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DENTAL
CERAMICS
Part II
Dr. Kriti Trehan
MDS I
Contents
– Introduction
– Advantages and disadvantages
– Conventional ceramics
– Castaable ceramics
– Pressable ceramics
– Infiltrated ceramics
– Machinable ceramics
– References
o Currently available all-ceramics can be broadly
categorized according to their method of fabrication :
 Conventional (powder – slurry) ceramics
 Castable ceramics
 Pressable ceramics
 Infiltrated ceramics
 Machinable ceramics
“All-Ceramic” refers to – Any restorative material
composed exclusively of ceramic, such as feldspathic
porcelain, glass ceramic,alumina core systems and certain
combination of these materials. (J.Esth Dent 1997, 9 (2):
86).
:
Advantages of all ceramic
1. Most life like and esthetically pleasing restoration.
2. It is translucent, color stable.
3. If constructed over a uniformly reduced and balanced
preparation, it has a long life expectancy in most patients.
4. The advent of vacuum firing has reduced bubbles, producing
a fine textured restoration with improved translucency and
increased impact strength.
4. Porcelain is biologically acceptable, and well tolerated by
the soft tissues.
4. Porcelain crowns cemented on natural abutments and
those cemented on artificial supports have the same
incidence of fracture; therefore, a porcelain crown can be
successfully used after a cast-metal post and core has
been placed on a non-vital tooth.
Disadvantages of all ceramic
1. Cost and time
2. Brittlesness of ceramics
3. Wear of opposing dentition
4. Low repair potential
Alumina – Reinforced porcelain (Aluminous Porcelain)
o Hi-Ceram
o Vitadur – N core
Magnesia–Reinforced porcelain(magnesia core
ceramics)
Leucite Reinforced (Non-pressed)
o Optec HSP
o Optec VP
CONVENTIONAL CERAMICS
o The high-strength ceramic core was first introduced to
dentistry by McLean and Hughes in 1965.
o It is composed of aluminum oxide (alumina) crystals
dispersed in a glassy matrix. Alumina has a high tensile
strength, fracture toughness and hardness.
Examples :
– Hi-Ceram (Vident),
– Vitadur – N core (Vident)
Aluminous core ceramics
o One method of producing aluminous porcelain crowns
was to form a tin oxide coating on platinum foil.
Advantages:
1. Withstand torque better than conventional porcelains with
fracture rate of slightly less than 0.5%.
2. As Abramowsky states, pure alumina is 6 times stronger
than standard porcelains. By combining an alumina core with
standard porcelain, the restoration is twice the strength of
porcelain alone.
3. Low thermal conductivity.
4. During processing, alumina and porcelain unite by a
chemical bond, so there is practically no problem in
adhesion.
5. Good color consistency. Provided the porcelain‘s maturing
temperature is not exceeded, the crowns may be fired 3 or 4
times without color loss.
Hi-ceram
 Dispersion Strengthened Core.
 Similar to traditional Alumina Core, with increased
alumina.
 Fired Directly On The Refractory Die - Rough Surface
Which aids in Retention.
Modifications
 Feldspathic porcelain higher leucite crystal
content.
 The leucite and glassy components are fused during the
baking process at 1020ºC.
 Advantages:
1. More esthetic due to a more translucent core.
2. Greater strength.
3. No special processing equipment required.
Leucite reinforced porcelain
 Drawbacks:
1. Increased leucite content contributes to the relatively
high in vitro wear of opposing teeth.
2. Potential to fracture in posterior teeth.
3. Potential marginal inaccuracy
Uses:
1. Inlays
2. Onlays
3. Low stress crowns.
 1968 - W.T. MacCulloch realised the usefulness of glass
ceramics and proposed its use for dental restorative
purposes.
o Fabricated in the vitreous (Glass or non
crystalline/amorphous) state and converted to a ceramic
(crystalline state) by controlled crystallization using nucleating
agents during heat treatment.
CASTABLE CERAMICS
Glass-ceramics are polycrystalline materials developed
for application by casting procedures using the lost wax
technique, hence referred to as “castable ceramic”.
(SiO2K2MgOA12O3ZrO2)
Dicor (CaOMgOP2O5SiO2)
CeraPearl(KyoceraBioceram)
Castable Dental Glass-Ceramics
Fluoromicas
Apatite Glass-
Ceramic
OtherGlass-
Ceramics
Based on
a) Lithia
b) Calcium
phosphate
 The first commercially available castable glass-ceramic.
 Developed by ‘The Corning Glass Works’ (Corning N.Y.)
and marketed by Dentsply International (Yord,
PA,U.S.A).
 Dicor is a castable polycrystalline fluorine containing
tetrasilicic mica glass-ceramic (55 vol%) material.
Dicor
Fabrication of castable ceramics restoration consists
of mainly 2 steps :
o Casting : The glass liquefies at 13700C to such a
degree that it can be cast into a mold using lost-wax and
centrifugal casting techniques.
o Ceramming : The cast glass material is subject to a
single-step heat treatment called “Ceramming” to
produce controlled crystallization by internal nucleation
and crystal growth of microscopic plate like mica crystals
within the glass matrix.
o Cast glass ceramic is composed of:
 Tetrasilicic flouromica crystals (crystalline) - 55% by
volume.
 Glass matrix (non-crystalline) - 45% by volume.
o The microstructure after ceramming consists of multiple
interlocking crystals of tetrasilicic flouromica
approximately 1 μm thick and 5-6mm in diameter.
o On the surface of the cerammed glass are ‘Enstatite
crystals’ which occur through fluorine depletion.
o The crystals function in following ways :
 Improved strength : Interlocking of randomly oriented
small plate-like mica crystals increases the resistance to
fracture.
 Improved esthetics : The refractive index of the mica
crystals is matched to that of the surrounding glass
phase thus reducing light scatter (as in aluminous
porcelains) and results in transparency close to that of
enamel.
 Reduced abrasive property : Since mica crystals
replace the more abrasive leucite crystals found in
traditional feldspathic porcelain.
Wax pattern Spruing Investing
Burnout
Divesting Cast glass coping Ceramming
1750 for 12hr
450 for 12 hr
Centrifugal
casting 2600 f
Ceramming Ceramming oven Crystallised glass coping
Conventional porcelain application & Firing Finished crown
Cerramming done in temperature- 650-1075 C for 1½ hrs and sustained
for 6hrs in order to form tetra silicic flouro mica crystals
ADVANTAGES:
 Excellent esthetics resulting from Chameleon effect.
 Relatively high strength (reported flexural strength of 152
MPa), surface hardness (abrasion resistance) and
occlusal wear similar to enamel.
 Inherent resistance to bacterial plaque and
biocompatibility with surrounding tissues.
 Low thermal conductivity.
DISADVANTAGES:
 Requires special and expensive equipments.
 Laboratory studies for use as veneers and inlays,
failure rates as high as 8% in the posterior region.
 The original cast form was colorless and prostheses
had to be colored by the application of a thin layer of
shading porcelain.
INDICATIONS:
oUsed for anterior single crown (low stress area)
oUsed in situations where high translucency is required.
CONTRAINDICATIONS:
oNot used as posterior crowns.
oNot used in high stress bearing areas.
o 1985 -Sumiya Hobo & Iwata developed a castable apatite
glass-ceramic which was commercially available as Cera
Pearl (Kyocera Bioceram, Japan).
