Dental Ceramics: A Guide to Materials, Properties and Applications

Dental Ceramics
DR.AHNAF ABDULLA P
1ST YEAR PG
1

Contents
 Introduction
 What are ceramics?
 History of dental ceramics
 Structure
 Composition
 Mechanical properties
 Classifications
 Metal-ceramic system
 Fabrication of metal ceramic prosthesis
 All ceramic system
 Strengthening of ceramics
 REVIEW OF LITERATURE
 Recent Advances
 ALL CERAMICS
 PFM
 SUMMARY
 CONCLUSION
2

What are ceramics???
 The word ceramic derived from Greek
word κεραμικός( keramikós) "potter's",
from κέραμος(kéramos), "potter's clay“
 Dental ceramic are non-metallic , inorganic
structures, primarily containing compounds of
oxygen with one or more metallic or semi-metallic
elements (aluminium, boron, calcium, cerium,
silicon, sodium, titanium, zirconium)
3
1.Shabalin, Igor. (2015). Ceramic Materials Science & Engineering (Part 1 - Classification & Application).
10.13140/RG.2.1.4181.4568. 2. Craig's Restorative Dental Materials. St. Louis, Mo: Mosby.13th edition Elsevier, 2006

 William David Kingery(July 27, 1926 – July 8, 2000)
"father of modern ceramics"
“The art and science of making and using solid articles,
which have, as their essential component, and are composed in
large part of inorganic non-metallic materials”
4
Shabalin, Igor. (2015). Ceramic Materials Science & Engineering (Part 1 - Classification
& Application). 10.13140/RG.2.1.4181.4568.

Definition
“compounds of one or more metals with a nonmetallic element, usually
oxygen; they are formed of chemical and biochemically stable substances that
are strong, hard, brittle, and inert nonconductors of thermal and electrical
energy” - GPT-9
5

What is Porcelain?
 The European name, porcelain in English, comes from the old Italian
word porcellana (cowrie shell) because of its resemblance to the surface of
the shell.
 In dentistry, the term porcelain generally associated with ceramic produced
with significant amount of kaolinite(Hydrated alumino sliciate).
 Kaolin is type of clay, only used in high fusing porcelain and ceramic
denture teeth
 None of the modern low fusing or ultra low fusing porcelains contains any
product such as kaolinite.
 These ceramics are technically not porcelain and they can be considered a
type of glass
6
1.Wikipedia contributors. Porcelain [Internet]. Wikipedia, The Free Encyclopedia; 2019 Nov 1, 23:03 UTC [cited 2019
Nov 3]. Available from: https://en.wikipedia.org/w/index.php?title=Porcelain&oldid=924121159
2. Craig's Restorative Dental Materials. St. Louis, Mo: Mosby.13th edition Elsevier, 2006

History of dental ceramics 7
In 1808, Fonzi, an Italian dentist, invented a “terrometallic” porcelain
tooth held in place by a platinum pin or frame
The first porcelain tooth material was patented in 1789 by de
Chemant, a French dentist in collaboration with Duchateau, a French
pharmacist
Because natural minerals are not tooth-colored,
subsequent civilizations used variety of materials like
ivory, bone, human teeth , animal teeth
Ceramic-like tools have been used by humans since the end of the
Old Stone Age around 10,000 B.C. to support the lifestyles and needs
of fisher-hunter-gatherer civilizations.

8
History of dental ceramics
Planteau, a French dentist, introduced porcelain teeth
to the United States in 1817, and Peale, an artist,
developed a baking process in Philadelphia for these
teeth in 1822.
Commercial production of these teeth began in 1825
1844 S.S White company started mass production of
porcelain denture teeth
Charles Land introduced one of the first ceramic
crowns to dentistry in 1903.
Excellent esthetics but low flexural strength.
Since 1960s, feldspathic porcelains are used in metal-
ceramic prosthesis.
Need of tougher core, firing shrinkage

9
In the early 1990s a pressebale glass-ceramic (IPS Empress), 37% leucite
Similar strength and marginal adaptation of Dicor , no need of specalised crystalisation treatment.
Introduction of Machinable glass-ceramic (Dicor MGC) -70% Tetrasilicic fluormica crystals
Improvement in all ceramic systems developed by controlled crystallization of a glass (Dicor) was demonstrated by
Adair and Grossman (1984).
Tetrasilicic fluormica crystals were present
A significant improvement of fracture toughness reported when Mc Lean & Hughes,1965 introduced aluminous
core ceramic consisting 40 to 50 % Al2O3 by weight.
High flexural strength, low fracture rate in anteriors
Need of porcelain veneer for esthetics
Two of the most important breakthroughs in the history metal-ceramic restorations are happened in 1962
1.Feldspathic porcelain that enable the systemic control of sintering temperature and CTE
2.Alloys that bond chemically and that are thermally compatible with the feldspathic porcelain

10
These improvement of composition of ceramic and the method of forming the core of all-
ceramic crowns and bridges have greatly enhanced our ability to produce more accurate and
fracture resistant all ceramic crowns.
1992: Ultralow fusing ceramic Duceram LFC
Late 1990s- IPS Empress 2 was developed containing approximately 70vol% of Lithia disilicate
crystals.
This core unit has been used for three-unit fixed prosthesis

Structure
GLASS
PHASE
CRYSTAL
PHASE
CERAMIC
12
Structure of ceramics

Silicate ceramics
Oxide ceramics
Nonoxide ceramics
Glass ceramics
13
Structure

 Silicate Ceramics
• Amorphous glass phase with a porous structure
• Main component is SiO2
• Al2O3,MgO,ZrO2 and other oxides
• Dental porcelains falls into this category
14
Structure

