4. DEFINITIONS
Ceramics : compounds of one or more metals with a non metallic element(usually
silicon,boron,oxygen) that may be used as a single structural component or as one of
the several layers that are used in the fabrication of a ceramic based prosthesis .
(G.P.T 7, Anusavice)
Porcelain : a ceramic material formed of infusible elements joined by lower fusing
materials.Most dental porcelains are glasses and are used in fabrication of teeth for
dentures, pontics & facings, crowns, inlays, onlays and other restorations. (G.P.T 7)
Ceramic is derived from Sanskrit word meaning Burnt earth
14. 14
Best mimic the optical properties of enamel and
dentine: Glassy material
Glasses: 3D network of atoms having no regular
pattern to the spacing between nearest
atoms, thus they are amorphous or without form.
Derived principally from a group of mined
minerals called FELDSPAR: based on silica and
alumina: Aluminosilicate glasses.
Resistant to crystallization during firing, long
firing ranges, biocompatible.
15. 15
Filler particles are added to the base glass
composition to improve mechanical properties
and to control optical effects like
Opalescence, Color, Opacity.
Fillers: Crystalline/Higher melting glass
Leucite: first fillers to be used, crystalline mineral
Feldspar forms crystalline mineral Leucite, when
mixed with metal oxides & fired to high
temperature
Leucite is potassium-aluminum-silicate mineral
with large coefficient of thermal expansion.
16. 16
This filler was added to create porcelains that
could be successfully fired on metal susbstruct.
Adding 17-25% Leucite filler to base glass
creates porcelains that are thermally compatible
with dental alloys.
- Index of refraction close to feldspar,
- “Selective etching”
Moderate strength increases can also be
achieved with appropriate fillers added and
uniformly dispersed: “Dispersion Strengthening”
17. 17
Special subset of particle-filled glass
The crystalline filler particles are grown inside
the glass object (pellet/prosthesis) by a special
heat treatment that causes the precipitation
within the glass.
This crystal nucleation and crystal growth
process is called “Ceramming”.
E.g. Dicor: crystalline mica: 55 vol%
Empress 2: lithium disilicate : 70 vol%
18. 18
No glassy components, atoms are densely
packed, regular network: Crack propagation
difficult.
Tougher and stronger than glassy ceramics.
Difficult to process, CAD-CAM.
Relatively opaque, core substructure.
E.g. Aluminum oxide, partially stabilized Zirconia.
Procera, Cercon, Lava.
19. COMPOSITION OF DENTAL
PORCELAINS:
Composition (Percentage) Use
- Feldspar 60-80% Basic glass
former
- Quartz 15-25% Filler
- Oxide 9-15% Fluxes
- Alumina 8-20% Glass former &
fluxes
-Metallic
pigments
1% Color matching
- Kaolin 3-5% Binder
21. Individual Components
Potash feldspar - K2O Al2O36SiO2
Soda feldspar - Na2O Al2O3 6 SiO2
Silica – SiO2
Crystalline quartz
Crystalline cristobalite
Crystalline tridymite
Non-crystalline fused silica- it acts as a
refractory skeleton provides strength and
hardness.
22. Glass modifiers: Boric oxide B2O3
Function:
•Lowers fusion temperature
•Increases flow of porcelain
•Removes impurities
•Help to produce dental porcelain with
different firing temperature
•Acts as a flux, by interrupting the
integrity of the silica network.
23. Kaolin:
•Acts as a binder
•Also imparts opacity
Alumina: Forms a network in conjunction with silica.
Alters softening viscosity.
Metallic Pigments: Pigment oxides
•Help to obtain various shades needed to stimulate natural
teeth.
Brown - Iron or nickel oxide
Green - Copper oxide
Yellow brown - Titanium oxide
Blue - Cobalt oxide
Pink - Chromium tin or chroma
•Opacity is achieved by addition of :-
Cerium oxide
Zirconium oxide
Titanium oxide
Tin oxide
26. 26
Less Reactivity ; Chemical Inertness
Brittle Fracture, Low fracture toughness,
Biocompatibility, Color Stability,
Refractory Nature, High Hardness,
Low Thermal Conductivity, Diffusibility and
Electrical Conductivity.
