Tooth Colored Restorative Materials describes in brief regarding the various materials used as cements and crown for loss of tooth structure either by caries or other factors like trauma, GERD, Abrasion etc
5. Silicate cements
The use of dental cement as a restorative material
began with silicate cement around the first half of the
20th century.
It is a fluoride-releasing cement based on silicate glass
and phosphoric acid.
The silicate cements demonstrate anti-cariogenic
potential because of the ability of Fluoride ions to
inhibit demineralization.
Yet they are no longer used for permanent teeth
because they become severely eroded within a few
years due to marginal leakage
Manappallil - Basic Dental Materials 3rd Edition
6. Acrylic resins
Acrylic resins replaced the silicates during the late
1940s and the early 1950s because of their tooth like
appearance, insolubility in oral fluids, ease of
manipulation, and low cost.
These acrylic resins too have relatively poor wear
resistance and they shrink severely during curing, which
causes them to pull away from the cavity walls and
produce leakage along margins.
Their excessive thermal expansion and contraction
cause further stresses to develop at the cavity margins
when hot or cold beverages and foods are consumed.
Manappallil - Basic Dental materials 3rd Edition
7. Glass ionomer cement
A glass ionomer cement (GIC) is a dental restorative
material used in dentistry for dental fillings and
luting cements. These materials are based on the reaction
of silicate glass powder and polyalkenoic acid, an ionomer.
Developed in Britain, and firstly described by Alan Wilson
and Brian Kent in 1972
Used for mostly Class V abrasion lesion/ Caries
Lack of aesthetic and translucency
Conserve tooth structure, assist in remineralization while
maintaining appeal.
ƒƒFormed from the reaction of an ion--leachable calcium
alumino-silicate glass powder and a poly-alkenoic acid.
“Glass polyalkenoate cements”
Types (1) Conventional (2) Resin Modified
Manappallil - Basic Dental Materials 3rd Edition
8. Wilson and Brian Kent established that the setting mechanism for these
materials was an acid–base reaction between the glass powder and
phosphoric acid, which formed a salt.
With this knowledge, they worked with Smith’s adhesive polyacid liquid
and the more esthetic silicate powder to develop a glass-ionomer cement.
Hence, today’s glass-ionomer cements combine polyacrylic acid liquid
with silicate cement powder, yielding a material that demonstrates the
best properties of both.
Components of Conventional Acid–Base Cements
Harry F. Albers. Tooth-colored restoratives principles and techniques. Ninth edition
10. In 1979 and 1980, there was a steady flow of new
products, including Fuji Ionomer (GC International,
Tokyo, Japan), Chemfil (Dentsply International Inc.,
Konstanz, Germany), and Ketac-fil (ESPE).
ESPE washed the glass powder with acid to remove
calcium ions from the surface, thus delaying initial set
and giving excellent working and setting characteristics.
ESPE was also the first company to use copolymers of
acrylic and maleic acid, which is a stronger and more
reactive acid, to accelerate setting.
Harry F. Albers. Tooth-colored restoratives principles and techniques. Ninth edition
11. GLASS-METAL IONOMER
MIXTURES
In 1957, Massler published an article about using a
restorative of amalgam powder mixed with zinc
phosphate cement for pulp capping.
In 1962, Mahler and Armen showed that adding amalgam
alloy to zinc phosphate cement improved the transverse
strength, solubility, and disintegration of the resulting
material compared with using zinc phosphate cement
alone.
Harry F. Albers. Tooth-colored restoratives principles and techniques. Ninth edition
12. In the early 1980s, prior to the introduction of
radiopaque glass ionomers, lucent glass ionomer
powders were mixed with amalgam powders to produce
glass-metal ionomer mixtures that are radiopaque yet
maintain many of the favorable properties of the glass
ionomers.
These restoratives are called admixtures. And, some
clinicians call this combination “miracle mix” and have
made metal-ionomer mixtures popular as core buildups,
bases, retrofills, endodontic sealers, and crown repairs.
Harry F. Albers. Tooth-colored restoratives principles and techniques. Ninth edition
13. The major material disadvantage of the glassmetal
ionomer mixture is the difficulty of achieving a
homogeneous mix of silver and glass throughout the
restorative.
