)ProcessProcess
grinding model made of gypsum digitizing
f i di fitt d th l i fil i
17Kübler Empa-HPC, ETHZ MW-II Ceramics-6.5, 2010A. David, SpectrumInternational •IDS 2003, p. 5-7
crown caps after grinding crown caps fitted on the gypsum model
glass infiltration
Introduction InCeram-Zirconia (Alumina)ProcessProcess
veneering the infiltrating the porous overworking the situation aftergframework with
VITADUR® ALPHA
infiltrating the porous alumina excess infiltration
glass
situation after cementation of the
3-unit bridge
18Kübler Empa-HPC, ETHZ MW-II Ceramics-6.5, 2010A. David, SpectrumInternational •IDS 2003, p. 5-7
Introduction Process of Machining in the Soft Sintered State
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� ���� W�� Cercon® (Degudent)
of Machining in the Soft Sintered State
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19Kübler Empa-HPC, ETHZ MW-II Ceramics-6.5, 2010
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F. Filser et al., ETH Hochschulverlag, ISBN 3-7281-2635-7, 1998, p. 165-189
Load Bearing Experimental Setupe g 3-unit bridges
Strength
e.g. 3 unit bridges
loadload
teflon disk
f kframework(dental bridge)
steel post
elastic bbrubber
hose
die holder
20Kübler Empa-HPC, ETHZ MW-II Ceramics-6.5, 2010
adapted fromH. Lüthy et al., Dental Materials, 21 (2005) p930
Strength
Load Bearing Capacity andg p yReliability of 4-Unit Frameworks
21Kübler Empa-HPC, ETHZ MW-II Ceramics-6.5, 2010
H. Lüthy et al.Dental Materials, 21 (2005) p930
Strength Mean Load Bearing Capacity of 3 d 4 it F k3- and 4-unit Frameworks
22Kübler Empa-HPC, ETHZ MW-II Ceramics-6.5, 2010
Strength
• Cercon Zirconia is the superior material
First conclusionsCercon Zirconia is the superior material
• in-vitro load bearing capacity and reliability of Cercon Zirconia 3-unit bridges are superiorZirconia 3 unit bridges are superior
• 7 mm2 connector area is sufficient for 3-unit Cercon bridgesg
• 7 mm2 connector area is NOT sufficient for Cercon 4-unit bridgesg
• 4-unit bridges need larger connector areas, or less span width or stronger materials
And what about lifetime ?
23Kübler Empa-HPC, ETHZ MW-II Ceramics-6.5, 2010
Subcritical crack growthTheoryLifetime
How fast does the crackHow fast does the crackt dt d
ICc Y
K=σ
σcσ < σc
propagate under propagate under subcritical conditions ?subcritical conditions ?
( )Kf ?
cc aY
Griffith‘sGriffith‘sac/2
ai/2
Zr
Zr
O
ac/2
Flaw size (μm)Flaw size (μm)
( )IKfv = ?lawlawσc
i
σ < σc
c
80
125756560(μ )
80
125756560(μ )
Inert strength500
ZrZr
40
60
ress
(MP
a)
40
60
ress
(MP
a)Zr
ZrO
OH
H
200
w s
ize
(μm
)
Zr
Zr
OH
H
O
Zr
O
HH
O Failure !
20 Stress appliedSt
20 Stress appliedSt
100
Flaw
Zr
24Kübler Empa-HPC, ETHZ MW-II Ceramics-6.5, 2010
0 1 2 3 40
Time (hours)0 1 2 3 4
0
Time (hours)0 1 2 3 4
50
Time (hours)
Lifetime predictionTheoryLifetime
125756560Flaw size (μm)( )IKfv = ?
60
80Fracture strength
MPa
)
40 Failure
Stre
ss (M
0 1 2 3 40
20 Stress applied
tf
⎟⎞
⎜⎛ 2222
0 1 2 3 4
Time (hours)n
IKAv .= Empirical relationEmpirical relation
De Aza et al., Biomaterials 23, 937 (2002)
( )nn
cnn
cn
ICf BKnAY
t −−−−− =⎟⎟⎠
⎞⎜⎜⎝
⎛−
= σσσσ 2222 22
ICc aY
K=σ Griffith‘sGriffith‘s
lawlaw For constant stressFor constant stress σσ !!
25Kübler Empa-HPC, ETHZ MW-II Ceramics-6.5, 2010
caY lawlaw For constant stress For constant stress σσ !!
