5. INTRODUCTION
Dental ceramic is one of the most biological
and esthetically acceptable material in dentistry.
Ceramics are used for manufacturing artificial
teeth, pontics, facing, crowns and fixed
bridges.
Dental porcelain in this domain is superior over
polymers and reinforced polymers regarding
toothshade reproduction, translucency, biological
compatibility, chemical stability and
abrasion resistance.
6. Ceramic is derived from GREEK word
“KERAMI KOS” meaning Burnt earth
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 8, Anusavice)
7.
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 8)
9. The first porcelain tooth material was patented in
1789 by a French dentist deChemant in
collaboration with a French pharmacist
Duchateau.
The first commercial porcelain was developed
by Vita Zahnfabrik in about 1963
JPD 1996 JAN 18-32; CERAMICS IN DENTISTRY : HISTORICAL ROOTS AND CURRENT
PERSPECTIVE
10. 1887 PJC – CH. Land (platinum foil technique)
1940 with advent of acrylics PJC lost popularity
1957 Vines and Sommelman – Vaccum firing
1962 PFM – Weinstein
1965 McLean and Hughes aluminium core porcelain
13. Composition of a dental porcelain (feldspathic)
Material
Silica
Alumina
Boric oxide
Potash
Soda
Other
oxides
weight%
63
17
7
7
4
2
F e ld s p a r
D e n ta l
P o r c e la in
D o m e s tic
P o r c e la in
S to n e
w a re
K a o lin
E a rth e n w a re
Q u a rtz
14.
15. The various ingredients used in different
formulations of ceramics are :
1.Silica (Quartz or Flint) – Filler
2.Kaolin (China clay) – Binder
3.Feldspar – Basic glass former
4.Water – Important glass modifier
5.Fluxes – Glass modifiers
6.Colour pigments
16. 7.Opacifying agents
8.Stains and colour modifiers
9.Fluorescent agents
10.Glazes and Add-on porcelain
11.Alumina
12.Alternative
porcelain
additives
to
17. Silica
Pure Quartz crystals (SiO2) are used for
manufacturing
dental
porcelain.
Quartz
(crystalline silica) is used in porcelain as a filler
and strengthening agent.
18.
19. Kaolin ( White China Clay)
Its functions are:
It increases the moldability of the plastic
porcelain
Acts as a binder and helps in maintaining the
shape of the unfired porcelain during firing.
At high temperature, it fuses and reacts with
other ingredients to form the glassy matrix.
20.
21. Feldspars
Types of feldspar :
Ø
Soda feldspar – Decreases fusion
temperature
Ø
Potash feldspar – Increases the
viscosity of glass.
22.
23. Role of feldspar
Ø
Glass phase formation: During firing, the
feldspar fuses and forms a glassy phase that
softens and flows slightly allowing the porcelain
powder particles to coalesce together.
The
glassy phase forms a translucent glassy matrix.
Ø
Leucite formation: Another important
property of feldspar is its tendency to form the
crystalline mineral leucite.
24. Leucite
Is a potassium-aluminum-silicate mineral with a high
coefficient of thermal expansion ( 20-25x10o/ oC)
compared to feldspathic glasses ( 10x10o/oC). It is an
artificial crystal feldspathoid ( K2O.Al2O3.4siO2) formed
by the incongruent melting (Incongruent melting is the
process by which one material melts to form a liquid
plus a different crystalline material) of feldspar
( K2O.Al2O3. Al2O3-4SiO2).
Annu Rev Mater Sci 1997 27:443-68 ceramics in restorative and prosthetic dentistry : J Robert
Kelly
25.
26. Functions of Leucite
To raise the coefficient of thermal
expansion of porcelain and bring it
closer to that of the metal substrate;
consequently
increasing
the
hardness and fusion temperature.
27. Glass formers
Glass is basically composed of silica (SiO2) with
oxides of Sodium, Potassium, Calcium, Barium
etc. The principal anion in all glasses is O2 ion,
which forms very stable bonds with small
multivalent cations such as Silicon, Boron,
Germanium or Phosphorus resulting in
formation of random networks of SiO4
tetrahedral in glass. These ions are thus termed
as Glass Formers.
28. Glass Modifiers
Can be defined as elements that interfere with the
integrity of the SiO2 (glass) network and alter their
three-dimensional state. Their functions are:
Ø to decrease the softening point by reducing the
amount of cross linking between oxygen and glass
forming elements.
Ø decrease the viscosity (flux action increasing
the flow)
29. Intermediate Oxides
Addition of glass modifiers to reduce the
softening point also decreases the viscosity,
resulting in slump or pyroplastic flow; hence it is
necessary to produce glasses with high
viscosity as well as low firing temperature. This
can be done by the incorporation of an
intermediate oxide such as alumina (Al2O3), to
increase the viscosity of glass.
30. Boric Oxide fluxes
Boric Oxide (B2 O3) although a powerful flux
(glass modifier), it can also act as a glass
former and form its own glass network,
producing Boron Glasses.
32. Colouring agents
Dental porcelains colored by the addition of
concentrated colour frits which are prepared
by fritting high-temperature resistant colouring
pigments (generally metallic oxides) into the
basic glass.
33. The color pigments used are:
Ø Pink - Chromium or chrome-aluminia
Ø Yellow-indium (lemon) – Titanium
Ø Blue -Cobalt salts in the form of oxide
Ø Green - Chromium oxide
Ø Grey -Iron oxide (black) or platinum
oxide
34. Ø Other pigments used may be Titanium
oxide
–yellow
brown,
manganese oxide- lavender, iron/nickel
oxide-brown, and copper oxide – green.