In addition, the metal particles are not well bonded to
the set material, which results in erosion and increased
wear as the poorly attached metal particles are plucked
from the surface.
Clinical problems also result from moisture
contamination during setting.
Harry F. Albers. Tooth-colored restoratives principles and techniques. Ninth edition
15. CERAMIC-METAL GLASS
IONOMERS
In 1987, the first cermet (ceramic + metal) glass
ionomer, Ketac-Silver® (ESPE), was introduced.
ESPE researchers McLean and Gasser developed these
ionomers filled with sintered metal and glass
compositions.
Their intention was to improve the bond between the
metal filler and the glass cement powder and produce a
material with better wear properties.
Using a silver-impregnated coating around the
aluminosilicate glass powder lowered the coefficient of
friction, thereby significantly improving abrasion
resistance.
Harry F. Albers. Tooth-colored restoratives principles and techniques. Ninth edition
16. Cermet ionomers are prepared by sintering (at 800°C)
compressed pellets made from a mixture of fine metal
powders and ion-leachable glass fillers.
The bond between these metals and glass particles
results in a seal that is similar to that of a
porcelainfused-to-metal restoration.
The resulting metalfused- to-glass filler particles can be
reacted with polyacid copolymers to form an ionomer
restorative.
The most suitable metals for these cermet ionomers are
gold and silver.
Harry F. Albers. Tooth-colored restoratives principles and techniques. Ninth edition
17. RESIN-MODIFIED GLASS
IONOMERS
Resin-modified glass-ionomer materials attempt to
combine the best properties of composite resins and
glass ionomers.
They have some cariostatic properties, a low thermal
expansion, and the hydrophilic qualities of the glass-
ionomer cements.
The polymerizing resin matrix of resin-modified glass
ionomers improves the fracture toughness, wear
resistance, and polish of these materials compared with
conventional glass ionomers.
Harry F. Albers. Tooth-colored restoratives principles and techniques. Ninth edition
18. Antonucci and co-workers introduced the lightcured
glass-ionomer cements in 1988. Vitrebond, the first
commercially viable cement of this type, was developed
by Mitra in 1989.
These early modified resin ionomers had two setting
mechanisms: a lightintiated polymerization reaction and
a glass ionomer acid–base reaction.
In 1992, Mitra added the first autocured resin
capabilities to resin-modified glass-ionomer cements.
Harry F. Albers. Tooth-colored restoratives principles and techniques. Ninth edition
19. These cements contained additional chemical initiators
to allow the resin to polymerize without light.
These materials are available in auto- and dual-cure
forms.
The dual-cured materials have three setting reactions:
Photocure,
Autocure, and
Acid–base reaction between the glass-ionomer powder
and the polyacid.
Harry F. Albers. Tooth-colored restoratives principles and techniques. Ninth edition
20. Regardless of their curing mechanism, the resinmodified
glass-ionomer cements develop strength more rapidly
because of the resin polymerization component of their
setting reaction.
One problem with these materials is that the modified
poly-acrylic acid is less soluble in water
Therefore, Hydroxyethyl methacrylate must be added as
a co-solvent to avoid phase separation of the resin from
the glass ionomer components
Harry F. Albers. Tooth-colored restoratives principles and techniques. Ninth edition
22. Classification by use
There can be eight classes formed
1. Glass-ionomer luting cements used as luting agents.
They are autocured.
2. Glass-ionomer restoratives used as restorative
materials. The major difference between luting and
restorative glass ionomers is that the restorative is
available in more shades, has a higher filler load, and
has a much higher film thickness. They are autocured.
3. Glass-metal ionomer mixtures are intended for bases
and buildups. These are sometimes called admixtures.
They are autocured.
Harry F. Albers. Tooth-colored restoratives principles and techniques. Ninth edition
23. 4. Cermet-ionomers are ionomers containing metal-fused-to-glass
particles. Neither the glassmetal nor the cermet-ionomers are
tooth-colored. They are autocured.
5. Glass-ionomer liners are rapid-setting radiopaque materials for
dentin liners under composites and amalgams. They are light-
cured.
