PORCELAINS USED IN METAL
CERAMICS.

INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.co...
INTRODUCTION
Metal ceramic restorations
combine the strength and
accuracy of cast metal with the
esthetics of porcelain.

...
Metal ceramic restoration:
• "a fixed restoration that
employs a metal substructure
on which a ceramic veneer is
fused" (G...
A 13- unit metal-ceramic
restoration.

www.indiandentalacademy.com

4
• HISTORY/ DEVELOPMENT OF
CERAMICS.
• PROPERTIES OF FUSED
PORCELAIN.
• TERMINOLOGY
• CHEMISTRY & COMPOSITION
• CLASSIFICAT...
Metal ceramic technology.
• METAL CERAMIC SUBSTRUCTURE
• BONDING BETWEEN THE METAL
DESIGN & PORCELAIN
• PORCELAIN APPLICAT...
• The word Ceramics is derived
from Greek word “keramos”
which means ‘pottery’ or ‘burnt
stuff’.
Porcelain in English mean...
Ceramics
Compounds of one or more metals
with a non metallic element,
usually oxygen. They are formed
of chemical and bioc...
Porcelain is defined as
A ceramic material formed of
infusible elements joined by lower
fusing materials. Most dental
porc...
Other designations of metal
ceramics
• Porcelain-fused to metal.
• Ceramo-metal crown.
• Porcelain veneer crown.
• Porcela...
Structure of ceramics
•Dental porcelain are glassy materials
Glasses may be regarded as a super
cooled liquids or as non c...
History
• CHINESE ARE CREDITED WITH
THE DEVELOPMENT OF
PORCELAIN AS EARLY AS 1000
AD.
• D’ENTRECOLLES, INGRATIED
HIMSELF W...
• IN 1760 FAUCHARD AND OTHERS
HAD REPORTED USING ‘BAKED
ENAMEL.
• IN 1774 ALEXIS DUCHATEAU &
NICOLAS DUBOIUS
CONSTRUCTED C...
• IN 1808 GIUSSEPPANGELO FONZI
DEVISED A METHOD TO MASS
PRODUCE INDIVIDUAL
PORCELAIN DENTURE TEETH

www.indiandentalacadem...
• 1850 Samuel Stockton was the first to
mass produce these teeth first in
America
• Claudius Ash created a artificial toot...
• 1889 Dr Charles H. Land gave the
idea of fusing porcelain to a thin
platinum foil. – he developed low
fusing porcelain i...
• 1907 Stockton developed dental
porcelain.
• 1962 –M. Weinstein, S.Katz, and
A.B.Weinstein patented a method to
fabricate...
• Two of the most important breakthroughs
responsible for the long-standing superb
aesthetic performance and clinical
surv...
• The other patent described the
components that could be
used to produce alloys that
bonded chemically to and
were therma...
What are ceramics?
– Dental ceramics may consist
primarily of glasses ,porcelains,
glass-ceramics.
– The properties of cer...
• Ceramics are more resistant to
corrosion. Ceramics generally do
not react with most liquids, gases,
alkalies & acids. An...
• Although ceramics are strong,
temperature-resistant & resilient
these materials are brittle and may
fracture when quickl...
Properties of ceramics.
• Most ceramics are
characterized by their refractory
nature, high hardness,
(relatively low tensi...
• For dental applications a
hardness of a ceramic less than
that of enamel and an easily
polishable surface are desirable
...
1) Strength.
• Porcelain is a material having good
strength. However, it is brittle and
tends to fracture.
• The strength ...
a) Flexure strength:
• It is a combination of compressive,
tensile, as well as shear strength.
• Glazed porcelain is stron...
b) Compressive strength:
• Porcelains have good compressive
strength.
• 331 Mpa (48,000psi)

www.indiandentalacademy.com

...
c) Tensile strength:
• Is low
• 34 MPa (5000psi).

www.indiandentalacademy.com

28
d) Shear strength:
• It is low and is due to the ductility
caused by the complex structure of
dental porcelain.
• 110 Mpa ...
Factors affecting strength.
• 1) Composition.
• 2) Surface integrity: Surface imperfections
like microscopic cracks and po...
2) Modulus of elasticity:
• Porcelain as high modulus of
elasticity.
• 69 GPa .

www.indiandentalacademy.com

31
3) Surface hardness:
• Porcelain is much harder than natural
teeth.
• 460 KHN

www.indiandentalacademy.com

32
4) Wear resistance:
• Porcelain is more resistant to wear
than natural teeth. Thus, it should not
be placed opposite to na...
5) Specific gravity:
• Is 2.242.
• The specific gravity of fired porcelain
is usually less, because of the
presence of air...
6) Dimensional stability:
• Porcelain is dimensionally stable after
firing.

www.indiandentalacademy.com

35
7) Chemical stability:
• It is insoluble and impermeable to oral
fluids. Also it is resistant to most
solvents. However, c...
8) Esthetic properties:
• Are excellent. It is able to match
adjacent tooth structure in
translucence, color and intensity...
9) Biocompatibility.
• It is compatible with the oral tissue.

www.indiandentalacademy.com

38
10) Thermal compatibility
• Refers to the ability of a metal
and its veneering porcelain to
contract at similar rates.
• T...
Thermal compatibility (contd.)
• When the co efficient of thermal
expansion of metal and porcelain
are compatible the tens...
• Porcelains have coefficient of thermal
expansion between 13.0 and 14.0 X
10-6 and metal between 13.5 and
14.5 X 10-6.
• ...
• This puts the ceramic under
slight residual compression
which makes it less sensitive
to applied tensile forces.

www.in...
Methods of strengthening ceramics
• Strengthening occurs through two
mechanism,
• 1) development of residual
compressive s...
• Development of residual compressive
stresses.
• 1) Ion exchange: (chemical
tempering)
• exchange of potassium ions (whic...
• Thermal tempering.
• By rapidly cooling the surface of the
object while it is hot and in the molten
state. This rapid co...
• THERMAL EXPANSION COEFFICIENT
MISMATCH:
• Ceramic in combination with metal are
heated together .The metal which is
vene...
Interruption of crack propagation.
• Two different types of dispersions used to
interrupt crack propagation are:
• 1) By a...
1) Dispersion of a crystalline phase.
• A tough crystalline material like alumina is
added in particulate form. The glass ...
Transformation toughening.
• A crystalline material is incorporated that
is capable of undergoing a change in
crystal stru...
Terminology.
Porcelain-fused-to-metal (PFM): a
popular alternative designation
for the metal ceramic restoration.

www.ind...
• Porcelain bonding: a term used to
explain the mechanisms by which
dental porcelain fuses or adheres to a
metal substruct...
• Framework: this term is often applied

to fixed partial dentures and identifies
a one-piece substructure composed
on eit...
• Degassing: the process of heat-treating
a cast metal substructure in a porcelain
furnace as one of the preparatory steps...
• Oxidation (or oxidizing): the
process by which a metal
substructure is heated in a
porcelain furnace to produce an
oxide...
ADVANTAGES OF DENTAL
PORCELAIN
• Dental ceramics are attractive
because of their biocompatibility,
long-term color stabili...
Disadvantages.
• They require costly processing
equipment and specialized
training.
• Susceptibility to brittle fracture
a...
The chemical components of dental
porcelain.
• Feldspar (K2O –Al 2O3-6SiO2 & Na2o –
Al2o3-6SiO2)
• Quartz (SiO2)
• Alumina...
Feldspar
• Found as a mix of two substances .
• It does not occur in pure form in
nature
• Mineral is crystalline and opaq...
Type of
feldspar

Chemical Other
formula
names

Properties

uses

Potassiu (K2O.Al orthocla
m
O3.6Si se or
2
potash
alumin...
• On heating it becomes glassy and
fuses at 1290 C, on overheating it
may loose its shape .
• Impurities : Mica
Iron –it i...
Removal of impurities
Iron• manually only light colored pieces of
feldspar are selected
• Feldspar is grounded into fine p...
Functions
• Primarily responsible for forming
glass matrix

www.indiandentalacademy.com

62
• Glass modifiers such as the oxides of
potassium, sodium, and calcium acts
as fluxes to increase a porcelains
coefficient...
Silica (Quartz or Flint) SiO2
• Primarily responsible for
forming glass matrix
• Has a fusion temperature

www.indiandenta...
SiO2

www.indiandentalacademy.com

65
Functions
• Silica contributes stability to the
mass of porcelain during heating
by providing a framework for the
other in...
KAOLIN (Al2 o3-2sio22H2o)

• It is deposited along the banks and at the bottom of streams in the form of clay.
• Only pure...
Preparation of clay
• Repeated washing until all foreign
materials are separated.
• Allowed to settle.
• Dried and screene...
Properties of clay
I.
II.