27. Advantages of porcelain
•High abrasion resistance
•Chemical inertness
•Excellent thermal and electrical insulators
•Excellent esthetic qualités
•Translucency
•Color stability
•Capacity of pigmentation
•Stain resistance
•Enhanced polishability
•High durable
28. Disadvantages of porcelain
•Highly brittle
•Excessive wear of opposing teeth
•High firing shrinkage
Methods used to overcome the deficiencies of
ceramics fall under 2 categories:-
•Methods of strengthening brittle materials
•Methods of designing components to minimize
stress concentration and tensile stress
30. Griffiths Flaw Crack Growth
Sintering Process
Why are Ceramics weak ?
On moisture exposure crack growth is accelerated
1. Brittle – Covalent bonds
2. Inherent flaws
3. > # in moist environment
31. Methods of Strengthening:-
•Development of residual compressive stresses within the
surface of the material.
•Interruption of crack propagation.
•Minimizing tensile stresses
•Avoiding stress concentration
1) Development of residual stresses:
Strengthening is gained by virtue of fact that these residual
stresses must be first be negated by developing tensile
stresses before any net tensile stress develops.
. Principle:
Strengthening is gained by the fact that the residual
stresses must be first negated by the developing tensile
stress before any net tensile stress develops.
E.g. Normal tensile strength : + 60 MPa
Residual comp. stress : - 40 MPa
Total tensile stress to induce fracture: + 100 MP
32. Methods:
1) Ion-exchange: (Chemical Tempering)
Involves exchange of large potassium ions for the
smaller sodium ions.
•Sodium containing glass articles is placed in a bath of
molten potassium nitrate.
•The potassium ion is 35% larger than sodium ion.
•Squeezing of the potassium ions into the place of sodium
ions creates a large residual compressive stress
33. 2.Thermal Tempering:-
Most common methods.
•Thermal tempering creates residual stresses by rapidly
cooling (quenching). The surface of object while it is hot
and in the softened (molten) state.
•This rapid cooling produces a skin of rigid glass
surrounding a soft (molten core).
•As molten core solidifies it tends to shrink, creates
residual tensile stresses within the outer surface.
Mismatch Coefficient of Thermal Expansion:-
•The metal and the porcelain used for the restoration are
designed with slight mismatch in their co-efficient of
thermal expansion.
•The coefficient of thermal expansion for metals is more
than porcelain thus the metal contacts more than the
porcelain on cooling provides additional strength.
34. Interruption of Crack Propagation:
Methods: Dispersion a crystalline phase
•Aluminous Porcelains (PJC): Alumina which is
a tough crystalline material is added to a glass
in the particulate form, the glass is toughened
as the cracks cannot penetrate the alumina
particles.
•Dicor Castable Glass Ceramics): Dicor utilizes
inhibition of crack prepagation by the growth of
mica crystals in the ceramic as a result of heat
treatment of the ceramic. Mica crystals in situ
interrupt crack propagation their by
strengthening the restoration.
.
35. Transformation Toughening:
•New technique of strengthening glasses. Strengthening
glasses involves the incorporation of crystalline material
that is capable of undergoing a change in crystal
structure when placed under stress.
•The crystalline material partially stabilized Zirconia.
The energy required for the transformation of is taken
from the energy that allows to crack to propagate
•Involves transformation of ZrO2 from a TETRAGONAL
phase to a MONOCLINIC phase at the tips of cracks that
are in the region of tensile stress.
37. Designed in such a way to overcome weakness.
To avoid exposure of the ceramic to high tensile
stresses.
To avoid stress concentration at sharp angles.
Minimizing Tensile Stresses:
High tensile stresses
Posterior segment of mouth
Deep overbite in the anterior region
A ductile metal coping prevents the formation of Tensile
stresses in the porcelain and prevents it failure.
Reducing Stress Raisers:
Stress raisers are discontinuities in ceramic
structures and in the brittle materials that cause stress
concentration.
38. Methods of strengthening brittle materials
1.Ion exchange
2.Thermal tempering
3.Thermal compatiability
Minimise stress concentration
1. Reducing stress raisers
2. Minimise tensile stresses
Residual compressive
stresses
Interruption of crack
propagation
Addition of
dispersion phase
Change in crystalline
structure
Particle stabilized
zirconia
Toughness of
particle
Al, dicor
40. 2 Options
1. Strong Core ( Unaesthetic )
Layered with Veneering Porcelain
2. Esthetic as well as
strong Core
41. Coping are prepared by
Electrodeposition of metal on duplicate die
Burnishing & heat treating metal foil on a die
Cad – cam
Casting pure metal by lost wax tecnique
Bonding of metal to ceramic, the ceramic must
have :
Fusion temp well above its sintering temp
Co efficient of thermal contraction closely matched to
that of the alloys.