6. Glass-ionomer bases intended as bases under other restoratives.
7. Glass-ionomer sealants for sealing pits and fissures. They are
autocured.
8. Resin-modified glass ionomers include light- and dual-cured
glass ionomers.
Harry F. Albers. Tooth-colored restoratives principles and techniques. Ninth edition
24. Advantages of glass ionomers
Form a rigid substance on setting
Good fluoride release (bacteriostatic, inhibit caries)
Low exothermic reaction on setting
Less shrinkage than polymerizing resins
Coefficient of thermal expansion similar to dentin
No free monomers
Dimensional stability at high humidity
Filler–matrix chemical bonding
Resistant to micro-leakage
Non-irritating to pulp
Good marginal integrity
Adhere chemically to enamel and dentin in the presence of moisture
Rechargeable fluoride component
Good bonding to enamel and dentin
High compressive strength
Harry F. Albers. Tooth-colored restoratives principles and techniques. Ninth edition
25. Disadvantages
• Susceptible to dehydration over lifetime
• Sensitivity to moisture at placement
• Poor abrasion resistance
• Average esthetics
• Less tensile strength than composites
• Technique sensitive powder-to-liquid ratio and mixing
• Less color-stable than resins
• Contraindicated for Class IV or other stressbearing
restorations
• Poor acid resistance
Harry F. Albers. Tooth-colored restoratives principles and techniques. Ninth edition
26. Bar graph illustrating the difference
in simulated occlusal wear between
amalgam, a composite, a
resinmodified glass-ionomer cement,
a glass-ionomer cement,and a silver
cermet.
Harry F. Albers. Tooth-colored restoratives principles and techniques. Ninth edition
27. Average tensile strengths of crown buildup
materials.
Harry F. Albers. Tooth-colored restoratives principles and techniques. Ninth edition
28. Resin-based Composite
Material
Dental composites, also called "white fillings", are a group
of restorative materials used in dentistry.
Composite typically consists of a resin-based matrix, such
as a bisphenol A-glycidyl methacrylate (BISGMA) resin
like urethane dimethacrylate (UDMA), and an inorganic
filler such as silica.
Compositions vary widely, with proprietary mixes of resins
forming the matrix, as well as engineered filler glasses and
glass ceramics.
The filler gives the composite wear resistance and
translucency.
A coupling agent such as silane is used to enhance the bond
between these two components.
An initiator package begins the polymerization reaction of
the resins when external energy (light/heat, etc.) is
applied.
Wikipedia
30. Composition of Composite
Resin
Enamel and dentin are good examples of natural
composite materials as both consist of organic and
inorganic materials, predominately hydroxyapatite
crystals.
Enamel consists of 5% organic and 95% inorganic
materials, while dentine consists of 25% organic and
water and 75% inorganic material.
Like enamel and dentine, resin composite is mainly
composed of an organic phase (resin matrix) and an
inorganic or dispersed phase (filler particles).
In addition, resin composite also contains and another
component which is a coupling agent (interfacial
phase).
(Feilzer and Dauvillier, 2003; Gonçalves et al., 2010; Gonçalves et al., 2011).
31. Resin matrix:
The resin matrix is a synthetic monomer that forms a
cross-linked structure after polymerisation.
Monomers originally used in resin composites were
methylmethacrylate [MMA].
The MMA was replaced by an aromatic dimethacrylate
oligomer and the reaction product of Bisphenol-A and
glycidyl methacrylate [Bis-GMA] (2,2-bis[4-(2-hydroxy-3-
methacryloxypropoxy) phenyl] propane) was developed
by Bowen in 1962 hence it is called Bowen’s resin, and
still the most often used resin in many resin composites
(Feilzer and Dauvillier, 2003; Gonçalves et al., 2010; Gonçalves et al., 2011).
32. BisGMA is a highly viscous monomer with a high
molecular weight, the difference in size of MMA and
BisGMA monomers is significant.
This difference gives BisGMA the benefit of producing a
material that has better mechanical properties and
much less polymerisation shrinkage than materials in
which small monomers such as MMA are used: 7.5 vol%
compared to 22 vol%.