Its gives OPAQUENESS to porcelain
MOULDABLE :On mixing with water it
becomes sticky and aids in...
• Little or no kaolin is found is
modern day low fusing
porcelain.
• Kaolin is not used in enamel
powder as it will decrea...
Alumina.(Al2o3)
• The hardest and perhaps the
strongest oxide.
• Its CTE is similar to the low fusing
porcelains.
• It als...
Manufacturing of ceramics
powder

www.indiandentalacademy.com

72
Fritting.
• The process of blending, melting and
quenching the glass components is
termed “fritting”.
• All the raw minera...
• Frits are ground to the specific particle
size established by individual
manufacturers for their particular brand of
por...
• TOOTH PREPARATION FOR
THE METAL CERAMIC
RESTORATION

www.indiandentalacademy.com

75
• Depth
orientation
grooves flat
end tapered
diamond.

www.indiandentalacademy.com

76
www.indiandentalacademy.com

77
• Make at least
two vertical
cuts in the
incisal portion
of the facial
surface.

www.indiandentalacademy.com

78
• Next align the
flat end tapered
diamond with
the gingival
portion of the
facial surface.

www.indiandentalacademy.com

7...
• Sink the side of
the diamond into
the mesiodistal
center of the
facial
surface,maintain
the instrument
alignment paralle...
• Make two incisal
orientation grooves
that are 2mm
deep.The diamond
should be parallel to
the incisal edge
faciolingally....
• Incisal
reduction is
done with the
flat end tapered
diamond.

www.indiandentalacademy.com

82
www.indiandentalacademy.com

83
• Facial
reduction;
incisal half,flat
end tapered
diamond.

www.indiandentalacademy.com

84
• If there sound
tooth structure
inter proximally,
wing
preparation is
done.

www.indiandentalacademy.com

85
• Begin the lingual
reduction with the
small round
diamond with
diameter of
1.4mm. Sink this
instrument into
the lingual t...
• Lingual axial reduction
torpedo diamond and carbide
finishing bur.

www.indiandentalacademy.com

87
• Lingual
reduction is
done with the
small wheel
diamond.

www.indiandentalacademy.com

88
• Smooth the entire
facial surface with
no.171 bur .Round
over the any sharp
angles on the incisal
angle or along the
edge...
Components of the metal
ceramic restoration
• Two major components:
• a metal substructure and a porcelain
veneer.
• The s...
www.indiandentalacademy.com

91
The basic components of a traditional
porcelain kit include
1.opaque porcelain.
2.dentin porcelains
3.enamel porcelain...
The metal substructure
• Conventional low-fusing dental
porcelain lacks the strength
required of an all-porcelain
restorat...
The oxide layer
• Most metal ceramic alloys are
oxidized after the porcelainbearing area of the restoration has
been prope...
• The metal oxides that form on the
alloy's surface during this heattreatment procedure play a key role
in bonding the den...
• Differences in alloy composition
require that oxidation techniques be
alloy specific
• Ideally this oxidation should be ...
Opaque porcelain layer
• These porcelains are made opaque by the
addition of insoluble oxides, such as
• tin oxide (SnO2),...
Opaque porcelain layer contd.
•
•
•
•

oxide, and
rubidium oxide,
barium zinc oxide.
Such oxides have high refractive
indi...
Composition on chemical
analysis

www.indiandentalacademy.com

99
• Between 8% and 15% of an opaque
powder is composed of metallic
oxides, and some particles may be
less than 5 um in size....
• The opaque porcelains three major
functions:
• (1) to establish the porcelain-metal
bond,
• (2) to mask the dark color o...
• A uniform thickness of 0.2 to 0.3
mm generally is regarded as ideal.
• That masking power is influenced
by the amount an...
• A casting alloy of a different
composition might generate a thick,
dark oxide layer (Naylor, 1986) and
require a thicker...
www.indiandentalacademy.com

104
Body porcelains
• Body porcelain collectively describes
four principal types of porcelain
powders used to recreate the "bo...
• They are applied directly over the fired
opaque layer .
• The dentin, enamel, translucent, and
modifier powders all have...
The dentin porcelain veneer
• The major color contribution is derived
from the pigmented metal oxides in the
dentin body p...
• For more accurate shade
duplication, estimates of the
combined thickness of fired dentin
and enamel porcelains range fro...
• For uniformity of shade and maximum
strength, it is desirable to have an even
thickness of porcelain covering the
metal ...
ENAMEL PORCELAIN VENEER
• Enamel porcelains are more
translucent than dentin porcelains.
• The enamel porcelains are usual...
• When fired, enamel porcelains are
more translucent than dentin porcelains
(McLean, 1979).
• They also have a more restri...
Translucent porcelains
• Translucent porcelains are not
transparent, they do not allow the
transmission of all light.
• Th...
BODY MODIFIERS
• These porcelains are more color concentrated &
were designed to aid in the achieving internal
color modif...
www.indiandentalacademy.com

114
STAINS
• Stain powders contain less silica or
alumina & more sodium & potassium
oxides.
• They contain high concentration ...
GLAZES
• Glazes are generally colorless, low fusing
porcelains.
• They possess considerable fluidity at high
temperatures....
www.indiandentalacademy.com

117
GLAZE (Contd.)
• A glazed ceramic surface is
generally considered beneficial by
increasing the fracture resistance
and red...
Color coding
• By convention dentin powders are pink
and enamel powders are blue.
• These organic colors burn off during f...
CLASSIFICATION OF DENTAL
CERAMICS
• Different types of dental ceramics are
available These include core ceramic,
liner cer...
• These products can be
classified in several possible
ways according to their: (1) use
or indications (anterior,
posterio...
• (2) composition (pure alumina,
pure zirconia, silica glass, leucitebased glass-ceramic, and lithiabased glass-ceramic
• ...
• Microstructure (glass, crystalline,
and crystal-containing glass);
• Translucency (opaque,
translucent, and transparent)...
Based on the method of fabrication
1. Condensation porcelains using
condensation and sintering
2. Castable ceramics –Dicor...
Classification (Mclean)
1) Regular feldspathic porcelain
2) Aluminous porcelain
3) Metal bonding porcelain.

www.indianden...
Based on their fusion temperature (Phillips,1982)
type

Fusing
temperature
range

uses

High fusing
porcelains-

1288 to 1...
METAL SUB STRUCTURE
DESIGN.
• Majority of the porcelain-to-metal bond
failures occur as a direct result of improper
substr...
METAL SUB STRUCTURE
DESIGN.

• TYPES
• FUNCTIONS.
• DESIGN.
www.indiandentalacademy.com

128
Types of metal ceramic system.
• A. Cast metal ceramic alloys:
• 1.Noble-metal alloy systems:
•
High gold - a) Gold platin...
• B.
•

Foil copings:

• a) Bonded platinum foil coping.

