This document discusses dental ceramics, including their classification, composition, and uses. It addresses: 1) The different types of dental ceramics classified by use, processing method, and fusion temperature including metal ceramics, ceramic denture teeth, and porcelain for jackets, crowns, veneers and inlays. 2) The composition and function of ingredients in high fusing porcelains including feldspar, quartz, and kaolin. 3) Methods for strengthening porcelain, such as chemical strengthening, dispersion strengthening, and thermal tempering. 4) Applications of all-ceramic systems including pressed ceramics, machinable ceramics, and

2. DEFINITION
Dental Ceramic
0An inorganic compound with nonmetallic
properties typically composed of oxygen and
one or more metallic (or semimetallic) elements,
e.g. aluminum, calcium, magnesium and
zirconium, etc. that is formulated to produce the
ceramic based prosthesis.

3. Classification of dental
ceramics
According to use:
••Metal ceramics
••Ceramic denture teeth
••Anterior bridge porcelain
••Jacket crown, veneer, inlay porcelain.

4. Classification of dental
ceramics
According to processing method:
••Sintering
••Partial sintering and glass infiltration
••CAD-CAM
••Copy milling.

5. Classification of dental
ceramics
According to fusion temperature:
••High fusing ceramics—1300°C
••Medium fusing ceramics—1101°C to 1300°C
••Low fusing ceramics—850°C to 1100°C
••Ultra low fusing ceramics—< 850°C

6. High Fusing Porcelains
The basic ingredients of these types of porcelains
are:
• Feldspar
• Kaolin (clay)
• Quartz.

7. Feldspar
• Primary constituent
• Present in concentration of 75 to 80 percent
• Potassium feldspar is selected because of increased
resistance to pyroplastic flow and increased viscosity
• Undergo incongruent melting at 1150°C to 1530°C to
form a liquid and crystalline material, i.e potassium
alumino silicate known as leucite.

8. Quartz
• Present in concentration of 13-14 percent
• Main function is to act as strengthener
• Also increases the translucency of
porcelain.

9. Kaolin
• Present in concentration of 4 to 5 percent
• Main function of Kaolin is to act as binder
• Lowers the translucency of porcelain.

10. High Fusing Porcelains
Composition Percentage Function
Feldspar 75 - 80 Increased viscosity
Quartz 13-14 Strengthener
Increases the
translucency
Kaolin 4 - 5 Binder
Lowers the
translucency

11. Medium and Low Fusing Ceramics
0The medium and low fusing ceramics are formed
by process known as fritting and product
obtained is termed as frit.
0The basic ingredients for medium and low fusing
ceramics are same as those of high fusing but in
addition, certain glass modifiers are also added.

12. Glass Modifiers
• Most commonly used are potassium, sodium and
calcium oxides
• Act as fluxes and reduces the softening
temperature of glass
• Also lowers the viscosity of glass.

13. Intermediate Oxides
• Most commonly used is aluminum oxide
(Al2O3)
• Lowers the softening temperature along with
viscosity

14. Boric Oxide (B2O3)
• Acts as glass former and glass modifier
• Lowers the melting point and viscosity of glass
• Matrix of B2O3 is formed by 3-dimensional
arrangement of BO3 triangles.

15. Opacifying Agents
Most commonly used agents are:
• Zirconium oxide
• Titanium oxide
• Cerium oxide.

16. Coloring Agents
Various coloring agents used to obtain proper hue
and chroma.

17. Metallic pigments Color
Ferric oxide Gray
Titanium oxide Yellowish brown
Manganese oxide Lavender
Cobalt oxide Blue
Nickel oxide Brown
Chromium-alumina Pink
Copper oxide Green

18. Stains or Color Modifiers
• Used to create markings like enamel check lines,
decalcification spots, etc.
• Used for creating gingival effects and in
highlighting body color of porcelain.

19. METHODS OF STRENGTHENING PORCELAIN
Chemical Strengthening:
0 Chemical strengthening is usually carried out by replacing
small sized cations in the surface layer with large sized
cations while matrix remains the same.
0 This is also known as low temperature ionic crowding.
0 Sodium ions present in the matrix are replaced by large size
potassium ions by placing porcelain crown in bath of
potassium nitrate.