(Feilzer and Dauvillier, 2003; Gonçalves et al., 2010; Gonçalves et al., 2011).
33. The major problem with BisGMA is that the monomer is highly
viscous and this makes the material difficult to handle.
This viscosity is due to the presence of two hydroxyl groups. In
order to achieve adequate handling properties and adequate
degree of conversion, BisGMA is diluted with monomers of lower
molecular mass such as triethyleneglycol dimethacrylate
[TEGDMA].
This dilution has the undesirable effect of increasing
polymerisation shrinkage. A way to overcome the problem is by
substituting the hydroxyl (-OH) groups with an ethoxy species (-
CH2-CH2-O) to give an ethoxylated BisGMA.
(Feilzer and Dauvillier, 2003; Gonçalves et al., 2010; Gonçalves et al., 2011).
34. Many resin composites now contain urethane dimethacrylate (1,6-
bis(methacryloyloxy-2-ethoxycarbonylamino)-2,4,4-
trimethylhexan) [UDMA] either alone or in combination with other
monomers.
This UDMA has the same molecular mass as BisGMA but it is less
viscous, this property of UDMA makes it superior to a BisGMA and
TEGDMA mixture because of a higher degree of conversion and
lower polymerisation shrinkage
(Peutzfeldt, 1997; Gonçalves et al., 2010).
35. Fillers
Filler particles are the dispersed phase of resin composite
materials and can be defined as “the inorganic and/or organic
resin particles that are designated to strengthen a composite,
decrease thermal expansion, minimise polymerisation shrinkage,
and reduce the amount of swelling caused by water sorption”
(Anusavice and Phillips, 2003).
36. Fillers positively influence many properties.
Such as increasing radiopacity , this radiopacity can be similar to
that of enamel and thus distinguish it from any marginal gap or
voids minimising polymerisation shrinkage, reinforce and increase
the strength and reducing dimensional changes
Alvarez-Gayosso et al., 2004; Gonçalves et al., 2011; Skovgaard et al., 2011
37. Composites can be classified according to :-
Types of fillers (quartz, silica, etc)
Size of fillers (Macrofilled, microfilled, nano, hybrid)
Method of curing
1) Chemical activation (Use almost obsolete)
2) Light Activation
Ramya Raghu
40. Macro-filled resin composites
The original resin composites, often termed traditional
or conventional, consisted of macro-filler particles.
These were ground, crushed or milled, splinter shaped
glass or quartz particles ranging from 1–100μm (later 5 –
30μm), typically the size of a human hair thickness
(about 50μm)
Adding large particles improved physical properties like
compressive strength
But there were several disadvantages: a reduced
surface area to volume ratio meant there was a small
interface between the two phases, reducing the bond
between filler and matrix
(Ferracane and Greener, 1984). (Venhoven et al., 1996)
41. The difference in hardness between the phases meant
that large particles eventually broke away leaving
relatively deep holes and leading to inevitable failure of
the filling due to poor wear resistance of the material.
The consequent surface roughness would leave the
filling prone to staining and plaque accumulation over
time.
(Lutz and Phillips, 1983).
42. Also, these materials were difficult to polish since the
particles were larger than the wavelength of visible
light.
Later use of smaller, rounder and softer filler
improved polishability, but these materials continued
to exhibit poor wear resistance because particles
were still dislodged under masticatory force
Used for Class II and IV restorations mostly.
(Lutz and Phillips, 1983).
43. Micro-filled resin composites
This type of composite has two subtypes, homogenous
and heterogeneous.
In homogenous micro-filled resin composites all the
filler particles are smaller than the wavelength of
visible light (less than 0.04 μm) so the material is highly
polishable and since there are no particles to be
dislodged this lustre is maintained over time.
Using only micro-filler particles meant an increased
surface area to volume ratio.
(Jorgensen and Asmussen, 1978; Braem et al., 1989; Bayne et al., 1992; Venhoven et
al., 1996).
44. Decreasing the filler load has a deleterious effect on the physical
properties of these materials and to overcome this problem, a
solution is found by combining micro-filler particles with larger
particles produced from prepolymerised pyrogenic silica in resin
matrix to produce what is called heterogeneous microfilled
composites.