CERA PEARL (Kyocera San Diego, CA): contains a glass
powder distributed in a vitreous or non-crystalline state.
Castable apatite glass
ceramic
Composition: Approximately (By weight)
 Calcium oxide (CaO) -45%
 Phosphorus Pentoxide (P2O5) -15% Aids in glass formation.
Magnesium oxide (MgO) -5% Decreases the viscosity
(antiflux)
 Silicon dioxide(SiO2)- 35% Forms the glass matrix.
 Other - Trace elements and nucleating agents.
Chemistry:
Apatite Glass-Ceramic Molten glass CaPO4
(CaO-P2O5-MgO-SiO2) Amorphous
1460°C
melting
1510°C
casting
CaPO4 Oxyapatite Hydroxyapatite
(Amorphous) (Crystalline) (Crystalline)
Ca10(PO4)820H
o Strength is dependent on these crystals and the bond between
the crystals and the non-crystalline inorganic matrix.
1460C
Ceramming
Exposure to
moisture
Desirable characteristics of Apatite Ceramics
Cerapearl is similar to natural enamel in composition,
density, refractive index, thermal conductivity, coefficient of
thermal expansion and hardness.
 Bonding to tooth structure : Cerapearl surface is
activated by air abrading (to provide mechanical interlocking
effect) or treatment with activator solution (etching of with 2N
HCI preferentially removes the glassy phase from the surface,
thus exposing the apatite phase).
o The glass ionomer can then bond to this apatite phase both
chemically (ion-exchange) and mechanically (interlocking
effect).
Advantages of castable glass ceramics
High strength because of controlled particle size
reinforcement.
Excellent esthetics resulting from light transmission
similar to that of natural teeth and convenient procedures
for imparting the required colour.
 Accurate form for occlusion, proximal contacts, and
marginal adaptation.
Favorable soft tissue response.
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.
1.Shrink free ceramics: Cerestore
Al-ceram
2.Leucite reinforced glass ceramics: IPS empress
Optec/OPC
3.Lithia reinforced glass ceramic: IPS empress 2
OPC 3G
PRESSABLE CERAMICS
oThe 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.
oThe development of non-shrinking ceramics such as the
Cerestore system was directed towards providing an
alternate treatment.
Brief History :
1983 - Sozio & Riley described the use of shrink-free ceramic
coping.
1987 - Hullah & Williams described the formulation of shrink
free ceramics
Shrink free Alumina Ceramics
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)
Chemistry: The shrink free ceramic material essentially
consists of Al2O3 and MgO mixed with Barium glass frits.
On firing a combination of chemical and crystalline
transformation produces Magnesium aluminate spinel, which
occupies a greater volume than the original mixed oxides (raw
ingredients), and thus compensates for the conventional firing
shrinkage of ceramic.
Chemical transformation : During firing from 160 °C to
800°C, the silicone resin (binder) converts from SiO to SiO2
which in turn combines with alumina to form aluminosilicate.
 Crystalline transformation:The aluminosilicate formed
reacts with the incorporated magnesia to form spinel, which
is also one of the strongest ceramic oxides.
 During firing from 900 to 1300°C, the glass frit takes
MgO and Al2O3 into solution subsequently precipitates the
spinel phase.
Advantages :
 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.
 Better accuracy of fit and marginal integrity.
 Esthetics enhanced due to depth of colour due to the lack
of metal coping.
 Biocompatible (inert) and resistant to plaque formation
(glazed surface).
 Low thermal conductivity; thus reduced thermal
sensitivity.
Low coefficient of thermal expansion and high modulus
of elasticity results in protection of cement seal.
Disadvantages :
 Complexity of the fabrication process.
 Need for specialized laboratory equipment (Transfer
molding process) and high cost.
.
 Inadequate flexural strength (89MPa) compared to the
metal-ceramic restorations.
 Poor abrasion resistance, hence not recommended in
patients with heavy bruxism or inadequate clearance.
 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).
Leucite reinforced porcelains can be broadly divided into:
 IPS Empress (Ivoclar Williams)
 Optec Pressable Ceramic / OPC (Jeneric/Pentron)
Leucite reinforced porcelains (transfer
moulded)
Pressed Ceramic / Injection Molded Glass Ceramic are
leucite-reinforced,vacuum-pressed glass-ceramic, also referred
to as Heat transfer-molded glass ceramics.
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,
subsequent process stages and heat treatment.
oThis technique was first described by Wohlwend & Scharer;
and marketed by Ivoclar (Vivadent Schaan, Liechtensein).
oThe glass contains latent nucleating agents and controlled
crystallization is used to produce leucite crystals measuring
a few microns in the glass matrix.
o It is a type of feldspathic porcelain containing a higher
concentration of leucite crystals, which increases the
resistance to crack propagation.
Leucite
content
Conventional
Porcelain
Dicor Glass-
ceramic
IPS Empress
Pressable
ceramic
30-35% 50-60% 80-85%
• A special furnace Empress
EP500 designed for this
system is capable of high
temperatures.
• The pressing furnace
contains an enlarged heat
dome, a pneumatic pressure
system, a reducing valve, and
a monometer to control the
pressure.
The crucible former placed
into automated furnace that
has an alumina plunger.
Fabrication
Wax pattern is
invested in a special
flask
Uses :
o Laminate veneers and full crowns for anterior teeth
o Inlays, Onlays and partial coverage crowns
Advantages :
o Lack of metal or an opaque ceramic core
o Excellent fit (low-shrinkage ceramic)
o Improved esthetics (translucent, fluorescence)
o Etchable
o Less susceptible to fatigue and stress failure
o Less abrasive to opposing tooth
o Biocompatible material
oUnlike previous glass-ceramic systems IPS Empress does not
require ceramming to initiate the crystalline phase of leucite
crystals (They are formed throughout the various temperature
cycles).
Disadvantages :
o Potential to fracture in posterior areas.
o Need for special laboratory equipment such as pressing oven
and die material (expensive).
o Inability to cover the colour of a darkened tooth preparation or
post and core, since the crowns are relatively translucent.
o Compressive strength and flexural strength lesser than metal-
ceramic or glass-infiltrated (In-Ceram) crowns.
IPS Empress 2 (Ivoclar Vivadent) and Optec OPC 3G
(Pentron Laboratory Technologies) contain approximately
65% to 70% by volume of lithia disilicate (Li2O•2SiO2) as
the principal crystal phase.
o The lithia disilicate materials used as glass-ceramics
have a narrow sintering range, which makes processing of
ceramic prostheses very technique sensitive.
o Composition :70% lithium disilicate
30% glass.
oIt is fairly translucent but somewhat more opaque with a
stronger core than leucite-based glass-ceramic.
Lithia reinforced porcelains
Uses :
1. Anterior and posterior crowns
2. Anterior three unit bridges
 Although the core ceramic fracture resistance is
moderately high, veneered prostheses have been reported
to be susceptible to chipping, which may require
replacement
Advantages:
1. Improved fracture resistance.
2. Very high chemical resistance of both framework and
layering ceramics.
3. High translucency.
4. Outstanding light optical properties due to apatite (also a
component of natural teeth).
5. Wear behavior similar to that of natural enamel.
6. Ingots available in the most popular Chromoscope
shades.