35. Opacifying agents
The translucency of porcelain is not suitable to produce dentin
colours in particular, which requires greater opacity than that of
enamel colors. An opacifying agent maybe incorporated, which
generally consists of a metal oxide.
The common metallic oxides used are –
Ø Cerium oxide
Ø Titanium oxide
36. Ø Tin oxide and
Ø Zirconium oxide (ZrO2)- most popularly used
opacifying agent (usually added with the concentrated
color frit to the porcelain during final preparation).
37. Stains & Colour Modifiers
The stains and colour modifiers
supplied with dental porcelain are
prepared in much the same way as
colour frits.
38.
39. Properties of porcelain:
Strength: Porcelain has got good strength, but is brittle and
tends to fracture. Strength is usually measured in terms of
flexural strength
Flexural stength:
– Ground porcelain - 75.8 Mpa.
– Glazed porcelain - 141.1Mpa.
Compressive strength – 331 Mpa.
Tensile strength – 34 Mpa .Low because of surface defects like
porosities & microscopic cracks
Shear strength - 110Mpa.
40. Specific Gravity: True Specific Gravity is 2.242. Fired
porcelains sp gravity is less due to presence of air voids
Dimensional stability: Dimensionally stable
Chemical stability: Insoluble and impermeable to oral
fluids. Resistant to most solvents. HF acid is used to etch
porcelain to improve bonding of the resin cement
41. Esthetic properties: Able to match adjacent tooth
structures in translucency, colour & intensity.
Colour stability – excellent ,retain its colour & gloss for
years.
Biocompatibility: Excellent compatibility with oral tissues.
43. Dental porcelains are classified according to the firing
temperatures as:
High fusing
1300°C (237°2F)
Medium fusing
1101 – 1300°C (2013 –2072°
F)
Low fusing 850 – 1100°C (1962 – 2012°F)
Ultra-low fusing
<850°C (1562°F)
44. Structure
Ceramics can apper as either crystalline or amorphous
solids (also called glasses); Thus, ceramics can be broadly
classified as :
Ceramics
Non-Crystalline Ceramics
Eg-feldspathic porcelain
Crystalline Ceramics
aluminous porcelain
45. ACC TO DENT CLIN N AM
Predominantly glassy materials
eg feldspathic porcelain
Particle filled glasses
eg dicor
Polycrystalline ceramics
eg procera
Dent Clin N Am 48 (2004) 513-530 Dental ceramics: current thinking and trends( J Robert Kelly)
47. 2) Castable Ceramics :
Using casting & ceramming
(a) Flouromicas e.g: Dicor
(b) Apatite based Glass-Ceramics e.g Cera pearl
(c) Other Glass-Ceramics e.g: Lithia based,
calcium phosphate based.
48. 3) Machinable Ceramics : Milling machining by
mechanical digital control
A)Analogous Systems (Pantograph systems –
copying methods)
1) Copy milling / grinding techniques
a) Mechanical
e.g. : Celay
b) Automatic
e.g:Ceramatic II. DCP
2) Erosive techniques :
a) Sono-erosion e.g: DFE, Erosonic
b) Spark-erosion e.g: DFE, Procera
49. B) Digital systems (CAD / CAM):
1)Direct e.g: Cerec 1 & Cerec 2
2) Indirect e.g : Cicero, Denti CAD, Automill,
DCS-President
50.
51. 5) Infiltrated Ceramics
by slip-casting, sintering & glass infiltration
1) Alumina based
2) Spinel based
3) Zirconia based
e.g: In-Ceram Alumina
e.g: In-Ceram Spinel
e.g.: In-Ceram Zirconia
52. MANUFACTURING ACC
TO JED
Platinum foil technique
Refractory die technique
Casting system technique
Heat pressing technique
Slip casting technique
Hand operated copy milling
Sonoerosion system
CAD CAM
Journal of esthetic dentistry : all ceramic restorations: a challenge for anterior esthetics : Nicola
Pietrobon
53. The advantages of All-ceramic restorations
include:
Ø Increased translucency
Ø Improved fluorescence
Ø Greater contribution of colour from the
underlying tooth structure
Ø Inertness
Ø Bio-compatibility
Ø Resistance to corrosion
Ø Low temperature / electrical conductivity
54. Characteristic Features of All-Ceramic
Crowns
Ø Excellent esthetic result.
Ø Moderate strength for single - unit anterior tooth
restorations when bonded with resin cement.
Ø Lack of gray/ brown metal show through since a
metal substructure is absent.
55. Ø Inability to cover the color of a darkened tooth
preparation or post core, since the crowns are
translucent.
Ø Laboratory costs higher than those for typical
PFM crowns.
56. Ø Wear of opposing occluding enamel or dentin if the
pressed all-ceramic crowns are a part of heavy incisal
guidance or canine rise.
Ø Difficulty in removing the crown and cementing
medium when replacement is necessary (Bonded pressed
ceramic crowns are much more difficult to remove than
standard PFM crowns)
57. Methods of strengthening ceramics
Strengthening of ceramics by
– i) Introduction of residual compressive
stresses into the surface of material by
a) Ion exchange (chemical tempering)
b) Thermal tempering
c) Thermal compatibility (mismatch of CTE)
Annu Rev Mater Sci 1997. 27:443-68 Ceramics in restorative and prosthetic dentistry : J Robert
Kelly
58. ii) Disruption of crack propagation
– a) Dispersion of a crystalline phase eg .