Thus, allowing increased filler loading without increasing viscosity
and jeopardizing handling characteristics.
Used mostly for class III and V carious lesions
(Jorgensen and Asmussen, 1978; Braem et al., 1989; Bayne et al., 1992; Venhoven et
al., 1996).
45. Hybrid resin composites
Most currently available commercial resin
composites are hybrid composites.
Hybrid composites contain more than one size of
filler particle in order to maximise filler loading
and result in better mechanical properties.
Macro-filler particles are interspersed with smaller
silica micro-filler particles.
These glass spheres are of the magnitude of
0.04μm (later 0.05 – 0.1μm).
(Jorgensen and Asmussen, 1978; Braem et al., 1989; Bayne et al., 1992; Venhoven et
al., 1996).
46. Due to the varying size, the percentage of volume of filler could be
increased which imparted increased stiffness, hardness,
compressive strength and wear resistance
Presumably by increasing the particle surface area to volume ratio
and reducing the area of unfilled resin exposed to food bolus fibres
during mastication.
Indicated for class I II III IV and V carious lesions
(Jorgensen and Asmussen, 1978; Braem et al., 1989; Bayne et al., 1992; Venhoven et al., 1996).
47. Nano-resin composites
More recently, developments in nanotechnology have
produced potentially clinically superior resin composites
for use in both aesthetic and load-bearing situations.
Nanotechnology permits the uses of nanoscale (1-
100nm) level of filler size. Thus microfilled composite
could have been called nanofilled composite, but they
were not due to lack of detection of nanotechnology at
that period.
Nanometre-sized filler particles and larger groups of
fused nano-particles (nano-clusters) are dispersed in a
resin matrix to produce a nanocomposite.
(Sharma et al., 2010). (Ferracane, 2011).
48. Combining individual particles and
clusters allows for increased filler
loading without increased viscosity
imparting improved physical properties
and good handling characteristics.
The material is highly polishable and
since nano-clusters will breakdown
under force as opposed to becoming
dislodged
(Sharma et al., 2010). (Ferracane, 2011).
53. Coupling agent
A coupling agent is an agent applied to filler particles to
ensure chemical bonding to the resin matrix.
This bond is essential to strengthen resin composite and
distribute the force generated under function between
the two pastes.
The most commonly used coupling agents are
organosilanes, which are bipolar molecules, in
particular γ-methacryloxypropyl trimethoxysilane.
The chemical bonding of fillers and resin matrix
improves mechanical properties of resin composite
materials and makes them stronger than materials with
non silanated fillers
Raghuramya
55. In addition, to the three main components resin
composite there are some other components which are:
Activator-initiator system
Inhibitors
Optical modifiers
Manappallil - Basice Dental Materials 3rd Edition
61. Inhibitors
Added to prevent spontaneous polymerization of the
monomers by inhibiting the free radical
Butylated hydroxyl toluene 0.01% is added as inhibitor
in composite resins
Raghuramya - Clinical operative dentistry 4th edition
62. Organically Modified Ceramics
(Ormocers) Restorative
Materials
Organically Modified Ceramic [Ormocers] is a hybrid
material which is made by special processing based on
nanoscale technology, mixing organic and inorganic
components at a nanoscopic scale rather than by
conventional means of physical mixing of different
component of a matrix.
Ormocers have been developed as an alternative to the
dimethacrylate based composites
The chemical structure of Ormocers is based on
organically modified alkoxides and functionalised
organic oligomers/polymers
Moszner and Salz, 2001
63. The organic constituent of Ormocers is used for cross
linking the network whilst the inorganic component
improves mechanical properties and other properties
such as thermal and chemical stability.
Another advantage of these materials is that the large
size of the monomer molecule minimises polymerisation
shrinkage.
Rosin et al 2002; Kournetas et al., 2004 and wear (Lutz and Krejci, 2000; Manhart et
al. 2002)
64. In a recent study, Ormocer-based material demonstrated the
lowest decrease in hardness following immersion in solvent for a
period of time compared with dimethacrylate-based composites
and as a result it has been proved to be more resistant to solvent
degradation than any other material tested
(Cavalcante et al., 2011).
