Dental ceramics part 2

Dental Ceramics part II
Dr.NAMITHA.A.P
Ist year MDS
DEPT.OF PROSTHODONTICS

 Need for strengthening
 Methods of strengthening
 All ceramic systems
1. Condensed/sintered
2. Castable ceramics
3. Hot isostaticallly pressed ceramics
4. Glass infiltrated core ceramics
5. CAD CAM ceramics

 Abrasiveness of Dental Ceramics
 Chemical Attack of Glass-Phase Ceramics by Acidulated
Phosphate Fluoride
 Porcelain DentureTeeth
 Shade guides
 Critical Observation and Analysis of Fractures
 Principles Governing the Selection of Dental Ceramics
 Recent advances in dental ceramics
 Conclusion
 References

Need of Strengthening
High
inter
atomic
forces
Still fails
to
exhibit
strength
Stress
concentration
points
Scratches
porosity
defects
cracks

Griffith’s microcracks
 Named after discoverer
 Minute submicroscopic surface defects (scratches and
cracks) present on the glass surface
 Act as stress concentration centers when subjected to
tensile stresses
 Large radius at tip causes large tensile stresses at their
tips leading to crack propagation

Stress concentration phenomenon
Numerous minute scratches/flaws
present on the surface
Behave as sharp slits(tip narrows as
spacing between several atoms in the
materials)
Under intra oral loading tensile stress
concentrated at tip of these flaws.
Stress concentration geometry at tip of
each surface flaw.

Stress concentration
phenomenon(continues)
Increased localized stress to
extremely high levels.
Induced tensile stress > nominal
strength of material structure
Bonds at notch tips rupture
Forms a crack!!

As the crack propagates;
Stress concentration
is maintained at
crack tip.
Meets another
crack/pore/crystalline
particle.
Crack moves
completely through
the material

cracks
processing
handlingproduction
Increase
in
strength
Removal
of surface
flaws
Reduction
in size of
cracks
Reduction
in number
of cracks

Stress raisers How to avoid stress raisers
 Discontinuities in brittle
materials
 Abrupt change in
shape/thickness in ceramic
contour
 Cause stress concentration
in these areas
 Restoration more prone to
fracture
 Sufficient bulk
 Minimum sharp angular
changes
 Proper proportioning
 Proper compaction
 Proper drying
 Firing under vacuum
 Slow cooling
 Glazing

Why ceramics fails far below their tensile
strength??
Flaws/cracks
Micro
structure
Residual
processing
stresses
Loading
rate
Load
orientation
Prosthesis
design

Methods of strengthening
Development of residual
compressive stresses
Interruption of crack
propagation
 Development of residual
compressive stresses
 Reduced number of firing
cycles
 Optimal design of
prostheses
 Ion exchange
 Thermal tempering
 Dispersion strengthening
 Transformation
toughening

Development of residual compressive
stresses
Fabrication of metal
ceramic/all ceramic
Sintering at high
temperature
Hot pressing a
veneering ceramic on
to the metal or core
ceramic
Process of cooling
to room
temperature
Mis match in coefficient
of thermal contraction
of adjacent materials
Metal contracts slightly
more than ceramics.
Metal pulls the
ceramics inwards-
compression of
porcelain
Bonded platinum foil
aluminous porcelain
crown technique
Swaged gold alloy
foil technique
1
2
3

Disadvantages
 There is a limit to coefficient mismatch that can be
tolerated
 Difference in coefficient of thermal contraction causes
considerable shear stress at interface
 Maximum tolerable difference 0.5 M/0K to 0.7 M/0K
 If more - premature failure in shear

Reduced number of firing cycles
Stresses during cooling
Induces crack formation and propagation
Multiple firings
Increase in thermal expansion
coefficient
Exceeds that of metal
Mismatch between porcelain and
metal
Increase in concentrations of crystalline leucite(K2O.Al2O3 .4SiO2)
High expansion crystal phase Affects coefficient of thermal contraction
Firing cycle
Chemical reactions

Optimal design of prostheses
• Can sustain higher tensile stresses before crack develop in areas of
tensile stress
1.Tougher and stronger ceramics
• Reduce stress concentration in the restoration where tensile
component of bending stress will develop
2.Well rounded line angles
• To avoid risk of cracking or chipping during firing
3.Avoid knife edge margins
• Reduce probability of forming microcracks and reduce depth of
microfissures produced by abrasive particles
4.Use finest grit abrasive

Atypical designs-leads to ceramic fracture
 a four-unit metal-ceramic
cast-joined bridge with
two connector fractures
at the two cast-joined
sections in the metal
framework.
 Fluorescent dye
illumination allows better
visibility of the two areas
of ceramic cracking.

 B)Schematic of a properly
designed cast-joined
three-unit bridge
framework.
 C) Five possible cross-
sectional designs for cast-
joining at the pontic.
 D)Plot of force versus
strain for a solid bar.
 Design 1 was the best
choice of the five designs
on the left.

5.Height of connector can be increased to a
maximum of 4 mm
 Tensile stresses can be reduced using greater connector
height
 a connector height > 4 mm - anatomic form in the buccal
area of a posterior FPD too bulky and unesthetic

When connector size < recommended

6.Radius of curvature of gingival embrasure portion
of the inter proximal connector is broadened
 Radius of curvature of gingival embrasure portion of the
inter proximal connector is broadened

Ion exchange
K+ions is 35% larger (133pm) than Na+ ion.
Large residual compressive
stresses
Ion exchange up to depth of 100
micro meter
Loses due to finishing,wear,long
term exposure to oral fluids
Concentration driven phenomenon
Equlibrium eventually established Not a complete exchange
Immersed in molten potassium salt
K+ exchanges place with Na+ Remain in place even after cooling
Sodium containing glass
Small ionic diameter(90 pm)

Thermal tempering
Rapid cooling of surface of
material while in molten
state/quenching
Rigid
surface
+
molten
inner core
Molten core
solidifies
;shrinks and
pull rigid
outer
surface
inwards
Residual
tensile
stresses in
inner core
+
Residual
compressive
stresses
within outer
surface

 Most widely used method of strengthening glass
 In dentistry silicone oil and other special liquids are used
for quenching ceramics instead of water/air

Dispersion strengthening and toughening
Increase in fracture resistance
Dispersed phase interferes with crack propagation
Absorbs energy from crack Prevents its driving force propagation
Reinforced with a dispersed phase of a different material
Addition of smaller and tougher filler particles

Examples of dispersed
crystalline phases Action depends on
 Leucite
 Lithium disilicate
 Alumina
 Magnesia alumina spinel
 Zirconia
 Tetra silicic flouromica
 Type
 Size
 Volume fractions
 Inter particle spacing
 Their CTE as compared
to glass matrix

fracture
toughness (KIc)
in Mpa/m2
Soda-lime-silica
glass
0.75
34 vol % of
leucite crystals
IPS Empress 1.3
70 vol %
lithium
disilicate
IPS e.max Press 3.3

Applications
• Al2O3 particles were dispersed in a glassy porcelain matrix
Aluminous porcelain
• IPS Empress-leucite crystals
• IPS Empress2-lithia disilicate
Hot pressed glass ceramics
• Leucite reinforced
OPTEC HSP
• In Ceram-alumina,In Ceram spinel-MgAl2O3 (Magnesia alumina spinel)
Glass infiltrated core ceramics

Transformation toughening
A change in crystal
structure under
stress
Absorbs energy
required for
propagation of
crack
Crack shielding
and toughening of
ceramic

Zirconium dioxide (ZrO2),
or zirconia Should not be confused with
 Biomaterial since the
1970s.
 hip replacement material
 in dentistry for crown and
bridge applications since
2004.
 white crystalline oxide of
zirconium.
1. with cubic zirconia, ZrO2,
which is a cubic crystalline
form of zirconia used as a
diamond simulant
2. zirconium, which is a
lustrous, gray-white, strong
transition metal
3. zircon (also known as
zirkon), which is zirconium
silicate, ZrSiO4..