Metal oxide on the metal is necessary for bonding
42. Porcelain condensation
Careful cleaning metal frame work and thin layer of
opaque porcelain is applied and baked.
Dentin porcelain powder in the shade selected for
body/dentine portion.
Porcelain is supplied in powder & mixed with water and
condensed into desired.
To achieve thorough condensation, 3 methods are used
Mild vibration
Cleaned excess water by tissue paper
Use brush to add dry powder to absorb excess water.
43.
44. Firing/ Sintering of porcelain
Porcelain restoration are fired either by temperature
control alone or temperature or time control.
Sintering is defined as a process of heating without
melting closely packed particles to form a cohert mass
by inter-particle bonding and sufficient diffusion to
decrease the surface area and increase the density of
the structure.
45. The aim of glazing is to seal the open pores in the
surface of a fired porcelain. Dental glazes are composed
of colorless glass powder, applied to the fired crown
surface, so as to produce a glossy surface.
Porcelain is cleaned and necessary stains applied.
Glazing is short, when glazing temperature is reached,
on thin glassy film (glaze) is formed by viscous flow on
the porcelain surface.
Fracture resistance of glazed porcelain is greater than
unglazed porcelain
47. CAPTEK SYSTEM : ( capillary casting technique)
Duplicated refractory die
Metal
impregnated
wax sheet
Final coping
Porcelain veneering
CAPTEK is the answer for the most challenging situation because of
its strength and excellent esthetics
Captek G-97.5 gold,
2.5 silver
Pt-pd
48. (HELIO FORM HF 600 SYSTEM)
Equipment Polyurethane dies
Completed restorations
ELECTRO FORMED
49. 1965 Mc lean and Hughes
40 t0 50 wt% of Al2O3
Flexural strength 131 Mpa
Platinum foil technique
ALUMINOUS CORE PORCELAIN
Finished CoresMaster model
with dies Platinum foil
adapted to die
(Hi-Ceram)
50. Unsintered CrownsDentin Ceramic
additions
Finished Crowns on dies
Post-Cementation
Mc lean 1979 Five year failure rate 2% for anteriors 15% for posteriors
Large sintering shrinkage
Seiber et al 1981 :light reflection better than porcelain fused to metal
51. IN-CERAM
A process used to form green ceramic shape by applying a
slurry of ceramic particles and water or a special liquid to a porous
substrate Such as a die material, there by allowing capillary action
to remove water and densify the mass of deposited particles
Flexural
strength
350 MPa 500 MPa 700 MPa
In-ceram
Alumina
In-ceram
Spinell
In-ceram
Zirconia
Crack deflection is the main Phenomenon
( Slip casting technique )
Saadoun 1989
54. Application of body
and incisal porcelain
Postoperative veiw of
In-Ceram crowns
Finished In-Ceram
copings
(Air abraded)
Finished crowns
Preoperative veiw
Probster et al : Strength of In-Ceram > IPS Empress < PFM
56. CASTABLE CERAMICS
A glass ceramic material that combines the properties of a
restorative material for function with the capability to be cast
using the lost wax process
Di-Cor
Cerestore
IPS Empress
New types
Cera pearl
Canasite glass ceramic
Optimal pressable ceramic
Olympus castable ceramics
Castable phosphate glass ceramic
1968 Mc Culloch
57. DI-COR
Non porous, homogenous, microstructure with uniform
crystal size which is derived from the controlled growth of crystals
within an amorphous matrix of glass.
Ancestry Fredrick carter corning glass works
Composition : SiO2, K2O and MgO, MgF2, Al2O3, ZrO2 and
flourescing agent – TETRA SILICIC FLUOROMICA GLASS
CERAMIC.
Mica crystals Feldspathic porcelain
59. Ceramming Ceramming oven Crystallised glass coping
Conventional porcelain application & Firing Finished crown
Cerramming done from room temparature- 1900 f for 1½ hrs and
sustained for 6hrs inorder to form tetra silicic flouro mica crystals
60. Properties :
Flexural strength 81 6.8 Mpa
Marginal adaptation :
Weaver et al 1988 – conducted a study on 10 dicor crowns
Marginal opening – 57 9 µm
Due to less seating pressure, increase in density of ceramic
after ceramming.
