Development of high-strength machinable glass ceramics for dental applications

1
Development of high-strength machinable glass
ceramics for dental applications
Dr Duangrudee Chaysuwan Dept of Materials
Engineering Faculty of Engineering Kasetsart
University THAILAND
Dr David J Wood Biomaterials Unit Div of
Restorative Dentistry Leeds Dental
Institute University of Leeds UK
2
Outline

• Introduction
• Materials and Methods
• Results and Discussion
• Conclusions
• Acknowledgements
• References

Development of high-strength machinable glass
ceramics for dental applications
D Chaysuwan
3
Introduction
Development of high-strength machinable glass
ceramics for dental applications
D Chaysuwan
4
Introduction

• Glasses designed to be stable against
  devitrification (crystallisation)
• Controlled crystallisation can be induced by the
  addition of nucleating agents to the glass system
• Suitable chemical compositions and heat
  treatments lead to the process of crystallisation
  of glasses from which are obtained glass
  ceramics

Development of high-strength machinable glass
ceramics for dental applications
D Chaysuwan
5
Introduction

• Machinability of mica - based glass - ceramics
  

The cleavage of interlocking layers of mica.(2)

• As the interlayer ions of mica crystals
  containing Ba2

Exhibit high strength(3)

• The mechanical properties depend on

Particle size and numbers of precipitated mica
crystals.(4)
Development of high-strength machinable glass
ceramics for dental applications
D Chaysuwan
6
Objectives
To develop and characterize machinable glass
ceramics for dental and industrial applications
based on the formation of a mica phase.
Development of high-strength machinable glass
ceramics for dental applications
D Chaysuwan
7
Objectives

• To convert the glasses to glass ceramics.
• To determine the nucleation behaviour for
  crystallization in these glasses.
• To develop heat treatments
• Promote the formation of a barium fluormica
  phase.

• To produce rods of glass .
• To convert to glass -ceramics

• To assess the mechanical properties of these
  glass - ceramics.
• Machinability and hardness

Development of high-strength machinable glass
ceramics for dental applications
D Chaysuwan
8
Glass Ceramics Processing
Glass - ceramics
Glass
Schematic of the basic temperature VS time of a
glass ceramics processing (1)
Development of high-strength machinable glass
ceramics for dental applications
D Chaysuwan
9
Materials and Method
Development of high-strength machinable glass
ceramics for dental applications
D Chaysuwan
10
Experimental Procedures
Preparing Glass
Glass
Melting
Quenching
Frit
Analysis
Sieving
Development of high-strength machinable glass
ceramics for dental applications
D Chaysuwan
11
Ternary phase diagram
Development of high-strength machinable glass
ceramics for dental applications
D Chaysuwan
12
Materials Weighing
MgF2
CaF2
MgF2
CaF2
MgO
MgO
CaCO3
CaCO3
Al2O3
Al2O3
BaCO3
BaCO3
SiO2
SiO2
P2O5
P2O5
High Alumina Crucible
Development of high-strength machinable glass
ceramics for dental applications
D Chaysuwan
13
Melting
1400 0C
140 minutes
1400
140
1000
100
500
50
Room Temp
Temp. (0C)
Time (minute)
10 0C / min ramp rate
cooling in furnace
Development of high-strength machinable glass
ceramics for dental applications
D Chaysuwan
14
Quenching
Frit
Stainless tank with cool water
Development of high-strength machinable glass
ceramics for dental applications
D Chaysuwan
15
Sieving
Frit gt 2 mm for SEM after heat treatment
Aperture 2 mm
Aperture 1 mm
Frit 12 mm for DTA
Frit lt 1 mm for remelting
Aperture 90 µm
Aperture 45 µm
Glass powder lt 45 µm for DTA and XRD
Development of high-strength machinable glass
ceramics for dental applications
D Chaysuwan
16
Glass Analysis

• XRD
• (X-Ray Diffraction Analysis)
• Glass Characterize
• DTA/TGA
• (Different Thermal Analysis/Thermogravimetric
  Analyzer)
• Glass transition temps., Crystallization temps.

