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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:


• 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.


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 …”


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


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


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


Crown (frame & veneer)

AbutmentAbutmentScrew

Jaw-bone

Implant


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


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 /


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 !


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 !


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


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


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


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

D��

� �� W�� Cercon® (Degudent)

of Machining in the Soft Sintered State

F��

��

M�� Cercon® (Degudent)system

��

A��

S��

��

C��

�� A��

M��


��

��

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


adapted fromH. Lüthy et al., Dental Materials, 21 (2005) p930

Strength

Load Bearing Capacity andg p yReliability of 4-Unit Frameworks


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


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 ?


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


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 !!


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


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


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 )


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)


240 samples (effective 232)

Detection of sample breakageExperimental

Aqueous environment


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


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


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


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


Results

Fatigue and subcritical crack growth

VeneerVeneer

10Ca2+ + 6PO43- + 2OH -

Ca10(PO4)6(OH)2

1 mm1 mm

Enamel: Apatite

10( 4)6( )2


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


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


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


300


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


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


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)


1400 cycles/day

Loadmax = 130 NVeneer and not framework dictates what’s feasible …..


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


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


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 …


Those relations, laws & equations you known by heart, now!

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