DENTAL CERAMICS,DEFINITION,CLASSIFICATION,HISTORY,METAL CERAMICS

1. Namitha.A.P
1st year MDS
Dept.of Prosthodontics

2. CONTENTS
Introduction
Definition
History of dental ceramics
Advantages and disadvantages
Structure
Basic constituents
Classification
Benefits and Drawbacks of metal ceramic
restorations
2

3. Metal Ceramic Systems
Composition
Fabrication of metal ceramic prosthesis
Cast metal for metal ceramic prostheses
Technical aspects of metal ceramic products
A. Cast metal coping and frameworks
B. Creep/sag
C. Bonding of porcelain to metal
D. Glazes and stain ceramics
Other metal ceramic systems
Methods of Strengthening Ceramics
3

4. All Ceramic Systems
Aluminous Porcelain
Effect of Design on Fracture Susceptibility of Metal-
Ceramic and All-Ceramic Restorations
Glass-Ceramics
Hot-Isostatically Pressed(HIP) Glass Ceramics
Glass Infiltrated Core Ceramics
Alumina Core Ceramic
Yttria-Stabilised Zirconia
Zirconia Toughened Alumina(ZTA)
Dispersion Strengthening and Toughening
Flourapatite Glass Ceramic
4

5. CAD-CAM Processing of Ceramics
Abrasiveness of Dental Ceramics
Clinical Performance of All-Ceramic Restorations
Chemical Attack of Glass-Phase Ceramics by Acidulated
Phosphate Fluoride
Porcelain Denture Teeth
Factors Affecting the Color and Appearance of Ceramics
Ceramic Veneers,Inlays,and Onlays
Critical Observation and Analysis of Fractures
Principles Governing the Selection of Dental Ceramics
Conclusion
References
5

6. INTRODUCTION
•Keramos
•Burned
earth
•Clay
6

7. Search for an ideal restorative
material!
Why ceramics? Challenges?!!
1. Biocompatible
2. Long term color stability
3. Chemical durability
4. Wear resistance
5. Ability to be formed into
precise shapes
1. Costly processing
equipments
2. Specialised training for lab
technicians
7

8. An inorganic compound with nonmetallic properties
typically consisting of oxygen and one or more
metallic or semi metallic elements( Eg: Aluminium,
calcium, lithium, magnesium, potassium, silicon,
sodium, tin, titanium and zirconium) that is
formulated to produce the whole or part of a ceramic
based prosthesis (GPT 7 Anusavice).
Definition
8

9. A journey through time!!!
9

10. Stone age>10,000 years ago!
• Craftman used rocks shaped in to
tools and artifacts by flaking
• Stone chips fractured away from
surface of hard,fine
grained/amorphous rocks
1. Chert
2. Flints
3. Ignimbrite
4. Indurated shale
5. Lava
6. Obsidian
7. Quartz
8. Silicified lime stone
6
1
8
7
2
5
3
4
7
10

11. Etruscans used teeth of
ivory and bone that were
held in place by a gold
framework. These were
obtained from hippopotamus
or elephants and were used
for many years thereafter.
•Animal bone
•Ivory from hippopotamus
and elephant
•Human teeth sold by poor
•Teeth obtained from dead
700 BC
11

12. Pierre Fauchard
(1728)Chinese (1000AD)
• First to suggest the
use of porcelain in
dentistry
12
•Porcelain
developed by
chinese

13. Pfaff(Germany)
1756
• Technique to make impression of mouth using
plaster of paris
13

14. John Greenwood
(1789)
• carved teeth from hippo ivory for complete
dentures he made for George Washington.
14

15. Dubois and Duchateau
(1774 A.D)
• French dentist Nicholas Dubois de Chemant
and his assistant Alexis Duchateau made the
first successful porcelain dentures for
Duchateau being tired of his stained and
malodorous ivory denture.
15

16. • 1774:Duchateau produced an
improved version of mineral
paste teeth
• Introduced to England by De
Chemant
• This baked compound was not
used to produce individual
teeth because there is no
effective way to attach the
teeth to denture base material
• •1789 Dubois continuously
improved porcelain
formulations and was awarded
French and British patents.
16

17. Guiseppangelo Fonzi (Italian dentist)
1808
• Practiced in paris
• Individual porcelain teeth
posterior porcelain blocks
originally dubbed as
‘terro-metallic teeth’
‘french bean teeth’
• Higher quality of
porcelain than chemant
• platinum attachment
mechanism
• Described as “little better
than crockery”
17