66. Silorane Restorative
Materials
The name silorane is derived from the combination of
its chemical building blocks siloxanes and oxiranes
The siloxane block acts like a backbone for the silorane
structure and also it improves the physical properties of
composite by providing hydrophobicity to the silorane
thus reducing the water sorption.
Moreover this hydrophobic nature tends to absorb less
stain from a normal daily diet.
Weinmann et al., 2005
67. Silorane based materials have lower polymerisation
shrinkage, but an overall mixed mechanical and higher
flexural strength and fracture toughness than
methacrylatebased restorative materials (Lien and
Vandewalle, 2010).
A recent study has shown that silorane based materials
exhibited higher colour change and surface degradation
(Pires-de-Souza et al., 2011).
Weinmann et al., 2005
68. Composition
Filtek Silorane Posterior Restorative:
• Silorane resin
• Initiating system: camphorquinone, iodonium salt,
electron donor
• Quartz filler
• Yttrium fluoride
• Stabilizers
• Pigments
Braem M. J., Davidson C. J., Lambrechts P., Vanherle G. (1994), In vitro flexural
fatigue
69. Silorane System Adhesive Self-Etch Primer:
• Phosphorylated methacrylates
• Vitrebond™ copolymer
• BisGMA
• HEMA
• Water
• Ethanol
• Silane-treated silica filler
• Initiators
• Stabilizers
Braem M. J., Davidson C. J., Lambrechts P., Vanherle G. (1994), In vitro flexural
fatigue
70. Silorane System Adhesive Bond:
• Hydrophobic dimethacrylate
• Phosphorylated methacrylates
• TEGDMA
• Silane-treated silica filler
• Initiators
• Stabilizers
Available in A2 , A3 , B2 , C2
Braem M. J., Davidson C. J., Lambrechts P., Vanherle G. (1994), In vitro flexural
fatigue
71. Compomers
A type of translucent hybrid dental resin which has the ben
efits of composites and of glass ionomers which are used fo
restorations of molars and cosmetic procedures
Introduced in 1990s
Compomer is a polyacid-modified composite resin.
Compomer is made predominantly from resin composite
(90%) with the addition of a polyacid-modified molecule
similar to that found in traditional GIC.
Compomers are initially light-cured, but subsequently
absorb water, allowing for an acid-based reaction to set the
polyacid-modified molecule.
They have normal adhesion to tooth structure and are
always attached with resin dentin bonding agents
Wikipedia ,Harry F. Albers
72. Consequently, the material shrinks, initially due to
polymerization contraction, and expands subsequently
as water is absorbed.
The addition of a polyacid-modified molecule makes the
material more hydrophilic.
Compomers are, therefore, relatively easy to handle
and apt for preparation.
A dentin-bonding agent is required for their successful
placement.
Harry F. Alber
73. Physically, their properties are similar to those of a
composite.
The wear rates and fracture resistance are less than for
a composite.
Compomers and composites have the same advantages .
Additional advantages of compomers include fluoride
release and ease of handling.
Harry F. Alber
75. Giomers
The material unites the chemistries of composite and
GIC in an effort to combine the advantages of both
materials, whilst minimizing the limitations of each.
Giomers are newly introduced hybrid aesthetic
restorative materials for dental restorative therapy.
They are based on pre-reached glass-ionomer (PRG)
technology.
Chemically, they consist of fluoroalumino silicate glass
reacted with polyalkenoic acid in water prior to
inclusion into the silica-filled urethane resin.
Giomers contain both of the essential components of
glass-ionomer cements and resins but they cannot be
classified as compomers, in which a variable amount of
dehydrated polyalkeonic acid is incorporated in the
resin matrix and the acid does not react with the glass
until water uptake occurs.
Journal of conservative dentistry, year 2002 Vol 5 issue 4
76. Giomers can be subdivided into two distinct groups of
materials, namely those in which the glass ionomer
particles have been surface reacted and those which
have been fully reacted.