7. Excellent aesthetic appearance.
IPS e.max
INDICATIONS
1. Thin veneers (0.3 mm)
2. Inlays , onlays, occlusal veneers
3. Crowns in the anterior and posterior region
4. Bridges in the anterior and premolar region
5. Implant superstructures
6. Hybrid abutments and abutment crowns
INFILTRATED CERAMICS
In-Ceram
Alumina
In – Ceram Spinell In -Ceram
Zirconia
The In-Ceram Crown (Vident) process involves three
basic steps :
1. Making an intensely dense core by slip casting of fine
grained alumina particles and sintering.
2. The sintered alumina core is infiltrated with molten
glass to yield a ceramic coping of high density and
strength.
3. The infiltrated core is veneered with feldspathic
porcelain and fired.
Developed by a French scientist and dentist Dr. Michael
Sadoun (1980) and first introduced in France in 1988.
In-Ceram Alumina
Duplication
In-Ceram
refractory dies
In-Ceram application
Al2O3 slip
10 hrs 1120 c-
2hrs
vita inceramat
Working model
Glass infiltration
4hrs 1100c
Shrinkage of dies
Application of body
and incisal porcelain
Postoperative veiw
of In-Ceram crowns
Finished crowns
Application of
body and incisal
porcelain
Postoperative veiw
of In-Ceram
crowns
Finished In-
Ceram
copings
(Air abraded)
Finished crowns
Preoperative veiw
oThe densely packed alumina crystals limit crack propagation,
while the glass infiltration eliminated residual porosity and
improves flexural strength upto 2-5 times that of glass-ceramic
and feldspathic porcelain.
Composition: In-Ceram ceramic consists of two three-
dimensional interpenetrating phases :
 Alumina/ Al203 crystalline (Volume fraction) 99.56 wt% of
with a particle size distribution averaging 3.8m
 An Infiltration glass lanthanum aluminosilicate with small
amounts of sodium and calcium.
Advantages :
 Minimal firing shrinkage, hence an accurate fit.
 High flexure strengths (almost 3 times of ordinary
porcelain) makes the material suitable even for multiple-unit
bridges.
Aluminous core being opaque can be used to cover
darkened teeth or post/ core.
Uses:
1. Single anterior & posterior crowns
2. Anterior 3-unit FPD's
Disadvantages :
1. Requires specialized equipment to fabricate the restoration,
hence laboratory expense is more.
2. Poor optical properties or esthetics (opaque alumina core
reduces the translucency of the final restoration).
3. Slip casting is a complex technique and requires considerable
practice.
4. Requires considerable reduction of tooth surface all over for
adequate thickness of restoration.
o The primary difference is a change in composition to
produce a more translucent core.
o The porous core is fabricated from a magnesium alumina
powder after sintering.This type of material has a specific
crystalline structure referred to as ―SPINELL‖.
oThe porous spinell is secondarily infiltrated with a low
viscosity, lanthanum aluminosilicate glass, which produces a
more translucent substructure upon which Vitadur Alpha is
veneered to form the final restoration.
In-Ceram Spinell (VitaZahnfabrik)
oINDICATIONS:
Anterior crowns, particularly
In clinical situations where maximum translucency is
needed.
oCONTRAINDICATIONS:
Posterior restorations.
Anterior and posterior FPDs.
In discolored preparations and cast posts as the level of
translucency is excessive and leads to an overly glassy low
value appearance.
Advantage:
1. The translucency closely matches that of dentin and is
twice more than Inceram alumina.
2. Spinell has extended uses: Inlay / Onlay, ceramic core
material and even Veneers.
Disadvantage: Incapable to be etched by HF.
(The Bateman Etch Retention Svstem (BERS) is suggested
to overcome this disadvantage It consists of incorporating
plastic chips (50 - 300 diameter) on the fitting or internal
surface of In-Ceram during their fabrication, which are
subsequently burnt out leaving behind a roughened
surface).
o A second-generation material based on INCERAM
fabrication technique.
o Pure ZrO2 has a monoclinic crystal structure at room
temperature and transforms to tetragonal and cubic
zirconia at elevated temperatures.
Inceram zirconia
o Zirconia is a nonmetal with an extremely low thermal
conductivity—about 20% as high as that of alumina (Al2O3).
o It is chemically inert and highly corrosion resistant.
o Structural expansion and high tensile stresses causes
zirconia to crack during cooling from the processing
temperatures.
o Stabilizing oxides such as magnesium oxide (MgO),
yttrium oxide (Y2O3), calcium oxide (CaO), and cerium
oxide (Ce2O3) are added to zirconia to provide stability.
oThe “transformation toughening” mechanism of crack
shielding results from the controlled transformation of the
metastable tetragonal phase to the stable monoclinic phase
next to the crack tip.
oIn this process a 3% expansion by volume of the
ZrO2 crystals or precipitates occurs that places the
crack under a state of compressive stress and crack
progression is arrested.
o Because of this strengthening and toughening
mechanism, the yttria-stabilized zirconia ceramic is
sometimes referred to as “ceramic steel.”
Disadvantages
o The risk for catastrophic wear of opposing enamel and
dental restorations is one of the major potential challenges to
the effective, safe use of solid zirconia prostheses.
o Difficulty in adjusting occlusion when significant premature
contacts are present.
o The cutting difficulty
oThe heat generated in removing defective crowns or when
making an endodontic access opening with diamond burs.
From 1998 , machined ceramics came into being. There
are two major systems for the fabrication of this technique.
1. Digital systems
• CAD CAM technology
2. Analogous systems
• Copy milling / grinding technique
• Erosive techniques
MACHINABLE CERAMICS
o Development of CAD-CAM systems for the dental profession
began in the 1970‘s with Duret in France, Altschuler in the US
and Mormann and Brandestini in Switzerland.
o CAD-CAM ceramic prostheses can be produced either as
monolithic lithia disilicate glass-ceramic or zirconia ceramic
structures or as bilayer structures made from milled copings
and layered manually, by hot pressing, or by fusing a CAM-
produced veneer to the framework (CAD-0n method).
o CAD-CAM prostheses can be produced either by industrial
milling processes or by chair-side milling units.
Unaesthetic amalgam restorations Restorations removed & preparations
Refined
Coat the preparations with Tio2 powder for Preparation of the virtual model
Optical scanning
Margins outlined for restoration design Occlusal view of the completed
restoration and ready for milling
Materials for CAD/CAM processing
The following materials can normally be processed on
dental CAD/CAM devices:
1. Silica based ceramics
 Grindable silica based ceramic blocks are offered by
several CAD/CAM systems for the production of inlays,
onlays, veneers, partial crowns and full crowns.
In addition to monochromatic blocks, various
manufacturers now offer blanks with multicoloured layers
[Vitablocs TriLuxe (Vita), IPS Empress CAD Multi
(IvoclarVivadent)], for the purpose of full anatomical
crowns.
 Due to their higher stability values, lithium disilicate
ceramic blocks are particularly important in this group;
They can be used for full anatomical anterior and
posterior crowns, for copings in the anterior and posterior
region and for three-unit FPD frameworks in the anterior
region due to their high mechanical stability of 360 MPa.
 Glass ceramics are particularly well suited to chairside
application as a result of their translucent characteristics,
similar to that of natural tooth structure; they provide
aesthetically pleasing results even without veneering.
2.Infiltration ceramics
 Grindable blocks of infiltration ceramics are processed
in porous, chalky condition and then infiltrated with
lanthanum glass.