Lifetime predictionTheoryLifetime
8080 Inert strength
( )IKfv = ?
40
60
s (M
Pa)
40
60
s (M
Pa)
failure (= fracture)
0
20Stress applied
Stre
ss
0
20Stress applied
Stre
ss
0 1 2 3 4 5 6 7 8
0
Time (hours)0 1 2 3 4 5 6 7 8
0
Time (hours)
tfTime (hours)Time (hours)
nIKAv .= Empirical relationEmpirical relation nn
cf Bt −−= σσ 2 Constant stress Constant stress σσ
De Aza et al., Biomaterials 23, 937 (2002)
ICc aY
K=σ Griffith‘sGriffith‘s
lawlaw ( )n
anc
amf B
nht −−= σσ
σσ2
,1 Any givenAny given
stressstressi tii ti
26Kübler Empa-HPC, ETHZ MW-II Ceramics-6.5, 2010
caY lawlaw ( )amnh σσ,variationvariation
Theory Lifetime Scheme of the ageing processa) Nucleation on a particular grain at the surface, leading
to microcracking and stresses to the neighbourso c oc ac g a d s esses o e e g bou sb) Growth of the transformed zone, leading to extensive
microcracking and surface roughening. c) Grain pull-out induced by wear
water induced
Chevalier, Leading Opinion: What future for zirconia
as a biomaterial? water inducedt → m
transformation
Biomaterials 27 (2006) 535–543
transformation(degradation of strength)
σ
MonoclinicMonoclinic
Tetragonal
27Kübler Empa-HPC, ETHZ MW-II Ceramics-6.5, 2010
σ( c )
Experimental ApproachExperimental
Sample preparation
Set-up fatigue preparation g
machine
Strength and lifetime measurements
0
20
40
60
80
100
Failu
re p
roba
bilit
y (%
)
Zirconia
0
20
40
60
80
100
Failu
re p
roba
blity
(%)
Zirconia
0200 400 600 800 1000 1200
Stress (MPa)
01 10 100 1000 10000 100000
Number of cycles
10-6
Li O 2SiO
Subcritical crackgrowth curves
1 2 3 4 5 6 710-13
10-12
10-11
10-10
10-9
10-8
10-7
Cra
ck v
eloc
ity, v
(m/c
ycle
)
Stress intensity factor K (MPa m1/2)
Li2O.2SiO
2
Al2O
3-ZrO
2-Glass
ZrO2
Stresses on posterior bridges
Stress intensity factor, KI,max (MPa.m )
28Kübler Empa-HPC, ETHZ MW-II Ceramics-6.5, 2010
Lifetime diagrams
Sample preparationExperimental
Framework Li2O.2SiO2(framework)
Framework + veneer Apatite(veneer) ( )
1 mm1 mm
inert strength + lifetime in waterX
coated + uncoatedX
3 materials + TZP rods=
240 samples (effective 232)
29Kübler Empa-HPC, ETHZ MW-II Ceramics-6.5, 2010
240 samples (effective 232)
Detection of sample breakageExperimental
Aqueous environment
30Kübler Empa-HPC, ETHZ MW-II Ceramics-6.5, 2010
Applied stress100
σmax100
0.5 5 30Time (min)Experimental
σmax
(MP
a)
650
0
10 Hz
60
80ba
bilit
y (%
)
peak stress foracceleratedfatigue tests 60
80
babl
ity (%
) AcceleratedFatigue
Stre
ss
650
0
20
40
Failu
re p
rob
Zirconia
g
20
40
Failu
re p
rob
Zirconia
Time (s)0.1 0.20
200 400 600 800 1000 1200
Stress (MPa)
01 10 100 1000 10000 100000
Number of cycles
31Kübler Empa-HPC, ETHZ MW-II Ceramics-6.5, 2010
Mechanical strengthMechanical strength FatigueFatigue
Determination of SCG behavior e.g. TZPResults
1
2
Inert strenght (MPa)
1300120011001000900800
90
700
) 1
2
90
501010.1 Lifetime (min)
)
-1
0 70
90
50
30
e pr
obab
ility
(%
1/(1
-F))
TZP
-1
0
90
7050
30
prob
abili
ty (%
)
1/(1
-F))
TZP
-4
-3
-210
Fai
lure
lnln
(
-4
-3
-210
Fai
lure
lnln
(
6.5 6.6 6.7 6.8 6.9 7.0 7.1 7.2lnσc
-6 -4 -2 0 2 4 6ln(Lifetime)
10-9
10-8
n = 79.8
v (m
/cyc
le)
Air
10-10
n = 66.5
Cra
ck v
eloc
ity v
Describes the Describes the properties of properties of
32Kübler Empa-HPC, ETHZ MW-II Ceramics-6.5, 2010
10-11
0.80.70.60.50.4
ΔKI / KIC
p pp pthe material !the material !