18. • 1817: Antoine
Plantou(French
dentist) : porcelain
teeth to America
• 1822:Peale,an artist
developed a baking
process in philadelphia
for these teeth
• 1837:ClaudiusAsh:an
improved version of
porcelain teeth
18

19. • 1825: Samuel Stockton: produces first
porcelain teeth in the US.
1839:invention of vulcanised rubber
allowed porcelain denture teeth to be used
effectively in a denture base.
• 1844: Stockton’s nephew found SS
White company : mass production of
porcelain teeth.
1903:Dr. Charles Land : introduced
first ceramic crown using platinum foil
matrix and high-fusing feldspathic
porcelain.

20. • Early 1960s- Weinstein et al introduced porcelain fused to
metal restoration(PFM)
• 1963: First commercial porcelain :Vita Zahnfabrik was developed.
• 1965 – aluminium porcelain was introduced by McLean and Huges
• 1968 – MacCulloch introduced the use of glass ceramic in
dentistry
• 1983 – the concept of bonding composite resin to acid-etched
porcelain was first reported by Simonsen and Calamia
• 1983 – Horn reported the successful cementation of porcelain
veeners using adhesive cements

21. • 1983-84 – the first castable
glass ceramic was introduced
by Grossman and Adair called
DICOR (tetrasilicic flouromica
crystals in glass matrix)
• 1985 – CAD/CAM technique
were developed.
• 1988- cerec1 system was
introduced.
• 1989 – Sadoun developed the
first slip cast alumina ceramic
called Inceram alumina.
21

22. • 1989: Wohlwend and Scharer : Pressable
ceramic systems.
• 1991 : Celay copy milling system.
• 1992: Ultralow fusing ceramic Duceram LFC
• Early 1990s- IPS Empress was developed containing
approx 34vol% leucite
• 1994 -CEREC II
• Late 1990s- IPS Empress 2 was developed containing
approx 70vol% of Lithia disilicate crystals.

23. Advantages
• Resistant to corrosion
• Chemical inertness
• Remain stable over long
time periods.
• Biocompatible
• High hardness
• Resilient
• Potential for matching
appearance of natural teeth
• Refractory nature
• Thermal insulating
properties(low thermal
conductivity and diffusivity)
• Freedom from galvanic
effects(low electrical
conductivity)
23

24. Disadvantages
• Susceptibility to tensile
fracture
• Brittleness
• Low to moderate strength
and fracture toughness
• Poor ductility/elongation
• Flexed easily when
heated and
cooled(Thermal shock)
24

25. 25

26. • Brittle fracture
• Plastic deformation
26

27. Structure
27
GLASS
PHASE
CRYSTAL
PHASE
CERAMIC

28. 28

29. 29

30. Feldspathic porcelain
Glassy/Vitreous/Matrix phase
• Acts as matrix
• Feldspars are mixture of
Anhydrated alumino-silicates
of both
• Potash feldspar = K2O. Al2O3.
6 SiO2 A
• Soda feldspar = Na2O. Al2O3.
6 SiO2
• Increasing the amount of
glassy phase lowers the
resistance to crack
propagation but increases
translucency
Crystalline/Mineral phase
• Dispersed within matrix
• Mineral phase including
silica and other oxides
• Improve strength and other
properties
• Eg.alumina,spinel,zirconia
ceramic restorations have
increased amounts of
crystalline phase (between
35% and 90%) for better
mechanical properties
30

31. 31

32. COMPOSITION
Feldspar
60 to 80%
basic glass former
Kaolin
3 to 5 %
binder
Quartz
15 to 25%
filler
Alumina
8 to 20 %
glass former and flux
Oxides of sodium,potassium
and calcium
9 to 15%
fluxes
Metal pigments
<1%
colour matching

33. 33

34. Feldspar
SiO2 MATRIX-52-65%
Al2O3-ALUMINA-11-20%
K2O-POTASH-10-15%
Na2O-SODA-4-15%
OTHER ADDITIVES
By weight. 34

35. Feldspar(Basic glass former)
• Naturally occurring mineral
• Also known as Albite
• Most of the components
needed to make dental
porcelain are present in it
• When fused at high
temperature it forms
feldspathic glass containing
potash feldspar/soda
feldspar
• Quite colorless and
transparent
35