 All blanks for infiltration ceramics originate from the
Vita In-Ceram system (Vita) and are offered in three
variations:
 Vita In-Ceram Alumina (Al2 O3 ):
Vita In-Ceram Zirconia
(70% Al2 O3, 30% ZrO2 ):
VITA In-Ceram Spinell (MgAl2 O4 ):
3.Oxide high performance ceramics
At present, aluminum oxide and zirconium oxide are
offered as blocks for CAD/CAM technology.
Aluminum Oxide is indicated in the case of crown
copings in the anterior and posterior area, primary crowns
and three-unit anterior FPD frameworks.
The ground frames can be individually stained in several
colours with Vita In-Ceram AL Coloring Liquid.
 Examples of grindable aluminum oxide blocks: In-Ceram
AL Block (Vita), inCoris Al (Sirona) available in an ivory-like
colour (Color F 0.7).
Yttrium stabilised zirconium oxide (ZrO2 , Y-TZP)
Zirconium dioxide is a high-performance oxide ceramic with
excellent mechanical characteristics.
Its high flexural strength and fracture toughness compared
with other dental ceramics offer the possibility of using this
material as framework material for crowns and FPDs, and, in
appropriate indications, for individual implant abutments.
Examples of Zirconium oxide blocks: Lava Frame (3M
ESPE), Cercon Smart Ceramics (DeguDent), Everest ZS und
ZH (KaVo), inCoris Zr (Sirona), In-Ceram YZ (Vita), zerion
(etkon) and Zeno Zr (Wieland-Imes)
ADVANTAGES
a) Less chairside time
b) Reduced porosity & greater strength
c) Single appointment
d) Decreases fabrication time by 90%
DISADVANTAGES
a) Cost
b) Technique sensitive
c) Inability to build layers of porcelain
The first commercially available CAD/CAM system
has been CEREC, developed by Mormann and
Brandestini.
Since its introduction to the dental field in 1986 as the
CEREC 1, this system has evolved through a series of
software and hardware upgrades up to the CEREC 3D.
Cerec System
The CEREC 1 System
First introduced in 1986.
It consisted of a mobile unit containing :
a) A small camera
b) A computer with scan.
c) 3-axis-of rotation milling machine- water-pressure
driven.
Clinical shortcomings:
a) Occlusal anatomy had to be created by the clinician
b) Inaccuracy of fit or large interfacial gaps
c) Clinical fracture
d) Relatively poor esthetics
CEREC 2 system
The major changes include :
 Enlargement of the grinding unit from 3 axes to 6 axes.
Upgrading of the software allows machining of the occlusal
surfaces and the complex machining of the floor parts.
CEREC 3 system
Different parts could be magnified in detail more finer
details noted.
Disadvantage: not capable of producing margins of
restoration.
CEREC 3-D System
 Marginal fit good

3 dimensionally movable camera
The clinical advantages of the Cerec system:
 Quality-controlled ceramic porcelain can be placed in one
visit.
 Translucency and color of porcelain very closely
approximate the natural tooth.
 Further, the quality of the ceramic porcelain is not
changed by the variations that may occur during processing
in dental laboratories.
The prefabricated ceramic is wear resistant.
The optimized structure of the ceramic enables
optimal polishability of the material and low abrasion
of the opposing tooth.
A tight marginal fit is provided by the adhesive
system used between the etched ceramic porcelain
and enamel surfaces.
o The Celay System (Mikrona AG, Spreintenbach,
Switzerland) became first commercially available in 1992.
o It is a high precision,manually operated copy milling
machine
o This system was originally designed and intended for
use in the dental laboratory, however it may also be used
at the chairside.
Celay System
Milling instruments Block being milled
Composite resin pro inlay Pro inlay being scanned
Finished restoration
Milled
Restoration
oBy combining the Celay system, with elements of In-Ceram
technology, copy milled glass-infiltrated aluminous core
restorations can be fabricated.
o In-Ceram or In-Ceram Spinell materials are machined by
Celay and then infiltrated with a sodium-lanthanum glass in a
manner similar to that of conventional In-Ceram restorations,
and finally veneered with Vitadur Alpha porcelain.
o The Procera System (Nobel Biocare, Gioteborg, Sweden)
was developed by Andersson .M & Oden .A in 1993,
through a co-operative effort between Nobel Biocare AB
(Sweden) and Sandvik Hard Materials AB (Stockholm,
Sweden).
o 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
powder technology and CAD/CAM technique.
Procera System
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.
Veneering : The sintered alumina coping is returned to the
dental laboratory for veneering thermally compatible low
fusing porcelains (All Ceram veneering porcelain) to create
the appropriate anatomic form and esthetic qualities.
oIt also has the fluorescent properties similar to that of
natural teeth and the veneering procedures require no
special considerations.
oThe 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).
ADVANTAGES
a) Flexural strength 687mpa.
b) Procera coping is translucent, thus will not allow any
staining of the underlying dentin
c) Occulsal surface will not damage the opposing natural
tooth
d) Aluminum oxide coping material does not show any
leakage or dissolution of aluminum at any of the pH
levels
Cercon and lava zirconia core ceramics
FABRICATION:
Tooth preparation Impression made Wax
pattern (0.8 mm)made on model Anchored on to
the Cercon Brain A presintered zirconia blank is
attached on to the other side of the brain unit
Unit activated..pattern scanned
Milled prosthesis then
removed from unit and
placed in the Cercon furnace
(1350 ºc for 6 hours)
Trimming
Finished ceramic core framework
After veneering
Greatest potential fracture toughness and flexural strength(>900 MPa)
Contraindications:
a) Severe bruxism
b) Extensive wear of tooth structure or restorations
c) Excessive bite-force capability
d) Previous history of all-ceramic inlay or crown
fractures.
Principles governing the selection of dental ceramics
Six criteria should be considered to minimize the risks of poor
esthetics, clinical failures, remakes, and possible disagreements
and misunderstandings between dentists, patients, technicians,
and manufacturers:
1. . The dentist should not consider all-ceramic crowns for
patients with evidence of extreme bruxism, clenching, or
malocclusion. In this case, metal-ceramic or all metal
prostheses should be used.
2. The experience of the laboratory technician should be
extensive and only technicians who demonstrate meticulous
attention to detail should be selected.
3. Specific patient would yield more predictable outcomes and
longevity than an all ceramic prosthesis.
4. Use all-ceramic crowns when the adjacent teeth exhibit
a high degree of translucency.
5. Informed consent must be obtained from the patient,
preferably in writing.
6. The dentist should be skillful and be able to take
perfect impressions derived from smooth preparations
free of undercuts with continuous, well-defined margins,
and with adequate total tooth reduction
Bonding of resin ceramic to dental
ceramics
Phillips science of dental materials –First South Asia
edition.
Craig’s Restorative dental materials –13th edition.
 Qualtrough A, Piddock V.Dental ceramics:whats
new?Dent Update 2002; 29: 25–33.
Guess et al.All-Ceramic Systems: Laboratory and Clinical
Performance Dent Clin N Am 2011 ;55:333–352
References
Freedman M, Quinn F, Sullivan MO.Single unit CAD/CAM
restorations: a literature review.JIDA 2007; 53(1):38-45 .
Jones D. W. - Developments in Dental ceramics – JDR
1999(Abst);44(2):61.
Marc.A.Rosenblum, Allan.Schulman - A Review of All-
Ceramic Restorations. – JADA 1997;128:297-307.
J. Robert Kelly, I. Nishimura, S. D. Campbell - Ceramics in
dentistry : Historical roots and current perspectives -
JPD1996;75(1):18-32.