Alumina
– b) Tranformation toughening by Zirconia
crystals (ZrO2)
59. Methods of strengthening brittle materials
Interruption of crack
propagation
Residual compressive
stresses
1.Ion exchange
2.Thermal tempering
3.Thermal compatiability
Addition of
dispersion phase
Toughness of
particle
Change in crystalline
structure
Al, dicor
Particle stabilized
zirconia
Minimise stress concentration
1. Reducing stress raisers
2. Minimise tensile stresses
60. Ion exchange/ chemical tempering
Increase in the flexural
strength of feldspathic
dental porcelain up to
80% is seen
depending on the ionic
species involved and
the composition of the
porcelain.
61. Thermal tempering
creates residual surface compressive stresses by
rapidly cooling (quenching) the surface of the object
while it is hot and in the softened(molten)state.
quench hot glass-phase ceramics in silicone oil or
other special liquids
This thermal tempering treatment induces a protective
region of compressive stress within the surface.
62. Thermal compatibility mismatch
The metal and ceramic should be selected with a slight
mismatch in their thermal contraction coefficients so that
the metal contracts slightly more than the ceramic on
cooling from the firing temperature to room temperature .
This mismatch leaves the ceramic in residual
compression and provides additional strength for the
prosthesis.
63. Dispersion of crystalline phase
Dispersion strengthening/ crystalline reinforcement
Reinforcing ceramic with a dispersed phase of a
different material that is capable of hindering a crack
from propagating through the material
Dental ceramics can be strengthened by increasing
the crystal content of leucite, lithia disilicate,
alumina ,magnesia-alumina spinel,and zirconia
64. Transformation toughening
When small tough crystals are homogenously distributed
in the glass, the ceramic structure is strengthened
because cracks cannot penetrate the fine particles as
easily as they can penetrate the glass.
Various dispersed crystalline phases includes
alumina,leucite,tetrasilicic fluormica, lithia disilicate, and
magnesia alumina spinel.
65. When pure zirconia is heated between 1470-2010 oC & is cooled at
room temperature its crystals begin to change from tetragonal to
monoclinic phase at about 1150 oC. Additives like 3 mol% yttrium
oxide can prevent this polymorhic transformation
In zirconia based ceramics, tranformation toughening involves a
tranformation of ZrO2 from a tetragonal crystal phase to a
monoclinic phase at the tips of cracks that are in regions of tensile
stress.
Dent Clin N Am 48(2004) 513-530 Dental ceramics : current thinking and trends
67. Glazing
The principle is the formation of a low-expansion surface
layer formed at high temperature. Upon cooling, the lowexpansion glaze places the surface of the ceramic in
compression and reduces the depth and width of surface
flaws.
With contemporary dental ceramics, self-glazing is the
standard technique
71. ALUMINA – REINFORCED PORCELAIN
(ALUMINOUS PORCELAINS )
Alumina glass composites used in dental ceramic work
have been termed “Aluminous Porcelain” (McLean
& Hughes, 1965).
72. Porcelains used in an all aluminous
porcelain crown consists of :
Aluminous core porcelain : which contains 40-50
% by wt fused alumina crystals fritted in a low- fusing
glass. The alumina (α - alumina ) particles dispersed in
the glass matrix have very high tensile strength. They are
stronger and more effective in interrupting crack
propagation; thus strengthening the crystal - glass
composite material progressively by two to three folds.
73. Incorporation of alumina produces dull/ opaque porcelain
with lack of translucency. Hence used as a core material (0.5
-1mm) over plantinum foil veneered with feldspathic
porcelain. Alhough improved in strength, it is still insufficient
to bear high stresses.
Eg:Vitadur – N(Vident)
Hi – Ceram (Vident)
74. Disadvantages
Ø Low coefficient of thermal expansion in the range of
8*10-6/0C.
Ø Requires specially formulated and compatible enamel
and dentin porcelains for veneering. Improvement in
strength is insufficient to bear high stresses.
75. Fracture resistance in the aluminous PJC was improved by a
technique, in which the platinum matrix was left in the
completed restoration . The plantium foil matrix not only
provided additional support to the porcelain ; it also allowed
a chemical bond between the tin-plated foil but it did
decrease the amount of light trasnmitted, which diminished
somewhat the esthetic advantages of an all-ceramic
restoration.
77. MAGNESIA – REINFORCED PORCELAIN
Magnesia Core Ceramics are high expansion ceramics
described by O’Brien in 1984 for use as core material .
The magnesia crystals strengthen the glass matrix by both
dispersion strengthening and crystallization within the
matrix .
78. The flexural strength of the material is 131 Mpa but may be
doubled (upto 269 Mpa) by
the application of a glaze
internally. In addition, glass
infiltration also significantly
increases the fracture strength of magnesia core.
79. Advantages:
Increased coefficient of thermal expansion (CTE 14.5x106/0C) improves its compatibility with conventional feldspathic
veneering porcelains . (CTE: 12 to 15x 10-6/0C).
Improved strength and a high expansion property
compared to conventional feldspathic porcelain makes it
suitable for use as a core material , thus substituting for a
metallic core as substructure.
80. LEUCITE – REINFORCED PORCELAINS
Leucite-Reinforced Glass Ceramics are
feldspathic porcelains, dispersion strengthened by
crystallization of leucite crystals in the glass matrix .