Lifetime prediction of dental materialsResults
10-8
n = 79.8ycle
)
Air
10-10
10-9
velo
city
v (m
/cy
10-11
10
0 8
n = 66.5
0.70 60.50.4
Cra
ck
1000
Water
Air
600
1350Inert strength (MPa)
ess
(MPa
)
0.80.70.60.50.4
ΔKI / KIC
Materials‘ propertiesMaterials‘ properties 100
a e
8 mm2
6 mm2
Stress at the connector of a 3-unit bridge
um a
pplie
d st
re
p pp p
Connector area
10 mm2loaded at 900 N
Max
imu
100 101 102 103 104 105 106 107 108 10910
Number of cycles
20 ith
33Kübler Empa-HPC, ETHZ MW-II Ceramics-6.5, 2010
Predict lifetime for any bridge !Predict lifetime for any bridge !20 years with1’400 cycles/day
Fracture modeResults
Imbeni et al,Nature Materials, 4, 229 (2005)
Enamel
DentinArrested
crack
EnamelEnamel
Dentin
34Kübler Empa-HPC, ETHZ MW-II Ceramics-6.5, 2010
Results
Fatigue and subcritical crack growth
VeneerVeneer
10Ca2+ + 6PO43- + 2OH -
Ca10(PO4)6(OH)2
1 mm1 mm
Enamel: Apatite
10( 4)6( )2
35Kübler Empa-HPC, ETHZ MW-II Ceramics-6.5, 2010
Results
FrameworkFrameworkFatigue and subcritical crack growth
10-6
Li2O.2SiO2
10
10-7
ycle
) Human dentin(Nalla et al, 2003)
Li2O.2SiO2
Al2O3-ZrO2-GlassNano-ZrO210-9
10-8
y, v
(m/c
y
Enamel: Apatite10-10
0
ck v
eloc
ity
10-12
10-11
Cra
c
Dentin:~ 75 % Apatite
+ 25 % collagen110-13
2 3 4 5 6 71/2
36Kübler Empa-HPC, ETHZ MW-II Ceramics-6.5, 2010
Stress intensity factor, KI,max (MPa.m1/2)
LifetimeResults
20 years withLifetimediagram
20 years with1’400 cycles/day and
Loadmax = 130 N
100
60
80
ailu
re (%
) Stress onthe bridge
Initialstrength
40
60
abilit
y of
fa
0
20
60 80 100 120
Prob
Improvedceramic
300 400 500 60060 80 100 120Stress (MPa)
300 400 500 600
37Kübler Empa-HPC, ETHZ MW-II Ceramics-6.5, 2010
Results
Lifetime diagram : Veneer
Glass ZGlass Z ApatiteApatiteGlass AGlass A
g
20
10
(μm
)
σ c(M
Pa)
σ c(M
Pa)
(μm
)
20
10
σ c(M
Pa)
(μm
)
20
10> 20 years 1 bite
100
40
20
Cra
ck s
ize
Ven
eer s
treng
th,
Ven
eer s
treng
th,
Cra
ck s
ize
100
40
20
Ven
eer s
treng
th,
Cra
ck s
ize
100
40
20
300
Stress on veneer surface, σ (MPa)
300
Stress on veneer surface, σ (MPa)
300
Stress on veneer surface, σ (MPa)
PP1.722.534 mm 1.722.534 mm 1.722.534 mm
P P2.633.54 mm 2.633.54 mm 2.633.54 mm
P P P3.13.54 mm 3.13.54 mm 3.13.54 mm
38Kübler Empa-HPC, ETHZ MW-II Ceramics-6.5, 2010
1400 cycles/day
Loadmax = 130 N
Results
Lifetime diagram : Framework
NanoNano--ZrOZrO22 LiLi22O.2SiOO.2SiO22AlAl22OO33--ZrOZrO22--GlassGlass
gh,
σc
(MP
a)
(μm
)
20
10
h, σ
c(M
Pa)
(μm
)
20
10
, σc
(MP
a)
(μm
)
20
10
20
amew
ork
stre
ngth
Cra
ck s
ize
100
40
20
amew
ork
stre
ngth
Cra
ck s
ize
100
40
20
mew
ork
stre
ngth
,
Cra
ck s
ize
(
100
40
20> 20 years
Fra
300
Stress on framework, σ (MPa)Fr
a
300
Stress on framework, σ (MPa)
Fra
300
100
Stress on framework, σ (MPa)
P
1 bite
P P
P1.722.534
2.833.54
mm
mm
1.722.534 mm
2.833.54 mm
1.722.534 mm
2.833.54 mm