J. K. Dong, H. Luthy, A. Wohlwend, P. Scharer - Heat
Pressed Ceramics : Technology and Strength – IJP
1992;5(1):9-16.

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Dental ceramics part II

  • 2. Contents – Introduction – Advantages and disadvantages – Conventional ceramics – Castaable ceramics – Pressable ceramics – Infiltrated ceramics – Machinable ceramics – References
  • 3. o Currently available all-ceramics can be broadly categorized according to their method of fabrication :  Conventional (powder – slurry) ceramics  Castable ceramics  Pressable ceramics  Infiltrated ceramics  Machinable ceramics “All-Ceramic” refers to – Any restorative material composed exclusively of ceramic, such as feldspathic porcelain, glass ceramic,alumina core systems and certain combination of these materials. (J.Esth Dent 1997, 9 (2): 86).
  • 4. : Advantages of all ceramic 1. Most life like and esthetically pleasing restoration. 2. It is translucent, color stable. 3. If constructed over a uniformly reduced and balanced preparation, it has a long life expectancy in most patients. 4. The advent of vacuum firing has reduced bubbles, producing a fine textured restoration with improved translucency and increased impact strength.
  • 5. 4. Porcelain is biologically acceptable, and well tolerated by the soft tissues. 4. Porcelain crowns cemented on natural abutments and those cemented on artificial supports have the same incidence of fracture; therefore, a porcelain crown can be successfully used after a cast-metal post and core has been placed on a non-vital tooth.
  • 6. Disadvantages of all ceramic 1. Cost and time 2. Brittlesness of ceramics 3. Wear of opposing dentition 4. Low repair potential
  • 7. Alumina – Reinforced porcelain (Aluminous Porcelain) o Hi-Ceram o Vitadur – N core Magnesia–Reinforced porcelain(magnesia core ceramics) Leucite Reinforced (Non-pressed) o Optec HSP o Optec VP CONVENTIONAL CERAMICS
  • 8. o The high-strength ceramic core was first introduced to dentistry by McLean and Hughes in 1965. o It is composed of aluminum oxide (alumina) crystals dispersed in a glassy matrix. Alumina has a high tensile strength, fracture toughness and hardness. Examples : – Hi-Ceram (Vident), – Vitadur – N core (Vident) Aluminous core ceramics
  • 9.
  • 10. o One method of producing aluminous porcelain crowns was to form a tin oxide coating on platinum foil.
  • 11. Advantages: 1. Withstand torque better than conventional porcelains with fracture rate of slightly less than 0.5%. 2. As Abramowsky states, pure alumina is 6 times stronger than standard porcelains. By combining an alumina core with standard porcelain, the restoration is twice the strength of porcelain alone. 3. Low thermal conductivity. 4. During processing, alumina and porcelain unite by a chemical bond, so there is practically no problem in adhesion. 5. Good color consistency. Provided the porcelain‘s maturing temperature is not exceeded, the crowns may be fired 3 or 4 times without color loss.
  • 12. Hi-ceram  Dispersion Strengthened Core.  Similar to traditional Alumina Core, with increased alumina.  Fired Directly On The Refractory Die - Rough Surface Which aids in Retention. Modifications
  • 13.  Feldspathic porcelain higher leucite crystal content.  The leucite and glassy components are fused during the baking process at 1020ºC.  Advantages: 1. More esthetic due to a more translucent core. 2. Greater strength. 3. No special processing equipment required. Leucite reinforced porcelain
  • 14.  Drawbacks: 1. Increased leucite content contributes to the relatively high in vitro wear of opposing teeth. 2. Potential to fracture in posterior teeth. 3. Potential marginal inaccuracy Uses: 1. Inlays 2. Onlays 3. Low stress crowns.
  • 15.  1968 - W.T. MacCulloch realised the usefulness of glass ceramics and proposed its use for dental restorative purposes. o Fabricated in the vitreous (Glass or non crystalline/amorphous) state and converted to a ceramic (crystalline state) by controlled crystallization using nucleating agents during heat treatment. CASTABLE CERAMICS Glass-ceramics are polycrystalline materials developed for application by casting procedures using the lost wax technique, hence referred to as “castable ceramic”.
  • 16. (SiO2K2MgOA12O3ZrO2) Dicor (CaOMgOP2O5SiO2) CeraPearl(KyoceraBioceram) Castable Dental Glass-Ceramics Fluoromicas Apatite Glass- Ceramic OtherGlass- Ceramics Based on a) Lithia b) Calcium phosphate
  • 17.  The first commercially available castable glass-ceramic.  Developed by ‘The Corning Glass Works’ (Corning N.Y.) and marketed by Dentsply International (Yord, PA,U.S.A).  Dicor is a castable polycrystalline fluorine containing tetrasilicic mica glass-ceramic (55 vol%) material. Dicor
  • 18. Fabrication of castable ceramics restoration consists of mainly 2 steps : o Casting : The glass liquefies at 13700C to such a degree that it can be cast into a mold using lost-wax and centrifugal casting techniques. o Ceramming : The cast glass material is subject to a single-step heat treatment called “Ceramming” to produce controlled crystallization by internal nucleation and crystal growth of microscopic plate like mica crystals within the glass matrix.
  • 19. o Cast glass ceramic is composed of:  Tetrasilicic flouromica crystals (crystalline) - 55% by volume.  Glass matrix (non-crystalline) - 45% by volume. o The microstructure after ceramming consists of multiple interlocking crystals of tetrasilicic flouromica approximately 1 μm thick and 5-6mm in diameter. o On the surface of the cerammed glass are ‘Enstatite crystals’ which occur through fluorine depletion.
  • 20. o The crystals function in following ways :  Improved strength : Interlocking of randomly oriented small plate-like mica crystals increases the resistance to fracture.  Improved esthetics : The refractive index of the mica crystals is matched to that of the surrounding glass phase thus reducing light scatter (as in aluminous porcelains) and results in transparency close to that of enamel.  Reduced abrasive property : Since mica crystals replace the more abrasive leucite crystals found in traditional feldspathic porcelain.
  • 21. Wax pattern Spruing Investing Burnout Divesting Cast glass coping Ceramming 1750 for 12hr 450 for 12 hr Centrifugal casting 2600 f
  • 22. Ceramming Ceramming oven Crystallised glass coping Conventional porcelain application & Firing Finished crown Cerramming done in temperature- 650-1075 C for 1½ hrs and sustained for 6hrs in order to form tetra silicic flouro mica crystals
  • 23. ADVANTAGES:  Excellent esthetics resulting from Chameleon effect.  Relatively high strength (reported flexural strength of 152 MPa), surface hardness (abrasion resistance) and occlusal wear similar to enamel.  Inherent resistance to bacterial plaque and biocompatibility with surrounding tissues.  Low thermal conductivity.
  • 24. DISADVANTAGES:  Requires special and expensive equipments.  Laboratory studies for use as veneers and inlays, failure rates as high as 8% in the posterior region.  The original cast form was colorless and prostheses had to be colored by the application of a thin layer of shading porcelain.
  • 25. INDICATIONS: oUsed for anterior single crown (low stress area) oUsed in situations where high translucency is required. CONTRAINDICATIONS: oNot used as posterior crowns. oNot used in high stress bearing areas.