Properties of zirconia
 unique mechanical and electrical properties
 extremely useful in heat insulators, oxygen sensors, and
fuel cells.
 nonmetal with an extremely low thermal conductivity
 chemically inert and highly corrosion resistant.
 tetragonal-to monoclinic phase transition results in cracks
in bulk zirconia samples and a reduction in strength and
toughness.
 Under this condition pure zirconia would be useless for
dental restorative applications.

Temp>23670C
CUBIC
STRUCTURE
Temp<1167
MONOCLINIC
1167 °C-2367 °C
TETRAGONAL
3% to 5%
volume
increase

High-temperature tetragonal phase can be
stabilized at room temperature by
.
 Doping with Mg, Ca, Sc,Y,
or Nd
 Reduce the crystal size to
less than 10 nm
 Yttria stabilized zirconia
ceramics is known as
ceramic steel(due to
transformation
toughening)
 stabilizing oxides
1.magnesium oxide (MgO),
2.yttrium oxide (Y2O3),
3.calcium oxide (CaO),
4.cerium oxide (Ce2O3)
(highly soluble trivalent
stabilizers)
Fracture toughness of PSZ=8-10 MPa/m
Flexural strength=900MPa
Conventional ceramics =1.1-3 Mpa/m

SIGNIFICANT
PROPORTION OF
META STABLE
TETRAGONAL PHASE
LOCALIZED
TRANSFORMA
TION IN TO
MONOCLINIC
PHASE
VOLUME
EXPANSION
ADJACENT TO
CRACK TIPS
HIGH LOCAL
COMPRESSIVE
STRESS
AROUND
CRACK TIPS
INCREASE
LOCALISED
FRACTURE
TOUGHNES
S AND
INHIBIT
CRACK
PROPAGATI
OAN

• Most common stabilizer
• 3-5 mol %
• yttria-stabilized zirconia or yttria-stabilized
tetragonal zirconia polycrystals (Y-TZP).Y203
• Mg-PSZ core ceramic (Denzir-M, Dentronic
AB, Skellefteå, Sweden).
MgO
• Ce-TZP/Al2O3 core ceramic
• (NanoZir, Panasonic, Japan).
Ce2O3

Classification Based On Their Type And
Method Of Fabrication
condensed sintered
Castable glass
ceramics
Glass
ceramics
Injection
moulded glass
ceramics
Hot
isostaically
pressed
glass
ceramics
Glass
infiltrated
core ceramics
Slip cast
ceramics
Machinable
ceramics
CAD CAM
Ceramics

ADVANTAGES
 Most life like and
esthetically pleasing
 It is translucent, color
stable, brilliant
 uniformly reduced and
balanced preparation
 long life expectancy
 fine textured restoration
 increased impact strength
 Biologically
acceptable(well tolerated
by the soft tissues)
 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
 Excessive tooth reduction
 High cost of materials and processing equipments
 Wear of opposing tooth and restoration
 Low repair potential
 Brittleness of ceramics
 Difficult intraoral polishing
 Fragility when cemented with conventional cements.

DISADVANTAGES
 Margin may not be as accurate as a cast margin and a
cement line of varying dimensions can form that tends to
wash out and stain when conventional cements are used.
Therefore resin of resin ionomer type cements are
recommended.
 Cervical shadowing or “ black line” is caused by “
disruption of the light harmony between the root and
crown” of the prepared tooth and the overlying soft
tissues.To avoid this esthetic problem, the facial margin
should be placed subgingivally, but no more than half way
between the gingival crest and the depth of the sulcus.

INDICATIONS
 Obtaining the best esthetic is the single most important
consideration.
 The patient is allergic to metal.

CONTRA INDICATIONS
 Preparation of all- ceramic crown would unavoidably cause
pulpal involvement.
 The patient participates in contact sports or has a
parafunctional habit such as pipe smoking that involves heavy
contact on small areas of the dentition.
 Severe bruxism/clenching/malocclusion
 Extensive wear of tooth structure/restoration
 Excessive bite force capability/heavy occlusal forces
 Previous history of all ceramic inlay/crown fracture
 Limited interocclusal distance : in cases of short clinical
crowns, deep overbite, natural tooth is not completely erupted
or with a supra erupted opposing tooth
 Inability to maintain a dry field

Sintered/Condensed
• Optec HSP
Leucite- reinforced feldspathic porcelain
•Vitadur- N TM core
Aluminous based porcelain( Pt foil)
• Hi Ceram
Alumina based porcelain
• Mirage II
Zirconia based porcelain: Mirage II
• experimental
Magnesia based feldspathic porcelain( Experimental)
• Duceram LFC
Hydrothermal low fusing Ceramics:

Porcelain Jacket Crown
Types
 Crowns made
entirely of
feldspathic
porcelain
 Constructed on a
platinum foil matrix
which is
subsequently
removed
 Porcelain Jacket Crown-
traditional
 Porcelain Jacket Crown
with Aluminous core
 Porcelain Jacket Crown-
with Leucite reinforced
core(Optec HSP)
Porcelain
jacketcrown
Ceramicjacketcrowns
/glassceramiccrowns

ALUMINOUS PORCELAIN
 McLean and Hughes (1965)
 Increased content of alumina crystals in the core(40-50%)
 Slightly better esthetics for anterior teeth than metal
ceramic crowns
 Inadequate to use for posterior teeth.

40 t0 50 wt% of Al2O3
Flexural strength 131 Mpa
Platinum foil technique
ALUMINOUS CORE PORCELAIN
Finished CoresMaster
model with
dies
Platinum foil
adapted to
die,Platinum
foil functions
as matrix
It supports
porcelain
during
condensati
on and
firing

Unsintered CrownsDentin Ceramic
additions
Finished Crowns on
dies
Post-Cementation
Mc lean 1979 Five year failure rate 2% for anteriors 15% for posteriors
Large sintering shrinkage
Seiber et al 1981 :light reflection better than porcelain fused to metal

INDICATIONS CONTRAINDICATIONS
 shoulder thickness of only
0.5mm possible on the
labial surface.
 occlusal clearance >
0.5mm in lateral
excursions.
 The preparation is conical
with a little retention.
 Short teeth or where there
is too little tooth structure
to support such a
restoration.
 occlusal clearance < 0.5mm.
 The patient habitually grinds
or clenches the teeth.
 The patient requires a
reinforced restoration, such
as a posterior FPD.

ADVANTAGES
 withstand torque better than conventional porcelains with
fracture rates slightly less than 0.5% (MCLEAN)
 Pure alumina is 6 times stronger than standard porcelains.Thus
by combining alumina core with standard porcelain, you get a
restoration which is twice the strength of porcelain alone
(ABRAMOWSKY)
 Low thermal conductivity
 During processing, the alumina and porcelain unite by chemical
bond thus no problem in the adhesion between the different
materials
 Both materials show the same co-efficient of expansion and
contraction
 Good color consistency

HI CERAM 1985
borrowing a technique from industrial manufacturing.
It is a system similar to aluminous core ceramic crown,
using an epoxy die, a swaged resin coping and
a conventionally applied ceramic

Indications Contra indications
 Anterior crowns
 Posterior crowns where
occlusal conditions are
favorable.
 Patients who do not want a
metal core.
 Patients who are allergic to
metals.
 Patients who require light
reflection from tooth
through the core of the
crown for esthetic purpose.
 For posterior crowns
where occlusal stress is
high.