Biocompatibility :
Less bacterial counts
Reason : smooth surface, low surface tension, flouride content,
Low thermal conductivity
61. Esthetics :
Gross man and adiar : Hue and chroma of metal ceramics
and castable ceramics matched natural teeth.
Value of only castable ceramics matched natural teeth.
Presence of mica crystals scatter light similar to enamel rods.
Cementation :
zinc phosphate, light activated urethane resin
Bailey&Bennet 1988 etching with ammonium biflouride for 2 min
62. Survival rate :
Kenneth et al 1999 14yr study
Crowns 82%
Cores 100%
Inlay and onlay 90%
Partial coverage 92%
Posterior 70% anterior 82.7% Expenstein et al 2000
64. TECHNIQUE :
Tooth preparation :
1.25 – 1.5 mm (Labial-lingual,interproximal)
1.5 – 2.mm (occlusal)
900 (full shoulder ) Conventional wax-up on
heat stable Epoxy dies
Investing Ceramic pellet in flask for pressing
160 c
65. Ceramic injected into mold
Plaster removal from
pressed coping
Refining green state
coping
Coping on master die fired
at 1300 c
66. Tooth preparation and impression
Cerestore epoxy die
Wax up and invest with master die
Boil out
Heat flask to 1800C
Transfer mould ceramic into lost wax
cavity directly on master die
Retrieve master die
Refine coping, add veneer porcelain
67. Properties :
• Flexural strength : 225 Mpa
• Fit : exceptional fit because of direct moulding process.
• Low thermal conductivity
• Radio density similar to enamel
• Biocompatible
69. LEUCITE REINFORCED IPS EMPRESS
Feldspar Leucite + glass phase
In congruent
Melting
Resistance to crack propagation
Pre cerammed Ingots
Processing :
70. Wax pattern
Ceramic ingot &
Al plunger
Investing
Pressing under vaccum
11500C
Sprue removal
Edward B Goldin 2005 compared leucite IPS Empress with PFM
Mean marginal discrepancy 94 + 41 PFM
81 +25 IPS
Burn out 8500 C
26 min hold
71. Properties :
Flexural strength : 117.3 - 167 Mpa
Ion exchange method used to strengthen IPS empress (KnO3)
204 Mpa 11 hr immersion
Esthetics : high esthetic value
Clinical survival : Deniz G in 2002
95% survival 2-4 years
Marginal adaptation : Shearer et al in 1996 : better marginal adaptation
with hot pressed ceramics than aluminous core material.
72. LITHIUM DISILICATE REINFORCED
Base glass Melted with raw materials1400 to 16000C
Poured into water
Glass grains 20-30 microns Cylindrical ingots obtained
Pressed into mold at 9000Cin
Vaccum for 10 minute
Automatic molding cycle 200
to 300 N
Manufacturing :
Mainly for post and core purposes Flexural strength :164+26 Mpa
Cosmo glass Ceramic
74. CERAPEARL
CaO – P2O5 – MgO – SiO2 – Hobo and Kyocera bioceram group 1985
Crystalline microstructure similar to natural enamel
Mechanical properties superior to enamel
Laboratory steps :
Tooth preparation, die preparation
Wax patterns
2 stage burn out (8000C final temperature)
Melted ceramic at 14600C casted under vaccum
(special ring liners required {1.2mm} )
Reheating -870 c – Crystalline oxy apatite - moisture exposure – hydroxy apatite
75. Clinical success : Nahara Y et al (1991)
2 year success rate – 100%
Burn out chamber Centrifugal casting machine
Ceramming unit and shading
A) Pretreatment
B) 3 months after
cementation
C) 2 yrs post-
cementation
Mainly indicated for inlays and full crowns
76. FLUORCANASITE
Multiple chain silicate glass ceramic that exhibits high strength
and fracture toughness.