81. Optec
HSP
(Optec
(Jeneric/Pentron)
high
is a
Strength
leucite
porcelain)
reinforced feldspathic
porcelain that is condensed and sintered like aluminous and
traditional feldspathic porcelain on a refractory die instead of
a platinum foil . Despite the increase in crystallization ,the
material retains its translucency apparently because of the
closeness of the refractive index of leucite with that of the
glass matrix . The flexure strength is approximately 140 Mpa.
82. Composition : It is a glass ceramic
with a leucite content of 50.6 weight
% dispersed in a glassy matrix
uses : Inlays , onlays, crowns and
veneers.
83. Advantages
Ø Despite lack of metal or opaque substructure, it
has high strength by leucite reinforcement, hence can
be used as a core material.
Ø Good translucency
Ø Moderate flexural strength
Ø No special laboratory equipment needed.
84. Disadvantages
Ø Potential marginal inaccuracy caused
by porcelain sintering shrinkage.
Ø Potential to fracture in posterior
regions.
Increased leucite content may contribute
to high
abrasive effect on
opposing teeth.
85. LOW FUSING CERAMICS
Hydrothermal ceramics are a new cateogory of
dental ceramics developed from industrial ceramics
by introducing hydroxyl groups into the ceramic
structure under heat and steam from which the term
‘hyrdothermal’ ceramic is derived.
86. The hydrothermal ceramic systems are basically low fusing porcelains
containing hydroxyl groups in the glass matrix . Although the
melting, softening and sintering temperatures had reduced,
these materials exhibited an increase in thermal expansion
and mechanical strength without a compromise in their
chemical solubility.
87. Advantage of hydrothermal ceramics over
conventional porcelains:
Ø Lower fusion temperature (680-700 C)
Ø Increased coefficient of thermal expansion
Ø Minimal abrasion of opposing dentition
Ø Greater toughness and durability
88. Duceram LFC: is a low fusing hydrothermal ceramic
composed of an amorphous glass containing hydroxyl (OH)
ions.
It was developed in mid 1980’s based on the ideas and studies
on industrial porcelain ceramic from the early 1960’s and was
first introduced to the market in 1989 for use in all ceramic
prostheses, ceramic / metal-ceramic inlay and partial crowns.
89.
90. Advantages over feldspathic porcelain:
Greater density
Higher flexural strength
Greater fracture resistance
Lower abrasion than feldspathic porcelain
Surface resistant to chemical attack by
fluoride containing agents
Highly polishable, not requiring re-glazing during
adjustment.
91. Disadvantages : low coefficient of thermal
expansion. Thus, an inner lining of conventional
high-fusing ceramic is required.
92. FINESSE ALL CERAMIC SYSTEM
The finesse all ceramic ingots are designed to be
used only with the finesse low fusing porcelain to
fabricate highly esthetic, all ceramic single unit
restoration, laminate veneers, inlays and onlays.
93. Indications:
Single unit anterior and posterior premolar restorations
Laminate veneers
Inlays
Onlays
The finesse all ceramic ingots are color coordinated and
thermally matched only to the finesse low fusing
porcelains.
94. Contra-Indications:
High fusing and other low fusing porcelains are not
thermally matched and will not have the correct coefficient of thermal expansion and therefore should not be
used.
While initial results with some materials may
appear acceptable internal stress can compromise long
term success.
99. Dicor:
Dicor, the first commercially available castable glass-ceramic
material for dental use was developed by The Corning Glass
Works (Corning N.Y.) and marketed by Dentsply
International (Yord, PA, U.S.A). The term “DICOR” is a
combination of the manufacturer’s names: Dentsply
International & Corning glass.
100. Dicor is a castable polycrystalline fluorine containing
tetrasilicic mica glass-ceramic material, initially cast as a
glass by a lost-wax technique and subsequently heat treated resulting in a controlled crystallization to produce a
glass - ceramic material.
101. Major Ingredients
SiO2 45-70%, K2O upto 20%; MgO 13-30%
MgF2 (nucleating agent & flux 4 to 9%)
Minor Ingredients
A12O3 upto 2% (durability & hardness)
ZrO2 upto 7%; Fluorescing agents (esthetics)
BaO 1 to 4% (radiopacity)
102. Advantages of Dicor
Ø Chemical and physical uniformity
Ø Excellent marginal adaptation (fit)
Ø Compatibility with lost-wax casting process
Ø Uncomplicated fabrication from wax-up to casting,
ceramming and colouring
Ø Ease of adjustment
103. Ø Excellent esthetics resulting from natural translucency, light
absorption, light refraction and natural colour for the
restoration.
Ø Relatively high strength (reported flexural strength of 152
MPa), surface hardness (abrasion resistance) and occlusal
wear similar to enamel.
Ø Inherent resistance to bacterial plaque and biocompatible
with surrounding tissues.
Ø Low thermal conductivity.
104. Disadvantages
Ø Requires special and expensive equipments such as
Dicor casting machine, ceramming oven.
Ø Failure rates as high as 8% (# of the restoration) were
reported, especially in the posterior region. In addition,
failure rates as high as 35% have been reported with full
coverage Dicor crowns not bonded to tooth.
106. Ceramming
Ceramming oven
Crystallised glass coping
Cerramming done from room temparature- 19000 f for 1½ hrs
and sustained for 6hrs inorder to form tetra silicic flouro mica
crystals
Conventional porcelain application & Firing
Finished crown
107. CASTABLE APATITE GLASS
CERAMIC
Castable apatite ceramic is classified as
CaO-P2O5-MgO-SiO glass ceramic.