 Oxide ceramics
• No or small content of glass phase
• Principal crystalline phase are Al2O3,MgO,ThO2 or ZrO2
• Zirconia is important because of its fracture toughness
• Y2O3(Y-CSZ) ,fully stabilized with yttria
• Examples: spinell (MgO.Al2O3) , mullite (3Al2O3.2SiO2) and Aluminium
(Al2TiO)
• In-Ceram spinell- The spinell structure used in a glass infiltrated ceramics
15
Structure

 Nonoxide ceramics
• Impractical in dentistry
• High processing temperature or complex methods
• Unaesthetic color and opacity
• Examples: Boaride,Carbide,Nitride,Selenide,Silicide,Sialon,Syalon
16
Structure

 Glass ceramics
• Partially crystalized glasses that are produced by nucleation and growth of
crystals in the glass matrix phase
• Dicor glass-ceramic is one of such products
• This material is supplied as glass ingots
17
Structure

18
There are only three main
classes of dental ceramics:
1. predominantly glassy materials
2. particle-filled glasses
3. Polycrystalline ceramics

1. predominantly glassy materials
 Dental ceramics that best mimic the optical properties of
enamel and dentine are predominantly glassy materials.
 Glasses are 3-D networks of atoms having no regular pattern
to the spacing (distance and angle) between nearest or next
nearest neighbours, thus their structure is ‘amorphous’ or
without form.
 Glasses in dental ceramics derive principally from a group of
mined minerals called feldspar and are based on silica (silicon
oxide) and alumina (aluminum oxide)
 feldspathic porcelains belong to a family called
aluminosilicate glasses
19

2. Particle-filled glasses
 Filler particles are added to the base glass composition in order to improve
mechanical properties and to control optical effects such as opalescence, colour
and opacity
 The first fillers to be used in dental ceramics Contained particles of a crystalline
mineral called Leucite.
 This filler was added to create porcelains that could be Successfully fired onto
metal substructures.leucite Has a very high thermal expansion ⁄ contraction
coefficient compared to feldspathic Glasses.
Glass-ceramics (special subset of particle-filled glasses)
 Crystalline filler particles can be added mechanically to the glass, by simply mixing
together crystalline and glass powders prior to firing.
 In a more recent approach, the filler particles are grown inside the glass object
(prosthesis or pellet for pressing into a mould) after the object has been formed.
 After forming, the glass object is given a special heat treatment, causing the
precipitation and growth of crystallites within the glass.
 Since these fillers are derived chemically from atoms of the glass itself, it stands to
reason that the composition of the remaining glass is altered as well during this
process (termed ‘ceraming’).
20

3. Polycrystalline ceramics
 Polycrystalline ceramics have no glassy components; all of the atoms are
densely packed into regular arrays that are much more difficult to drive a
crack through than atoms in the less dense and irregular network found in
glasses.
 Hence, polycrystalline ceramics are generally much tougher and stronger
than glassy ceramics.
 Polycrystalline ceramics are more difficult to process into complex shapes
(e.g. a prosthesis) than are glassy Ceramics
 Polycrystalline ceramics tend to be relatively opaque compared to glassy
ceramics, thus these stronger materials cannot be used for the whole wall
thickness in aesthetic areas of prostheses
21

Feldspar
 It is the most abundant group of minerals in the earth's crust, forming
about 60% of terrestrial rocks.
 Most of the products we use on a daily basis are made with feldspar: glass
for drinking, glass for protection, fiberglass for insulation, the floor tiles
and shower basins
 Chemically, the feldspars are silicates of aluminum, containing sodium,
potassium, iron, calcium, or barium or combinations of these elements.
 Feldspars are used as fluxing agents to form a glassy phase at low
temperatures and as a source of alkalis and alumina in glazes. They
improve the strength, toughness, and durability of the ceramic body,
22

Silica
 It is one of the most abundant elements on earth and can exist in many
different forms such as crystalline materials like Quartz,Cristobalite,
Tridymite and amorphous materials like Fused quartz,Agate, Jasper and
Onyx.
 Pure Quartz crystals (SiO 2 ) are used for manufacturing dental porcelain.
 Quartz (crystalline silica) used in porcelain as a filler and strengthening
agent.
23

Kaolin
 IT is a type of clay material which is usually obtained from igneous rock
containing alumina.
 Kaolin acts as a binder and increases the moldability of the unfired
porcelain.
 It also imparts opacity to the porcelain restoration so dental porcelains are
formulated with limited quantity of kaolin.
24

Cont..
 Glass modifiers are used as fluxes and they also lower the softening
temperature and increase the fluidity
 Color pigments or frits are added to provide the characteristic shade.
 Stains created by mixing the metallic oxides with low fusing glasses. Stains
also permit surface characterization and color modification for custom
shade matching.
25

Why ceramics?
 Biocompatibility
 Esthetic potential
 Refractory nature
 High hardness
 High flexural strength
 Excellent wear resistance
 Chemically inert
27
Mechanical properties

Advantages
 Resistant to corrosion
 Chemical inertness
 Remain stable over longtime periods.
 Biocompatible
 High hardness
 Potential for matching appearance of natural teeth
 Refractory nature
 low thermal low electrical conductivity
28

Disadvantages
 Susceptibility to tensile fracture
 Brittleness
 Low to moderate strength and fracture toughness
 Poor ductility/elongation
29

 Toughness
Amount of elastic and plastic deformation energy
required to break a material.
 Brittle
Relative inability of a material to sustain
plastic deformation before fracture of a
material occurs.
 Ductile
Ability of a material to sustain a large permanent
deformation under a tensile load up to the point
of fracture.
30

32
1. What are ceramics?
2. What are porcelains?
3. History
4. Structure
5. Why ceramics?