36. Kaolin(Binder)
• White clay like material
(hydrated aluminum
silicate).
• Acts as a binder
• Gives opacity to the
mass.
• Some manufacturers
use sugar or starch
instead of kaolin.
36

37. SILICA
CRYSTALLINE
QUARTZ
NON
CRYSTALLINE
FUSED SILICA
CRYSTALLINE
TRIDYMITE
CRYSTALLINE
CRISTOBALITE
37

38. Quartz(Filler)
• Form of silica.
• Ground quartz acts as a
refractory skeleton
• Provides strength and
hardness to porcelain
during firing.
• It remains relatively
unchanged during and
after firing
38

39. Alumina
• Replaces some of the
silica in the glass
network.
• Strength and opacity
• It alters the softening
point and increases the
viscosity of porcelain
during firing.
39

40. Glass modifiers/Fluxes
Too high modifier concentration
glass may crystallize (devitrify) during porcelain firing
operations
reduces the chemical durability
.Three-dimensional silica network contains many linear chains of silica tetrahedra that are able to move easily at lower temperatures than the
atoms that are locked into the three-dimensional structure of silica tetrahedra.
Increases thermal expansionLower softening /fusion temperature
increased fluidity (decreased
viscosity)
Bonds between the silica tetrahedra can be broken by the addition of alkali metal ions such as sodium, potassium, and calcium
These ions are associated with the oxygen atoms at the
corners of the tetrahedra
Interruption of oxygen silicon bonds
Sintering temperature of crystalline silica is too high to use as a veneer on dental cast alloys
Alloys would melt
Coefficient of thermal contraction of crystalline silica is too
low for alloys
40

41. Color Modifiers
Metallic oxide colour
Titanium oxide yellowish brown
Nickel oxide Brown
Copper oxide Green
Cobalt oxide Blue
Manganese oxide Lavender
Zirconia, alumina, silica White
41

42. METAL COMPOSITION
42

43. Requirements of the metal
1. Melting temperature higher than the
porcelain firing temperature
2. Able to form an oxide layer that provides the
chemical bond to porcelain
3. Coefficient of thermal expansion a little bit
higher than that of porcelain
4. No greening effect on the porcelain color
5. High elastic modulus
43

44. CLASSIFICATION
1.Based on use/indications
Anterior crowns
Posterior crowns
Inlays
Onlays
Veneers
Post and cores
FPDs
Stain ceramic
Glaze ceramic.
44

45. 2.Composition
3.Principal crystal
phase and /or matrix
phase
• Pure alumina
• Pure zirconia
• Silica glass
• Leucite based glass
• Lithia based glass
• Silica glass
• Leucite based
feldspathic porcelain
• Leucite based glass
ceramic
• Aluminous porcelain
• Alumina
• Glass infused alumina
• Glass infused spinel
• Glass infused
alumina/zirconia 45

46. 4) Processing method:
• Sintering
• Partial sintering
• Glass infiltration
• CAD-CAM
• Copy milling
• Condensation
• Heat pressing
• Casting
• Slip-casting
46

47. VENEERED AND STAINED
• Traditional metal-
ceramic restorations,
some aluminous
porcelains (Vitadur-N,
Vitadur Alpha, Hi-
Ceram), and pure
alumina ceramic
(Procera AllCeram) are
condensed by vibration
and sintered at high
temperatures.
47

48. HOT PRESSED CERAMICS
• (IPS Empress, IPS Empress 2, Finesse All-
Ceramic, and OPC-3G) are heated, injected
under pressure into a mold, and then
veneered.
48

49. CAST AND CERAMMED CROWNS
• Glass-ceramic
• Made using the lost-
wax technique.
• The glass was cast into
a mold, heat-treated to
form a glassceramic,
and colored with
shading porcelain and
surface stains.
49

50. SLIP CAST CERAMICS
• In-Ceram
• In-Ceram Spinell
• In-Ceram Zirconia
• A slurry of liquid and particles
of alumina, magnesia-alumina
silicate (spinel), or zirconia and
alumina are placed on a dry
refractory die that draws out the
water from the slurry.
• The slip-cast deposit is sintered
on this die
• coated with a slurry of a glass-
phase layer.
• During firing, the glass melts
and infiltrates the porous
ceramic core.
• Translucent porcelain veneers
are then fired onto the core to
provide final contour and color 50