1985 -Sumiya Hobo & Iwata developed
a castable apatite glass-ceramic which was
commercially available as Cera Pearl
(Kyocera Bioceram, Japan).
108. CERA PEARL (Kyocera San Diego, CA): contains a
glass powder distributed in a vitreous or non-crystalline
state.
Composition: Approximately (By weight)
Ø Calcium oxide
-45%
Ø Phosphorus Pentoxide -15% glass formation
Ø Magnesium oxide
-5% Decreases viscosity
Ø Silicon dioxide
-35% glass matrix
Ø Other -Trace elements
Nucleating agents
109. Desirable characteristics of Apatite
Ceramics
Ø Cerapearl is similar to natural enamel in
composition, density, refractive index, thermal
conductivity, coefficient of thermal expansion
and hardness. Similarity in hardness prevents
wear of opposing enamel.
110. Lithia Based Glass-Ceramic
Developed by Uryu; and commercially
available as -Olympus Castable Ceramic
(OCC)
Composition: It contains mica crystals of NaMg3
(Si3AlO10) F2 and Beta Spodumene crystals of
LiO.AI2O3.4SiO2 after heat treatment.
111. Calcium Phosphate Glass-Ceramic
Reported by Kihara and others, for fabrication of allceramic crowns by the lost wax technique. It is a
combination of calcium phosphate and phosphorus
pentoxide plus trace elements. The glass ceramic is
cast at 1050°C in gypsum investment mold. The clear
cast crown is converted to a crystalline ceramic by heat
treating at 645°C for 12 hours.
Reported Flexural strength (116 Mpa); Hardness close
to tooth structure.
113. Advantages of castable glass ceramics
Ø High strength
Ø Excellent esthetics resulting from light
transmission
Ø Accurate form for occlusion, proximal contacts,
and marginal adaptation.
Ø Uniformity and purity of the material.
Ø Favorable soft tissue response.
Ø X-ray density allowing examination by
radiograph
114.
Hardness and wear properties closely
matched to those of natural enamel
Similar thermal conductivity and thermal
expansion to natural enamel
Dimensional stability regardless of any
porcelain
corrective
procedure
and
subsequent firings
116. Triad of fabrication:
Fabrication of a restoration whether with traditional
lost-wax casting technique or a highly sophisticatedtechnology such as a CAD/CAM system has three
functional components:
Data acquisition
Restoration design
Restoration fabrication
117. Machinable Ceramic system (MCS) for dental
restorations:
Ø Digital Systems (CAD/CAM):
Direct
Indirect
Three steps :
§ 3-dimensional surface scanning
§ CAD -Modelling of the restoration
§ Fabrication of restoration.
118. Ø Analogous systems (Copying methods)
Copy Milling / Copy Grinding or Pantography
Systems
Two steps :
§ Fabrication of prototype for scanning.
§ Copying and reproducing by milling
119. DIGITAL SYSTEMS
Computer aided design and computer aided manufacturing
(CAD/ CAM) technologies have been integrated into systems
to automate the fabrication of the equivalent of cast
restorations.
120. CAD/CAM milling uses digital information about the
tooth preparation or a pattern of the restoration to provide a
computer-aided design (CAD) on the video monitor for
inspection and modification. The image is the reference for
designing a restoration on the video monitor. Once the 3-D
image for the restoration design is accepted, the computer
translates the image into a set of instructions to guide a
milling tool (computer-assisted manufacturing [CAM]) in
cutting the restoration from a block of material.
121. CEREC SYSTEM (direct CAD CAM)
The CEREC (Ceramic Reconstruction) system
( Siemen/sirna corp)
Cerec System consists of :
Ø A 3-D video camera (scan head)
Ø An electronic image processor (video processor)
with memory unit (contour memory)
Ø A digital processor connected to,
Ø A miniature milling machine (3-axis machine)
122.
123. Machinable ceramics ( Ceramics used in machining
systems) are pre-fired blocks of feldspathic or glass ceramics.
Composition : Modified feldspathic porcelain or special
fluoro-alumino-silicate compositions are used for machining
restorations.
124. Properties
Ø Excellent fracture and wear resistance
Ø Pore-free
Ø Possess both crystalline and non-crystalline phase (a
2-phase composition permits differential etching of the
internal surface for bonding).
125. Ceramic CAD/ CAM restorations are bonded to
tooth structure by :
Ø Etching for a bond to enamel(with HF)
Ø Conditioning, priming and bonding (when
appropriate)
Ø Cementing with luting resin.
126. Two classes of machinable
ceramics available are:
Fine-scale feldspathic porcelain
Glass-ceramics
127. Cerec Vitabloc Mark I : This feldspathic porcelain was the first
composition used with the Cerec system (Siemens) with a large
particle size (10 - 50µm). It is similar in composition, strength, and wear
properties to feldspathic porcelain used for metal-ceramic restorations.
Cerec Vitabloc Mark II : This is also a feldspathic porcelain
reinforced with aluminum oxide (20-30%) for increased strength and
has a finer grain size (4µm) than the Mark I composition to reduce
abrasive wear of opposing tooth
JADA VOL 137 : sept 2006: Clinical performance of chairside CAD/CAM restorations: Dennis J
Fasbinder
134. Dicor MGC (Dentsply, L.D. Caulk Division) :
This is a machinable glass-ceramic composed of
fluorosilica mica crystals in a glass matrix. The micaplates
are smaller (average diameter 2 um) than in conventional
Dicor (available as Dicor MGC - light and Dicor MGC dark). Greater flexural strength than castable Dicor and the
Cerec compositions. Softer than conventional feldspathic
porcelain. Less abrasive to opposing tooth than Cerec Mark
I, and more than Cerec Mark II (invitro study results).