• b) Swaged gold alloy foil coping.

www.indiandentalacademy.com...
a) Bonded platinum foil coping:
• Another method of bonding porcelain to
metal is the use of tin oxide coatings on
platinu...
• The objective of this type of
restoration is to improve esthetics.
• The thicker cast metal coping that is
normally used...
b) Swaged Gold Alloy Foil Coping:
• A laminated gold alloy supplied in fluted
shape is also used as an alternative to the
...
Primary functions:• The casting provides fit of the
restoration to the prepared tooth.
• The metal forms oxides that bond
...
• The coping serves as a rigid
foundation to which the brittle
porcelain can be attached for
increased strength & support....
Secondary functions.
• Metal occlusal & lingual articulating
surfaces generally less destructive to
the enamel of the oppo...
• Occlusal surfaces can be easily
adjusted & repolished intraorally.
• The metal axial walls can support
the removable par...
Metal sub structure design
• Majority of the porcelain-to-metal
bond failures occur as a direct result
of improper substru...
Sub structure design (contd)
• Hence necessary to understand
the essentials of proper
substructure design, since it will
h...
Principles of substructure
design.
• Are the occlusal contacts to be
in metal or porcelain?

www.indiandentalacademy.com

...
• Occlusion in metal requires less tooth
reduction (1 to 1.5 mm).
• Approximately 2 mm of occlusal
reduction is necessary ...
• Metal surfaces can be more easily
adjusted and repolished at chair side
without adversely affecting the
restoration.
• O...
• 2. Are the centric occlusal
contacts 1.5 to 2mm from the
porcelain-metal junction?

www.indiandentalacademy.com

143
• occlusal contacts when placed
directly on or close to the porcelainmetal junction, there is an increased
likelihood the ...
• A substructure should be designed so
the functional incisal or occlusal
contacts are located at least 1 .5 mm
and perhap...
• When the
anterior teeth
contact in the
incisal region,it is
often necessary
to consider a
design with
lingual surface in...
• Do not design
the sub
structure so
contact
occurs at the
porcelain
metal
junction.
www.indiandentalacademy.com

147
• When the anterior
teeth occlude in the
gingival half of the
maxillary teeth or
when the lingual
tooth reduction is
less ...
• 3.Are the interproximal contacts
to be restored in metal or
porcelain?

www.indiandentalacademy.com

149
• The inter proximal contact areas of
anterior teeth, and at least the mesial
contacts of posterior teeth, are
frequently ...
• It is important to provide proper metal
support to a porcelain marginal ridge
in the substructure design to prevent
poss...
• 4.Are the cusp tips (or incisal
edges )adequately supported by
the metal substructure with no
more than 2mm of unsupport...
• The ultimate goal of any substructure
is to support an even thickness (1mm
minimum, 2 mm maximum) of the
porcelain venee...
• 5. Is the substructure thick
enough to provide a rigid
foundation for the porcelain
veneer?

www.indiandentalacademy.com...
• Areas to be veneered with
porcelain must be at least 0.3 mm
thick.
• with base metal alloys, the
coping can be reduced t...
How does dental porcelain bond to
metal?
(1) van der Waals forces (Lacy, 1977),

• (2) mechanical retention,
• (3) compres...
van der Waals forces
• The attraction between charged
atoms that are in intimate contact yet
do not actually exchange elec...
www.indiandentalacademy.com

158
• The better the wetting of the
metal surface, the greater the van
der Waals forces.
• porcelain's adhesion to metal can
b...
• van der Waals forces are only
minor contributors to the overall
attachment process.

www.indiandentalacademy.com

160
Mechanical retention
• The porcelain-bearing area of a metal
casting contains many microscopic
irregularities into which o...
Mechanical retention's
contribution to bonding may be
relatively limited.
• Dental porcelain does not require
a roughened ...
www.indiandentalacademy.com

163
www.indiandentalacademy.com

164
Compression bonding
• Dental porcelain is strongest under
compression and weakest under
tension; hence, if the coefficient...
• the metal contracts faster than the
porcelain but is resisted by the
porcelain's lower coefficient of
thermal expansion....
Chemical bonding
• The single most significant
mechanism of porcelain-metal
attachment is a chemical bond
between dental p...
• The two hypothesis that explains
chemical bonding are
• 1, The sandwich theory
the oxide layer is permanently
bonded to ...
• The oxide layer itself is
sandwiched in between the metal
substructure and the opaque
porcelain. This "sandwich" theory
...
• The second, and more likely, theory
suggests that the surface oxides
dissolve, or are dissolved by, the
opaque layer. Th...
• Chemical "bonding" is generally
accepted as the primary
mechanism in the porcelain-metal
attachment process

www.indiand...
www.indiandentalacademy.com

172
www.indiandentalacademy.com

173
The oxidation (degassing) process
• After the cast metal ceramic
castings have been properly
finished
with
uncontaminated
...
• The
heat-treatment
process
allows specific oxides to form on
the metal surface. These oxides
are responsible for the che...
• A high-gold-content alloy contains
oxidizable trace elements such as tin,
indium, and iron to produce an
adherent oxide ...
• The base metal alloys readily
oxidize, but trace elements are
still added in an effort to form a
particular type of oxid...
• Allowing certain base metal alloys
to oxidize in air, or to remain at
temperature, could lead to over
oxidation. An exce...
www.indiandentalacademy.com

179
• A properly oxidized casting often
has a distinctive appearance in
terms of color and character
(texture, thickness, etc)...
www.indiandentalacademy.com

181
• Some manufacturers do not
recommend
an
oxidation/
degassing step; instead, they
advocate minimizing the number
of firing...
Removing the oxide layer
• Two principal methods for
removing oxides are
– Acid treatment (chemical method)
– Nonacid trea...
Acid treatment
(chemical method)
• Different types of acids are used to reduce
or eliminate surface oxides, including
hydr...
• A rubber-tipped instrument should be
used to place oxidized castings into
the acid appropriate for the alloy.
• Place th...
Nonacid treatment
(Mechanical method)
• Castings can be air-abraded with pure, 50um aluminum oxide (Al2o3) that is nonrecy...
Porcelain-metal bond failures
• Metal ceramic alloys, whether noble
or base metals, all oxidize differently
because of var...
www.indiandentalacademy.com

188
Porcelain delamination
• With base metal alloys, the
separation of the porcelain veneer
from the metal substrate can be
mo...
www.indiandentalacademy.com

190
Porcelain delamination contd
• Overoxidation has been a particular
problem with the heavily oxidizing
base metal alloys an...
• Bond failures are not caused by a loss
of the chemical bond between the
ceramic and the oxide layer
• on the contrary, t...
www.indiandentalacademy.com

193
www.indiandentalacademy.com

194
Classification of bond failures in
metal-ceramics.
•
(Given by O’ Brien (1977).
• 1) Metal – Porcelain:
•
Fracture leaves ...
• 2) Metal oxide – Porcelain:
•
Porcelain fractures at metal oxide
surface, leaving oxide firmly attached to
metal .Seen m...
• 4) Metal Oxide –Metal Oxide:
•
Fracture occurs through the metal
oxide. Results from overproduction of
oxide causing san...
• 6) Cohesive within Porcelain:
•
Tensile failure within porcelain. Bond
strength exceeds strength of porcelain.
Seen in h...
• Excessive
absorption of
oxides by the
porcelain can lower
the porcelain's
coefficient of
thermal expansion,
alter the fi...
• Changes in the
shade of the
porcelain may
not be noticeable
with posterior
restorations,
particularly if a
greater thick...
Incompatible materials
• Further more, bond failures are not always
attributable to improper oxidation but may
actually be...
www.indiandentalacademy.com