51. CAD-CAM
• The ceramic block materials (Dicor MGC, VITA
Cerec Mk I, and VITA Cerec Mk II) are shaped
into inlays, onlays, or crowns using a
CAD/CAM system (Cerec).
• These blocks can also be used in copy-milling
devices (Celay) that mill or machine blocks
into core shapes
51

52. 52

53. 5) Firing temperature:
53

54. 6.Microstructure
• Glass
• Crystalline
• Crystal-containing glass
8.Fracture resistance
1. Low
2. Medium
3. High
7.Translucency
• Opaque
• Translucent
• Transparent
9.Abrasiveness
• (comparison relative to
restorstion against tooth
enamel).
54

55. 10.It’s function within ceramics
• Core ceramics-supports and reinforces the
restoration
• Opaquer ceramics-masks or hides the metal
• Veneering ceramics
1. Body/dentin- dentin portion of natural teeth
2. Incisal - enamel portion of natural teeth
3. Gingival –gingival portion of teeth
• Translucent-translucent incisal enamel
• Stains
• Glazes
55

56. Applications of ceramics in dentistry
56

58. Metal ceramic/PFM(porcelain
fused to metal
All ceramic
58

59. METAL CARAMICS
Advantages
• High overall survival
percentage
• Low fracture rate
• Less removal of tooth
structure
• Less wear of antagonist
enamel
• Better marginal fit
Disadvantages
• Potential for metal allergy
• Poor esthetics(Can not be
used when when a
relatively high degree of
translucency is desired.)
• metal framework and lack
of translucency sometimes
shows through gingiva
resulting in dark margins
59

60. Mandibular teeth abraded by
opposing porcelain surfaces
60

61. Metal ceramic system
61

62. Types of Metal Ceramic Systems
1. Cast metal ceramic restorations
Cast noble metal alloys (feldspathic porcelain)
Cast base metal alloys (feldspathic porcelain)
Cast titanium (ultra low fusing porcelain)
2. Swaged metal ceramic restorations
Gold alloy foil coping (Renaissance, Captek)
Bonded platinum foil coping.
62

63. COMPOSITION OF METAL CERAMIC
• Higher alkali content
• The opaquer powder -
high content of
opacifiers.
• Glazes - Higher
concentration of glass
modifiers like soda,
potash and boric oxide.
DENTIN
PORCELAIN
ENAMEL
PORCELAIN
Silica (SiO2) 59.2 63.5
Soda (Na2O) 4.8 5
Alumina
(Al2O3)
18.5 18.9
Potash
(K2O)
11.8 2.3
Boric oxide
(B2O3)
4.6 0.12
Zinc oxide
(ZnO)
0.58 0.11
Zirconium
oxide (ZrO2)
0.39 0.13
A sample percentage composition
of porcelain powder for metal
ceramics
63

64. Supplied as
1. Enamel porcelain powders in various shades (in bottles)
2. Dentin porcelain powders in various shades (in bottles)
3. Liquid for mixing enamel, dentin, gingival and transparent
4. Opaquer powders in various shades/ together with a liquid
for mixing
5. Gingival porcelain powder in various shades
6. Transparent porcelain powder
7. A variety of stain (color) powders
8. Glaze powder
9. Special liquid for mixing stains and glaze.
64

65. Manipulation and technical
considerations
Condensation/packing
Pre-heating/drying
Sintering /firing
Surface treatments
Porcelain cooling
• Conventional powder/slurry
technique
65

66. Condensation/packing
• Process of packing the
powder particles together
and removing excess water
Benefits
1. Lower firing shrinkage
2. Less porosity (Improves
substructure of the
porcelain & dispense
trapped air )
3. Improved strength and
density
4. Remove excess water
5. Enhanced surface texture
66

67. Techniques
1. Vibration-tapping/running
serrated instrument on the
forceps holding the metal
frame
2. Ultrasonic vibrators
3. Spatulation-a small spatula
to apply and smoothen
wet porcelain
4. Dry powder-placed on the
opposite side of wet
increment.water moves
towards the dry powder
pulling wet particles
together
67

68. •Advantages of ultrasonic
condensation
• Reduces the fluid content of
layered ceramics; resulting
in denser and more vibrant
porcelain mass.
• Enhances translucency and
the shade qualities of the
fired ceramic.
• Shrinkage can be reduced to
below 5%!
• Time-saving as it reduces
the number of
compensatory firing cycles
68