Development of high-strength machinable glass
ceramics for dental applications
D Chaysuwan
17
Experimental Procedures
Glass Ceramic
Development of high-strength machinable glass
ceramics for dental applications
D Chaysuwan
18
Remelting
Remelting at 1400 0C
Development of high-strength machinable glass
ceramics for dental applications
D Chaysuwan
19
Pouring and Annealing
Carbon Mould
Glass Rod (transparent)
Development of high-strength machinable glass
ceramics for dental applications
D Chaysuwan
20
Pouring and Annealing
Heat Carbon Mould at Tg 50 0C
Glass Rod (transparent)
Development of high-strength machinable glass
ceramics for dental applications
D Chaysuwan
21
Pouring and Annealing
Annealing at Tg 50 0C 1 Hour
Glass Rod (transparent)
Development of high-strength machinable glass
ceramics for dental applications
D Chaysuwan
22
Pouring and Annealing
Cool down in furnace
Glass Rod (transparent)
Development of high-strength machinable glass
ceramics for dental applications
D Chaysuwan
23
Recrystallizing
600-700 0C
1Hour
140
1500
6
1000
4
500
2
Room Temp
Temp. (0C)
Time (Hour)
10 0C / Minute Ramp Rate
Development of high-strength machinable glass
ceramics for dental applications
D Chaysuwan
24
Recrystallizing
600-700 0C
3 Hours
140
1500
6
1000
4
500
2
Room Temp
Temp. (0C)
Time (Hour)
Soaking 2 Hour
Development of high-strength machinable glass
ceramics for dental applications
D Chaysuwan
25
Recrystallizing
800-850 0C
3.5 Hours
140
1500
6
1000
4
500
2
Room Temp
Temp. (0C)
Time (Hour)
10 0C / Minute Ramp Rate
Development of high-strength machinable glass
ceramics for dental applications
D Chaysuwan
26
Recrystallizing
800-850 0C
6.5 Hours
140
1500
6
1000
4
500
2
Room Temp
Temp. (0C)
Time (Hour)
Soaking 3 Hour
Development of high-strength machinable glass
ceramics for dental applications
D Chaysuwan
27
Glass Ceramic Rod
Development of high-strength machinable glass
ceramics for dental applications
D Chaysuwan
28
Glass Ceramic Analysis

• XRD (X-Ray Diffraction)
• Glass Ceramic Characterize
• SEM (Scanning Electron Microscopy)
• Grain size, grain shape and aspect ratio
• Machinability (by filing and drilling)
• Hardness (Knoop)

Development of high-strength machinable glass
ceramics for dental applications
D Chaysuwan
29
Results and Discussion
Development of high-strength machinable glass
ceramics for dental applications
D Chaysuwan
30
Results and discussions
DTA
Tp1 745.63 OC
Tp2 935.86OC
Tp3 1044.90OC
Tm 1081.93OC
Tg 635.50 OC
Development of high-strength machinable glass
ceramics for dental applications
D Chaysuwan
31
Results and discussions
XRD
Intensity (arbitrary unit)
B Bariumfluormica F Fluorapatite Fo
Forsterite
B
B
B
Fo,B
B
F
B
Fo,B
F
Fo,B
F
B
B
B
F
F
Fo
Heat treated frits _at_ 1070 oC 1 hr
B
B
B
F
B
B
B
F
B
B
B
B
Heat treated frits _at_ 955 oC 1 hr
B
B
B
B
B
B
B
B
B
Heat treated frits _at_ 835 oC 1 hr
As-quenched glass
2?
Development of high-strength machinable glass
ceramics for dental applications
D Chaysuwan
32
Results and discussions
SEM
(Surface)
835 OC
955 OC
1070 OC
(Bulk)
Feather like flakes
Feather like flakes
33
Results and discussions
Hardness Biaxial Strength Machinability
Products Microhardness (KHN100)
Porcelain 460
Amalgam 110
Dentin 343
Enamel 379
DICOR 362
KUG 573
Machinability with difficulties due to its high
hardness
Development of high-strength machinable glass
ceramics for dental applications
D Chaysuwan
34
Conclusions
Development of high-strength machinable glass
ceramics for dental applications
D Chaysuwan
35
Conclusions

• Glass systems were successfully produced
• Basic thermal parameters were determined for
  each glass
• XRD determinations confirmed that the samples
  crystallised to BFM
• Microstructures consisted of fine feather-like
  crystals in the bulk of samples but there was
  also evidence of surface nucleation

Development of high-strength machinable glass
ceramics for dental applications
D Chaysuwan
36
Conclusions

• Selected compositions could be successfully cast
  and heat treated to give glass ceramic rods
• These samples , however, were not easily
  machined. This is attributed to their
  microstructures of very fine crystals
• These materials would not be suitable for
  industrial or dental applications unless they are
  improved by increasing crystal size and aspect
  ratio to reduce the hardness

Development of high-strength machinable glass
ceramics for dental applications
D Chaysuwan
37
Acknowledgements

• The authors would like to thank
• - The Thai government and
• Faculty of Engineering , Kasetsart University
  for
• the fund of the research
• - Mr Anothai Tansuwan, Dept of Materials
  Eng,
• Faculty of Engineering, Kasetsart University

Development of high-strength machinable glass
ceramics for dental applications
D Chaysuwan
38
References
1. H.D. Pfaender, Schott Guide to Glass, Chapman
Hall, 1996. 2. D.G. Grossman, Machinable
Glass-Ceramics Based on Tetrasilicic Mica,
J.Am.Ceram.Soc., 55 9 446-49 ,1972. 3. K.
Chyung, G.H. Beall and D.G. Grossman,
Fluorphlogopite Mica Glass-ceramics pp. 33-40
in Proceedings of 10th International Glass
Congress, No. 14 (Kyoto, Japan, July). Ceramic
Society of Japan, Tokyo, Japan, 1974 4. W.
Holand, W. Vogel, W.J. Motier, P.H. Duvigneaud,
G. Naessens and E. Plumet, A New Type of
Phlogopite Crystal in Machinable Glass-ceramic.
Glass Technol. 24 6 318-22 ,1983.
Development of high-strength machinable glass
ceramics for dental applications
D Chaysuwan