Back to basics
 What is stress?
 What is strain?
 Tensile stress vs compressive stress
33

Why are we avoiding shear stress in dental
ceramics?
34
The force that resist the sliding or twisting of one portion of body
over another

Cont.
1. Many of the brittle materials used in a restored tooth
surface generally have rough, curved surfaces.
2. The presence of chamfer, bevels, or changes in the curvature
of a bonded tooth would also make shear stress failure of a
bonded material highly unlikely.
3. To produce a shear failure, the applied force must be
located immediately adjacent to the interface.
4. Because the tensile strength of a brittle material is usually
well below their shear strength value, tensile failure is more
likely to occur.
35

Difference between proportional limit and elastic limit
Proportional limit Elastic limit
It is defined as the point up to which
the stress and the strain are directly
proportional
It is defined as the point up to which
the material remains elastic
materials are elastic and the strain is
proportional to stress below this point.
In the region between elastic limit and
proportional limit, the materials are
elastic but the strain is not proportional
the stress
36
For many materials the elastic limit is equivalent or nearly equivalent to
the proportional limit. For other materials, such as elastomers, the stress-
strain relationship is non-linear and the material will still be within its
elastic region long after it has passed through its proportional limit.

Difference between elastic limit and yield strength
the yield strength is defined as the stress which
will produce a small amount of permanent
deformation, generally occur to a strain of 0.002 or
0.2%
A yield strength or yield point is the material property
defined as the stress at which a material begins to
deform plastically. Prior to the yield point the material
will deform elastically and will return to its original
shape when the applied stress is removed.
37

Flexural strength (or the modulus of rupture) is
the amount of force an object can take without
breaking or permanently deforming
1. 3.0 bend test
𝜎 = 3𝑃𝐿 ÷ 2𝑊𝑇2
2. 4.0 bend test
𝜎 = 3𝑃𝐿 ÷ 4𝑊𝑇2
This test is a collective measurement
of tensile, compressive, and shear stresses
simultaneously
For sufficiently thin specimen, dominated
by tensile stress
38
Flexural strength

Fracture toughness/critical stress intensity
Resistance of brittle materials to the catastrophic propagation
of flaws under an applied stress or in other words, indicates the
amount of force that needs to be applied to cause crack extension
o The higher the value, the lower will be the probability of the crack
spreading in a material.
o A high value, therefore, is an indicator of superior clinical long-term
performance – and consequently a longer lasting material.
o Clinically, restorations are not loaded to failure as is done in a
flexural strength test; instead, millions of subcritical loads (chewing)
are applied.
o Materials ultimately fail because of this cyclic fatigue by crack
propagation.
o Thus, materials with higher fracture toughness are more ideal
clinically as it takes more energy to cause crack growth.
39
Dental ceramics: An update
Arvind Shenoy, Nina Shenoy
J Conserv Dent. 2010 Oct-Dec; 13(4): 195–203. doi: 10.4103/0972-0707.73379

Methods of testing
 The ISO (International Organization for Standardization) has
adopted the single-edge precracked beam (SEPB) method as
the standard technique for measuring fracture toughness
 The indentation fracture (IF) method has been widely used for
dental ceramics because specimen preparation is easy and no
special devices are required
41
MAEHARA et a, Fracture Toughness Measurement of Dental Ceramics Using the Indentation
Fracture Method with Different Formulas :Dental Materials Journal 24 (3) : 328-334, 2005

43
Based on indications
1. Anterior crowns
2. Posterior crowns
3. Veneers
4. Post and cores
5. FPDs
6. Stain ceramic
7. Glaze ceramic
Based on composition
1. Silica glass,
2. Leucite-based glass-
ceramic,
3. Lithia disilicate-based glass
ceramic,
4. Pure Alumina,
5. Pure Zirconia,
Based on processing
method
1. Sintering,
2. Partial sintering
and glass
infiltration,
3. Hot-isostatic
pressing,
4. CAD-CAM,
5. Copy milling,
Based on firing
temperature
1. Ultralow fusing
2. Low fusing
3. Medium fusing
4. High fusing
Classification of ceramics

44
Based on microstructure
1. Glass
2. Crystalline
3. Crystal-
containing glass
Based on composition
1. Opaque
2. Translucent
3. Transparent
Based on fracture
resistance
1. Low
2. Medium
3. High

45Based on methods of
processing
METAL CERAMIC SYSTEM ALL CERAMIC SYSTEM
1. Manually condensed feldspathic
porcelain
2. Hot isostatically pressed(HIP)
veneering ceramic
3. Ceramic stains
4. Glazes
1. HIP or CAD-CAM ceramics
2. Manually condensed veneering
ceramics
3. Hot-pressed veneering ceramics
4. Liners
5. Ceramic stains
6. Ceramic glaze

Metal-ceramic system 46
Dental porcelain
• Less tensile, fracture toughness
Metal coping
• Unesthetic
Veneering with porcelain
• Superior mechanical properties
• esthetic

47
Metal-ceramic restorations consist of a cast metallic core on
which at least two layers of ceramic are baked.
i. Opaque layer – To mask the metal framework, helps in
metal ceramic bond.
ii. Dentin and enamel porcelain – For esthetic appearance.
Metal-ceramic system

The metal/ceramic pair then combines good aesthetic properties
of ceramic materials with good mechanical properties of base metal,
achieving an oral rehabilitation in a functional and aesthetic context.
48
Nieva, N., Arreguez, C., Carrizo, R. N., Molé, C. S., & Lagarrigue, G. M. (2012). Bonding Strength
Evaluation on Metal/Ceramic Interfaces in Dental Materials. Procedia Materials Science, 1, 475–
482.