OPTEC-HSP-Leucite reinforced porcelain
 feldspathic porcelain with a
higher leucite crystal content
(leucite reinforced).
 Its manipulation, condensation
and firing is quite similar to the
alumina reinforced porcelain
jacket crowns (using platinum
foil matrix).
 Uses Inlays, onlays, veneers and
low stress crowns.
 Advantages
1. more esthetic - core is less
opaque (more translucent)
compared to the aluminous
porcelain
2. Higher strength
3. No need of special laboratory
equipment
 Disadvantages
1. Fit is not as good as metal
ceramic crowns
2. Potential marginal inaccuracy.
3. Not strong enough for
posterior use.

Duceram LFC/Hydrothermal low fusing
ceramics
Advantages
 It’s a low fusing
hydrothermal ceramic
 consists of an amorphous
glass containing hydroxyl (-
OH) ions.
 was developed in mid-1980
 first time marketed in 1989
 use in all ceramic prostheses,
ceramic/ metal-ceramic inlay,
and partial crowns.
 greater density
 higher flexural strength
 greater fracture resistance
 lower abrasion than
feldspathic porcelain.
 Being highly polishable
they do not require
glazing

• The base layer containing Leucite
• condensed on a refractory die using conventional
powder slurry technique and sintered at 930 0C.
Duracem MC
(Duceram Metal
Ceramic )
• The veneering layer
• Duceram LFC is condensed with this base layer
and sintered at 660oC
Duceram LFC
(Duceram Low
Fusing Ceramic)

Castable Glass ceramics
• flouromicas
Dicor
Dicor MGC
• Apatite based
Cerapearl(bioceram)

Glass ceramics
TYPES OF GLASS
CERAMICS
 MacCulloch in 1968.
 used a continuous glass-
molding process to
produce denture teeth.
 suggested that it should be
possible to fabricate
crowns and inlays by
centrifugal casting of
molten glass.
CASTABLE
CERAMICS
MACHINABLE
CERAMICS
HOT
ISOSTATIC
ALLY
PRESSED
CERAMICS

GLASS CERAMICS
Promotes increased strength and toughness
Loss of glassy structure by crystallisation of glass
when an intraoral force was applied
Crystalline particles, needles, or plates
interrupt the propagation of cracks in the
material
Material is formed into the desired shape as a glass
Subjected to heat treatment to induce partial devitrification

CASTABLE GLASS CERAMICS
Supplied as
 Properties are more
closer to glass
 Only porcelain restoration
made by centrifugal
casting technique
 Unique ceramming
process-enhance growth
of mica crystals
 Glass ingots
 Pre crystallised form-
Dicor MGC(as machinable
blanks for CAD CAM)
Uses
 Inlays
 Onlays
 Veneers
 Low stress crowns

Dicor
 The first commercially available castable ceramic material
for dental use
 Developed by Corning GlassWorks
 Marketed by Dentsply International
 Adair and Grossman

Fabrication of DICOR crown
Pattern constructed in wax
Invested in refractory material like a
regular cast metal crown
After buring out wax,nuggets of Dicor
glass are melted and cast into the
mould in a centrifugal casting machine

Glass casting is carefully removed from the
investment by sandblasting and the sprues are
gently cut away
The glass was then covered by a protective
“embedment” material and subjected to a heat
treatment(ceramming)
microscopic platelike crystals of tetrasilicic
fluormica to grow within the glass matrix.This
crystal nucleation and growth process is called
ceramming
Once the glass was cerammed, it was fit on the
prepared dies, ground as necessary, and coated with
veneering porcelain and a stain and glaze layer to
match the shape and appearance of adjacent teeth

Advantages
 Ease of fabrication
 Good esthetics(greater
translucency and
chameleon effect)
 Improved strength and
fracture toughness
 Good marginal fit
 Very low processing
shrinkage
 Low abrasion of opposing
teeth
Disadvantages
 Inadequate strength for
posterior use
 Internal characteristaion
not possible
 Has to be stained
externally to improve
esthetics

CHAMELEON EFFECT
 Dicor glass-ceramic was capable of producing remarkably good
esthetics, perhaps because of the “chameleon” effect, in which
part of the color of the restoration was picked up from the
adjacent teeth as well as from the tinted cements used for
luting the restorations.
 The transparent crystals scatter the incoming light.The light
and also its color, is disbursed as if the light is bouncing off a
large number of small mirrors that reflect the light and spread
it over the entire glass-ceramic.

Dicor
 characterized by the controlled crystallization (termed
ceramming) of a glass through the presence of one or
more nucleating agents.
 55% by volume of tetrasilicic fluormica
(KMg2.5Si4O10F2)
 was derived from the quaternary ceramic system, K2O-
MgF2MgO-SiO2.
 low flexural strength (110 to 172 MPa)
 low fracture toughness (1.6 to 2.1 MPa•m1/2)

Difference between Dicor and Dicor MGC.
Dicor Dicor MGC
55%vol of tetrasilicic
fluoramica crystals.
70% vol of tetrasilicic
flouramica crystals which are
2 µm in diameter
Crystallization done by the
technician.
Higher quality product that is
crystallized by the
manufacturer and provided
as cadcam blanks or ingots.
Mechanical properties
similar.
Less translucent than Dicor.
Only one shade Dark and light shades
available
Flexural strength is more
.

Hydroxyapatite based castable glass
ceramics: Cerapearl.
Sumiya Hobo and Kyocera Bioceram group of Kyoto
City, Japan .
Castable glass ceramic :CaO- P205- MgO-Si O2
Cerapearl
Oxyapatite
Hydroxyapatite
Moisture
Enamel

Melts at 14600C and flows like a melting glass.
CTE small enough to obtain accurate castings.
The cast material has an amorphous microstructure when
reheated at 8700C forms crystalline HA.
Biocompatible: Crystalline structure similar to enamel.
Enamel: Regular arrangement.
Cerapearl: Irregular arrangement.
Hence same crystal components but superior mechanical
strength.
Modulus of rupture :150 Mpa.
Enamel
Cerapearl
Properties of Cerapearl

Crowns thicker than metal ceramic because of poor flexural characteristics.
Tooth
preparation
2mm: occlusal reduction
1.5 mm: axial reduction.
1.2 mm on the margin.
Heavy chamfer or shoulder finish line.
All sharp edges should be rounded.
Procedure For Cerapearl
Waxing
A full arch impression is made.
Working cast fabricated with Type IV stone.
Dowel pins are employed.
Die spacer of 25μm is applied on the die
except within 1 mm of the finish line
Wax pattern is fabricated

Casting
Wax sprue 2.5 mm in diameter and 35 mm long. is
attached to the thick portion of the wax pattern. Other
end :orifice of the ceramic crucible.
A spl. phosphate bonded high heat investment
Investment exhibits the same CTE as Cerapearl’s casting
shrinkage( 0.53%).
The sprued wax pattern is located inside preformed
silicone form used for fabrication of ringless investment
mold and investment is poured.
Burnout procedure for cerapearl
Temperature less than 1000C for 30 min.
Temperature is raised to 5000C ,next 30 min.
Temperature is held at 8000C for 30 min.
Electric oven
Ringless investment mold with ceramic
crucible on the top

Casting of cerapearl Investment mold is transferred to
a specially designed casting machine.
8-10 g of raw Cerapearl is placed
in the ceramic crucible,
Melted under vacuum at 14600C
and cast into the mold.
Crystallization of Cerapearl.
Started at 7500C ,maintained for 15 min.
Temperature is then raised 500C per min until it
reaches 8700C and then held for one hour.
The apatite crystals would have occurred during the
process.

Cerastain by Bioceram
Trial insertion:Cerapearl.
Investment mold is removed from the oven and
cooled to room temperature.
Air abrading with 20 μ alumina oxide of the
casting.
The sprue is cut and polishing is done.
Staining and glazing:
Cerapearl is very white compared to enamel
Requires application of an external stain.