20. METHODS OF STRENGTHENING PORCELAIN
Dispersion Strengthening:
0 Dispersion strengthening is process in which strengthening is
done with dispersed phase of different material with a
capability of blocking a crack from propagating the material.
0 Dispersion strengthening of ceramic can be obtained by
increasing the crystal content of alumina, leucite and
zirconia..

21. METHODS OF STRENGTHENING PORCELAIN
Thermal Tempering
0 It is most common method for strengthening glass.
0 This process creates residual compressive stresses in the
glass by heating and when it is in molten state, it is
immediately quenched.
0 This quenching (rapid cooling) produces a rigid glass
surrounding a soft molten metal.

22. METHODS OF STRENGTHENING PORCELAIN
Reduce the Number of Firing Cycles
0 The main function of firing cycle is to sinter the powder particles
together and produce a relatively smooth surface.
0 If number of firing cycles is increased, the leucite content of
porcelain also increases which further increases the coefficient of
thermal expansion of porcelain.
0 The expansion mismatch between porcelain and metal creates
stresses on cooling which can cause crack formation in the porcelain.
0 Thus reduction in number of firing cycles can help in reducing crack
formation.

23. METHODS OF STRENGTHENING PORCELAIN
Creating residual compressive stresses
0 In this technique inner layer (core) has high coefficient of
thermal expansion than outer layers, creating stresses and
strengthening the porcelain.

24. METHODS OF STRENGTHENING PORCELAIN
Transformation Toughening
0 In this process, small and tough particles are uniformly
dispersed in the matrix so that cracks cannot pass through these
crystals.
0 Ceramics can be toughened by variety of crystalline particles
such as:
• Alumina
• Leucite
• Lithium di-silicate.

25. METAL CERAMIC RESTORATIONS
All ceramic restorations though look very natural
but are very brittle and subject to fracture.

26. Composition of Metal Ceramic Alloys
Nickel-chromium
alloys
Nickel 62 to 76 %
Chromium 13 to 28 %
Cobalt chromium Cobalt 52 to 68%
Chromium 24 to 33 %
Molybdenum. 2 to 7 %

27. Failures of Metal Ceramic Restorations
0 Fusion of porcelain grains inside the
coping
0 Thin margins of metal buckle due to
contraction of porcelain
0 Casting contamination by low fusing alloy
components from the metallic die
0 Forceful fitting may result in elastic
deformation of the metal and breakdown
in porcelain bond.

28. ALL CERAMIC SYSTEM
0All ceramic system have high strength and
precision fit close to that of ceramometal in
addition to esthetics.

29. Classification of all ceramic systems
Traditional powder slurry
ceramic
Alumina reinforced ceramic (Hi-
ceram)
••Leucite reinforced ceramic (Optec-
HSP).
Infiltrated ceramic In ceram
••In ceram spinel.
Castable ceramic Dicor.
Pressable ceramic IPS empress 1 and 2.
Machinable ceramic Cerec vitablocks mark I and II
••Dicor MGC
••Celay.

30. Traditional Powder Slurry Ceramic
These are supplied in powders which are mixed with
water to form ‘slurry’.
This slurry formed can be built up in different layers on a
die to form the restoration.
Alumina
Reinforced
Ceramic
• This type of ceramic is based on dispersion
strengthening— one of the method used for
strengthening of ceramic.
• Alumina crystals are dispersed uniformly in
glass matrix to increase strength, toughness
and elasticity of the material.

31. Leucite
Reinforced
Ceramic
• In this type, leucite crystals (potassium alumino
silicate) are dispersed in glassy matrix.
• Leucite is added in feldspathic porcelain to match
the thermal contraction of ceramic to the metal but
it also acts as reinforcing filler because of very
high tensile strength.
• The leucite and glassy components are fused
together and baked at 1020°C to form the ceramic.
• These ceramics have high strength and good
translucency.

32. Infiltrated Ceramic
0 To overcome the disadvantages of aluminous porcelain, a
new system is introduced known as infilterable ceramic
in which alumina/spinel is used as the core material.