202
Overoxidation/underoxidation
• The oxidation procedure varies for alloys
of different compositions.
• Careful processing f...
• Contamination
– castings that demonstrate some form
of contamination may not have to be
remade but by simply refinishing...
www.indiandentalacademy.com

205
• Simply
refinishing this
casting removed
the surface and
subsurface
contamination
and resulted in
an appropriate
porcelai...
Applying Porcelain to the Metal
Substructure
• The application of dental porcelain to
the metal substructure is the single...
Instruments and equipment
• Brushes
• A variety of brush sizes and styles are
available in porcelain instrument kits, the
...
• Another frequently used instrument is a
large no.10 brush, often referred to as a
whipping brush
• A basic instrument ki...
• Very small no. 0 to no. 000 sable
brushes are required for the
placement of stains or small
increments of porcelain. The...
Carving Instruments
• Porcelain carving instruments, designed for
shaping and carving porcelain buildups.
• Carving instru...
Spatula
• Small, flexible, metal spatula is used
to dispense and mix porcelain.
• Any small metal fragments generated
duri...
• This metal debris can dramatically discolor
the mix as well as the fired porcelain
restoration. With careful use, howeve...
Razor knives
• Another necessity in the basic set of
instruments is
some type of razor knife,
equipped with a thin, flexib...
Hemostat

• A small, straight or curved hemostat is
needed to hold the work during the
opaquing process and during porcela...
Glass or ceramic mixing slab
• Finally, either a glass slab, ceramic tile, or
ceramic tray can serve as a plate for
mixing...
• As modifiers are added and more
complex buildups are attempted,a larger
working surface will be required to
accommodate ...
PORCELAIN CONDENSATION.
• Condensing dental porcelain actually
refers to any procedure that results in the
unfired porcela...
• Any liquid or air that remains trapped in
the unfired porcelain will form voids in the
unfired ceramic.
• The presence o...
• In well-condensed porcelain there is
reduction in the amount of firing
shrinkage.
• Methods of porcelain condensation.
•...
Capillary action.
• The technique of blotting a wet
built up with absorbent paper
uses surface tension.

www.indiandentala...
Vibration.
• Is created by passing a serrated
instrument over the neck of a
hemostat in which the restoration is
held.
• V...
Spatulation.
• A spatula is used to apply ,
then rub the porcelain built up
to force the liquid to the
surface.

www.india...
Whipping.
• A no. 10 sable brush is rapidly
moved over the porcelain surface
with a whipping motion. The
whipping motion b...
Dry powder addition.
• Requires dry porcelain powder be
sprinkled on an area of wet
porcelain, using the existing liquid
t...
Opaquing the metal
substructure
• The areas of the substructure that will
be veneered with porcelain must not
be touched a...
www.indiandentalacademy.com

227
Applying opaque porcelain—
glass rod technique
• First wet the oxidized metal substructure
to be veneered with distilled w...
www.indiandentalacademy.com

229
Glass rod technique.
• Use the pointed end of the glass rod to
apply the opaque porcelain. Begin by
opaquing the most conv...
www.indiandentalacademy.com

231
• Then move the opaque over the incisal
edge to cover the porcelain-bearing
surface on the lingual aspect. Once the
porcel...
www.indiandentalacademy.com

233
• If, during the opaque application,
areas of opaque appear rough and
irregular, lightly tap the hemostat
handle or move t...
www.indiandentalacademy.com

235
• Excess moisture should be removed
before the opaque is applied to the metal.
Gently blend the opaque at the porcelainmet...
www.indiandentalacademy.com

237
• Dry the opaque layer
by exposing it to the
heat radiating from
the porcelain muffle.

www.indiandentalacademy.com

238
www.indiandentalacademy.com

239
• A properly fired
(sintered)
opaque layer
should have a
sheen or
eggshell glisten.

www.indiandentalacademy.com

240
• If a second application of opaque
porcelain is required, lightly wet the
opaqued surface with opaque liquid.
• Apply the...
www.indiandentalacademy.com

242
www.indiandentalacademy.com

243
Applying opaque porcelain—
brush technique
• Simply mix the
opaque porcelain
.Use the tip of
porcelain brush to lift
a por...
• Apply the porcelain on the most
convex part of the oxidized coping.
Repeat the process several times
until the porcelain...
www.indiandentalacademy.com

246
www.indiandentalacademy.com

247
Mixing dentin porcelains
– The technique for mixing body
porcelains is same as that used
to mix opaque porcelains in that ...
•

Mix the body
powders (dentin
and enamel) with
the
recommended
liquid (Vita VMK
68 porcelain and
modeling liquid )

www....
• When properly
mixed, dentin
porcelain should
have a
smooth,cream
consistency.

www.indiandentalacademy.com

250
• If too much liquid is
added to the mix,
use a tissue or
blotting paper to
remove excess
liquid until the
proper consiste...
Appling dentin porcelain.
• The dentin porcelain buildup
procedure is to apply and condense
enough porcelain to create a
r...
• This overbuilding will accommodate
the enamel veneer that will be placed
over the dentin layer and help to
compensate fo...
The dentin built up technique.
• Return the
cleaned,
opaqued coping
to the master
cast.

www.indiandentalacademy.com

254
• To minimize the
entrapment of air in
the porcelain,
move the tip of the
pointed brush
through the mixed
dentin porcelain...
• Apply the
porcelain to the
most convex
surface (midfacial
area) on the
restoration.

www.indiandentalacademy.com

256
• Coax the porcelain
toward the
interproximal and
incisal areas. Add
more porcelain to
the facial surface
and use a light
...
• Move the porcelain
down to the incisal
edge and lightly blot
the buildup to
condense the
porcelain on the
substructure. ...
• Control the flow of
the material and
condense the
buildup by
periodically blotting
the wet porcelain
with the tissue. us...
• Add additional
porcelain to the
incisal aspect of
the incisal edge.

www.indiandentalacademy.com

260
• Add additional
porcelain to
complete the
mesial and distal
corners.

www.indiandentalacademy.com

261
Cutting back the dentin buildup
• With the buildup complete, dentin
porcelain as to be removed from those
areas of the cro...
If dentin porcelain is overbuilt(A), the amount of
dentin remaining after the cutback may also be
incorrect.

www.indiande...
When the restoration has the correct
anatomical contours and is slightly
overbuilt(A) by 10% to 15%, the dentin
cutback wi...
Dentin cut back technique
• With a razor
knife cut back
the incisal edge
from between 1
to 1.5 mm.

www.indiandentalacadem...
• Remove dentin
porcelain at the
mesial
interproximal line
angle. Extend the
cut to the junction
of the middle and
gingiva...
• Cut across the
middle one third.
Stop the cut
back at the distal
interproximal
area.

www.indiandentalacademy.com

267
• At the distal
interproximal line
angle, make a cut
from the incisal edge
toward the gingival
one third as far as
require...
• Examine the
restoration from
an incisal view
for symmetry
and adequacy of
the cutback.

www.indiandentalacademy.com

269
• Smooth the
cutback areas
with the
porcelain brush
so the transitions
from dentin to
enamel porcelain
are gradual.
www.in...
• For younger
patients ,develop
mamelons.With a
pointed brush
,create two
depressions on the
facial surface with
vertical ...
Mixing the enamel
porcelain.

www.indiandentalacademy.com

272
• Glass rod is used
to mix the powder
and liquid .The
enamel mix is
slightly wetter than
the dentin mix to
facilitate its
...
• The mixed enamel
porcelain should have
a consistency that
permits it to be readily
picked up by a
properly pointed
porce...
• With a pointed
brush, apply
enamel porcelain
to one corner of
the cutback.