  • 26. o 1985 -Sumiya Hobo & Iwata developed a castable apatite glass-ceramic which was commercially available as Cera Pearl (Kyocera Bioceram, Japan). CERA PEARL (Kyocera San Diego, CA): contains a glass powder distributed in a vitreous or non-crystalline state. Castable apatite glass ceramic
  • 27. Composition: Approximately (By weight)  Calcium oxide (CaO) -45%  Phosphorus Pentoxide (P2O5) -15% Aids in glass formation. Magnesium oxide (MgO) -5% Decreases the viscosity (antiflux)  Silicon dioxide(SiO2)- 35% Forms the glass matrix.  Other - Trace elements and nucleating agents. Chemistry: Apatite Glass-Ceramic Molten glass CaPO4 (CaO-P2O5-MgO-SiO2) Amorphous 1460°C melting 1510°C casting
  • 28. CaPO4 Oxyapatite Hydroxyapatite (Amorphous) (Crystalline) (Crystalline) Ca10(PO4)820H o Strength is dependent on these crystals and the bond between the crystals and the non-crystalline inorganic matrix. 1460C Ceramming Exposure to moisture
  • 29. Desirable characteristics of Apatite Ceramics Cerapearl is similar to natural enamel in composition, density, refractive index, thermal conductivity, coefficient of thermal expansion and hardness.  Bonding to tooth structure : Cerapearl surface is activated by air abrading (to provide mechanical interlocking effect) or treatment with activator solution (etching of with 2N HCI preferentially removes the glassy phase from the surface, thus exposing the apatite phase). o The glass ionomer can then bond to this apatite phase both chemically (ion-exchange) and mechanically (interlocking effect).
  • 30. Advantages of castable glass ceramics High strength because of controlled particle size reinforcement. Excellent esthetics resulting from light transmission similar to that of natural teeth and convenient procedures for imparting the required colour.  Accurate form for occlusion, proximal contacts, and marginal adaptation. Favorable soft tissue response.
  • 31. 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.
  • 32. 1.Shrink free ceramics: Cerestore Al-ceram 2.Leucite reinforced glass ceramics: IPS empress Optec/OPC 3.Lithia reinforced glass ceramic: IPS empress 2 OPC 3G PRESSABLE CERAMICS
  • 33. oThe 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. oThe development of non-shrinking ceramics such as the Cerestore system was directed towards providing an alternate treatment. Brief History : 1983 - Sozio & Riley described the use of shrink-free ceramic coping. 1987 - Hullah & Williams described the formulation of shrink free ceramics Shrink free Alumina Ceramics
  • 34. 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) Chemistry: The shrink free ceramic material essentially consists of Al2O3 and MgO mixed with Barium glass frits. On firing a combination of chemical and crystalline transformation produces Magnesium aluminate spinel, which occupies a greater volume than the original mixed oxides (raw ingredients), and thus compensates for the conventional firing shrinkage of ceramic.
  • 35. Chemical transformation : During firing from 160 °C to 800°C, the silicone resin (binder) converts from SiO to SiO2 which in turn combines with alumina to form aluminosilicate.  Crystalline transformation:The aluminosilicate formed reacts with the incorporated magnesia to form spinel, which is also one of the strongest ceramic oxides.  During firing from 900 to 1300°C, the glass frit takes MgO and Al2O3 into solution subsequently precipitates the spinel phase.
  • 36. Advantages :  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.  Better accuracy of fit and marginal integrity.  Esthetics enhanced due to depth of colour due to the lack of metal coping.  Biocompatible (inert) and resistant to plaque formation (glazed surface).
  • 37.  Low thermal conductivity; thus reduced thermal sensitivity. Low coefficient of thermal expansion and high modulus of elasticity results in protection of cement seal. Disadvantages :  Complexity of the fabrication process.  Need for specialized laboratory equipment (Transfer molding process) and high cost. .
  • 38.  Inadequate flexural strength (89MPa) compared to the metal-ceramic restorations.  Poor abrasion resistance, hence not recommended in patients with heavy bruxism or inadequate clearance.  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).
  • 39. Leucite reinforced porcelains can be broadly divided into:  IPS Empress (Ivoclar Williams)  Optec Pressable Ceramic / OPC (Jeneric/Pentron) Leucite reinforced porcelains (transfer moulded) Pressed Ceramic / Injection Molded Glass Ceramic are leucite-reinforced,vacuum-pressed glass-ceramic, also referred to as Heat transfer-molded glass ceramics.
  • 40. 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, subsequent process stages and heat treatment. oThis technique was first described by Wohlwend & Scharer; and marketed by Ivoclar (Vivadent Schaan, Liechtensein). oThe glass contains latent nucleating agents and controlled crystallization is used to produce leucite crystals measuring a few microns in the glass matrix.
  • 41. o It is a type of feldspathic porcelain containing a higher concentration of leucite crystals, which increases the resistance to crack propagation. Leucite content Conventional Porcelain Dicor Glass- ceramic IPS Empress Pressable ceramic 30-35% 50-60% 80-85%
  • 42. • A special furnace Empress EP500 designed for this system is capable of high temperatures. • The pressing furnace contains an enlarged heat dome, a pneumatic pressure system, a reducing valve, and a monometer to control the pressure.
  • 43. The crucible former placed into automated furnace that has an alumina plunger. Fabrication Wax pattern is invested in a special flask
  • 44.
  • 45. Uses : o Laminate veneers and full crowns for anterior teeth o Inlays, Onlays and partial coverage crowns
  • 46. Advantages : o Lack of metal or an opaque ceramic core o Excellent fit (low-shrinkage ceramic) o Improved esthetics (translucent, fluorescence) o Etchable o Less susceptible to fatigue and stress failure o Less abrasive to opposing tooth o Biocompatible material oUnlike previous glass-ceramic systems IPS Empress does not require ceramming to initiate the crystalline phase of leucite crystals (They are formed throughout the various temperature cycles).
  • 47. Disadvantages : o Potential to fracture in posterior areas. o Need for special laboratory equipment such as pressing oven and die material (expensive). o Inability to cover the colour of a darkened tooth preparation or post and core, since the crowns are relatively translucent. o Compressive strength and flexural strength lesser than metal- ceramic or glass-infiltrated (In-Ceram) crowns.
  • 48. IPS Empress 2 (Ivoclar Vivadent) and Optec OPC 3G (Pentron Laboratory Technologies) contain approximately 65% to 70% by volume of lithia disilicate (Li2O•2SiO2) as the principal crystal phase. o The lithia disilicate materials used as glass-ceramics have a narrow sintering range, which makes processing of ceramic prostheses very technique sensitive. o Composition :70% lithium disilicate 30% glass. oIt is fairly translucent but somewhat more opaque with a stronger core than leucite-based glass-ceramic. Lithia reinforced porcelains
  • 49. Uses : 1. Anterior and posterior crowns 2. Anterior three unit bridges  Although the core ceramic fracture resistance is moderately high, veneered prostheses have been reported to be susceptible to chipping, which may require replacement
  • 50. Advantages: 1. Improved fracture resistance. 2. Very high chemical resistance of both framework and layering ceramics. 3. High translucency. 4. Outstanding light optical properties due to apatite (also a component of natural teeth). 5. Wear behavior similar to that of natural enamel. 6. Ingots available in the most popular Chromoscope shades. 7. Excellent aesthetic appearance.
  • 51.