136. The clinical advantages of the Cerec system:
Ø The restorations made from prefabricated and
optimized, quality-controlled ceramic porcelain can be
placed in one visit.
Ø Transluency and color of porcelain very closely
approximate the natural hard dental tissues.
Ø Further, the quality of the ceramic porcelain is not
changed by the variations that may occur during
processing in dental laboratories.
Ø The prefabricated ceramic is wear resistant.
137.
138. COMET System
(Coordinate M Easuri ng Technique, Steinbichler Optotechnik,
GmbH, Neubeurn, Germany) This system allows the
generation of a 3-dimensional data record for each
superstructure with or without the use of a wax-pattern. For
imaging, 2 - dimensional line grids are projected onto an
object, which allows mathematical reproduction of the tooth
surfaces.
139. It uses a pattern digitization and surface feedback technique,
which accelerates and simplifies the 3-dimensional
representation of tooth shapes while allowing, individual
customization and correction in the visualized monitor
image.
140. Advantage of CAD/CAM (Cerec system)over
other systems
Ø Eliminates impression model making and fabrication
of temporary prosthesis.
Ø Dentist controls the manufacturing of the restoration
entirely without laboratory assistance.
Ø Single visit restoration and good patient acceptance.
Ø Alternative materials can be used, since milling is not
limited to castable materials.
Ø The use of CAD/ CAM system has helped provide void
free porcelain restorations, without firing shrinkage and
with better adaptation.
141. Ø CAD - CAM device can fabricate a ceramic
restoration such as inlay/ onlay at the chair-side.
Ø Eliminates the asepsis link between the
patient, the dentist, operational field and ceramist.
The shapes created in the CAD unit are well
defined, and thus a factor such as correct
dimensions can be evaluated and
corrections/modifications can be carried out on the
display screen itself .
142. Glazing is not required and Cerec inlay onlays can
easily be polished.
Minimal abrasion of opposing tooth structure
because of homogeneity of the material (abrasion
does not exceed that of conventional and hybrid
posterior composite resins).
The mobile character of the entire system enables
easy transport from one dental laboratory to another.
143. Disadvantages:
Ø Limitations in the fabrication of multiple units.
Ø Inability to characterize shades and translucency.
Ø Inability to image in a wet environment (incapable of
obtaining an accurate image in the presence of excessive
saliva, water or blood).
Ø Incompatibility with other imaging system.
Ø Extremely expensive and limited availability.
Ø Still in early introductory stage with few long-term
studies on the durability of the restorations.
144. Lack of computer-controlled processing support for
occlusal adjustment.
Technique sensitive nature of surface imaging that is
required for the prepared teeth.
Time and cost must be invested for mastering the
technique and the fabrication of several restorations,
to develop proficiency in the operator.
145.
146. PROCERA System :
The Procera System (Nobel Biocare, Gioteborg, Sweden)
embraces the concept of CAD/CAM to fabricate dental
restorations.
It consists of a computer controlled design station in the
dental laboratory that is joined through a modern
communication link to Procera Sandvik AB in Stockholm,
Sweden, where the coping is manufactured with advanced
CAD/CAM technique.
147.
148. Procedure requires 3 steps for fabrication:
Scanning : At the design station, a computer controlled
optical scanning device maps the surface of the master die
and is sent via modem to the Procera production facility.
Machining : At the production facility, an enlarged die is
fabricated that compensates for the 15-20% sintering
shrinkage of the alumina core material. High-purity alumina
powder is pressed onto the die under very high pressure,
milled to required shape, and fired at a high temperature
(1550°C) to form a Procera coping.
149. veneering :
The sintered alumina coping is returned to the dental
laboratory for veneering with thermally compatible low fusing
porcelains (All Ceram veneering porcelain) to create the
appropriate anatomic form and esthetic qualities. All Ceram
veneering porcelain (Ducera) has a coefficient of thermal
expansion adjusted to match that of aluminium oxide (7x106 /°C).
150. Advantages
It has the fluorescent properties similar to that of natural
teeth and the veneering procedures require no special
considerations.
The reported flexural strength of the Procera All Ceram
crown (687 Mpa) is relatively the highest amongst all the
all-ceramic restorations used in dentistry (attributed to
the 99.9% alumina content).
151. PROCERA SYSTEM
Dies are enlarged to compensate for sintering shrinkage.
Scanning
Contact scanner
Shape on computer screen
Milling machine
154. This system can be used to fabricate two types of dental
restorations :
A Porcelain-fused-to-metal restoration made of
titanium substructure with a compatible veneering
porcelain using a combination of machine duplication and
spark-erosion (The Procera Method, Noble Biocare).
An all-ceramic restoration using a densely sintered
high-purity (99.9%) alumina coping combined with a
compatible veneering porcelain.
157. SHRINK FREE ALUMINA CERAMICS
The shortcomings of the traditional ceramic material and
techniques; like failures related to poor functional strength
and firing shrinkage limited the use of "all-ceramic" jacket
crowns. The development of non-shrinking ceramics such
as the Cerestore was directed towards providing an
alternate treatment
Shrink-free ceramics were marketed as two generation of
materials under the commercial names :
• Cerestore (Johnson & Johnson. NJ, USA)
•
Al-Ceram (Innotek Dental Corp, USA)
158. CERESTORE Non-Shrink Alumina Ceramic (Coors
Biomedical Co., Lakewood, Colo.) is a shrink-free
ceramic with crystallized magnesium alumina spinel
fabricated by the injection molded technique to form a
dispersion strengthened core.