Copings for metal-ceramic prosthesis
Electrodeposition of gold or other metal on a duplicate die
Casting of a pure metal or an alloy through the lost wax
process
Burnishing and heat-treating metal foils on a die
CAD-CAM processing of a metal ingot
49

Requirements of metal coping
1) The alloy must have a high melting temperature.
2) The veneering porcelain must have a low fusing temperature so that no creep, sag
or distortion of framework take place during sintering.
3) The porcelain must wet the alloy readily when applied as a slurry to prevent void
formation.
4) A good bond between metal and ceramic is essential
5) Coefficient of thermal expansion of the porcelain and metal must be compatible
6) Adequate stiffness and strength of metal framework is important
7) High resistance to deformation at high temperature is essential
8) Adequate design of the restoration
50

Ceramics
 The addition of the soda, potash and leucite in ceramic is necessary to
increase thermal expansion to a level compatible with the metal coping.
 Problem with the high alkali content is that, repeated firing may cause
devitrification as well as changes in the thermal contraction behaviour.
51

 Conventional dental porcelain is a ceramic based on a silica(SiO2) network
and potash feldspar(K2O.Al2O3.6SiO2), soda feldspar(Na2O.Al2O3.6SiO2)
or both.
 Feldspar used for dental porcelain are relatively pure and colourless.
 Thus pigments, opacifiers, and glasses are added into the porcelain.
 silica is the basic structural units of the glass network.
 Different forms of silica:
 Crystalline quartz
 Crystalline cristobalite
 Crystalline tridymite
 Non crystalline fused silica
52

Glass modifiers
Problems with the
silica
High sintering
temperature
Low thermal
contraction coefficient
53
Solution:
Addition of alkali ions such as sodium, potassium or calcium

Porcelains according to their firing temperature
 Ultralow fusing <850°C
 Low fusing 850 to 1100 °C
 Medium fusing 1101 to 1300 °C
 High fusing >1300 °C
Potential advantage of ultralow-fusing ceramics are the reduction in
sintering times, decrease in sag formation of FPD frameworks, less thermal
degradation of ceramics.
Some of ultralow-fusing porcelain are used for titanium and titanium
alloys, to reduce risk of growth of metal oxides.
54

Water as a glass modifier
 Water acts as glass modifier in moist oral environment.
 The hydronium ion in the water can replace sodium or other
metal ions in a ceramic that contains glass modifiers.
 This leads to “slow crack growth” of ceramics that are exposed
to tensile stresses and moist environments, may account for
the occasional long-term failure of porcelain restorations after
several years of service.
55

Feldspathic porcelain
 Potassium and sodium feldspar are naturally occurring minerals composed
primarily of potash(K20) and soda(Na2O) respectively.
 They also contain alumina and silica components.
 Feldspar(K2O.Al2O3.6SiO2) has a tendency to form leucite
(K2O.Al2O3.4SiO2) when its melted.
 Leucite has large coefficient of thermal expansion compared with feldspar
glasses.
 Many dental porcelain glasses do not contain as a raw material , so these
glasses are modified with the addition of leucite to control their thermal
contraction coefficient.
56

Other additives
Boric oxide forms a separate lattice interspersed with the silica lattice, it
interrupts the rigid silica network and lowers the softening point and
decrease the viscosity of the glass.
Colouring pigments:
 Metallic oxide fused together with fine glass and feldspar and then
regrinding to a powder.
 These powders are blended with unpigmented powder to frit to provide
the proper hue and chroma.
 Iron or nickel oxide –brown
 Copper oxide – green
 Titanium oxide – yellowish brown
 Manganese oxide – lavender
 Cobalt oxide - blue
57

Porcelain condensation
 Porcelain is supplied as a fine powder that is designed to be mixed with water or
another vehicle and condensed into the desire form.
Benefits of dense packing of powder
1. Lower firing shrinkage
2. Less porosity
58

Various condensation methods
59
vibration
Spatulation
Brush technique

Sintering porcelain
 Purpose of firing is simply to sinter the particles of powder together
properly to form the prosthesis.
 Some chemical reactions occur during prolonged firing times or multiple
firings like changes in the leucite content.
61

62
Condensed porcelain
mass is placed below the
muffle of a preheated
furnace at approximately
650°C for low-fusing
porcelain
After preheating for 5 min
the porcelain is placed
into the furnace
At the initial firing, the
voids are occupied by air
As the temperature raises
sintered glass gradually
flows to fill up the air
space
When the vacuum is
introduced the pressure
inside the muffle is
reduced
As temperature rises
further particles sinter
together and closes the
voids present inside the
porcelain mass
At temperature below
55°C below upper firing,
the vacuum is released
and the pressure inside
the furnace is increases
10 times
The voids are compressed
to one-tenth of their
original size
Cont..