  • 53. INDICATIONS 1. Thin veneers (0.3 mm) 2. Inlays , onlays, occlusal veneers 3. Crowns in the anterior and posterior region 4. Bridges in the anterior and premolar region 5. Implant superstructures 6. Hybrid abutments and abutment crowns
  • 54. INFILTRATED CERAMICS In-Ceram Alumina In – Ceram Spinell In -Ceram Zirconia
  • 55. The In-Ceram Crown (Vident) process involves three basic steps : 1. Making an intensely dense core by slip casting of fine grained alumina particles and sintering. 2. The sintered alumina core is infiltrated with molten glass to yield a ceramic coping of high density and strength. 3. The infiltrated core is veneered with feldspathic porcelain and fired. Developed by a French scientist and dentist Dr. Michael Sadoun (1980) and first introduced in France in 1988. In-Ceram Alumina
  • 56. Duplication In-Ceram refractory dies In-Ceram application Al2O3 slip 10 hrs 1120 c- 2hrs vita inceramat Working model Glass infiltration 4hrs 1100c Shrinkage of dies
  • 57. Application of body and incisal porcelain Postoperative veiw of In-Ceram crowns Finished crowns Application of body and incisal porcelain Postoperative veiw of In-Ceram crowns Finished In- Ceram copings (Air abraded) Finished crowns Preoperative veiw
  • 58. oThe densely packed alumina crystals limit crack propagation, while the glass infiltration eliminated residual porosity and improves flexural strength upto 2-5 times that of glass-ceramic and feldspathic porcelain. Composition: In-Ceram ceramic consists of two three- dimensional interpenetrating phases :  Alumina/ Al203 crystalline (Volume fraction) 99.56 wt% of with a particle size distribution averaging 3.8m  An Infiltration glass lanthanum aluminosilicate with small amounts of sodium and calcium.
  • 59. Advantages :  Minimal firing shrinkage, hence an accurate fit.  High flexure strengths (almost 3 times of ordinary porcelain) makes the material suitable even for multiple-unit bridges. Aluminous core being opaque can be used to cover darkened teeth or post/ core. Uses: 1. Single anterior & posterior crowns 2. Anterior 3-unit FPD's
  • 60. Disadvantages : 1. Requires specialized equipment to fabricate the restoration, hence laboratory expense is more. 2. Poor optical properties or esthetics (opaque alumina core reduces the translucency of the final restoration). 3. Slip casting is a complex technique and requires considerable practice. 4. Requires considerable reduction of tooth surface all over for adequate thickness of restoration.
  • 61. o The primary difference is a change in composition to produce a more translucent core. o The porous core is fabricated from a magnesium alumina powder after sintering.This type of material has a specific crystalline structure referred to as ―SPINELL‖. oThe porous spinell is secondarily infiltrated with a low viscosity, lanthanum aluminosilicate glass, which produces a more translucent substructure upon which Vitadur Alpha is veneered to form the final restoration. In-Ceram Spinell (VitaZahnfabrik)
  • 62. oINDICATIONS: Anterior crowns, particularly In clinical situations where maximum translucency is needed. oCONTRAINDICATIONS: Posterior restorations. Anterior and posterior FPDs. In discolored preparations and cast posts as the level of translucency is excessive and leads to an overly glassy low value appearance.
  • 63. Advantage: 1. The translucency closely matches that of dentin and is twice more than Inceram alumina. 2. Spinell has extended uses: Inlay / Onlay, ceramic core material and even Veneers. Disadvantage: Incapable to be etched by HF. (The Bateman Etch Retention Svstem (BERS) is suggested to overcome this disadvantage It consists of incorporating plastic chips (50 - 300 diameter) on the fitting or internal surface of In-Ceram during their fabrication, which are subsequently burnt out leaving behind a roughened surface).
  • 64. o A second-generation material based on INCERAM fabrication technique. o Pure ZrO2 has a monoclinic crystal structure at room temperature and transforms to tetragonal and cubic zirconia at elevated temperatures. Inceram zirconia o Zirconia is a nonmetal with an extremely low thermal conductivity—about 20% as high as that of alumina (Al2O3). o It is chemically inert and highly corrosion resistant.
  • 65. o Structural expansion and high tensile stresses causes zirconia to crack during cooling from the processing temperatures. o Stabilizing oxides such as magnesium oxide (MgO), yttrium oxide (Y2O3), calcium oxide (CaO), and cerium oxide (Ce2O3) are added to zirconia to provide stability. oThe “transformation toughening” mechanism of crack shielding results from the controlled transformation of the metastable tetragonal phase to the stable monoclinic phase next to the crack tip.
  • 66. oIn this process a 3% expansion by volume of the ZrO2 crystals or precipitates occurs that places the crack under a state of compressive stress and crack progression is arrested. o Because of this strengthening and toughening mechanism, the yttria-stabilized zirconia ceramic is sometimes referred to as “ceramic steel.”
  • 67. Disadvantages o The risk for catastrophic wear of opposing enamel and dental restorations is one of the major potential challenges to the effective, safe use of solid zirconia prostheses. o Difficulty in adjusting occlusion when significant premature contacts are present. o The cutting difficulty oThe heat generated in removing defective crowns or when making an endodontic access opening with diamond burs.
  • 68. From 1998 , machined ceramics came into being. There are two major systems for the fabrication of this technique. 1. Digital systems • CAD CAM technology 2. Analogous systems • Copy milling / grinding technique • Erosive techniques MACHINABLE CERAMICS
  • 69. o Development of CAD-CAM systems for the dental profession began in the 1970‘s with Duret in France, Altschuler in the US and Mormann and Brandestini in Switzerland. o CAD-CAM ceramic prostheses can be produced either as monolithic lithia disilicate glass-ceramic or zirconia ceramic structures or as bilayer structures made from milled copings and layered manually, by hot pressing, or by fusing a CAM- produced veneer to the framework (CAD-0n method). o CAD-CAM prostheses can be produced either by industrial milling processes or by chair-side milling units.
  • 70.
  • 71. Unaesthetic amalgam restorations Restorations removed & preparations Refined Coat the preparations with Tio2 powder for Preparation of the virtual model Optical scanning Margins outlined for restoration design Occlusal view of the completed restoration and ready for milling
  • 72.
  • 73. Materials for CAD/CAM processing The following materials can normally be processed on dental CAD/CAM devices: 1. Silica based ceramics  Grindable silica based ceramic blocks are offered by several CAD/CAM systems for the production of inlays, onlays, veneers, partial crowns and full crowns. In addition to monochromatic blocks, various manufacturers now offer blanks with multicoloured layers [Vitablocs TriLuxe (Vita), IPS Empress CAD Multi (IvoclarVivadent)], for the purpose of full anatomical crowns.
  • 74.  Due to their higher stability values, lithium disilicate ceramic blocks are particularly important in this group; They can be used for full anatomical anterior and posterior crowns, for copings in the anterior and posterior region and for three-unit FPD frameworks in the anterior region due to their high mechanical stability of 360 MPa.  Glass ceramics are particularly well suited to chairside application as a result of their translucent characteristics, similar to that of natural tooth structure; they provide aesthetically pleasing results even without veneering.