Surface pre-reacted glass ionomer giomers are suitable for
composite indications
Fully pre-reacted glass ionomer giomers are used in dentin
adhesive systems, fissure sealants, and as restorative
material for nonloaded-bearing areas
Journal of conservative dentistry, year 2002 Vol 5 issue 4
78. Ceramics
Ceramics derived from greek word keramos.
Dental ceramics are chemical mixtures of nonmetallic
and metallic elements that allow ionic and covalent
bonding to form periodic crystalline structures.
The most common dental ceramics are composed of
metal oxides (SiO2, AL2O3, K2O) and other traditional
ceramic materials.
They are semicrystalline, sillicates, oxides and
derivative structures.
Simple structures are bonded ionically and complex
involve ionic and covalent bonding.
wikipedia
79. When preparing inlay or onlay it is mandatory to adhere to
the requirement profile of the ceramic material.
The adhesive technique box preparations used to achieve
mechanical retention are not required and will also lead to
unfavourable ceramic designs.
Observing the defined minimum layer thickness is essential.
To ensure increased resistance of material, shaping of deep
fissures can be omitted.
Ceramics can be classified by their microstructure (i.e.,
amount and type of crystalline phase and glass
composition).[6]
They can also be classified by the processing technique
(power-liquid, pressed, or machined)
wikipedia
82. Zirconia
Zirconia is a very hard ceramic that is used as a strong
base material in some full ceramic restorations. The
zirconia used in dentistry is zirconium oxide which has
been stabilized with the addition of yttrium oxide.
The full name of zirconia used in dentistry is yttria-
stabilized zirconia or YSZ.
The zirconia substructure (core) is usually designed on a
digital representation of the patients mouth, which is
captured with a 3d digital scan of the patient,
impression, or model.
The core is then milled from a block of zirconia in a soft
pre-sintered state. Once milled, the zirconia
is sintered in a furnace where it shrinks by 20% and
reaches its full strength of approximately 850MPa.
Wikipedia
83. The zirconia core structure can be layered with
aesthetic feldspathic porcelain to create the final color
and shape of the tooth.
Because bond strength of layered porcelain fused to
zirconia is not strong, "monolithic" zirconia crowns are
often made entirely of the zirconia ceramic with no
aesthetic porcelain layered on top.
Zirconia is the hardest known ceramic in industry and
the strongest material used in dentistry. Monolithic
zirconia crowns tend to be dense in appearance with a
high value and they lack translucency and fluorescence.
Wikipedia
84. For aesthetic reasons, many dentists will not use
monolithic crowns on anterior (front) teeth
By using crowns made of metal zirconia, then merge the
porcelain on the outside, zirconia crowns allow light to
pass as a normal tooth would and that gives a natural
look, unlike other metal cores that block the light.
The normal too hot/cold sensations that can be felt
with other crowns does not normally occur because of
reduced thermal conductivity, this being another strong
point for zirconia.
: "Where and When Is It Appropriate to Place Monolithic vs. Layered Restorations,"
Inside Dentistry, August 2012, Vol. 8, Issue 8, E. McLaren, R. Margeas, N. Fahl.
86. References
http://is.muni.cz/do/1411/scripta_medica/archive/200
9/2/scripta_medica_2_2009_108_114.pdf
Kenneth J Anusavice. Phillips’ science of dental
materials. 11th edition. Elsevier. 2004.
Harry F. Albers. Tooth-colored restoratives principles
and techniques. Ninth edition
Wikipedia
Manappallil Basic Dental materials 3rd Edition
Google Images
: "Where and When Is It Appropriate to Place Monolithic
vs. Layered Restorations," Inside Dentistry, August 2012,
Vol. 8, Issue 8, E. McLaren, R. Margeas, N. Fahl.
www.zerodonto.com
Journal of conservative dentistry, year 2002 Vol 5 issue
4
(Jorgensen and Asmussen, 1978; Braem et al., 1989;
Bayne et al., 1992; Venhoven et al., 1996).
87. Braem M. J., Davidson C. J., Lambrechts P., Vanherle G.
(1994), In vitro flexural fatigue
Ramya Raghu 4th Edition
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