Al2O3 – CaO – F – K2O – SiO2
CaF2 Nucleating agent
Procedure :
Wax pattern invested in Crystoballite investment
Burn out at 7000C Heat soak for 0.5 hours
Temperature drop to 5900C
Centrifugal casting machine used at 12000C
Direct ceramming Heat soaking
5200C
Heating at
8600C CANASITE
77. Properties :
Flexural strength : 116 12 MPa
Johnson et al in 2000 : Biaxial flexural strength 280.4 Mpa
Fracture toughness : 660 Mpa
78. OLYMPUS CASTABLE CERAMIC
It consists of glass phase of LiO2 – Na2O – ZnO – Al2O3 –
TiO2 – SiO2 and crystalline phase of Na Mg3 (SiO3AlO10) F2 and
Li2OAl2O3 – 4SiO2
Procedure :
Burn out 3000C 30 min 8000C for 30 min
Casting at 5500C Ceramming at 7500C for 2 hrs.
Shimida et al 2000 : prior to cementation : Silane coupling agent +Primer
increases bond strength
79. OPTIMAL PRESSABLE CERAMIC
1996 Janeric Pentron Company
Optimally pressable
ceramic system
Glass ceramic with leucite phase
Crystalline compacted ceramic
on heating
Die fabrication Wax pattern
80. Sprued wax patterns ready for
investing
Paper casting ring is closed from top
as the material sets
Paper casting ring is peeled Investment placed in burnout furnace
850 c -90min
81. Colored pellets
used for casting
Hot mold placed in optimal
auto press machine
Pressed molds cooled
to room temperature
mold is scored and broken apart Recovering of casting
Removal of remaining investment
1150 c -20min hold
82. CASTABLE PHOSPHATE GLASS CERAMIC
Contains :
Natural phosphate as natural teeth
Marketed as ‘Crys-Cera’
84. CEREC SYSTEMS
Materials involved :
Vita mart II, Dicor MGC and Pro Cad
Sanidine
KAlSi3O8
Mica
crystals 70%
Leucite containing
ceramic
CERamic REConstruction,
Optical scanning
85. The compact, mobile unit consists of three components: a
small camera, a computer screen and a three – axis – of – rotation
milling machine.
86. The cad/cam cerec system has evolved from the: cerec-
1,which fabricated only marginally fitting single and dual surface
ceramic inlays.
Cerec-2,which showed advances in computing, upgraded
software and expanded form of grinding technique.
87. Cerec-3 that can design well-fitting inlays, onlays, crowns,
veneers etc., in a single visit.
89. CELAY SYSTEM
Uses copy milling technique
Resin pattern fabricated directly on master die and pattern is used
for milling porcelain restorations
Jacot et al 1998 : in ceram blanks in celay system.
Inlay pattern mounted
(copy side)
Copy milling pattern out
of ceramic material
(milling side)
Sorenson 1994 : marginal fit of CELAY > CEREC
90. PROCERA SYSTEM
Dies are enlarged to compensate for sintering shrinkage.
Scanning
Milling machine
Shape on computer screen
Contact scanner
96. Porcelain laminate veneers
Laminate : Is an extremely thin shell of porcelain applied directly to tooth structure
1930-1940 Charles Pincus used thin porcelain shells, denture adhesives were used
1970-1980 Composite resin laminate veneers Monochromatic appearance
Staining
Loss of luster
97. 1980s Bonding porcelain to etched surfaces
Hsu et al 1985 - Mechanical retention increased by etching porcelain
Shear bond strength of etched 4 > Unetched
Calamia et al 1984 - Application of silane coupling agent-
Improved bond strength
*min thickness of laminate: 0.3 – 0.5 mm
98. All ceramic F P D
Two part build up Bulk in lingual connector region
Pre (PFM)
Post (All Ceramic)3 unit FPD
99. DC – ZIRKON technique : Vult von steyern et al in 2004
< 5% flaws, flexural strength : 900 Mpa
Used for posterior FPD’s
DC-Zirkon Blocks Milled Block
Tried on Working Cast
100. All ceramic Resin bonded fixed partial dentures
Introduced 1986-1988 Ibsen et al and Garber et al
Matthias kern 2005 :Cantilever resin bonded FPD
101. Ceramic veneer F P D
Ceramic inlay metal reinforced F P D
Ceramic veneer / Composite substructure F P D
102. All ceramic Posts
1993 Luthy et al – Post made of TZP-ZrO2
High flexural strength 1400 Mpa
1994 Sandhaus – Zirconia post with composite core
1995 Akagawa et al - Castable ceramic attached to zirconia post
1997 Ivoclar – introduced Ceramic core directly pressed onto Zirconia post
IPS Empress Cosmo ingot
Direct method
Indirect method