ldb openlab_licciulli-prototipazione di materiali avanziati (parte 2)

Materials modelling and 3D prin2ng in the future of den2stry

Antonio Licciulli

University of SalentoUniversity of Modena

21 3

1 Licciulli "Open lab" tribute 2 - 07 gennaio 2015

Outline

Introduction: ceramics for prosthetic dentistry

The innovative process of glass infiltrated alumina composites

Microstructure and properties of infiltrated alumina composites

Conclusions


The future of dentistry


Full ceramic prosthetic dentistry

Metal ceramic systems in prosthetic dentistry involve complex, tedious, time consuming lost vax processes

they have potential immunologic and esthetic concerns

All ceramic prosthetic and implant solution are under investigation

The novel technologies must provide the same success rates of metal implants


Dental core ceramic families Leucite reinforced glass ceramics, fabricated by hot pressing the molten glass into a mold

σMOR ∼ 95-180 MPa, K1c= 1,3 MPa m1/2

Lithium disilicate reinforced glass ceramics, fabricated by hot pressing

σMOR ∼ 340-400 MPa, K1c= 2-3,5 MPa m1/2

Glass infiltrated alumina pressed or slip cast

σMOR ∼ 350-500 MPa, K1c= 4-5 MPa m1/2

Zirconia fabricated by CAD/CAM

σMOR ∼ 800-1000 MPa, K1c > 5 MPa m1/2

Lithium dislocate GC

Leucite GC

MI alumina

3Y TZP

5μm

5μm

2μm

2μm5 Licciulli "Open lab" tribute 2 - 07 gennaio 2015

Our innovation: ceramic cores from oxide/oxide composites

Chopped fibers reinforced CMC microstructure

Crown, veneers, bridges partial dentures can be conveniently produced

The tooth replica is immersed in to a special ceramic slurry(dip moulding)


Prosthetic dentistry: The restoration or replacement of teeth

CROWNS are placed when a significant amount of tooth structure is lost

Biting forces:

incisors 200-250N

premolars 150-500N,

Molars 400 - 600N with maximum up to 1000N

lateral load application 20-60N

BRIDGES are placed when there are one or more teeth missing


Smile modelling


Structural analysis on all ceramic dental bridge

The dimensions of the connector cross-sections depend on the physical properties of the core ceramics

Maximum stress above 300MPa in small gingival region at the connectors,

Up to now only zirconia (TSZ) fulfill requirements on strength and Weibull modulus

Our glass infiltrated composite may represent a reliable solution thank to its high strength and Weibull modulus


Prosthetic dentistry: the restoration or replacement of teeth

DENTURES: replacement of an entire or partial arch of teeth with a fixed appliance

Load application on implant sustained prosthesis 40 - 400N

Strength requirement 800MPa

An IMPLANT is typically a titanium screw that is placed into the jaw bone. It is left in the bone for a period of approximately 3-4 months to let it "fuse" with the adjacent bone. A metal or ceramic abutment is placed for the crown to emerge from.


All Zirconia Dental Implant prototype obtained by CNC lathe

Zirconia dental Implants

Modified Titanium implant with zirconia transgingival collar


Implant design and reliability analysis

Implant modeling by CAD

Results feedback and optimization

CNC manufacturing

FEM analysis

Reliability analysis


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CAD-CAM processIn production, several roughing cuts are

usually taken on the part, followed by one or two finishing cuts

• Roughing - removes large amounts of material from starting work part – Creates shape close to desired

geometry, but leaves some material for finish cutting

– High feeds and depths, low speeds • Finishing - completes part geometry

– Final dimensions, tolerances, and finish

– Low feeds and depths, high cutting speeds


Area1

Area 2

Area 3

Area 4

Area 5

Area 6

m σ0 σpeak Vi σi Bi B A

Area 1 9,2 841

171

0,227 171 9,82E-‐08

2,09E-‐070,9999998

(prob. of failure 1 on 1.000.000)

Area 2 9,2 841 0,364 110 2,71E-‐09

Area 3 9,2 841 0,182 125 4,40E-‐09

Area 4 9,2 841 0,455 110 3,39E-‐09

Area 5 9,2 841 0,727 150 9,41E-‐08

Area 6 9,2 841 1,364 105 6,63E-‐09

Stress state distribution and reliability calculation

Thin wall design implant Fillet radius 0,7mm


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CNC MILLING

15


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CAD-CAM approach(zirconia)Study of design(CAD) Toolpath design(CAM)

Materials, Tools, cut parameter,

etc….