Slip cast ceramics/glass infiltrated core
ceramics
• ALUMINA
In Ceram
• MAGNESIA ALUMINA SPINELL
In Ceram Spinell(ICS)
• ZIRCONIA
In Ceram Zirconia
In Ceram 2000

GLASS INFILTRATED CERAMICS
 A process used to form
green ceramic shape by
applying a slurry of
ceramic particles and
water or a special liquid
to a porous substrate
Such as a die material,
there by allowing
capillary action to
remove water and
densify the mass of
deposited particles

GLASS INFILTRATED CORE
CERAMICS/SLIP CAST CERAMICS
3 GLASS INFILTRATED
CORE CERAMIC SYSTEMS Minimize sintering
shrinkage
 Ensure adequate fit
 Each of these partially
sintered ceramics can be
infiltrated with a
lanthanum glass without
any significant dimensional
change.
Magnesia-
alumina
spinel
(MgAl2O4)
Zirconia-
alumina core.
Partially
sintered
alumina

• 85%alumina by volume
• Mean flexural strength-600MPa
VITA In-
Ceram
Alumina
• magnesia alumina spinel (MgAl2O4)
• More translucent
• Mean strength-350MPa
In-Ceram
Spinell
(ICS)
• 62% alumina, 20% zirconia, and 18%
infiltrated glass
• Mean flexural strength-620MPa
In-Ceram
Zirconia

Glass infiltrated ceramics
Uses
 In addition to the usual inlays,
onlays, veneers and low
stress(anterior and posterior)
crowns, this material can be
used to construct low stress
anterior bridges. Because of its
occasional tendency to fracture
when used for bridge
construction its use should be
carefully selected
 For people allergic to metal
based bridges
 Where esthetics is absolutely
critical

Infiltrated with lanthanum based glass
Lanthanum glass melts Flows into pores
Forms inter penetrating
network
Sintered (11200 C for 10 hrs or more)
Porous core
Slip applied on to the gypsum die with brush-ceramic core
Water is removed by capillary action of porous
gypsum
Packed rigid network of ceramic particles
Powder particles coated with a polymer – even suspension
pH of water adjusted to create a charge on ceramic particles

Fabrication
 Two dies are required
1. In stone
2. In refractory die material
Working model
Duplication
In-Ceram refractory
dies

 Preparing the slips- A slurry of alumina is prepared and
deposited on the refractory die using the slip cast
method (the water from the slurry is absorbed by the
porous die leaving a layer of alumina on the surface).The
process is continued until a alumina coping of sufficient
thickness is obtained.
 Prepared slip should be
smooth and homogenous

vita inceramat
The fragile slip cast alumina coping is dried
at 120°C for 2 hours.
The coping is sintered (Inceramat
furnace ) for 10 hrs at11200 C
After sintering the coping are tested
for cracks using a special dye

A slurry of glass material
is applied on to the
sintered alumina coping
and fired for 3 to 5 hours
at 1120°C.
The glass fuses and
infiltrates into the porous
alumina coping through
capillary action

 The excess glass forms a glassy layer on the surface
which is trimmed off using special diamond burs.
 The coping is now ready for the rest of the build up
using dentin and enamel veneering material (Vita
VM7)
Vaccumat 4000 Premium

Application of body
and incisal porcelain
Postoperative veiw of
In-Ceram crowns
Finished In-
Ceram copings
(Air abraded)
Finished crowns
Preoperative veiw
Probster et al : Strength of In-Ceram > IPS Empress < PFM

ADVANTAGES DISADVANTAGES
 Good fit and marginal
adaptation
 Good strength
 Giordono 1995 : Al2O3
Core glass infiltrated
Ceramic > Strength than
Hi-Ceram, Di-Cor &
Feldspathic Porcelain
 Strong enough for
posterior single crowns
and anterior FPD use
 Comparatively less
esthetic because of the
opacity of the alumina
core.
 Quite tedious to fabricate.
 Not all the bridges were
successful, a few of them
did fracture occasionally.

Pressable/Hot Isostatically
Pressed/Injection Moulded Ceramics
• IvoclarVivadent
IPS Empress
• Leach and Dillon
Cerpress SL Pressable Ceramic System
• DENSTSPLY Ceramco
Finesse All Ceramic System
• IvoclarVivadent
IPS Empress11
• Pentron laboratory technologies
OptecOPC 3G
Contain
35% vol of
Leucite
crystals
Contain
65-70%
vol lithia
disilicate

HOT-ISOSTATICALLY PRESSED(HIP)
GLASS-CERAMICS

PRESSABLE
CERAMICS
HEAT PRESSED
GLASS
CERAMICS
Leucite
reinforcedK2O –
Al2O3 – 4 SiO2
IPS
Empress,Finesse,
Optimal,Cerpress
Lithium Disilicate
reinforcedSiO2 –
LiO2 – P2O5 – ZrO2
IPS Empress
II,OPC 3G
HEAT PRESSED
VENEERING
CERAMICS
IPS
ZirPress,VitaPM9

The most well-known
leucite-based products
 IPS Empress (Ivoclar
Vivadent)
 Cerpress SL Pressable
Ceramic System (Leach
and Dillon)
 Finesse All-Ceramic
System (DENTSPLY
Ceramco).
 The glassmatrix layering
ceramic for these core
materials also contains leucite.
 low flexural strength (up to
112 MPa) and fracture
toughness (0.9 to 1.3
MPa•m1/2) but twice that of
feldspathic ceramic
 Higher porosity (9%)
 not recommended for molar
crowns or bridges.
First generation pressable ceramics

Second generation pressable ceramics
 contain approximately
65% to 70% by volume of
lithia disilicate
(Li2O•2SiO2) as the
principal crystal phase.
 narrow sintering range-
processing of ceramic
prostheses very technique
sensitive
 IPS Empress 2 (Ivoclar
Vivadent) and Optec OPC
3G (Pentron Laboratory
Technologies)
 Initially lithium
metasilicate,cristobalite
forms
 Final structure- highly
interlocked lithium
disilicate crystals(0.5µ in
length and 0.8µ in
diameter)

Second generation pressable ceramics
Advantages
 Improved strength ( Inter
locked micro structure
and layered crystals)
 crack propagation is
difficult in a direction
perpendicular to the
crystals alignment
 Flexural strength twice
that of 1st generation.
 mean flexural strength is
approximately 350 MPa
compared with the 112-MPa
strength of leucite-based
glass-ceramics.
 This strength and a fracture
toughness of 3.3 MPa·m1/2
for lithia disilicate–based
glass-ceramics are generally
sufficient for
1.most anterior and posterior
crowns
2.anterior three unit bridges

Reasons for improved flexural strength
Additional re crystallisation during firing
Additional firings Improved flexural strength
Contributes to crack deflection
Prevent crack propagation Improved mechanical properties
Difference in coefficient of thermal expansion of glassy matrix and crystals
Tangential compressive stresses develop around leucite/lithium disilicate crystals

Fabrication of Pressable ceramics
 Technique similar to
injection moulding
 Since from a single ingot –
mono chromatic
 Can be cast as coping and
layered with veneering
ceramics
 Used for inlays, onlays,
single crowns and veneers
Glass ceramic
ingot is heated
Allowed to flow
under pressure into
mould using lost
wax technique
Contoured, stained,
and glazed for final
finish

FABRICATION
 The wax patterns of the restoration are invested in
refractory material and heated to 8500 C in a furnace to
burn off the wax and to create mould space

Burn out 8500 C
It is then transferred to the
pressing furnace

Ceramic ingot &an
Alumina plunger is
inserted in to the
sprue
Pressing temperature
1075-11800 C-IPS
Empress
9200 C-IPS Empress II
Under air pressure-1500
psi