33. In Ceram Composition 1. Powder: Aluminum oxide
2. Low viscosity glass.
Procedure: • Alumina powder is mixed with water
to form slurry known as ‘Slip’ which
is painted on die.
• This procedure leaves a layer of solid
alumina on the surface
• Sintering is done at 1120°C for 10
hours to form porous core
• Glass is selected and applied on the
porous core and firing is done at
1100°C for 3 to 5 hours
• The molten glass infiltrates by
capillary action into core
• This results in high strength
composite structure, i.e. In ceram.

34. In Ceram
Spinel
Composition spinel (aluminum and magnesium oxide)
is used as the core material.
Advantages: • It has better translucency than In
ceram
• High opacity due to higher
concentration of alumina crystals.
• This type of ceramic can be used for
crowns—both anterior and posterior
crowns.

35. Castable Ceramic
0 Castable ceramic was first introduced in 1984.
0 In this, a glass ceramic is a material which is modified
into the desired shape and size as a glass and heat
treatment is given to induce crystallization. The process
of crystallization is known as ceramming.

36. DICOR. Composition After ceramming, the material contains:
• 55 percent—Tetrasilicic fluoride
crystals
• 45 percent—Glass ceramic.
Advantages: • It has better translucency than In
ceram
• High opacity due to higher
concentration of alumina crystals.
• This type of ceramic can be used for
crowns—both anterior and posterior
crowns.

37. Pressable Ceramic
0 This type of ceramic is available as core ingot which is
heated at high temperature and pressed into a mold.
0 The pressing process is done for duration of 45 mintues
at high temperature to get ceramic substructure which
further can be shaded with stains or by glazing.

38. Pressable
Ceramic
Types 1. IPS Empress 1:
Contains 35 vol.
percent of leucite
crystals
2. IPS Empress 2:
Contains 70 vol.
percent of lithia
disilicate crystals.
Advantages: • Lack of metal
• High flexural strength
• Excellent fit
• Excellent esthetics.
Disadvantage • Prone to fracture in posterior areas.

39. Machinable Ceramic
0 These ceramics are supplied in the form of ceramic
blocks under various shades.
0 Later on, these blocks are fabricated into inlays, onlays
and crown with the help of CAD-CAM or copymilling.

40. Computer Generated Ceramic Restorations
0 Indirect computer generated ceramic restorations can be made
chair side in CEREC® SYSTEM–CAD (Computer aided
design), CAM (Computer aided manufacturing).
0 Using a special camera, an accurate picture of the tooth is
taken which is transferred and displayed on a color computer
screen, where CAD technology is used to design the
restoration.
0 Then CAM takes over and automatically creates the restoration
in a matter of minutes.

42. Advantages
:
1. Total time required for an inlay or onlay from
tooth preparation to cementation is about one
hour
2. A single appointment restoration Conventional
impression, multiple sittings and temporary
restorations are not required
3. Quality of the ceramic restorative material is very
good.
4. Blocks of very good quality machinable ceramics
are used
5. No laboratory expenses in inlays and onlays
6. A natural looking filling with excellent esthetics
7. Results in a restoration that is antiabrasive, bio-
compatible and resistant to plaque.

43. Disadvantages: 1. High cost of the equipment
2. Special training is required
3. More conservative tooth preparation is
required
4. Computer prepares rough occlusal anatomy
without consideration of opposing occlusal
anatomy
5. Requires final occlusal adjustments.

44. PORCELAIN LAMINATE VENEERS
Indications Extrinsic permanent staining, not masked by
bleaching techniques.
• Intrinsic staining caused by:
– Physiological aging
– Erosion and abrasion
– Trauma
– Amelogenesis imperfecta
– Fluorosis
– Enamel hypoplasia
– Tetracycline staining.
• Nonvital tooth
• To correct malformed tooth like peg shaped lateral
incisors
• To repair fractured incisal edges
• For treatment of diastema

45. Contraindications • Patient with high caries risk
• Teeth with poor periodontal condition
• Tooth with gingival recession
• In cases where the preparation has to be
extended up to
cervical tooth structure
• In malaligned teeth (rotated and overlapped
teeth)
• In deep bite cases (because of unfavorable
occlusal forces)
• In severely discolored teeth (crown is better
option in
these teeth)
• In tooth with interproximal caries
• Poorly motivated patient.