 Internal staining and characterisation can produce a lifelike appearance
and permanent results rather than merely applied to the surface.
 A fine polishing of roughened surface followed by glazing produces best
results rather than polishing alone.
63

Bonding porcelain to metal
 The primary requirement for the success of a metal-ceramic prosthesis is
the development of a durable bond between the porcelain and the alloy.
 Theories of metal-ceramic bonding:
1. Mechanical interlocking
2. Chemical bonding
64

 The oxidation behaviour of alloys largely determines their potential for
bonding with porcelain.
 Rather than the thickness of the oxide layer the quality of the oxide and
its adhesion to the metal substrate is the most important factors.
65

Glazing and shading of ceramics
 The glazing is a effective way in bridging the surface flaws and the surface
will be under a state of compressive stress reducing the crack propagation.
 If the glaze is removed by grinding, the transverse strength may will
reduce to 40% to 46% less than that of porcelain with the glaze layer
intact.
 The clinical importance of this is, it is common practice for the dentist to
adjust the occlusion by grinding the surface of the porcelain, unfortunately
this procedure weakens the porcelain.
 Characterising the porcelain with stains and glaze also produce more life
like appearance.
66

 Ceramics have been the mainstay of esthetic dentistry for more than 100
years.
 Beginning with John McLean’s introduction of aluminous porcelain in the
mid-1960s, there have been continuous improvements in strength,
esthetics, and methods of fabrication, resulting in dozens of products for
clinicians to choose from.
68
Gracis et al: “A new classification system for all-ceramic and ceramic-like restorative
materials.” Int J Prosthodont. 2015 May-Jun;28(3):227-35.

An often-used classification system by Kelly and
Benetti, describes ceramic materials according to glass
content and can be described as follows:
(1) predominantly glassy materials
(2) particle-filled glasses
(3) polycrystalline ceramics in which no glass is present
69

Classification
In light of this and other considerations, the authors proposed a new
approach to classifying ceramic restorative materials into three families,
1. Glass-matrix ceramics: nonmetallic inorganic ceramic materials that contain a
glass phase
2. Polycrystalline ceramics: nonmetallic inorganic ceramic materials that do not
contain any glass phase
3. Resin-matrix ceramics: polymer-matrices containing predominantly inorganic
refractory compounds that may include porcelains, glasses, ceramics, and
glass-ceramics.
70

71
Gracis et al: “A new classification system for all-ceramic and ceramic-like
restorative materials.” Int J Prosthodont. 2015 May-Jun;28(3):227-35.

1. Glass-Matrix Ceramics
1. Feldspathic
(eg, IPS Empress Esthetic, IPS Empress CAD, IPS Classic, Ivoclar Vivadent;
Vitadur, Vita VMK 68, Vitablocs, Vident)
 This material system composed of clay/kaolin (hydrated aluminosilicate),
quartz (silica), and naturally occurring feldspar (a mixture of potassium and
sodium aluminosilicates)
 These materials are still used as a veneering material on metal alloy and
ceramic substrates and as an esthetic material bonded onto tooth
structure.
72

2. Synthetic
a) leucite-based (eg, IPS d.Sign, Ivoclar Vivadent; Vita VM7, VM9, VM13,
Vident; Noritake EX-3, Cerabien, Cerabien ZR, Noritake);
b) lithium disilicate and derivatives (eg, 3G HS, Pentron Ceramics; IPS e.max
CAD, IPS e.max Press, Ivoclar Vivadent; Obsidian, Glidewell Laboratories;
Suprinity, Vita; Celtra Duo, Dentsply)
c) fluorapatite-based (eg, IPS e.max Ceram, ZirPress, Ivoclar Vivadent)
These materials are modified to match the coefficient of thermal
expansion of their respective frameworks to be used as a veneer material on
all-ceramic frameworks,
73

What are pressable ceramics?
 Proposed by MacCulloch in 1968
76
•Forces the
ceramic ingot
into a moldCeramic ingot Allow it to cool
Ceramic take
Shape of the
mold
Debribd and
stained and
glazed or
veneered with
conventional
technique.
Ceramic is
removed from
the mold
The hot pressing process occur over 45 minutes.
ALL CERAMIC SYSTEM

 During heat treatment partial devitrification of ceramic happens.
 Crystalline particles produced during ceramming process serve to interrupt
the propagation of crack in the material.
 IPS Empress is a glass ceramic which contains higher concentration of
leucite crystals.
 Leucite crystals increase the resistance to crack propagation.
77
ALL CERAMIC SYSTEM

78
Compositio
n
Flexural
strength(M
pa)
Fracture
toughness(
Mpa.m1/2)
Pressing
temperatur
e(0°C)
Thermal
expansion
coefficient
Property
35% vol
of leucite
112±10
1.3±0.1
1180
15.0±0.25
IPS
Empress
70% vol of lithia
disilicate
crystals+Lithium
orthophosphate
crystals
400±40
3.3±0.3
920
10.6±0.25
IPS
Empress
2
ALL CERAMIC SYSTEM

Advantage:
 Lack of metal core
 Translucent ceramic core
 Moderately high flexural strength
 Excellent fit
 Excellent aesthetics
Disadvantage:
 Potential to fracture in posterior areas
 Need of resin to bonding
79
ALL CERAMIC SYSTEM

 Veneering ceramic layer of IPS Empress2 contains apatite crystals which causes
scattering of light similar to tooth enamel.
 IPS Empress2 has slightly decrease in translucency due to difference in
microstructure.
 Advantage:
• Accurate fit
• Excellent translucency and aesthetics
• metal-free structure
80
 Disadvantage
• Low to moderately high
flexural strength and
fracture toughness
ALL CERAMIC SYSTEM

Third generation
IPS e.max Press
 Introduced in 2005
 IPS e.max is not the same product as E2 (Empress 2). The microstructure of
IPS e.max is different than E2. Of the IPS e.max Lithium Disilicate, 70% is
the actual Lithium Disilicate crystal. E2 was only 60% Lithium Disilicate
crystal, which accounts for the increased strength and full contour
esthetics of IPS e.max.
 It has better physical properties and improved esthetics.
81