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Questions(?) before to startCan we make it?

How to make it? (setup)

How to make it? (Toolpath, NC code)


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Questions(?) before to start

➢ how to turn the workpiece? ➢ what are the supports of the

workpiece during machining? ➢ which tools should I use? ➢ how should I position the

workpiece on the chuck? ➢ Which parameters should I

use in roughing and finishing????

➢ ????

Titatium screw

Zirconia component


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Fixture planning

Zirconia workpieceOne sacrifical support(red) –

fixture on workpiece

CAD MODEL

40x15x15 mm


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Fixture PlanningFragile materials: metallic support is needed!

Metallic pin(fixture on chuck)


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Fixture Planning

Metallic support Toolpath planning


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Machining step by step


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Toolpath Planning➢ Layer based toolpaths

➢ Machine visible surfaces from approach direction ➢ It consist in several tool movements; ➢ A gouge-free approach, given flute and shank diameter are same (or shank <

flute) ➢ Can approach finish machining using very small depths of cut

➢ We assume that tool length, not diameter will be active constraint ➢ To avoid collision, tool length > maximum swept diameter of part (Same as

stock diameter) ➢ Tool diameter chosen as smallest available for required length (not conventional

tools)


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Toolpath Planning

Which is the goal?➢ Generate the shortest

tool-path for machining of a part

➢ Minor number of movements tools means high efficienty

Shorter production time

Decrease production cost


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% O0000(STAMPOCOPERCHIO_PORTASONDA) N102 G0 G17 G40 G49 G80 G90 N104 T1 M6 N106 G0 G90 G54 X185. Y4.8 A0. S6366 M3 N108 G43 H1 Z64.978 N110 Z44.978 N112 G1 Z39.978 F1018.6 N114 X184.638 F2037.1 N116 X183.936 Z39.805

Toolpath planningCad Model Toolpath design

SimulationNC Program


Accelerated aging and fatigue test Test conditions: saline environment, 1.000.000 of cyclic bending stress loading with peak stress of 320 MPa and frequency of 20 Hz.

ISO 13356:2008 “Implants for surgery – ceramic materials based on yttria stabilized tetragonal zirconia (Y-TZP)

Salentec ZirconiaCE displays no break during fatigue test 0"

200"

400"

600"

800"

1000"

before" a.er"1.000.000"of"cyclic"loading"

σMOR%[M

Pa]%

941"±"136"

768"±"137"


3D scanning system Teeth design by CAD CAM software for mill programming

Computer numerical control machining

Components of a CAD CAM system

Sintering Presintered ceramic disk28 Licciulli "Open lab" tribute 2 - 07 gennaio 2015

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Ceramic CNC machining in Dentistry application


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Salentec ZrO2

Blocks, Blanks, and several dimensions are available

Properties: - Pure ZrO2 presintered; - Bar code guarantees material properties and

contraction - 98 mm diameter and different

thicknesses (10-25 mm) - Approximately 25 elements

per disk milled - Even bridges 14 Merged


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Computer assisted design(CAD)


Plaster replica of tooth Dip plaster replica on

“magics slurry”Drying and presintering

Excess glass removal, porcelain enamelling

Melt infiltration of alumina composite

Sintering Melt infiltration32 Licciulli "Open lab" tribute 2 - 07 gennaio 2015

The Alumina matrixFine and reactive grade Al2O3 powder (AES-23, Sumitomo chemicals, Japan) and CT530 and CT1200 from Almatis have been compared

Size of α crystal from 0,3-4μm

Bimodal distribution, fired density 3,77g/cm3

Green density 2,57 3,77g/cm3, sintered density 3,77g/cm3

10μm

Presintered AES23


The fibrous preformChopped fibres from Saffil were produced by ball milling a fibrous mat

Alumina content 95-97 %

Median Diameter 3.0-3.5 μm

Median length 20-50 μm

Tensile Strength 1.5GPa

Melting Point > 2000°C

Young's Modulus 300GPa

40μm


!

Main feature of CMC dental core Instantly 0,5mm thick uncracked crown are obtained

Net shape forming and sintering

❏35 Licciulli "Open lab" tribute 2 - 07 gennaio 2015

!