 Core of restoration is retrieved from the flask
 Compatible veneering porcelains are added to core to
build up final restoration

Property IPS Empress IPS Empress II
Core ceramic Glass ceramic with 35% vol of
leucite crystals.
Glass ceramic with 70%
vol of lithium disilicate
crystals.Lithium
orthophosphate in
much lower
concentrations.
Veneering
ceramic
Also contain leucite crystals in
glass matrix
Contains apatite
crystals which causes
light scattering similar to
tooth structure.
Processing
temperature
11800C 9200C

Property IPS Empress IPS Empress II
Flexural strength 112±10Mpa 400±40
Fracture
toughness MPa/
m1/2
1.3±0.1 3.3±0.3
Thermal
Expansion
coefficient(ppm/
0C)
15±0.25 10.6±0.25
Veneering
temperature
9100C 8000C
Chemical
durability(μg/
cm2
100-200 50

Heat pressed(hot isostatically
pressed)ceramics /injection moulded
ceramics
Advantages Disadvantages
 Better fit- because of
lower firing shrinkage
 Better esthetics-absence
of metal or an opaque
core
 Need for costly
equipment
 Potential fracture of
posterior areas
Edward B Goldin 2005 compared leucite IPS Empress with PFM
Mean marginal discrepancy 94 + 41 PFM
81 +25 IPS

Machinable ceramics
Milled or machined ceramics
CAD CAM Systems
Copy milled systems

Essentials of a CAD CAM System
• Virtual impression
Scanner/digitizer
• Virtual design (CAD)
Computer
• Produces the restoration or framework
Milling station
• Raw material for restoration
Ceramic blanks
• Post sintering,ceramming
Furnace

Schematic representation of CAD CAM
production
Tooth preparation
Conventional impression and die
fabrication
Wax pattern
Restoration or
framework
design(CAD)
Restoration or framework
milling(CAM)
Furthur processing-simple glazing
and staining to post sintering and
build up with veneering ceramics
Contact probes
/ optical
scanning

SCANNER OR DIGITIZER
 CONTACT PROBES
 Physically contacts the die
as it moves along its
surface while transmitting
the information to the
computer
 Eg.Procera Forte contact
scanner

Scanners
Intra oral hand held wands Laboratory scanners
 Chair side scanners
 Reflects light(visible
light,laser or LED)
 Captures it with a camera
 Create an optical
impression of prepared
tooth and adjacent
structures
 Stitch multiple images to a
3D image in computer
 Larger scanners
 Scan the cast or die
1. use a camera to capture
multiple images
 Eg.white light optical scanner
2.Two cameras to capture the
object from multiple
angles using white light
Eg.Kavo Everest
3.Laser planes projected in a
grid pattern

Procera
optical
scanner-
conoscopic
holography

Most recent versions of digital impression
softwares
 3M ESPE Lava Chairside
Oral Scanner C.O.S
 3M ESPE CEREC AC
 Sirona Dental Systems
 LLC;E4D Dentist
 D4DTechnologies
 iTero
 Cadent,Inc.
 Allow complete 3D
visualisation of the
projected restoration with
virtual seating capabilities
 Various surfaces of the
virtual restoration can be
modified in all three
dimensions prior to
machining

Lava Chairside Oral Scanner
C.O.SiTero
Parallel
confocal
imaging-100000
point maps at
300 focal
depths spaced
50µ apart
Based on active optical wavefront
sampling
3 sensors collect video data from
different perspectives
20 3D datas per second
24 million datapoints per arch

3M ESPE CEREC AC
High speed swept laser beam
combined with a camera
Series of 3D SCANS
Principle of LASER
triangulation
CEREC Bluecam-blue light
emitting diode and camera
system
Active triangulation to
create images of the tooth
surface

Computer/CAD Process
 Restoration/core is designed based on software
 Can automatically detect finish line
 Some use a library of tooth shapes stored in computer
and suggest the proposed restoration
 A recording of bite registration is also added to the data
 Combined information+3D optical impression-establishes
approximate zone in which the new restroration can
exist
 Can modify and correct the design if required

MILLING STATION
 Signals from computer - milling tool which shapes the
ceramic block (according to the computer generated
designs)
 Performed by a diamond or carbide milling tool
 Cerec station-2 diamond bur to grind internal and
external surface simultaneously
 Other machines-single tool moving along multiple axis(2-
5 axis)
 Everest or kavo engine-5 axis milling station;Can mill both
ceramic and titanium

Can be
produced by
by chair-side
milling units
industrial
milling
processes
 processing multiple jobs with a
high level of accuracy and
reproducibility.
 very expensive( with typical
costs in excess of several
hundred thousand USD for
industrial CAD CAMS)
limited in their
processing speed and
their ability to process
large cases.

CERAMIC BLANKS
• Vitablocs Mark II (Vita)
Feldspathic porcelain blanks
• DIcor MGC,(tetrasilicis flouromica)Pro Cad,Everest G(Kavo)(leucite),IPS emax
CAD(Kavo)(lithia disilicate)
Glass ceramic blanks
• Alumina,(Vita InCeram Alumina)spinell,(Vita InCeram Spinell),zirconia(Vita In Ceram Zircona)
Glass infiltrated blanks
• Alumina (Vita In Ceram AL),
• Yttria stabilized zirconia (Vita In CeramYZ)
Pre sintered blanks
• Yttria stabilized zirconia (Everest ZH blanks)
Sintered blanks

Machinable ceramicsFromCADCAMceramic
blanks
Feldspathic porcelain-
Vitablocs Mark II
Lithia disilicate glass
ceramic-IPS e max
CAD,Kavo
Glass infiltrated
Partially sintered
zirconia-Vita In
CeramYZ
Sintered zirconia-
Everest ZH
FromCopymilledceramic
blanks
Alumina blocks-Celay
In Ceram
MgAl2O3 blocks-In
Ceram spinell

• Can be milled to full contour
Feldspathic porcelain blanks
• Can be milled into full contour
Leucite reinforced
• Usually machined as cores or FPD substructures
• Subsequent glass infiltration,veneering,and glazing
Glass infiltrated blanks
• Machined in intermediate crystalline state-material shows characteristic
blue shade
• In this stage easier to shape and try in mouth
• Followed by simple, quick crystallization process-30 mnts
Lithium disilicate

MACHINABLE ALL CERAMIC MATERIALS
HARD MACHINING
SOFT MACHINING
FOLLOWING SINTERING
 Machined in
fully sintered
state
 Restoration is
machined
directly to final
size
 In partially sintered state
 Later fully sintered
 Requires milling of an enlarged restoration
to compensate for sintering shrinkage
 Used for alumina,spinell,zirconia(difficult to
machine in fully sintered state) Copings are
furthur glass infiltrated
 Microstructure similar to that of slip cast
ceramics
 Final marginal accuracy within 50µ

Hard machining
Machining of restoration from ceramic blocks by a computer controlled milling machine
Takes only few minutes
Bond to tooth preparation with resin
cements
Design restoration with aid of computer
Tooth preparation
Optical scanning Computerisation of image

Presintered Zirconia Sintered Zirconia
 Most zirconia frameworks
are fabricated by machining a
porous or partially fired
block
 Used as cores for crowns
and FPDs
 Softer and easier to mill
 Milled to larger size(20%)
 Shaped by carbide burs
 Post sintering
 Sintering time-6-7.5 hours
 Sintering temperature-1350-
15300 C
 No need of post sintering
 No shrinkage is expected
 Takes more time(2hrs for a
single crown) and wear of
milling tool(extreme
hardness)
 Shaped by diamond disks
and burs
 Core construction for
crowns and long span
anterior and posterior FPDS

• Cercon (Degudent/DENTSPLY Ceramco)
• Lava (3M ESPE),
• ZirkonZahn (USA),
• HintEls Zirkon TPZ-G (DigiDent)
GREEN
STATE
MILLING
• IPS e.max ZirCAD (IvoclarVivadent)
• VITA In-CeramYZ Cubes (VITA Zahnfabrik),
• Everest (Kavo Dental),
• Hint-Els Zirkon TZP-W (Digident)
• DC-Shrink (DCS)
• Precident DCS (DCS)
PARTIALLY
SINTERED
MILLING
• Denzir Premium HIP Zirconia (Etkon USA)
• Zirkon Pro 50 (Cynovad)
• Kavo Everest ZH Blanks (Kavo Dental)
FULLY
SINTERED
STATE
MILLING

a simulated digitized image of a crown to
be produced from a ceramic blank and an
adjacent image of a partially milled crown.