3. Glass-Infiltrated
I. alumina (eg, In-Ceram Alumina, Vita);
II. alumina and magnesium (eg, In-Ceram Spinell, Vita);
III. alumina and zirconia (eg, In-Ceram Zirconia, Vita)
82

 The first glass-infiltrated material, In-Ceram Alumina, introduced in 1989, is fabricated utilizing
the slip-casting technique.
 In-Ceram Spinell, introduced in 1994, is processed in a similar manner, but the glass is
infiltrated into a synthetically produced porous magnesium aluminate (MgAl2O4 ) core.
 In-Ceram Zirconia is a modification of In-Ceram Alumina where partially stabilized zirconia
oxide is added to the slip composition of the Al2O3 to strengthen the ceramic. According to
the manufacturer, the composition is Al2O3 (62%), ZnO (20%), La2O3 (12%), SiO2 (4.5%), CaO
(0.8%), and other oxides (0.7%).
 The use of this class of materials is diminished due to the increased popularity of lithium
disilicate and zirconia, particularly for CAD/CAM fabrication.
83

What is slip casting?
(In-ceram Alumina, In-Ceram Spinell, and In-Ceram Zirconia)
 Principal indication of In-Ceram alumina is restoration of anterior crowns
when aesthetics becomes important.
 But among three ,Most translucent one In-Ceram Spinell, was introduced
as an alternative to In-ceram alumina.
 Because of high opacity In-Ceram zirconia is not recommended for
anterior restorations.
 Because of its extremely high strength and fracture toughness, it can be
used for posterior crowns and FPDs.
84
ALL CERAMIC SYSTEM

85
Ceramic block Ceramic core Final composition indication
In ceram spinell MgO-Al2O3 Glass infiltrated
magnesium spinel
Anterior crowns
In ceram alumina Al2O3 70wt% Alumina+
30wt% Sodium
lanthanum glass
Anterior and
posterior crowns,
Anterior FPDs
In ceram zirconia Al2O3-ZrO2 30wt% Zirconia +
70wt% Alumina
Posterior crowns
and Posterior FPDs
ALL CERAMIC SYSTEM

Fabrication
86
ALL CERAMIC SYSTEM

Advantages:
• High flexural strength and toughness
• conventional cements can be used
• Metal free structure
Disadvantages:
• Inability to be etched
• Technique sensitivity
• Great amount o skill required
87
ALL CERAMIC SYSTEM

2. Polycrystalline Ceramics
Fine-grain crystalline structure providing strength and fracture toughness,
but tending to have limited translucency
I. Alumina (eg, Procera AllCeram, Nobel Biocare; In-Ceram AL)
This material consists of high-purity Al2O3 (to 99.5%). It was first introduced by
Nobel Biocare in the mid-1990s as a core material for fabrication with CAD/CAM. It
has very high hardness (17 to 20 GPa) and relatively high strength.
The elastic modulus highest of all dental ceramics, has led to vulnerability to bulk
fractures.This tendency to core fracture and the introduction of materials with
improved mechanical properties, such as the transformation toughening
capabilities found in stabilized zirconia, has led to a decreased use of alumina.
88

2. Stabilized zirconia (eg, NobelProcera Zirconia, Nobel Biocare;
Lava/Lava Plus, 3M ESPE; In-Ceram YZ, Vita; Zirkon, DCS; Katana Zirconia
ML, Noritake; Cercon ht, Dentsply; Prettau Zirconia, Zirkonzahn; IPS e.max
ZirCAD, Ivoclar Vivadent; Zenostar, Wieland)
89

According to their microstructure it can be classified as,
 Fully stabilized zirconia (FSZ)
 Partially stabilized zirconia (PSZ)
 Tetragonal zirconia polycrystals (TZP)
o In FSZ, zirconia is in its cubic form and contains more than 8 mol% yttrium
oxide (Y2O3).
o PSZ is formed by nanosized tetragonal or monoclinic particles in a cubic
matrix.
o TZPs are monolithic materials mainly of tetragonal phase stabilized most
commonly with yttria or ceria.
o Dental zirconias are all of the TZP type, most commonly Y-TZP, as this form has
the highest strength and fracture toughness after machining and sintering.
90

3. Zirconia-toughened alumina and alumina-toughened
zirconia
ZTA > 50% by weight of Al
ATZ > 50% by weight of Zr
91

3. Resin-Matrix Ceramics
 This category comprises materials with an organic matrix highly filled with
ceramic particles.
 The presence of an organic matrix would theoretically exclude resin-matrix
ceramic materials from the authors’ classification proposal if the traditional
definition of ceramics were considered
 But according to 2013 version of the ADA Code on Dental Procedures and
Nomenclature ceramics are
“pressed, fired, polished, or milled materials containing predominantly
inorganic refractory compounds—including porcelains, glasses, ceramics, and
glass-ceramics.”
92

1. Resin nanoceramic (eg, Lava Ultimate, 3M ESPE)
It consists of a highly cured resin matrix reinforced with approximately
80% by weight nanoceramic particles. The combination of discrete silica
nanoparticles (20 nm diameter), zirconia nanoparticles (4 to 11 nm diameter),
and zirconia-silica nanoclusters (bound aggregates of nanoparticles) reduces
the interstitial spacing of the filler particles, enabling this high nanoceramic
content (information from 3M ESPE).
93