Composition Of Shrink Free Ceramic
Fired Composition (Core)
A12O3 (Corundum) 60%
MgA12O4 (Spinel) 22%
BaMg2A13(Barium Osomilite) 10%
160. Advantages :
Ø Innovative feature is the dimensional stability of the
core material in the molded (unfired) and fired states. Hence,
failures related to firing shrinkage are eliminated.
Ø Better accuracy of fit and marginal integrity.
Ø Esthetics enhanced due to depth of colour due to the
lack of metal coping.
Ø Biocompatible (inert) and resistant to plaque formation
(glazed surface).
161. Ø Radiodensity similar to that of enamel (presence of
Barium osomilite phase in the fired core allows
radiographic examination of marginal adaptation).
Ø Low thermal conductivity; thus reduced thermal
sensitivity.
Low coefficient of thermal expansion and high modulus
of elasticity results in protection of cement seal.
162. Disadvantages :
Ø Complexity of the fabrication process.
Ø Need for specialized laboratory equipment (Transfer
molding process) and high cost.
Ø Inadequate flexural strength (89MPa) compared to the
metal-ceramic restorations.
Ø Poor abrasion resistance, hence not recommended in
patients with heavy bruxism or inadequate clearance.
163. Limitations and high clinical failure rates of the Cerestore
led to the withdrawal of this product from the market. The
material underwent further improvement and developed
into a product with a 70 to 90% higher flexural strength.
This was marketed under the commercial name Al Ceram
(Innotek Dental, Lakewood, Colo.).
165. Pressed Ceramic / Injection Molded Glass Ceramic
are leucite-reinforced, vacuum-pressed glass-ceramic, also
referred to as Heat transfer-molded glass ceramics.
Eg: IPS Empress (Ivoclar Williams); Optec (Jeneric Pentron)
IPS EMPRESS (Ivoclar Williams) is a pre-cerammed,
pre-coloured leucite reinforced glass-ceramic formed from the
leucite system (SiO2-AI2O3-K20) by controlled surface
crystallization and heat treatment.
166.
167. The glass contains latent nucleating agents and controlled
crystallization is used to produce leucite crystals measuring a
few microns in the glass matrix. The partially pre-cerammed
product of leucite-reinforced ceramic powder available in
different shades is pressed into ingots and sintered. The
ingots are heated in the pressing furnace until molten and
then injected into the investment mold.
168. Uses :
Ø Laminate veneers and full crowns for
anterior teeth
Ø Inlays, Onlays and partial coverage
crowns
Ø Complete crowns on posterior teeth.
JED: vol 9 no 3: Indirect ceramic system for posterior teeth: Luca L Dalloca, Roberto Brambilla
169. Advantages :
Ø Lack of metal or an opaque ceramic core
Ø Moderate flexural strength (120-180MPa range)
Ø Excellent fit (low-shrinkage ceramic)
Ø Improved esthetics (translucent, fluorescence)
Ø Etchable
Ø Less susceptible to fatigue and stress failure
Ø Less abrasive to opposing tooth
Ø Biocompatible material
170. Disadvantages :
Ø Potential to fracture in posterior areas.
Ø Need for special laboratory equipment such as
pressing oven and die material (expensive)
Ø Inability to cover the colour of a darkened tooth
preparation or post and core, since the crowns are
relatively translucent.
Ø Difficulty in removing the crown and cementing
medium during replacement.
Compressive strength and flexural strength lesser
than metal-ceramic or glass-infiltrated (In-Ceram)
crowns.
171. OPTEC (Optimal Pressable Ceramic/OPC): Optec
stands for Optimal Technology. It is a type of feldspathic
porcelain with increased Ieucite content designed to press
restorations using leucite-reinforced ceramic in a press
furnace that doubles as a conventional porcelain furnace.
172. However, because of its high leucite content, it can be
expected that its abrasion against natural teeth will be
higher than that of conventional feldspathic porcelain.
Fabrication is similar to IPS Empress
173. Uses :
Full contour restorations (inlays, veneers full
crowns)
Alternately used as a core material, veneered
with conventional feldspathic porcelain (similar to
Optec HSP).
174. IPS EMPRESS 2 (Ivoclar)
-Second generation of pressable materials for all-ceramic
bridges. It is made from a lithium disilicate framework with an
apatite layered ceramic. The glass-ceramic ingots are made
from lithium silicate glass crystals with crystal content of more
than 60 volume%. The apatite crystals incorporated are
responsible for the improved optical properties (translucency,
light scattering) which contribute to the unique chameleon
effect of leucite glass-ceramic materials.
175. IPS Empress 2 is used with special investment material,
an EP500 press furnace and a fully automatic high-tech
furnace.
Other applications : Cosmopost and IPS Empress
cosmoingot - core build-up system with the pre-fabricated
zircon oxide root canal posts and the optimally coordinated
ingot.
176. Wax pattern
Ceramic ingot &
Al plunger
Investing
Pressing under vaccum
11500C 26 min hold
Burn out 8500 C
Sprue removal
Edward B Goldin 2005 compared leucite IPS Empress with PFM
Mean marginal discrepancy 94 + 41 PFM
81 +25 IPS
178. IN-CERAM ALUMINA, IN-SPINELL,
AND IN-CERAM ZIRCONIA
Slip casting technique: A slurry of one of these
materials is slip-cast on a porous refractory die
and heated in a furnace at 1200c for 2 hr to
produce a partially sintered coping. The partially
sintered core is infiltrated with a glass at 1100 0c for
4 hr to eliminate porosity and to strengthen the
slip –cast core.