Cerec ceramic block, a milled inlay form,
and the final inlay.

A four-unit Cercon core ceramic framework
can be milled in the green state

after sintering, staining, and glazing the
veneering ceramic

Procedural sequence for producing
ceramic prostheses by a CAD-CAM
system using partially sintered blanks:
Set the blank in
milling machine
Set the
enlargement
factor
Insert appropriate
milling/machining
tool
Remove the
framework and
residual blank
Cut the
framework from
blank using
diamond disk
Clean the partially
sintered
framework
completely

Dry the framework
completely
Place the
framework in the
isothermal hot zone
of the sintering
furnace
Set the thermal
processing
conditions according
to sintering
instructions
Sinter the
framework to
achieve optimal
density
After cooling
remove framework
Inspect for surface
and sub surface flaws
using fibre optic
trans illumination

Evaluate the
framework for
adequacy of wall
thickness,ease of
seating,and marginal
fit
Use water cooled
diamond tool to
perform minor
adjustment
corrections
Rinse the
framework
thouroughly with
water and dry it
completely
Depanding on the
zirconia product
framework used
with or without
veneering ceramic
Transitional liner
prior to application
of veneering
ceramic

COPY MILLED (CAM) SYSTEMS
 Wax pattern of restoration is scanned
 Replica is milled out of the ceramic blank
Celay
• Mikrona
Technologies,
Spreitenbach,
Switzerland
Cercon
• Degudent,
• Dentsply
• Has both
CAD CAM
and copy
milling system
Ceramill system

CELAY SYSTEMS
 Uses copy milling technique
 Resin pattern fabricated directly on master die and
pattern is used for milling porcelain restorations
 Jacot et al 1998 : in ceram blanks in celay system.
Sorenson 1994 : marginal fit of CELAY > CEREC
Inlay pattern mounted
(copy side)
Copy milling pattern out
of ceramic material
(milling side)

 It is an innovative system developed by Dr.Stefan I.
Eidenbenz at the university of Zurich in 1994
 It is a high precision, manually operated copy milling
machine and the fabrication principle is the same as for
'Key' duplication.

prefabricated pattern of the
designed restoration made
from a blue resin-based
composite (Celay-Tech, ESPE,
Seefeld-Oberbay, Germany).
The resin pattern can be
produced directly on
prepared teeth or indirectly on
dies made from impressions

As the tracing tool passes over
the pattern, a milling machine
duplicates these movements as it
grinds a copy of the pattern from
a block of Alumina or other
ceramic material

Advantages Disadvantages
 Precisely fitting ceramic
restorations can be
developed without a lab
technician in high grade
factory fired porcelain, in a
very short time in one
session.
 The grains are finer than
conventional In-Ceram,
therefore the strength is
more than conventional.
 the accuracy of the copy-
milled crowns is
dependent on the care,
time, and the profile
tracing ability of the
technician, the marginal
quality of crowns made
from the copy-milling
technique is likely to be
inferior to that of copings
made from the hot
pressing method.

3.CERCON
 It is commonly called as a CAM system as it does not
have a CAD component.
 This system scans the wax pattern and mills a zirconia
bridge coping from presintered zirconia blanks, which is
sintered at 1,3500C for 6-8 hrs.
 Veneering is done later on to provide esthetic contour.
 Marginal adaptation for the cercon crowns and fixed
partial dentures was reported 31.3 μm and 29.3 μm
respectively.

Ceramill system
 Based on pantograph type of copy milling
 ‘puts material back in the hands of technician,
 To create a zirconia coping,user applies light cure resin
over a traditional die
 Attaches resin pattern into a plastic plate
 Inserts it into milling unit side by side withYtZP zirconia
blank

Two conjoined arms of Ceramill system
• User manually traces
the resin build up
with probe tip
Holds the
probe tip
• Simultaneously mills a
duplicate coping out
of the zirconia block
Milling
handpiece

1.CEREC(Chair Side Economic
Reconstruction of Esthetic Ceramic)
CEREC 1
• 1980-s
CEREC II
• 1996
CEREC III
• 2000
Optical scanner is used to scan
the preparation or the impression
and a 3D image is formed on the
monitor.There is a milling unit to
prepare the restoration
Can record multiple images within a
few seconds, which enables the
clinician to prepare multiple teeth in
same quadrant thereby creating a
virtual cast for that quadrant

Cerec System consists of :
 A 3-D video camera
(scan head)
 An electronic image
processor (video
processor) with memory
unit (contour memory)
 A digital processor
(computer) connected to,
 A miniature milling
machine (3-axis machine)

Materials used with CEREC
 Dicor MGC (Machinable Glass Ceramic)(Dentsply)-mica
based machinable glass ceramic containing 70% vol of
crystalline phase
 Vita Mark II (Vident):contain sanidine (KALSi3O8) as a
major crystalline phase within a glassy matrix.

 ProCad (Ivoclar):Like Ivoclar's popular Empress™
material, ProCAD is reinforced with tiny leucite particles,
and has been referred to as: "Empress on a stick".
 Vita IN-Ceram Blanks (Vita Zhanfabrik):
 IN-Ceram Spinell.
 IN-Ceram Alumina.
 IN-Ceram Zirconia

Clinical Procedure:
 Tooth preparation follows typical all-ceramic guidelines.
 Optical impression

Clinical shortcoming of Cerec 1 system :
 Although the CEREC system generated all internal and
external aspects of the restoration, the occlusal anatomy
had to be developed by the clinician using a flame-shaped,
fine-particle diamond instrument and conventional
porcelain polishing procedures were required to finalize
the restoration.
 Inaccuracy of fit or large interfacial gaps.
 Clinical fracture related to insufficient depth of
preparation.
 Relatively poor esthetics due to the uniform colour and
lack of characterization in the materials used.

Cerec 2
 The changes include :
 Enlargement of the grinding unit from 3 axis to 6 axis
 Upgrading of the software with more sophisticated technology
which allows machining of the occlusal surfaces for the
occlusion and the complex machining of the floor parts.
 Other technical innovations of Cerec 2 compared to Cerec 1:
 The improved Cerec 2 camera : new design, easy to handle, a
detachable cover (asepsis/sterilization), reduction in the pixel
size/picture element to improve accuracy and reduce errors.

 Data representation in the image memory and processing
increased by 8 times, while the computing capacity is 6
times more efficient.
 Magnification factor increased from x8 to x12 for
improved accuracy during measurements.
 Improved in rigidity and grinding precision by 24 times.
 Improved accuracy of fit

Cerec 3
 Software still easy and user friendly which uses windows
as operating system.
 Two compatible cameras available- SIROCAM 2 /
SIDEXIS.
 Precise restorations.
 Extra-oral and intra-oral measuring.
 Rapid production.
 The imaging unit and the milling unit can be linked via
cable, IRD port, networked.
 Supported with online help and design.