!

With and without fibre reinforcement: advantages in forming

The slurry without fibrous reinforcement cannot withstand the mechanical stresses due to shrinkage on the convex mold

Thank to the fibre reinforcement the green will not crack


Net shape forming and sintering

The linear shrinkage in pre-sintered blocks was 0.045 ± 0.019 %

After glass infiltration the linear shrinkage was 0.078 ± 0.015 %.

The shrinkage was found to be uniform in all three axes with no warping or cracking of the samples

shrinkage was found be ∼4 times less than than the lowest found in literature (VITA In-ceram alumina samples which showed 0.21%)°under similar pre-sintering conditions

Green

Sintered


Total porosity approx. 20%

Bulk density 3.2 g/cm3

Fibre addition spreads the pore size distribution toward high dimensions, reduces total porosity increasing the volume of big pores at a time

Porosity of alumina preform


11

Oxide are mixed and fused at 1300°C

Frits are obtained quenching the molten oxide in water

La2O3 behaves like glass modifier

B2O3 behaves like network former but also reduces melting temperature

Lantanide glass frits developmentOxide La-1 La-2 La-3

SiO2 16 % 14,5 % 13.89 %

Al2O3 16 % 16 % 12.22 %

B2O3 13 % 14,5 % 17.89 %

La2O3 45 % 45 % 47.43 %

CeO2 3 % 3 % 2.95 %

CaO 3 % 3 % 2.88 %

TiO2 4 % 4% 2,74 %


11

Lantanide based glass are obtained in a full amorphous structure

BO4- tetrahedrons form in presence of alkaline, alkaline earth cations

BO4- tetrahedrons, should lead to a strengthening of the glass

Microstructure of lantanide glass frits

Silica tetrahedrals + tetragonal planar BO3

BO4 tetrahedrons


!

Differential thermal analysis on glass fritsTg glass transition temperature (650°C)

Tc crystallization temperature

Tx onset of crystallization (863°C)

∆T = Tx-Tg stability interval (213°C)

TgTx

Tc


!11

jlkl

Thermal evolution of lantanide glass frits

Sintering Softnening Sphere

Hemisphere Fusion


Morphology and composition of infiltrated composite

30μm


11

XRD analysis of La-3 infiltrated samples revealed small crystalline peaks of Lanthanum silicate (La2Si2O7).

The calculations revealed that ~13 % of the glass phase has crystallized

Microstructure of infiltrated CMC


!

Glass infiltration

300μm


Melt infiltration vs temperature and time

Penetration rate of glass into alumina is limited by glass viscosity

Temperature is the main element at a fixed glass composition influencing glass viscosity

1150°C

1200°C

1250°CMel

t infi

ltrat

ed L

a3 o

n AE

S23


Melt infiltration vs porosityInfiltration is driven by capillarity

Glass penetration increases with increasing pore radious and porosity

AES23 20% porosity

CT1200 36% porosity

CT530 32% porosity

Mel

t infi

ltrat

ed L

a3 a

t 125

0°C


Strength increase after glass infiltration

Flexural strength (MPa)

0,0

150,0

300,0

450,0

600,0

VITA La-‐1 La-‐2 La-‐3

The infiltrated glass greatly increases the mechanical strengthThe La-2 glass infiltrated sample is similar to the best performing alumina

before melt infiltration


Weibull plot of preform and glass infiltrated composite

Melt infiltrated composites display very high strength and Weibull modulus (14) The calculated value is significantly higher than conventionally sintered alumina ∿ 5-10


Conclusions

All ceramic prosthesis and implants are the new frontier in dentistry. With respect to metal/ceramic, they may become more performing and affordable

Ceramic scientists have to face important challenges in terms of material innovation, structural performances

Net shape forming process was developed using an alumina based composite suitable for crown, veneers and bridges

The glass infiltrated composites showed significant increase in strength combined with a significant increase in the Weibull modulus.


Thank you

for your kind attention

for your warm hospitality


ldb openlab_licciulli-prototipazione di materiali avanziati (parte 2)

Presentations & Public Speaking

mpa m12 zirconia

mpa m12lithium

ceramic cores

ceramic abutment

implant solution

molten glass

special ceramic slurrydip

mpaan implant