P P P3.33.54 mm 3.33.54 mm 3.33.54 mm
39Kübler Empa-HPC, ETHZ MW-II Ceramics-6.5, 2010
1400 cycles/day
Loadmax = 130 N
Summary
Framework:Framework: Framework:Framework: Framework:Framework:
AlAl22OO33--ZrOZrO22--GlassGlass NanoNano--ZrOZrO22 LiLi22O.2SiOO.2SiO22
Veneer: Veneer: Glass AGlass A Veneer: Veneer: Glass ZGlass Z Veneer: Veneer: ApatiteApatite
P P P
P P P P P P
1.722.534 mm
Max ∅ (≥ 4 mm) Max ∅ (≥ 4 mm)
1.722.534 mm
P P P P P P P P PMax ∅ (≥ 4 mm)
40Kübler Empa-HPC, ETHZ MW-II Ceramics-6.5, 2010
1400 cycles/day
Loadmax = 130 NVeneer and not framework dictates what’s feasible …..
41Kübler Empa-HPC, ETHZ MW-II Ceramics-6.5, 2010
Courtesy: University of Zürich, Center for Dental & Oral Medicine
Conclusions
Nano-ZrO2 ceramics and ZrO2-based ceramic composites can withstand the high stresses
- 9p g
applied on posterior bridges during mastication9
34
- 4151015202530
Long-term failure due to fatigue and subcritical crack growth can be avoided through proper bridge design
1.722.534 mm
Max ∅ (> 4 mm)
Max ∅ (> 4 mm)
1.722.534 1.722.534 mm
Max ∅ (> 4 mm)
Max ∅ (> 4 mm)bridge design Max ∅ (> 4 mm)Max ∅ (> 4 mm)
Lifetime diagrams are suitable tools for the a)
10
1.722.534Connector diameter (mm)
a)
1010
1.722.534Connector diameter (mm)
Lifetime diagrams are suitable tools for the selection of new materials and fabrication technologies for dental restorations
Fram
ewor
k st
reng
th, σ
c(M
P
Cra
ck s
ize
(μm
)
300
100
40
20
Fram
ewor
k st
reng
th, σ
c(M
P
Cra
ck s
ize
(μm
)
300
100
40
20
300
100
40
20
Stress on framework, σ (MPa)Stress on framework, σ (MPa)
Apatite-based materials should be avoided in the connector region of posterior bridges d e to the
Ca10(PO4)6(OH)2
42Kübler Empa-HPC, ETHZ MW-II Ceramics-6.5, 2010
connector region of posterior bridges due to the pronounced subcritical crack growth 10Ca2+ + 6PO4
3- + 2OH -
Outlook
Etruscianprosthesis
Metal-porcelain
bridge
All-ceramicbridgebridge
200 BC 1960s 2005200 BC 1960s 2005
Ceramic high Natural tooth genesis
20
strength, non veneer bridge ?
2
genesis mediated by stem cells ?
20yy 2zzz
different materials -strength not anymore the issue -
- wishful- 1st steps successful
43Kübler Empa-HPC, ETHZ MW-II Ceramics-6.5, 2010
strength not anymore the issue -treatment methods shifting -
- 1 steps successful- lots of challenges ahead
Summary:What you know and understand now!
Hook’s law
What you know and understand, now!
earn
ed! Hook s law …
Stress … Griffith’s law …
d ha
ve le Weibull statistic …
Influence of surface, volume, microstructure …R-curve …
u sh
ould
R curve …Environment …Sub-critical crack growth … St ti & d i f ti
This
you Static & dynamic fatigue …
Proof-testing …Deformation & failure @ elevated temperatures … Thermal shock …
44Kübler Empa-HPC, ETHZ MW-II Ceramics-6.5, 2010
Those relations, laws & equations you known by heart, now!