69. CONDENSATION STEPS
1.Build up of cervical
porcelain
2.Build up of body
porcelain
3.Cut back
4.Build up of enamel
porcelain
69

70. Dentin
• Pink powder+distilled
water/supplied liquid
• Glass spatula should be
used
• The main bulk of tooth
• A portion of the dentin in
the incisal area is cut back
for enamel porcelain.
Enamel
• White powder
• build the restoration
• Transparent porcelains used
near incisal edges
Gingival porcelain
• More darker cervical
portion
• (gingival/neck dentin)
70

71. • Return to furnace for sintering
• Additions in deficient areas
• Each additional firing is done at lower
temperature
71

72. Pre-heating
• Placing the porcelain object
on a tray in front of/below
the muffle of a preheated
furnace
• at 650C for 5min for low
fusing porcelain
• at 480C for 8min for high
fusing porcelains till
reaching the green or
leathery state.
Significance of pre-heating stage:
• Removal of excess water
allowing the porcelain object
to gain its green strength.
• Preventing sudden production
of steam that could result in
voids or fractures.
• Ceramic particles held
together in the “green state”
after all liquid has been dried
off
72

73. Pre- heating
73

74. Sintering procedure/firing
• The purpose of firing is to sinter the particles of
powder together properly for a specific time and
temperature combination to form the prosthesis
• The thermochemical reactions between the
porcelain powder components are virtually
completed during the original manufacturing
process. Thus. Some chemical reactions occur
during prolonged firing times or multiple firings
74

75. Sintering procedure/firing
The initial firing temperature
• The voids are occupied by
the atmosphere of the
furnace.
• As the sintering of the
particles begins, the
porcelain particles bond at
their points of contact.
As temperature is raised
• The sintered glass gradually
flows to fill up the air
spaces.
• The particles fuse together
by sintering forming a
continuous mass, this
results in a decrease in
volume referred to as firing
shrinkage
75

76. With progression of firing
• The gaps between particles
become porosities. The
viscosity of the glass is low
enough for it to flow due to
its own surface tension. The
result is that the porosity
voids will gradually become
rounded as firing proceeds
The final firing stage
• The voids slowly rise to free
surfaces and disappear
76

77. 77

78. Stages of porcelain maturity
•porcelain surface is quite porous porcelain grains begin to soften
and ‘tense’ at their contact points
•minimal Shrinkage
•the fired porcelain body is extremely weak or friable
Low
bisque
•Pores still exist on the surface of porcelain The flow of glass grains is
increased. As a result, any entrapped furnace atmosphere that
could not escape via the grain boundaries becomes trapped and
sphere shaped
•A definite shrinkage is evident
Medium
bisque
•shrinkage smooth porcelain surface The flow of glass grains is
further increased, thereby completely sealing the surface and
presenting smoothness to the porcelain.
•The fired porcelain body is strong and any corrections by grinding
can be made
High
bisque
78

79. Low bisque Medium
bisque
High bisque
79

80. Over firing
1.Firing at above the correct firing
temperature 2.longer firing time
1.reduce the strength due to
formation of undesirable crystal
phases at higher temperature [de-
vitrification]
2.increases the chances of slumping
[eliminate the shape we made and
leave a globule of ceramic].
Under
firing
The porcelain object will have a
chalky white color overlaying its
shade ,Because light is reflected
and scattered at boundaries
between particles and at the
surfaces of porosity
80

81. Vacuum(negative pressure) firing
• Porcelain in furnace- packed powderparticles+air
channels around
• Air pressure reduced to 1/10th by vacuum pump
• Air around particles reduced,as temperature rises
the particles sinter together
• Closed pores with in porcelain mass.
• This helps to reduce porosity
• Air inside these pores are isolated from the
furnace atmosphere
81

82. Porcelain surface treatment
Natural/auto glaze
Applied/add-on glaze
Polishing
Custom staining
82

83. Cooling
• Should be well
controlled
• slowly
• Uniformly
• Usually computer
controlled
• Rapid cooling can cause
cracks
• Induce stresses and
weakens ceramic
83

84. If it cools too slowly
• Crystals form within the
glass body which will
degrade its optical
properties, turning if from a
clear glass into a cloudy
one. Devitrification.
[annealing]
if it is cooled too quickly
• Stress build up in the glass.
• To reduce the stresses ,it is
kept near the glass transition
temperature (its solidus) for a
long time so that the atoms in
the glass can rearrange just
enough to relieve the stress.
• When most of the stress has
been eliminated, the finished
glass is finally allowed to cool
to room temperature
84