Cerec-3 that can design well-fitting inlays, onlays, crowns, veneers etc.,
in a single visit.

Advantages of CEREC System
 One or two appointments.
 Optical impression, max time required is 5 sec.
 Wear hardness similar to enamel.
 Less fracture due to single homogenous block.
 Excellent polish.
 Improved esthetics.
 Time saving.
 Good occlusal morphology in relation to antagonist.

INDIRECT CAD - CAM
System that consists of several modules with at least, two
distinctive CAD & CAM stations
 The optical impression is taken in the dental office, where
CAD is done; data are transmitted to CAM station for
restoration fabrication.
 The optical impression is taken in the dental office;
collected information is then transmitted to a central
station, where CAD & CAM modules operate.

 Because of the overall dimensions and the cost of the
indirect CAD – CAM devices, they are usually not located
in the dental office, but more likely in a central laboratory
where data is collected from different treatment places.
E.g.
 Duret system.
 Procera system (Noble Bio-Care).
 Cicero system(Elephant Industries).
 President system (DCS Dental).
 CEREC SCAN & CEREC InLAB (Sirona Dental company)

CEREC SCAN
 CEREC SCAN (inclusive of both scanning and milling
device)with lap top(imaging device).

 Tooth preparation.
 Conventional impressions.
 Die preparation.
 Controlled by one of the practice pc’s.
 Works upon CEREC 3 software.
 Intra oral scanning device is not present.

Parallel milling with two tools

High speed milling of copings and bridge frame work.

2. DCS Precident
 Consists of a laser Scanner called as Preciscan and a
multitool milling center called Precimill CAM.
 The DCS software automatically provides suggestions for
connector sizes and pontic forms.
 It can scan upto 14 dies simultaneously and mill 30
frameworks in one fully automated operation.
 It can also mill titanium and fully dense sintered zirconia.
An in vitro study showed that marginal discrepancies of
alumina and zirconia based posterior fixed partial denture
machined by the DCS system was between 60 μm to
70μm

3. Procera All Ceram System
 introduced in 1994.
 first system which provides outsourced fabrication using a
network connection.
 According to research data average marginal gap for
Procera all Ceram restoration ranges from 54 μm to 64
μm.

Procera All-Ceram
 Developed by Dr. Matts Andersson for Nobel Biocare
embraces the concept of computer assisted design and
computer assisted machining .
 The technician can design a coping for a full crown
restoration controlling the thickness, emergence profile,
and precision of fit.
 The design data can be forwarded to the manufacturing
facility and the coping produced in various materials.
 The Procera AllCeram Crown involves a densely sintered
high-purity alumina core combined with a low fusing
veneering porcelain fabricated by the pressed powder
technology.

Advantages:
 The finished crown has a translucence very similar to the
natural tooth.
 Aluminum oxide is a highly biocompatible material,
comparable to titanium.
 The coping is made of dense-sintered aluminum oxide to
maximize strength.
 The Procera technique guarantees high precision for
optimal fit.

 A technician using the special Procera design station
scans the die and designs the coping to be fabricated.This
station consists of a computer, a modem and the Procera
scanner
 Once positioned on the scanner, a probe lightly touches
the die as it is rotated.A 3D map is produced from this
"tactile scan" that consists of approximately 50,000 data
points from around the die.

 After the master die is
scanned all the 3-D images
are transferred to the
processing center through
an internet link
 an enlarged die is milled
by a computer controlled
milling machines.
 The coping is sent to the
lab for veneering of
porcelain
Contact scanner
Shape on computer screen

4. CICERO system (computer integrated
crown Reconstruction)
 it was introduced by Denison et al in 1999,
 it includes optical scanning, metal and Ceramic sintering
and computer assisted milling to obtain restoration.
 The aim of CICERO is mass production of ceramic
restorations at one integrated site.
 It includes rapid custom fabrication of high strength
alumina coping and also partially finished crowns to be
delivered to dental laboratories where porcelain layering
or finishing can be done.

5.Lava system
 introduced in 2002
 mainly used for fabricating zirconia framework for the all
ceramic restorations.
 Yttria stabilized tetragonal zirconia poly crystals (Y-TZP)
are used in this system are better than the conventional
ceramics as they have greater fracture resistance.
 uses a laser optical system to transfer and digitize
information received from the preparation.
 The Lava CAD software suggests a pontic automatically
according to the margin.

Cementing of ceramic restorations
-Resin bonding agents
 Increase the retention of all-ceramic crowns and bridges.
 High bond strength
 Esthetics at margins is better
 Improved translucence
 Increase the fracture resistance and survivability of
ceramic restorations
 Reduces water access to the inner ceramic surface
 Etching blunts the tips of microcracks within the
ceramic,thereby inhibiting crack propagation

Bonding of cement to porcelain can be
improved by
• Create minute irregularities on the inner surface-
help the cement to retain better
• Clean in distilled water in an ultrasonic bath-10
minutes
1.Sandblasting
• Done with hydroflourous acid or ammonium
biflouride
• 2minutes
2.Chemical
etching
• Functions as coupling agent(difunctional
molecule)
• for silica based porcelains
3.Use of silane
primers

SILANE PRIMERS/COUPLING AGENTS
 Contain one or more silicon
atoms
 3-methacryloxypropyl
trimethoxysilane
 Silane primers provide
covalent bonds that
promote adhesion at the
interface between polymers
and hydrolytically stable
silica based substrates,
assuming that the substrate
is free of contaminants
The bonding stage of silane
primer or adhesive to a
silicabased ceramic.

Silane as a di functional molecule
Methacrylate
group
• Capable of co
polymerisation with
methacrylate based
adhesives and resins
Methoxy
group(–
OCH3)
• that are hydrolyzed to
silanols (Si–OH) for
bonding to inorganics
such as silica-based
ceramics or metal oxide
substrates through the
formation of siloxane (–
Si–O–Si–) bonds.

Reaction of silanes with slica based
ceramics-4 stages
• Of methoxy groups
Hydrolysis
• Of oligomers
Condensation
• the oligomers then hydrogen bond with OH groups of the substrate.
Hydrogen bonding
• during curing, covalent links are formed with the substrate with
simultaneous loss of water
Bond formation

Factors affecting abrasiveness of dental
ceramics
Properties of the crystal phase particles and the glass
matrix (if present)
 hardness
 tensile strength
 fracture toughness
 fatigue resistance
 particle-glass bonding
 particle-glass interface
integrity
 chemical durability
 exposure frequency to
corrosive chemical agents
 acidulated phosphate fluoride,
carbonated beverages
 abrasiveness of foods,
 residual stress
 subsurface quality (voids or
other imperfections)
 magnitude and orientation
of applied forces
 chewing patterns
 bruxing frequency
 contact area
 lubrication by saliva
 duration of exposure to
abrasive particles.

Minimizing excessive wear of enamel
(1) ensure cuspid-guided disocclusion
(2) eliminate occlusal prematurities
(3) use metal in functional bruxing areas
(4) if occlusion is in ceramic, use ultralow-fusing ceramics
(5) polish functional ceramic surfaces
(6) re polish ceramic surfaces periodically
(7) readjust occlusion periodically if needed.