www.indiandentalacademy.com

275
• Add more enamel
porcelain and
move it across the
facial surface in the
incisal one third.
Push the wet mix
toward the mi...
• Blend the enamel
porcelain at the
junction of the
middle and gingival
one thirds and
begin to establish
the incisal edge...
• With additional
enamel porcelain,
complete the
incisal edge length
and the mesialincisal line angle.
Work your way
along...
• Blend the enamel
porcelain into the
gingival one third
on the facial
surface. Re-create
the interproximal
contours and l...
• Shape the mesialincisal corner as
required for each
case. Examine the
builtup from an
incisal view and
evaluate the
over...
• Condense the built
up.

www.indiandentalacademy.com

281
• Use your thin razor
knife to cut and
shape the mesial
and distal
interproximal
areas. This
procedure also
removes any
un...
• Carefully remove
the crown from the
master cast. Add
enamel porcelain
to the small
dimples in each
interproximal
contact...
• Remove excess
porcelain from the
porcelain-metal
junction and clean the
facial metal collar of
any porcelain with a
smal...
Firing procedure.
• The large bulk need more time to dry and
pre-heat.
• Adhere to manufacturers recommended
drying time.
...
Adjusting and finishing the metal
ceramic restoration.
• Applying and firing the porcelain veneer to
a metal substructure ...
• Consequently, the fired porcelain requires
additional adjustments to reduce any
overcontouring and recreate a lifelike
c...
Armamentarium.
• 1. Equipment – Handpiece with speeds of
50,000 rpm or below.
• 2. Instruments – Iwanson metal caliper.
• ...
• The iwanson
metal calipers
can be used for
thickness
measurements
of metal or metal
and porcelain.

www.indiandentalacad...
• Diamond abrasive
instruments.

www.indiandentalacademy.com

290
•

Porcelain
prepolish
wheel .Designed
for smoothening
and polishing
ceramic
surfaces.

www.indiandentalacademy.com

291
• Diamond disks
• For adjusting
and contouring
interproximal
areas.

www.indiandentalacademy.com

292
Procedures in adjusting and
finishing the metal ceramic
restoration.
• 1. To ensure the
casting
completely seats
on the di...
2.Adjusting the interproximal contacts.
• a) Mark the
mesial
interproximal
contact using
thin double –
sided marking
film....
• b) Marking
identifies the
location and
intensity of
contact.

www.indiandentalacademy.com

295
• Adjustments in
the contact area
with pre-polish
wheel.

www.indiandentalacademy.com

296
• The thickness of
the restoration is
periodically
checked to
ensure that it is
not over
contoured.
www.indiandentalacadem...
• The desired
characterization
is marked and
with an
abrasive the
appropriate
shape is
created with
desired effect.
www.in...
Staining and glazing.
• After a restoration has been adjusted and
finished, it is necessary to make color
corrections or a...
• Surface stains
should be
applied with a
small sable
brush.

www.indiandentalacademy.com

300
• Stain is placed
in area where
the
characterization
is intended.
Blend or dilute
the effect of the
stain

www.indiandenta...
• The glaze is
picked up with
a staining
brush and
applied to the
ceramic
surface where
desired.

www.indiandentalacademy....
• Dry the
restoration in the
porcelain
furnace.

www.indiandentalacademy.com

303
• The restoration is
fired according to the
porcelain
manufacturers
direction.

www.indiandentalacademy.com

304
• Typically
glazed
restoration.

www.indiandentalacademy.com

305
Mechanical polishing.
• Mechanical polishing of the
restoration after glazing gives the
restoration a natural life like
ap...
A diamond polishing
paste.

www.indiandentalacademy.com

Pumice flour

307
• After
mechanical
polishing. A life
like luster is
created in the
ceramic yet
the surface
characterizatio
n remains.

www...
www.indiandentalacademy.com
Leader in continuing dental education

www.indiandentalacademy.com

309
Upcoming SlideShare
Loading in …5
×

Porcelines used in metal ceramics /certified fixed orthodontic courses by Indian dental academy

10,249 views

Published on

Welcome to Indian Dental Academy
The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and offering a wide range of dental certified courses in different formats.


Indian dental academy has a unique training program & curriculum that provides students with exceptional clinical skills and enabling them to return to their office with high level confidence and start treating patients

State of the art comprehensive training-Faculty of world wide repute &Very affordable

Porcelines used in metal ceramics /certified fixed orthodontic courses by Indian dental academy