85. 1.Construction of the cast metal
copings and framework
• Can be produced by
1. Casting of molten metal
2. CAD-CAM Machining
3. Electrolytic deposition
techniques
4. Swaged metal processes
Most common method is
melting and casting.
• A wax pattern of
restoration constructed
• Cast in metal
• High melting temperature
of alloys-phosphate
bonded investment
85

86. 2.Metal preparation
• Clean metal surface-
essential for good bonding
• Oil from fingers and other
sources such as airlines –
possible contaminant
• Cleanse surface
• Finish with clean ceramic
bonded stones/sintered
diamonds
• Final sandblasting with high
purity alumina
3.Degassing and oxidizing
• Heat in porcelain furnace to
burn off any impurities to
the form thin oxide layer.
• Degas the interior structure
of alloy
• Eg.Olympia (Heraeus
Kulzer), a gold-palladium,
silver-free alloy, is heated in
the porcelain furnace to a
temperature of 1038 °C
86

87. 4.Opaqer
• Dense yellowish white powder+special liquid
• Mask/cover the metal frame and prevent it
from being visible
• Bond the veneering porcelains to the
underlying frame
87

88. • Condensed on the oxidized surface at a thickness of approximately
0.3 mm
• Fired to its sintering temperature.
• Translucent porcelain is applied
• Tooth form is created.
• Porcelain powder is applied by the condensation methods
• The unit is again fired.
• Several cycles of porcelain application and firing may be necessary
to complete the restoration.
• A final glaze is then produced either by self-glazing or firing an
overglaze layer.
88

89. Creep/sag
• When an alloy is heated close
to its solidus temperature, it
may become susceptible to
flow under its own mass
• The degree of creep can be
enhanced by the size of the
prosthesis and the number of
firings that are required for
porcelain veneering.
• All metal-ceramic alloys
should have a solidus
temperature that is
significantly higher than the
sintering temperature of the
porcelain so as to minimize
creep deformation
89

90. Bonding of porcelain to metal
1.Chemical/atomic bonding
• Primary bonding mechanism
• An adherent oxide layer is
essential
1. Base metal alloys-chromic
oxide
2. Noble metal alloys-iridium
oxide
• Inadequate oxide
formation/excessive oxide
build up
Delamination of overlying
porcelain
2.Mechanical interlocking
• Principal bond in some
systems
• Infiltration (flow) of the
fused ceramic into the
surface irregularities of the
metal coping
• Sandblasting prepares metal
surface
90

91. Sand blasting
91

92. 92

93. Chemical bonding
• Ionic bond between the metal
oxide layer and the opaque
porcelain.
• Metal degassing is important
for oxide formation, removing
the surface contaminants and
greases.
• Thin oxide layer (in case of
noble alloys) provides stronger
bond than the thick one (in
case of base metal alloys)
93

94. 3.Coeff. of thermal expansion
mismatch:
• As a result of higher metal
contraction on cooling , -
The fused porcelain will be
sucked (attracted) more
strongly into the metal
surface irregularities. -
Residual compressive
stresses will developed in
and strengthen the
porcelain.
4. Application of a special
bonding agent:
• Certain metal system
(electro-forming) requires
the application of specific
bonding paste before
building-up the porcelain.
Bonding of porcelain to the
metal Coping
94

95. Durability of metal ceramic bonding
Inter atomic
bonding across the
oxide-porcelain
interface
Type and magnitude of residual
stress in the veneering ceramic
Mechanical inter
locking/inter atomic
bonding at the
inteface between
porcelain and metal
oxide
95

96. Glazing
Objectives
• Life like appearance/Esthetics
• Improves Strength and life
• Color match to adjacent teeth
or restorations
• Seal surface flaws
• Reduce stress concentrations
• Inhibits crack propagation
• Enhances Hygiene
• Reduces wear of opposing
teeth
Steps
• Restoration is tried in
mouth
• Occlusion checked
• Adjusted by grinding
• Smoothen with a fine stone
• Restoration is ready for
glazing!
96
Auto glazed veneer ceramic