  • 75. 2.Infiltration ceramics  Grindable blocks of infiltration ceramics are processed in porous, chalky condition and then infiltrated with lanthanum glass.  All blanks for infiltration ceramics originate from the Vita In-Ceram system (Vita) and are offered in three variations:  Vita In-Ceram Alumina (Al2 O3 ):
  • 76. Vita In-Ceram Zirconia (70% Al2 O3, 30% ZrO2 ): VITA In-Ceram Spinell (MgAl2 O4 ):
  • 77. 3.Oxide high performance ceramics At present, aluminum oxide and zirconium oxide are offered as blocks for CAD/CAM technology. Aluminum Oxide is indicated in the case of crown copings in the anterior and posterior area, primary crowns and three-unit anterior FPD frameworks. The ground frames can be individually stained in several colours with Vita In-Ceram AL Coloring Liquid.  Examples of grindable aluminum oxide blocks: In-Ceram AL Block (Vita), inCoris Al (Sirona) available in an ivory-like colour (Color F 0.7).
  • 78. Yttrium stabilised zirconium oxide (ZrO2 , Y-TZP) Zirconium dioxide is a high-performance oxide ceramic with excellent mechanical characteristics. Its high flexural strength and fracture toughness compared with other dental ceramics offer the possibility of using this material as framework material for crowns and FPDs, and, in appropriate indications, for individual implant abutments. Examples of Zirconium oxide blocks: Lava Frame (3M ESPE), Cercon Smart Ceramics (DeguDent), Everest ZS und ZH (KaVo), inCoris Zr (Sirona), In-Ceram YZ (Vita), zerion (etkon) and Zeno Zr (Wieland-Imes)
  • 79.
  • 80. ADVANTAGES a) Less chairside time b) Reduced porosity & greater strength c) Single appointment d) Decreases fabrication time by 90% DISADVANTAGES a) Cost b) Technique sensitive c) Inability to build layers of porcelain
  • 81. The first commercially available CAD/CAM system has been CEREC, developed by Mormann and Brandestini. Since its introduction to the dental field in 1986 as the CEREC 1, this system has evolved through a series of software and hardware upgrades up to the CEREC 3D. Cerec System
  • 82. The CEREC 1 System First introduced in 1986. It consisted of a mobile unit containing : a) A small camera b) A computer with scan. c) 3-axis-of rotation milling machine- water-pressure driven. Clinical shortcomings: a) Occlusal anatomy had to be created by the clinician b) Inaccuracy of fit or large interfacial gaps c) Clinical fracture d) Relatively poor esthetics
  • 83. CEREC 2 system The major changes include :  Enlargement of the grinding unit from 3 axes to 6 axes. Upgrading of the software allows machining of the occlusal surfaces and the complex machining of the floor parts. CEREC 3 system Different parts could be magnified in detail more finer details noted. Disadvantage: not capable of producing margins of restoration.
  • 84.
  • 85. CEREC 3-D System  Marginal fit good  3 dimensionally movable camera The clinical advantages of the Cerec system:  Quality-controlled ceramic porcelain can be placed in one visit.  Translucency and color of porcelain very closely approximate the natural tooth.  Further, the quality of the ceramic porcelain is not changed by the variations that may occur during processing in dental laboratories.
  • 86. The prefabricated ceramic is wear resistant. The optimized structure of the ceramic enables optimal polishability of the material and low abrasion of the opposing tooth. A tight marginal fit is provided by the adhesive system used between the etched ceramic porcelain and enamel surfaces.
  • 87. o The Celay System (Mikrona AG, Spreintenbach, Switzerland) became first commercially available in 1992. o It is a high precision,manually operated copy milling machine o This system was originally designed and intended for use in the dental laboratory, however it may also be used at the chairside. Celay System
  • 88. Milling instruments Block being milled Composite resin pro inlay Pro inlay being scanned
  • 90. oBy combining the Celay system, with elements of In-Ceram technology, copy milled glass-infiltrated aluminous core restorations can be fabricated. o In-Ceram or In-Ceram Spinell materials are machined by Celay and then infiltrated with a sodium-lanthanum glass in a manner similar to that of conventional In-Ceram restorations, and finally veneered with Vitadur Alpha porcelain.
  • 91. o The Procera System (Nobel Biocare, Gioteborg, Sweden) was developed by Andersson .M & Oden .A in 1993, through a co-operative effort between Nobel Biocare AB (Sweden) and Sandvik Hard Materials AB (Stockholm, Sweden). o 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 powder technology and CAD/CAM technique. Procera System
  • 92. 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.
  • 93. Veneering : The sintered alumina coping is returned to the dental laboratory for veneering thermally compatible low fusing porcelains (All Ceram veneering porcelain) to create the appropriate anatomic form and esthetic qualities. oIt also has the fluorescent properties similar to that of natural teeth and the veneering procedures require no special considerations. oThe 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).
  • 94. ADVANTAGES a) Flexural strength 687mpa. b) Procera coping is translucent, thus will not allow any staining of the underlying dentin c) Occulsal surface will not damage the opposing natural tooth d) Aluminum oxide coping material does not show any leakage or dissolution of aluminum at any of the pH levels
  • 95. Cercon and lava zirconia core ceramics FABRICATION: Tooth preparation Impression made Wax pattern (0.8 mm)made on model Anchored on to the Cercon Brain A presintered zirconia blank is attached on to the other side of the brain unit Unit activated..pattern scanned
  • 96. Milled prosthesis then removed from unit and placed in the Cercon furnace (1350 ºc for 6 hours) Trimming
  • 97. Finished ceramic core framework After veneering Greatest potential fracture toughness and flexural strength(>900 MPa)
  • 98. Contraindications: a) Severe bruxism b) Extensive wear of tooth structure or restorations c) Excessive bite-force capability d) Previous history of all-ceramic inlay or crown fractures. Principles governing the selection of dental ceramics
  • 99. Six criteria should be considered to minimize the risks of poor esthetics, clinical failures, remakes, and possible disagreements and misunderstandings between dentists, patients, technicians, and manufacturers: 1. . The dentist should not consider all-ceramic crowns for patients with evidence of extreme bruxism, clenching, or malocclusion. In this case, metal-ceramic or all metal prostheses should be used. 2. The experience of the laboratory technician should be extensive and only technicians who demonstrate meticulous attention to detail should be selected. 3. Specific patient would yield more predictable outcomes and longevity than an all ceramic prosthesis.
  • 100. 4. Use all-ceramic crowns when the adjacent teeth exhibit a high degree of translucency. 5. Informed consent must be obtained from the patient, preferably in writing. 6. The dentist should be skillful and be able to take perfect impressions derived from smooth preparations free of undercuts with continuous, well-defined margins, and with adequate total tooth reduction
  • 101. Bonding of resin ceramic to dental ceramics
  • 102.
  • 103. Phillips science of dental materials –First South Asia edition. Craig’s Restorative dental materials –13th edition.  Qualtrough A, Piddock V.Dental ceramics:whats new?Dent Update 2002; 29: 25–33. Guess et al.All-Ceramic Systems: Laboratory and Clinical Performance Dent Clin N Am 2011 ;55:333–352 References
  • 104. Freedman M, Quinn F, Sullivan MO.Single unit CAD/CAM restorations: a literature review.JIDA 2007; 53(1):38-45 . Jones D. W. - Developments in Dental ceramics – JDR 1999(Abst);44(2):61. Marc.A.Rosenblum, Allan.Schulman - A Review of All- Ceramic Restorations. – JADA 1997;128:297-307. J. Robert Kelly, I. Nishimura, S. D. Campbell - Ceramics in dentistry : Historical roots and current perspectives - JPD1996;75(1):18-32. J. K. Dong, H. Luthy, A. Wohlwend, P. Scharer - Heat Pressed Ceramics : Technology and Strength – IJP 1992;5(1):9-16.