  1. 1. PORCELAINS USED IN METAL CERAMICS. INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com 1
  2. 2. INTRODUCTION Metal ceramic restorations combine the strength and accuracy of cast metal with the esthetics of porcelain. www.indiandentalacademy.com 2
  3. 3. Metal ceramic restoration: • "a fixed restoration that employs a metal substructure on which a ceramic veneer is fused" (Glossary of Prosthodontic Terms, 1987). • www.indiandentalacademy.com 3
  4. 4. A 13- unit metal-ceramic restoration. www.indiandentalacademy.com 4
  5. 5. • HISTORY/ DEVELOPMENT OF CERAMICS. • PROPERTIES OF FUSED PORCELAIN. • TERMINOLOGY • CHEMISTRY & COMPOSITION • CLASSIFICATION OF DENTAL CERAMICS. www.indiandentalacademy.com 5
  6. 6. Metal ceramic technology. • METAL CERAMIC SUBSTRUCTURE • BONDING BETWEEN THE METAL DESIGN & PORCELAIN • PORCELAIN APPLICATION METHOD • FIRING PROCEDURES • FINISHING & ADJUSTMENTS www.indiandentalacademy.com 6
  7. 7. • The word Ceramics is derived from Greek word “keramos” which means ‘pottery’ or ‘burnt stuff’. Porcelain in English means “china”. www.indiandentalacademy.com 7
  8. 8. Ceramics Compounds of one or more metals with a non metallic element, usually oxygen. They are formed of chemical and biochemical stable substances that are strong, hard , brittle, and inert non conductors of thermal and electrical energy(GPT-7). www.indiandentalacademy.com 8
  9. 9. Porcelain is defined as A ceramic material formed of infusible elements joined by lower fusing materials. Most dental porcelain are glasses and are used in the fabrication of teeth for dentures, pontics and facings, metal ceramic restorations, crowns, inlays, onlays, and other restorations. www.indiandentalacademy.com 9
  10. 10. Other designations of metal ceramics • Porcelain-fused to metal. • Ceramo-metal crown. • Porcelain veneer crown. • Porcelain bonded to metal crown. www.indiandentalacademy.com 10
  11. 11. Structure of ceramics •Dental porcelain are glassy materials Glasses may be regarded as a super cooled liquids or as non crystalline solids • Their atomic structure and resultant properties depend, not only on composition, but also on thermal history. www.indiandentalacademy.com 11
  12. 12. History • CHINESE ARE CREDITED WITH THE DEVELOPMENT OF PORCELAIN AS EARLY AS 1000 AD. • D’ENTRECOLLES, INGRATIED HIMSELF WITH CHINESE POTTERS AROUND 1717 IN ORDER TO LEARN THE COVETED PORCELAIN MANUFACTURING PROCESS www.indiandentalacademy.com 12
  13. 13. • IN 1760 FAUCHARD AND OTHERS HAD REPORTED USING ‘BAKED ENAMEL. • IN 1774 ALEXIS DUCHATEAU & NICOLAS DUBOIUS CONSTRUCTED COMPLETE DENTURES FROM A MATERIAL THEY REFERRED TO AS “MINERAL PASTE”. www.indiandentalacademy.com 13
  14. 14. • IN 1808 GIUSSEPPANGELO FONZI DEVISED A METHOD TO MASS PRODUCE INDIVIDUAL PORCELAIN DENTURE TEETH www.indiandentalacademy.com 14
  15. 15. • 1850 Samuel Stockton was the first to mass produce these teeth first in America • Claudius Ash created a artificial tooth that could be placed over a post on either a complete denture of FPD. It was known as “tube” tooth. www.indiandentalacademy.com 15
  16. 16. • 1889 Dr Charles H. Land gave the idea of fusing porcelain to a thin platinum foil. – he developed low fusing porcelain in 1898. 1903 he introduced the porcelain jacket crown to dentistry www.indiandentalacademy.com 16
  17. 17. • 1907 Stockton developed dental porcelain. • 1962 –M. Weinstein, S.Katz, and A.B.Weinstein patented a method to fabricate the first metal ceramic crown. www.indiandentalacademy.com 17
  18. 18. • Two of the most important breakthroughs responsible for the long-standing superb aesthetic performance and clinical survivability of metal-ceramic restorations are the patents of Weinstein and Weinstein (1962) and Weinstein et al (1962). • One of these patents described the formulations of feldspathic porcelain that allowed systematic control of the sintering temperature and thermal expansion coefficient. www.indiandentalacademy.com 18
  19. 19. • The other patent described the components that could be used to produce alloys that bonded chemically to and were thermally compatible with feldspathic porcelains www.indiandentalacademy.com 19
  20. 20. What are ceramics? – Dental ceramics may consist primarily of glasses ,porcelains, glass-ceramics. – The properties of ceramics are customized for dental application by precise control of the type & amount of the components used in their production. www.indiandentalacademy.com 20
  21. 21. • Ceramics are more resistant to corrosion. Ceramics generally do not react with most liquids, gases, alkalies & acids. And they remain stable over long time. • Dental ceramics exhibit far to excellent flexure strength & fracture toughness. www.indiandentalacademy.com 21
  22. 22. • Although ceramics are strong, temperature-resistant & resilient these materials are brittle and may fracture when quickly heated and cooled. • Dental ceramics are non-metallic inorganic structures,primarily containing components of oxygen with one or more metallic or semi metallic elements. www.indiandentalacademy.com 22
  23. 23. Properties of ceramics. • Most ceramics are characterized by their refractory nature, high hardness, (relatively low tensile strength and essentially zero percent elongation), and chemical inertness. www.indiandentalacademy.com 23
  24. 24. • For dental applications a hardness of a ceramic less than that of enamel and an easily polishable surface are desirable to minimize the wear damage that can be produced on enamel by the ceramic surface. www.indiandentalacademy.com 24
  25. 25. 1) Strength. • Porcelain is a material having good strength. However, it is brittle and tends to fracture. • The strength of porcelain is usually measured in terms of its flexure strength or modulus of rupture. www.indiandentalacademy.com 25
  26. 26. a) Flexure strength: • It is a combination of compressive, tensile, as well as shear strength. • Glazed porcelain is stronger than ground porcelain. • Ground-75.8 Mpa (11,000 psi) • Glazed-141.1 Mpa (20,465 psi) www.indiandentalacademy.com 26
  27. 27. b) Compressive strength: • Porcelains have good compressive strength. • 331 Mpa (48,000psi) www.indiandentalacademy.com 27
  28. 28. c) Tensile strength: • Is low • 34 MPa (5000psi). www.indiandentalacademy.com 28
  29. 29. d) Shear strength: • It is low and is due to the ductility caused by the complex structure of dental porcelain. • 110 Mpa (16000psi). www.indiandentalacademy.com 29
  30. 30. Factors affecting strength. • 1) Composition. • 2) Surface integrity: Surface imperfections like microscopic cracks and porosities reduce the strength. • 3) Firing procedure: Inadequate firing weakens the structure as vitrification is not complete. Overfiring also decrease strength as more of the core gets dissolved in the fluxes, thereby weakening the core network. www.indiandentalacademy.com 30
  31. 31. 2) Modulus of elasticity: • Porcelain as high modulus of elasticity. • 69 GPa . www.indiandentalacademy.com 31
  32. 32. 3) Surface hardness: • Porcelain is much harder than natural teeth. • 460 KHN www.indiandentalacademy.com 32
  33. 33. 4) Wear resistance: • Porcelain is more resistant to wear than natural teeth. Thus, it should not be placed opposite to natural teeth. www.indiandentalacademy.com 33
  34. 34. 5) Specific gravity: • Is 2.242. • The specific gravity of fired porcelain is usually less, because of the presence of air voids. It varies from 2.2 to 2.3. www.indiandentalacademy.com 34
  35. 35. 6) Dimensional stability: • Porcelain is dimensionally stable after firing. www.indiandentalacademy.com 35
  36. 36. 7) Chemical stability: • It is insoluble and impermeable to oral fluids. Also it is resistant to most solvents. However, contact with hydrofluoric acid causes etching of the porcelain surface. www.indiandentalacademy.com 36
  37. 37. 8) Esthetic properties: • Are excellent. It is able to match adjacent tooth structure in translucence, color and intensity. www.indiandentalacademy.com 37
  38. 38. 9) Biocompatibility. • It is compatible with the oral tissue. www.indiandentalacademy.com 38
  39. 39. 10) Thermal compatibility • Refers to the ability of a metal and its veneering porcelain to contract at similar rates. • The coefficient of thermal expansion by definition is the change in length per unit of original length of a material when its temperature is raised by 1o K •. www.indiandentalacademy.com 39
  40. 40. Thermal compatibility (contd.) • When the co efficient of thermal expansion of metal and porcelain are compatible the tensile stress that develop during cooling are insufficient to cause immediate cracking of porcelain or delayed cracking after cooling at room temperature. www.indiandentalacademy.com 40
  41. 41. • Porcelains have coefficient of thermal expansion between 13.0 and 14.0 X 10-6 and metal between 13.5 and 14.5 X 10-6. • The difference of 0.5 X10-6 in thermal expansion between metal and porcelain causes the metal to contract slightly more than does the ceramic during cooling after firing the porcelain. www.indiandentalacademy.com 41
  42. 42. • This puts the ceramic under slight residual compression which makes it less sensitive to applied tensile forces. www.indiandentalacademy.com 42