97. Smooth and glossy surface to the
restoration
Over glaze
• Glaze powder+special liquid
• Applied on to restoration
• Firing temperature<that of
body porcelain
• Firing cycles does not
include vacuum
• Disadvantage-Chemical
durability less compared to
self glaze(because of the
high flux content)
Self glaze
• No separate glaze layer
• Restoration subjected to
controlled heating at fusion
temperature
• Only surface layer melts and
flows to form a vitreous layer
resembling glaze
• Disadvantage-porcelain must
be stripped completely if it is
unacceptable
97

98. Glazing
• Have adequate durability
when produced in thickness
of 50micron or more
• If dentist is adjusting the
occlusion by grinding with
diamond bur can weaken
glaze
Polishing
• Using special abrasives
• Sof-
Lex(3M,Minneapolis,MN),Fi
nishing disks (Shofu, Kyoto,
Japan) porcelain laminate
polishing kit, or other
abrasive system.
• Difficult to polish
98

99. • Even after polish/glaze
surface will breakdown
in presence of solvants
in our everyday diets
• Further degradation
during exposure of glass
phase ceramics such as
porcelain to acidulated
phosphate fluoride
99

100. Surface staining
characterisation and effects
• Stain powders + special liquid
• Applied and blended with brush
Porcelain stains and glazes
Stains-tinted glazes
Natural teeth- variety of hues and
colors
1. Intrinsic( like white flourosis
stains)
2. Acquired (like coffee,tobacco)
By staining and characterisation more
emphasis on recreating natural
look
Can include
1. Defects
2. Cracks
3. Other anomalies on enamel
100

101. 101

102. Glazes
• Colorless porcelain
• Do not contain opacifiers
• Lower fusion temperature
• Increased content of glass
modifiers
• Less chemically durable
Stains
• High concentration of color
modifiers
• Lower fusion temperature
• Increased content of glass
modifiers
• To provide individual color
variation
102

103. 103

104. Other metal ceramic systems
Swaged gold alloy foil ceramic
crowns
Bonded platinum foil ceramic
crowns/Aluminous core porcelain
104

105. Swaged gold alloy foil ceramic crowns
Renaissance and Captek
• Novel way of making a
metal frame without having
to cast it.
• Developed by Shoher and
Whiteman
• Captek(capillary casting
technique)
Advantages
• Thinner foil alloy
• Greater thickness of
ceramic
• Improved esthetics!
• Gold color of alloy
105

106. CAPTEK P CAPTEK G
• 97.5%-GOLD
• 2.5%-SILVER
• Provides characteristic gold
color
•Platinum/palladium/
gold
•Porous structure
•Serves as internal
reinforcing skeleton.
•On heating in a
furnace captek P acts
as metal sponge
draws hot liquid gold
completely into it
Final coping is a composite structure 106

107. Technique
107

108. Bonded platinum foil ceramic crowns
• Platinum foil coping
adapted on to the die
• Electrodeposition
technique-to improve
bonding and esthetics
• Thin layer of tin is
electrodeposited on to the
foil and then oxidized in a
furnace
Advantages
• Gold color enhances vitality
of porcelain thereby
esthetics
• Tin helps in chemical
bonding
• Improves wetting and
reduce porosity.
108

109. Electrodeposition Technique
• Improve both esthetics and bonding
• A layer of gold is electrodeposited on to the
metal
• Followed by a quick minimal deposition of tin
• Can be used on metals such as stainless
steel,cobalt chromium,titanium,and other non
gold and low gold alloys
109

110. Platinum matrix fabrication. A, A diamond-shaped foil is adapted to the facial surface (a cutting guide
is provided with the foil). B, Two cuts are made, one to each incisal corner, and a triangle of foil is
removed by cutting at 45 degrees toward the corners. C, The foil is folded onto the lingual surface and
burnished. D and E, It is then gathered on the lingual surface with tweezers and adapted with finger
pressure. F, The foil is trimmed to follow the lingual contour evenly. The two ends are separated, and
one is trimmed to exactly half the width of the other. G and H, The long end is folded over the short
end, and relieving cuts are made . Then the three-thickness joint is folded toward the short end. I, The
foil is adapted with a wooden point, always starting from the incisal edge and working toward the
margin. 110

111. J. A beaver-tail burnisher is used to adapt the
margin, working the foil toward the internal angle
to prevent a perforation. Better adaptation can be
achieved by swaging at this stage. The matrix is
removed with sticky wax
K. and annealed in a Bunsen flame
L.to relieve work hardening.
M. The completed platinum foil matrix.
111