46. Advantages • Conservative tooth preparation (only about 0.5 mm
of facial reduction is needed)
• Since tooth preparation is confined to the enamel
layer.
• Local anesthesia is not usually required
• Excellent esthetics and color match
• Chemically inert, so resistance to fluid absorption
• Biocompatible in nature
• Good abrasion resistance.

47. Disadvantages • Fragile and brittle in nature
• Difficult to repair or modify after cementation
• Expensive than amalgam or composite
• Need special and expensive laboratory
equipment
• Intraoral finishing and polishing is a time
consuming procedure
• Highly technique sensitive
• Needs precise tooth preparation.

48. Tooth
Preparation
• Generally a minimum of 0.5 mm depth is required,
though amount of reduction depends upon the
extent of discoloration.
• The margin should follow the gingival crest.
• This results in veneering of whole discolored
enamel without unnecessary involvement of the
gingival sulcus
• Place the “long chamfer” margin.
• This design results in an obtuse cavo-surface angle,
which exposes the enamel rods at the margin for
better etching.
• Provide clearance for separating the working cast
and for accessing the proximal margins for
finishing and polishing.
• This can be done using a diamond finishing strip.
• Finally confirm that all prepared surfaces are
rounded so as to prevent areas of stress
concentration in the porcelain

49. CERAMIC INLAYS AND ONLAYS
Indications • When esthetics is main concern
• Patient having good oral hygiene status
• Suitable for large preparations
• When accessibility and isolation of tooth are easy
to achieve
• When there are no excessive undercuts in the tooth
preparation
• When preparation margins are on enamel and
sound tooth structure making it feasible for bonding.

50. Contraindications • In patients with poor oral hygiene
• Patient with multiple active caries
• Because of their brittle nature, they are
contraindicated in patients with excessive
occlusal loading, such as bruxers
• When esthetic is not main requirement
• In cases with minimal tooth loss
• When moisture control is difficult to achieve
• In cases with excessive attrition of teeth
• Inadequate enamel for bonding
• When marked undercuts are present in the
tooth preparation.

51. Advantages
• Excellent esthetic
• Low thermal conductivity
• Long lasting
• Chemically inert
• Low coefficient of thermal expansion
• Biocompatible nature.

52. Disadvantages • More expensive than amalgam or composite
• Requires special and expensive laboratory
equipment
• Takes two appointments
• Intraoral finishing and polishing is a time
consuming procedure
• Fragile and brittle, so, intraoral occlusal
adjustment is not possible before it is bonded to
place
• Abrasive to the opposing enamel
• Highly technique sensitive.

53. Initial Tooth
Preparation
• Outline form is usually governed by the existing
restoration and caries.
• It is grossly similar to that for conventional metal
inlays and onlays except that bevels and flares are
not given here.
• In Initial tooth preparation the carbide burs are
used.
• Bur should be held tapering to make straight facial
and lingual walls that diverge occlusally to allow
the insertion and removal of restoration.

54. Final Tooth
Preparation
• During final tooth preparations, coarse diamond
preparation points are used.
• Always remove the undermined or weakened
enamel.
• Do the central groove reduction (approximately
1.5-2 mm) following the anatomy of the
unprepared tooth.
• This provides additional bulk for the ceramic so as
to have strength.
• There should be at least 1.5 mm of clearance in all
excursions to prevent ceramic fracture.
• Preparation walls should exhibit 6 to 8 degree of
occlusal divergence per wall.

55. Proximal box
and line
angles
preparation
• Extend the proximal box to have a minimum of
0.6 mm of clearance for impression making.
• Isthmus width should be minimum of 1.5 mm to
prevent fracture.
• Margins of the preparation should be kept
supragingival.
• The width of the gingival floor of the box should
be approximately 1.0 mm.
• All internal angles should be rounded and
preparation walls should be smooth and even.
• All cavosurface margins should be made butt
angled.
• Bevels are contraindicated because bulk is needed
to prevent fracture.
• A distinct heavy chamfer is recommended for
ceramic onlay margins.