  43. 43. Methods of strengthening ceramics • Strengthening occurs through two mechanism, • 1) development of residual compressive stresses. • 2) interruption of crack propagation. www.indiandentalacademy.com 43
  44. 44. • Development of residual compressive stresses. • 1) Ion exchange: (chemical tempering) • exchange of potassium ions (which is 35% larger) for sodium ions. thus there is squeezing of the potassium ion into smaller spaces. This creates a residual compressive stresses on the surface of the glass. www.indiandentalacademy.com 44
  45. 45. • Thermal tempering. • By rapidly cooling the surface of the object while it is hot and in the molten state. This rapid cooling produces a layer of rigid glass surrounding a soft core. As the molten core solidifies ,it tends to shrink, creates a residual tensile stress in the core thus leaving the outer layer in residual compressive stress. www.indiandentalacademy.com 45
  46. 46. • THERMAL EXPANSION COEFFICIENT MISMATCH: • Ceramic in combination with metal are heated together .The metal which is veneered with ceramic has a higher coefficient of thermal expansion than the ceramic. Hence on cooling, the metal contracts more than the ceramics thus leaving the outer layer, of ceramic in residual compressive stress. www.indiandentalacademy.com 46
  47. 47. Interruption of crack propagation. • Two different types of dispersions used to interrupt crack propagation are: • 1) By absorption of energy by the dispersed tough particle from the crack and thus depleting its driving force for propagation. • 2) By change of crystal structure under stress to absorb energy from the crack. www.indiandentalacademy.com 47
  48. 48. 1) Dispersion of a crystalline phase. • A tough crystalline material like alumina is added in particulate form. The glass is toughened and strengthened because the crack cannot penetrate the alumina particles as easily as it can propagate in the glass. Thus the aluminous porcelains were developed for Porcelain Jacket Crown. (PJC) www.indiandentalacademy.com 48
  49. 49. Transformation toughening. • A crystalline material is incorporated that is capable of undergoing a change in crystal structure when placed under stress. The crystalline material used is termed as partially stabilized zirconia (PSZ).The refractive index of PSZ is higher than glass matrix. Thus the PSZ scatters the light producing an opacifying effect. www.indiandentalacademy.com 49
  50. 50. Terminology. Porcelain-fused-to-metal (PFM): a popular alternative designation for the metal ceramic restoration. www.indiandentalacademy.com 50
  51. 51. • Porcelain bonding: a term used to explain the mechanisms by which dental porcelain fuses or adheres to a metal substructure • Coping: the word coping can be used to identify the metal substructure of singleunit crowns designed for bonding to dental porcelain. Copings are made on a single tooth preparation, which may be a single unit or attached to pontics for a fixed partial denture. www.indiandentalacademy.com 51
  52. 52. • Framework: this term is often applied to fixed partial dentures and identifies a one-piece substructure composed on either several copings attached to a pontic or multiple single units that are joined together as a single structure. www.indiandentalacademy.com 52
  53. 53. • Degassing: the process of heat-treating a cast metal substructure in a porcelain furnace as one of the preparatory steps to applying an opaque porcelain. Subjecting the finished metal to elevated temperatures (980° to 1,050°C) in a reduced atmosphere (vacuum) or in air reportedly burns off organic surface impurities and eliminates entrapped gaseous contaminants. A newer and perhaps more appropriate term—oxidizing—has emerged in the literature to describe this procedure. www.indiandentalacademy.com 53
  54. 54. • Oxidation (or oxidizing): the process by which a metal substructure is heated in a porcelain furnace to produce an oxide layer for porcelain bonding as well as to cleanse the porcelain-bearing surfaces of contaminants www.indiandentalacademy.com 54
  55. 55. ADVANTAGES OF DENTAL PORCELAIN • Dental ceramics are attractive because of their biocompatibility, long-term color stability, wear resistance, and their ability to be formed into precise shapes. www.indiandentalacademy.com 55
  56. 56. Disadvantages. • They require costly processing equipment and specialized training. • Susceptibility to brittle fracture at relatively low stresses www.indiandentalacademy.com 56
  57. 57. The chemical components of dental porcelain. • Feldspar (K2O –Al 2O3-6SiO2 & Na2o – Al2o3-6SiO2) • Quartz (SiO2) • Alumina (Al2O3) • Kaolin (Al2O3 -2SiO2 2H2O) www.indiandentalacademy.com 57
  58. 58. Feldspar • Found as a mix of two substances . • It does not occur in pure form in nature • Mineral is crystalline and opaque • Color is indefinite and between gray and pink. www.indiandentalacademy.com 58
  59. 59. Type of feldspar Chemical Other formula names Properties uses Potassiu (K2O.Al orthocla m O3.6Si se or 2 potash aluminiu O ) feldspar 2 m silicate. 1.Reduces the fluidity of the molten materials 2.helps to maintain the form of the porcelain buildup 3.adds translucent qualities to fired restorations. Found in majority of the porcelain systems Sodium aluminu m silicate (Na2O. Al2O3. 6SiO2) 1.Lowers fusion temperature of the porcelain. Less preferred Lime feldspar CaO.2 Al2O3.2 albite or sodium feldspar . www.indiandentalacademy.com 59
  60. 60. • On heating it becomes glassy and fuses at 1290 C, on overheating it may loose its shape . • Impurities : Mica Iron –it is important to remove it as its oxides act as strong coloring agents. www.indiandentalacademy.com 60
  61. 61. Removal of impurities Iron• manually only light colored pieces of feldspar are selected • Feldspar is grounded into fine powder and vibrated down inclined planes surrounded by induction magnets www.indiandentalacademy.com 61
  62. 62. Functions • Primarily responsible for forming glass matrix www.indiandentalacademy.com 62
  63. 63. • Glass modifiers such as the oxides of potassium, sodium, and calcium acts as fluxes to increase a porcelains coefficient of thermal expansion. • The fluxes increase the porcelains coefficient of thermal expansion by breaking up oxygen crosslinking. www.indiandentalacademy.com 63
  64. 64. Silica (Quartz or Flint) SiO2 • Primarily responsible for forming glass matrix • Has a fusion temperature www.indiandentalacademy.com 64
  65. 65. SiO2 www.indiandentalacademy.com 65
  66. 66. Functions • Silica contributes stability to the mass of porcelain during heating by providing a framework for the other ingredients. • Also acts to strengthen the porcelain. www.indiandentalacademy.com 66
  67. 67. KAOLIN (Al2 o3-2sio22H2o) • It is deposited along the banks and at the bottom of streams in the form of clay. • Only purest form of clay are used for dental porcelain. www.indiandentalacademy.com 67
  68. 68. Preparation of clay • Repeated washing until all foreign materials are separated. • Allowed to settle. • Dried and screened. • Nearly white powder is obtained. www.indiandentalacademy.com 68
  69. 69. Properties of clay I. II. Its gives OPAQUENESS to porcelain MOULDABLE :On mixing with water it becomes sticky and aids in forming a workable mass of the porcelain during molding. III. Clay-water suspension maintains its shape during firing in a furnace. IV. On subjecting to high heat it adheres to the framework of Quartz particles and shrinks considerably. www.indiandentalacademy.com 69
  70. 70. • Little or no kaolin is found is modern day low fusing porcelain. • Kaolin is not used in enamel powder as it will decrease its translucency. www.indiandentalacademy.com 70
  71. 71. Alumina.(Al2o3) • The hardest and perhaps the strongest oxide. • Its CTE is similar to the low fusing porcelains. • It also strengthens the porcelain. www.indiandentalacademy.com 71
  72. 72. Manufacturing of ceramics powder www.indiandentalacademy.com 72
  73. 73. Fritting. • The process of blending, melting and quenching the glass components is termed “fritting”. • All the raw mineral powders are mixed together in a refractory crucible and heated till a molten mass is formed. • It is then quenched in water. • It immediately breaks into fragments and this is termed the “frit”. www.indiandentalacademy.com 73
  74. 74. • Frits are ground to the specific particle size established by individual manufacturers for their particular brand of porcelain. www.indiandentalacademy.com 74
  75. 75. • TOOTH PREPARATION FOR THE METAL CERAMIC RESTORATION www.indiandentalacademy.com 75
  76. 76. • Depth orientation grooves flat end tapered diamond. www.indiandentalacademy.com 76
  77. 77. www.indiandentalacademy.com 77
  78. 78. • Make at least two vertical cuts in the incisal portion of the facial surface. www.indiandentalacademy.com 78
  79. 79. • Next align the flat end tapered diamond with the gingival portion of the facial surface. www.indiandentalacademy.com 79
  80. 80. • Sink the side of the diamond into the mesiodistal center of the facial surface,maintain the instrument alignment parallel to the gingival surface of the facial segment. www.indiandentalacademy.com 80