2. Glass ceramic in a resin interpenetrating matrix (eg, Enamic, Vita)
This is typically composed of a dual network: a feldspathic ceramic
network (86% by weight / 75% by volume) and a polymer network (14% by
weight / 25% by volume). The specific composition of the ceramic part is 58%
to 63% SiO2, 20% to 23% Al2O3, 9% to 11% Na2O, 4% to 6% K2O, 0.5% to 2%
B2O3, less than 1% of Zr2O and CaO. The polymer network is composed of
urethane dimethacrylate (UDMA) and triethylene glycol dimethacrylate
(TEGDMA). The manufacturer refers to this as a hybrid ceramic.
94

3. Zirconia-silica ceramic in a resin interpenetrating matrix
Tailored with different organic matrices as well as variation in ceramic
weight percentage, eg, silica powder, zirconium silicate, UDMA, TEGDMA,
micro-fumed silica, pigments (eg, Shofu Block HC, Shofu), its inorganic
content comprises more than 60% by weight. Another example is the
composite composed of 85% ultrafine zirconia-silica ceramic particles
(spherical 0.6 µm) embedded in a polymer matrix of bisphenol A glycidyl
methacrylate (bisGMA), TEGDMA, and a patented ternary initiator system
(MZ100 Block, Paradigm MZ-100 Blocks, 3M ESPE).
95

Castable ceramic and Machinable Glass-
ceramic(Dicor and Dicor MGC)
 Dicor is a castable glass that is formed into an inlay, facial veneer, or full-
crown restoration by a lost-wax casting process.
 After the glass casting is recovered, it is then subjected to sandblasting.
 The glass is then subjected to heat treatment.
 This heat treatment causes crystal growth process is called ceramming.
97
ALL CERAMIC SYSTEM

 Once the glass has been cerammed, it is fit on prepared dies, ground as
necessary and then coated with veneering porcelain.
 The ceramming process results in increased strength and toughness,
increased resistance to abrasion, thermal shock resistance, chemical
durability and decreased translucency.
 Dicor glass-ceramic contains 55 vol% of tetrasilicic fluormica crystals and
Dicor MGC contains 70 vol% of tetrasilicic fluormica crystals.
98
ALL CERAMIC SYSTEM

 Chameleon effect
The term chameleon effect comes from a
psychological theory that suggest we mimic the
behavior of people we're with in social settings.
Dicor glass ceramic is capable of picking the
part of the color of the restoration from the
adjacent teeth as well as from the tinted
cements used for luting the restorations.
99
ALL CERAMIC SYSTEM

 Aesthetically Dicor crown more life like crown than metal ceramic crown.
 But life expectancy of Dicor crowns in high stress area is not as good as
that of PFM crowns.
 Veneering material used in Dicor:
• Dicor Plus – pigmented feldspathic porcelain veneer
• Wili’s Glass – veneer of Vitadur N aluminous porcelain
100
ALL CERAMIC SYSTEM

CAD-CAM ceramics
 CAD/CAM dentistry is a branch of dentistry and prosthodontics where
computer aided design and computer aided manufacturing is used to get
better design to create better dental restorations.
 The ceramic block which are supplied as small blocks is being grounded by
a diamond-coated disk whose translational movements is guided by
computer input.
101
ALL CERAMIC SYSTEM

What are the steps in CAD_CAM? 102
1.scanning

 Advantages:
 Negligible porosity
 No need for impression making
 Need for only single patient appointment (with cerec system)
 Good patient accepectance
 Disadvantages
 Need of costly equipment
 Technique sensitive.
107

The CEREC system 25 years of
chairside CAD/CAM dentistry
 I n September 1985 at the University of Zurich Dental School, Mörmann1
placed the first chairside ceramic restoration with the CEREC 1 system
(Sirona Dental Systems, Charlotte, N.C.) by using computer-aided
design/computer-aided manufacturing (CAD/ CAM) technology
108

The most recent evolution, the CEREC, has introduced a newly developed light-
emitting diode (LED) camera called the Bluecam. This camera is based on a blue
LED that replaces the infrared-emitting camera in the CEREC.
109

110

Glazing and Its Significance
Ceramists classify the various stages of the firing or sintering, of dental
porcelain as:
1.low bisque — the porcelain surface is very porous and will easily absorb
water soluble dyes;
2.medium bisque — the porcelain surface is still porous and shrinkage will
have taken place;
3.high bisque — the porcelain surface is now sealed and strong enough to be
corrected by grinding prior to final glazing.1
111
Al-Wahadni, Ahed & Martin, D. (1998). Glazing and finishing dental porcelain:
A literature review. Journal (Canadian Dental Association). 64. 580-3.

 The adjusted rough surface may lead to abrasive wear of the opposing
dentition or increase the rate of plaque accumulation.
 Unglazed or trimmed porcelain may also lead to inflammation of the soft
tissues it contacts.
 Trimming of porcelain may cause some reduction in the strength of a
ceramic restoration.
 Occlusal contacts between unglazed porcelain and opposing unglazed
porcelain or enamel are undesirable because of the high rate of wear of
enamel and porcelain.
112
Al-Wahadni, Ahed & Martin, D. (1998). Glazing and finishing dental porcelain: A
literature review. Journal (Canadian Dental Association). 64. 580-3.

Need of Strengthening??
Surface flaws
• scratches
• Cracks
• porosity
Behave as sharp
slits
• Narrow spacing
between atoms
Stress
concentration
geometry at tip of
each surface flaw.
• Low average stress exist
in the bulk of the
material
Increased localized
stress to extremely
high levels.
115
Strengthening of ceramics

116
Breakage of
bonds
• Induced
mechanical
strength
exceed actual
strength of the
material
Bonds at notch
tips rupture
Forms a crack!!