CHEMICAL ATTACK OF GLASS-PHASE CERAMICS
BY ACIDULATED PHOSPHATE FLUORIDE
 When glazed feldspathic porcelain is exposed to 1.23%
APF or by 8% stannous fluoride, a surface roughness is
produced within 4 min.
 a 30-min exposure to 1.23% APF gel appears to
preferentially attack the glass phase (areas with white
precipitate particles) of a gingival (body) porcelain.
ROUGHNESS STAINING
PLAQUE
ACCUMULATION
BREAKDOWN OF
THE STRUCTURE

CHEMICAL ATTACK OF GLASS-PHASE
CERAMICS BY ACIDULATED PHOSPHATE
FLUORIDE
 Acidulated phosphate fluoride (APF), one of the most
commonly used fluoride gels, is known to etch glass by
selective leaching of sodium ions, thereby disrupting the
silica network.
 Use of lower concentrations( 0.4% stannous fluoride and
2% sodium fluoride)-no significant effect
 Avoid the use of APF gels when composites and ceramics
are present.
 Should not be used on glazed porcelain surfaces. If such a
gel is used, surface of the restoration should be protected
with petroleum jelly, cocoa butter, or wax.

PORCELAIN DENTURE TEETH
 Denture teeth are made by packing two or more
porcelains of differing translucencies(High fusing
porcelains) for each tooth into metal molds.
 They are fired on large trays in high-temperature ovens.
 Porcelain teeth are designed to be retained on the
denture base by mechanical interlocking.

• are made with
projecting metal pins
that become
surrounded with the
denture base resin
during processing,
Anterior
teeth
• are molded with
diatoric spaces(holes)
into which the
denture base resin
may flow.
Posterior
teeth

DISADVANTAGES
 more esthetically satisfactory
(natural looking)
 much more resistant to wear
 Excellent biocompatibility
 only type of denture teeth
that allow the denture to be
rebased (replacement of the
entire acrylic denture base)
 Brittleness
 Need for mechanical retention
 Extra time required to grind
and contour the surfaces
 Clicking sound produced on
contact with the opposing
teeth.
 Higher density;increased
weight
 Require a greater interridge
distance because they cannot
be ground as thin in the ridge
lap area as acrylic teeth
without destroying the diatoric
channels that provide their
only means of retention to the
denture base resin.
ADVANTAGES

SHADE GUIDES
 Shade guides are produced by dental ceramic
manufacturers
1.to assist dentists and lab technicians in selecting optimum
ceramic shades
2. for communicating the desired prosthesis appearance to
each other.
 Shade guides made of porcelain are used most often by
dentists to describe a desired appearance of a natural
tooth or ceramic prosthesis.

Hue-is the basic color
A
SHADES OF
ORANGISH
BROWN
B
SHADES OF
YELLOW
D
YELLOWISH
BROWN
Chroma is
the intensity of
that color, so
that a higher
degree of
chroma would
have a higher
concentration
of hue.
Value is the
amount of
grayness or
whiteness. To
lower the value
means to
darken, and to
raise the value
means to
lighten. The
"C" shades can
be used to
indicate four
basic values.

Value Saturation Hue
DetermineThe Lightness
Level (Value)
• Hold shade guide to
patient’s mouth at
arms length
• Start with darkest
group moving
right to left
• SelectValue group 1, 2,
3, 4, or 5
From your
selectedValue
group,
remove the middle
tab (M) and
spread the
samples out like a
fan
Select one of the
three shade
samples
to determine
Chroma/saturatio
n
Check whether
the natural
tooth is
more yellowish
or more reddish
than
the shade
sample

Deficiencies of shade guides
1. Shade guide tabs are much thicker than the thickness of
ceramic that is used for dental crowns or veneers, and they
are more translucent than teeth and ceramic crowns backed
by a nontranslucent dentin substructure or veneering
ceramics backed by an opaque core ceramic, or a metal
framework
2. Much of the incident light is transmitted through a tab. In
contrast, most of the incident light on a crown is reflected
except at the incisal edge and at proximal incisal areas.
3. the necks of shade tabs are made from a deeper hue—that
is, higher chroma—and this region tends to distract the
observer’s matching ability in the gingival third of the tab.To
avoid this situation, some clinicians grind away the neck area
of a set of shade tabs

The VITA Easyshade
 It is a simple-to-use point and click digital
spectrophotometer that provides instant dental
shade readouts regardless of the lighting conditions.
• Defines how the desired shade is developing between
biscuit firings, regardless if the crown is wet or dry.
• This approach assures that the final
success of the shade will exhibit
color from within, rather than a
stained external surface
.

Fracture of ceramic-ceramic prostheses
(Hientze and Rousson-2010)
• Need polishingGrade 1
• Need repairGrade 2
• Need replacementGrade 3

Repair of ceramic restorations
Porcelain
etching gel(HFl
acid)
Bonding agent
Opaquer(mask
the metal)
Glaze

Repair of ceramic restorations
Gingival
tissues are
protected
with a
protective
gel(Kool
Dam)
Ceramic is
etched with
the gel
Bonding
agent is
applied and
light cured
Opaquer(for
metal
ceramics)
After
trimming and
shaping –final
glaze
For bulk repair a regular light cured composite is used

FACTORS ASSOCIATED WITH FRACTURE
OF ALL CERAMIC PROSTHESES
design
inherent
surface
defects
loading bite force
and load
orientation
processing
defects
diet
procedural
errors
residual
stress
material
properties

Factors contributing
to
Surface
treatment Excessive
loading
during try in
Bruxing
loads
Loading
location
Load
distribution
Load
magnitude Transient
cooling
stresses
Crack
propagation
chipping
Crack
initiation
Bulk
fracture
Residual
cooling
stresses
Inadequate
tooth
preparation
Improper
core
framework
design
Inadequate
crown
thickness
Inadequate
core
thickness
Improper
connector
size
Quality of
cement
layer
Bond
quality of
ceramic
veneer to
core
ceramic
Voids in
cement
layer or at
cement
ceramic
interface
Elastic
moduli of
components
Elastic
moduli of
supporting
substrate
materials

How to reduce risk for ceramic fracture?
Sufficient tooth
reduction
Adequate prostheses
design
Distributed vertical
loading
sufficient thickness of
ceramics
meticulous attention
to the recommended
manufacturers’
procedures

Selection criteria for dental ceramics
Esthetic
demands of
patient
Type of
luting
cement
Amount
of tooth
reduction

Selection criteria for dental ceramics
• All types of metal ceramics
• up to 2nd molar
Single crowns
• Glass ceramics
• up to pre molars
• Maximum of four units
Anterior bridge
• Zirconia-based ceramicsLong span
bridges
• Zirconia based restorations
• Only when adequate tooth preparation is possible
• Proper veneering of zirconia core
Anterior
esthetic zone

How to make a decision?
Material to
be
used/design
Intra oral
conditions
Esthetic
needs
expectations
Financial
resources of
the patient
Anticipated
success
rates
Survival
time
Minimize
risk factors
Optimal
treatment
options

Longevity of ceramic restoration
Factors
 Material factors
 Dentist,lab,technician
factors
 Patient factors
 Operator reliability
 Prevailing oral conditions
Longevity
Metal ceramic
restorations
5-8 years
All ceramic
restorations
15 years-up to
90% retention
3-5 years-100%
retention

Survival rate of all ceramics
Powder
condensation
CAD-CAM
ceramics
Hot
pressing
technique

IDENT-CERAM System for identification of
ceramic products
 Introduced in 2007
 To identify
1.manufacturer/company
2.brand name
3.composition of materials
 Six in number
 Recognizable letter code-
helps to ensure proper
insurance coding
 practical way to document
informations

The letter codes
Ident Ceram Ident Alloy
• FDA LISTED ALUMINIUM OXIDE
AO
• FDA APPROVEDYTTRIUM
ZIRCONIAYZ
• FDA REGISTERED LITHIUM
DISILICATE GLASS CERAMICLD
• FDA CLEARED LEUCITE GLASS
CERAMICLG
• FDA REGISTERED
• FLUORAPATITE GLASS CERAMICFE
• FDA REGISTERED LEUCITE GLASS
LE
• HIGH NOBLE
HN
• NOBLE
N
• PREDOMINANTLY BASE
METAL
PB

Dental ceramics part 2

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