179. Flex st
In-ceram
Alumina
350 MPa
In-ceram
Spinell
500 MPa
In-ceram
Zirconia
700 MPa
The final ICA core consists of 70 wt% alumina
infiltrated with 30 wt% sodium lanthanum glass.
ICS core- Glass infiltrated magnesium spinel
(Mgal2O4).
ICZ Core- 30 wt% zirconia and 70 wt% alumina
180. • The flexural strength of in-ceram is greater than
that of Dicor, OPC, IPS Empress I and Empress II.
• ICS is the most translucent of the three ceramics.
• ICZ is not recommended for anterior prostheses
because of its high level of opacity.
181. INDICATIONS FOR USE
• ICA- Anterior and posterior crowns and anterior three-unit
FPDs.
• ICS-Anterior single unit inlays, onlays, crowns and veneers.
• ICZ-posterior crowns and posterior three-unit FPDs.
182. ADVANTAGES OF IN-CERAM
Lack of metal.
Relatively high flexural strength and toughness.
Ability to be successfully cemented with any cement.
186. Finished InCeram copings
(Air abraded)
Application of body
and incisal porcelain
Preoperative veiw
Finished crowns
Postoperative veiw
of In-Ceram crowns
Probster et al : Strength of In-Ceram > IPS Empress < PFM
187. ZIRCONIA BASED SYSTEMS
YTTRIUM TETRAGONAL ZIRCONIAPOLYCRYSTALS
(Y-TPZ) BASED
The most recent core materials for all-ceramic FPDs,
(Y-TPZ) based materials were first used in orthopedics
for total hip replacement, and were successful
because of the material’s excellent mechanical
properties and biocompatibility.It was introduced into
dentistry in the early 1990s for using as implant
abutments.
188. • As Y-TPZ core are glass free and because they
have a polycrystalline microstructure they do not
exhibit the phenomenon of sub critical crack
propagation and stress corrosion caused by water
in the saliva reacting with the glass.
189. • Y-TPZ based materials demonstrated a flexural strength of
900 to 1200 MPa and fracture toughness of 9 to 10 MPa.m ½.
• It also demonstrated a fracture resistance of more than
2000 N under static load.
JPD DEC 2004 ; 92:557-62 Contemporary materials and technologies for all ceramic fixed partial
dentures: a review of literature
190. • Y-TPZ core is relatively translucent and, at the same time
may mask the underlying discolored abutment.
• Moreover it can be colored in 1 to 7 shades corresponding
to the Vita- Lumin shade guide.
• This ability to control the shade of the core may eliminate
the need for veneering.
191. • Y-TPZ based core is radio-opaque which facilitates
radiographic evaluation of the restoration.
• Adhesive cementation is not mandatory and traditional luting
agents may be used.
• They also require relatively small connector area as
compared to most other all-ceramic systems.
193. THE CERCON ZIRCONIA SYSTEM
• Manufacturer-Dentsply Ceramco NJ
• For posterior crowns and three unit FPDs
• Fracture resistance of three unit FPD is 1278 N. (for ICA it
is 514N and for Empress2 it is 621 N)
194. After preparing the teeth an impression is made and sent to
the laboratory, where it is poured with a model material. A
wax pattern approximately 0.8mm in thickness is made for
each coping or crown areas of the framework of an FPD
195. The wax pattern is anchored on the holding appliance
on the left side of the scanning and milling unit. A
presintered zirconia blank is attached to the right side
of the unit. After the unit is activated the blank is
rough-milled and fine-milled on occlusal and gingival
aspects in an enlarged size to compensate for the
20% shrinkage that will occur during subsequent
sintering at 13500C.
The processing time for milling is approximately 35
min for crowns and 80 min for a four-unit FPD.
196. • The zirconia copping is then placed in the Cercon furnace
and fired at 13500C for 6 hrs to fully sinter the yttria
stabilized zirconia core copping or framework.
• The sintering shrinkage is achieved uniformly and linearly in
the 3 dimensional space.
• After any subsequent trimming with a water cooled highspeed diamond bur the finished ceramic core is then
veneered with a veneering ceramic and stain ceramic.
198. ..........
• LAVA and Cercon systems use partially sintered blocks
of Y- TZP for milling the framework, but DCM ( direct
ceramic machining process ) uses fully sintered blanks
or HIP (hot isostatically pressed blanks)
Prague medical report vol 108 ( 2007) no 1 pg 5-12 : Zirconia- a new dental ceramic material
199. CONCLUSION
No currently available restorative system can be
considered the ideal replacement for natural tooth
structure. However, in recent years there has been a great
amount of attention given to research on and development
of ceramic systems for restorative use. Ceramics are
playing an increasingly important role in restorative
dentistry, and further improvements in fracture resistance
and wear properties will no doubt enhance their
restorative use. The demand for esthetic dentistry is
expected to continue and will be influencial in determining
the range of the products available.
200. REFERENCES
David A Graber, Ronald E Goldstein- porcelain and
composite inlays and onlays esthetic posterior resorations.
Aschheim Dale- esthetic dentistry 2nd edition
Robert G Craig- restorative dental materials
Phillips- science of dental materials 10th edition
John McLean- the science and art of dental ceramics
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