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
2μm

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


‹N›
SALENTEC CAD-CAM process
In 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-‐07
0,9999998
(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

‹N›
SALENTEC CNC MILLING
15

‹N›
SALENTEC CAD-CAM approach(zirconia)
Study of design(CAD) Toolpath design(CAM)
Materials, Tools,
cut parameter,
etc….

‹N›
SALENTEC Questions(?) before to start
Can we make it?
How to make it?
(setup)
How to make it?
(Toolpath, NC code)

‹N›
SALENTEC 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

‹N›
SALENTEC Fixture planning
Zirconia workpiece
One sacrifical support(red) –
fixture on workpiece
CAD
MODEL
40x15x15 mm

‹N›
SALENTEC Fixture Planning
Fragile materials: metallic support
is needed!
Metallic pin(fixture on
chuck)

‹N›
SALENTEC Fixture Planning
Metallic support Toolpath planning

‹N›
SALENTEC Machining step by step

‹N›
SALENTEC 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)

‹N›
SALENTEC 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

‹N›
SALENTEC
%
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 planning
Cad 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%[MPa]%
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 disk

‹N›
SALENTEC
Ceramic CNC machining in
Dentistry application

‹N›
SALENTEC 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

‹N›
SALENTEC
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 inﬁltration

The Alumina matrix
Fine 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 preform
Chopped 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 development
Oxide 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 frits
Tg glass transition temperature (650°C)

Tc crystallization temperature

Tx onset of crystallization (863°C)

∆T = Tx-Tg stability interval (213°C)
Tg
Tx
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°C
MeltinfiltratedLa3onAES23

Melt infiltration vs porosity
Infiltration is driven by capillarity

Glass penetration increases with
increasing pore radious and
porosity
AES23 20% porosity
CT1200 36% porosity
CT530 32% porosity
MeltinfiltratedLa3at1250°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
strength

The 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)

Recommended

Recommended

More Related Content

Similar to Ldb OpenLab_Licciulli-prototipazione di materiali avanziati (parte 2)

Similar to Ldb OpenLab_Licciulli-prototipazione di materiali avanziati (parte 2) (20)

More from laboratoridalbasso

More from laboratoridalbasso (20)

Recently uploaded

Recently uploaded (20)

Ldb OpenLab_Licciulli-prototipazione di materiali avanziati (parte 2)