Low tensile stress vs high compressive stress
 It is well known that the compressive strengths of ceramics
are generally severalfold greater than their tensile
strengths, which is why ceramics are used in compression
wherever feasible.
 Brittle materials such as ceramics are highly susceptible to
microscopic surface fractures, or cracks. If you place a
ceramic under tension, you’re placing significant stress at
the tip of these cracks.
 When the ceramic is under compression, no such stress
concentrations develop. Thus, a much greater stress is
needed to reach failure
117
W. W. Kriegel et al. (eds.), Ceramics in Severe Environments © Plenum Press, New York
1971

Methods of strengthening ceramics
 The principal deficiencies faced by ceramics are -brittleness, low fracture
toughness and low tensile strength.
 Methods used to overcome the deficiencies fall into 2 general categories:
1. Method of strengthening brittle materials.
2. Method of minimizing the stress concentrations and tensile stresses
118

A. Development of residual compressive stresses
1. Mismatch of coefficient of thermal expansion
2. Minimize the number of firing cycles
3. Minimize tensile strength through optimal design
4. Ion exchange
5. Thermal tempering
119
1. Method of strengthening brittle
materials

B. Interruption of crack propagation
1. Dispersion strengthening
2. Transformation toughening
120

2. Method of minimizing the stress concentrations and
tensile stresses
1. Reducing stress raisers.
2. Design the ceramic FPD prosthesis with greater bulk and broader radii of
curvature to minimize the magnitude of tensile stresses and stress
concentrations during function.
3. Appropriate selection of stiffer supporting materials.
121

Develop residual compressive strength
Fabrication of metal/all
ceramic
Mismatch of coefficient
of thermal expansion
Development of residual
compressive stress
122

Minimize the 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 concentration of crystalline leucite(K2O.Al2O3 .4SiO2)
High expansion crystal phase Affects coefficient of thermal contraction
Firing cycles
Chemical reactions
123

Optimal design of prostheses
1.Tougher
and stronger
ceramics
• Can sustain higher tensile stresses before
crack develop in areas of tensile stress
2.Well
rounded line
angles
• Reduce stress concentration in the
restoration where tensile component of
bending stress will develop3.Avoid knife
edge margins
• To avoid risk of cracking or chipping
during firing
4.Use finest
grit abrasive
• Reduce probability of forming
microcracks and reduce depth of
microfissures produced by abrasive
particles
124

Ion exchange/chemical tempering
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)
125

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
126

Dispersion strengthening
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
127

Recent advances in ceramics 129
Chandrashekaran nair:TDPI:July
2010,Vol 1, No 2

130
Chandrashekaran nair:TDPI:July 2010,Vol 1, No 2

131
Chandrashekaran nair:TDPI:July 2010,Vol 1, No 2

Summary
 The development of metal-bonding porcelains in the early 1960s freed dentists from
the discipline of using full or partial gold-veneered crowns as the retainers for fixed
partial dentures, Porcelain crowns could be reinforced with metal and were designed
to conform to the tooth anatomy;
 The translucency now achievable in enamel porcelains had its beginning in the 1950s
with the production of gap-graded fine porcelain powders that could be fired in
vacuo. For ceramists working at that time, it was a revolution in esthetics.
 High-alumina ceramics and aluminous porcelains were developed in the 1960s.
 The last 2 decades have allowed us to build on this original work; improvements in
color systems and ceramic building techniques and a greater appreciation of tooth
anatomy have transformed the esthetics of porcelain restorations.
 It is no exaggeration to state that the last century saw a revolution in dental esthetics.
In the 21st century, the challenge of producing high-strength ceramics without
sacrificing translucency may be solved, but the metal-ceramic restoration is likely to
be with us for a long time.
132

Conclusion
 Dental ceramics and processing technologies have evolved significantly in
the past ten years, with most of the evolution being related to new
microstructures and CAD-CAM methods.
 So this new generation of ceramic materials present interesting options,
both in terms of material selection and in terms of fabrication techniques.
 A closer understanding of the dynamics of the materials with respect to
design of the restoration and the intended use is required to enable these
restorations to perform productively.
133

References
1. Shabalin, Igor. (2015). Ceramic Materials Science & Engineering (Part 1 -
Classification & Application). 10.13140/RG.2.1.4181.4568.
2. Craig's Restorative Dental Materials. St. Louis, Mo: Mosby.13th edition
Elsevier, 2006
3. Shabalin, Igor. (2015). Ceramic Materials Science & Engineering (Part 1 -
Classification & Application). 10.13140/RG.2.1.4181.4568.
4. Wikipedia contributors. Porcelain [Internet]. Wikipedia, The Free Encyclopedia;
2019 Nov 1, 23:03 UTC [cited 2019 Nov 3]. Available
from: https://en.wikipedia.org/w/index.php?title=Porcelain&oldid=924121159
5. Dental ceramics: An update Arvind Shenoy, Nina Shenoy J Conserv Dent. 2010
Oct-Dec; 13(4): 195–203. doi: 10.4103/0972-0707.73379
134

 MAEHARA et a, Fracture Toughness Measurement of Dental Ceramics Using the
Indentation Fracture Method with Different Formulas :Dental Materials Journal 24 (3) :
328-334, 2005
 Nieva, N., Arreguez, C., Carrizo, R. N., Molé, C. S., & Lagarrigue, G. M.
(2012). Bonding Strength Evaluation on Metal/Ceramic Interfaces in Dental
Materials. Procedia Materials Science, 1, 475–482.
 Gracis et al: “A new classification system for all-ceramic and ceramic-like
135

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