  81. 81. • Make two incisal orientation grooves that are 2mm deep.The diamond should be parallel to the incisal edge faciolingally. www.indiandentalacademy.com 81
  82. 82. • Incisal reduction is done with the flat end tapered diamond. www.indiandentalacademy.com 82
  83. 83. www.indiandentalacademy.com 83
  84. 84. • Facial reduction; incisal half,flat end tapered diamond. www.indiandentalacademy.com 84
  85. 85. • If there sound tooth structure inter proximally, wing preparation is done. www.indiandentalacademy.com 85
  86. 86. • Begin the lingual reduction with the small round diamond with diameter of 1.4mm. Sink this instrument into the lingual tooth structure up to 0.7mm. www.indiandentalacademy.com 86
  87. 87. • Lingual axial reduction torpedo diamond and carbide finishing bur. www.indiandentalacademy.com 87
  88. 88. • Lingual reduction is done with the small wheel diamond. www.indiandentalacademy.com 88
  89. 89. • Smooth the entire facial surface with no.171 bur .Round over the any sharp angles on the incisal angle or along the edges of the incisal notches with no.171 bur. www.indiandentalacademy.com 89
  90. 90. Components of the metal ceramic restoration • Two major components: • a metal substructure and a porcelain veneer. • The surface oxide layer that lies between the metal and the porcelain veneer could be considered a separate component, but it is an integral part of the casting alloy substructure. www.indiandentalacademy.com 90
  91. 91. www.indiandentalacademy.com 91
  92. 92. The basic components of a traditional porcelain kit include 1.opaque porcelain. 2.dentin porcelains 3.enamel porcelains Modifiers, stains & glazes. Newest products has high fusing shoulder porcelains. www.indiandentalacademy.com 92
  93. 93. The metal substructure • Conventional low-fusing dental porcelain lacks the strength required of an all-porcelain restoration, so a metal substructure is added to support the porcelain veneer. • The thickness of the metal coping can vary, depending on the type of casting alloy used and the amount of tooth structure reduced by the dentist. www.indiandentalacademy.com 93
  94. 94. The oxide layer • Most metal ceramic alloys are oxidized after the porcelainbearing area of the restoration has been properly finished and cleaned. www.indiandentalacademy.com 94
  95. 95. • The metal oxides that form on the alloy's surface during this heattreatment procedure play a key role in bonding the dental porcelain to the underlying metal substructure. • Because noble elements do not oxidize, an alloy's base metal constituents are principally responsible for forming this oxide layer. www.indiandentalacademy.com 95
  96. 96. • Differences in alloy composition require that oxidation techniques be alloy specific • Ideally this oxidation should be no more than a discrete, monomolecular film on the alloy's surface for all metal ceramic alloys, irrespective of compositional differences. www.indiandentalacademy.com 96
  97. 97. Opaque porcelain layer • These porcelains are made opaque by the addition of insoluble oxides, such as • tin oxide (SnO2), • titanium oxide (TiO2), • zirconium oxide (ZrO2), • cerium oxide (CeO2), www.indiandentalacademy.com 97
  98. 98. Opaque porcelain layer contd. • • • • oxide, and rubidium oxide, barium zinc oxide. Such oxides have high refractive indices, so they scatter light. www.indiandentalacademy.com 98
  99. 99. Composition on chemical analysis www.indiandentalacademy.com 99
  100. 100. • Between 8% and 15% of an opaque powder is composed of metallic oxides, and some particles may be less than 5 um in size. • Even small differences in particle size distribution are thought to influence the ability of opaques to mask the color of a metal substructure. www.indiandentalacademy.com 100
  101. 101. • The opaque porcelains three major functions: • (1) to establish the porcelain-metal bond, • (2) to mask the dark color of the metal substructure, and • (3) to initiate the development of the selected shade of porcelain. www.indiandentalacademy.com 101
  102. 102. • A uniform thickness of 0.2 to 0.3 mm generally is regarded as ideal. • That masking power is influenced by the amount and the color of the oxidized (degassed) metal casting (Naylor, 1986) www.indiandentalacademy.com 102
  103. 103. • A casting alloy of a different composition might generate a thick, dark oxide layer (Naylor, 1986) and require a thicker opaque covering. • The thickness of the opaque layer needed to veneer the metal and mask the surface oxides differs among brands of porcelain and even varies for different shades within the same porcelain system www.indiandentalacademy.com 103
  104. 104. www.indiandentalacademy.com 104
  105. 105. Body porcelains • Body porcelain collectively describes four principal types of porcelain powders used to recreate the "body" of a restoration: dentin (body or gingival), enamel (or incisal), translucent, and modifier. • These body porcelains are mixed with either distilled water or a special liquid (provided with the porcelain kit) that helps to prevent the buildup from drying out rapidly. www.indiandentalacademy.com 105
  106. 106. • They are applied directly over the fired opaque layer . • The dentin, enamel, translucent, and modifier powders all have the same chemical and physical properties, they may be intermixed freely if custom shading is desired. • They differ in appearance in the fired state because of variations in the amount and type of metallic oxide pigments each contains. www.indiandentalacademy.com 106
  107. 107. The dentin porcelain veneer • The major color contribution is derived from the pigmented metal oxides in the dentin body porcelain • It is this initial layer of dental porcelain that imparts the dentin shade associated with, but not confined to, the gingival two thirds of a tooth. • The dentinal layer is overbuilt slightly, cut back, and overlaid with enamel porcelain in those sections of the restoration where greater translucency is desired. www.indiandentalacademy.com 107
  108. 108. • For more accurate shade duplication, estimates of the combined thickness of fired dentin and enamel porcelains range from a minimum of 0.5 to 1.0 mm to a maximum thickness of 1.5 to 2.0 mm www.indiandentalacademy.com 108
  109. 109. • For uniformity of shade and maximum strength, it is desirable to have an even thickness of porcelain covering the metal substructure. • The minimum total thickness of porcelain may be between 1.2 to 1.3 mm at the middle one third of the restoration and 1.5 to 1.6 mm at the incisal edge (Yamamoto, 1985). www.indiandentalacademy.com 109
  110. 110. ENAMEL PORCELAIN VENEER • Enamel porcelains are more translucent than dentin porcelains. • The enamel porcelains are usually in the violet to grayish range & impart a combination of true translucency & the illusion of the translucency by virtue of their grayish or some times bluish appearance. • www.indiandentalacademy.com 110
  111. 111. • When fired, enamel porcelains are more translucent than dentin porcelains (McLean, 1979). • They also have a more restricted range of shades. A typical porcelain system may provide only four or five bottles of enamel powders to cover the entire range of shades in the kit. www.indiandentalacademy.com 111
  112. 112. Translucent porcelains • Translucent porcelains are not transparent, they do not allow the transmission of all light. • They are applied as a veneer over nearly the entire surface of a typical porcelain buildup. • This veneer imparts depth and a natural enamel-like translucency without substantially altering the body shade that is overlaid. www.indiandentalacademy.com 112
  113. 113. BODY MODIFIERS • These porcelains are more color concentrated & were designed to aid in the achieving internal color modifications. • They are used to distinguish the dentin, enamel & translucent porcelains, because they have the same basic physical & chemical properties. • All these powders are basically same materials, they do differ in the appearance because of the modifiers. www.indiandentalacademy.com 113
  114. 114. www.indiandentalacademy.com 114
  115. 115. STAINS • Stain powders contain less silica or alumina & more sodium & potassium oxides. • They contain high concentration of metallic oxides. • They are created by mixing the metallic oxides with lower fusion point glasses www.indiandentalacademy.com 115
  116. 116. GLAZES • Glazes are generally colorless, low fusing porcelains. • They possess considerable fluidity at high temperatures. • They fill small surface porosities & irregularities. when fired helps to recreate the external glazy appearance of the natural tooth www.indiandentalacademy.com 116
  117. 117. www.indiandentalacademy.com 117
  118. 118. GLAZE (Contd.) • A glazed ceramic surface is generally considered beneficial by increasing the fracture resistance and reducing the potential abrasiveness of ceramic surfaces www.indiandentalacademy.com 118
  119. 119. Color coding • By convention dentin powders are pink and enamel powders are blue. • These organic colors burn off during firing procedure and do not affect the shade of the fired restoration in any way. • Some manufacturers color code the distilled water instead of the powder.e.g. pencraft porcelain www.indiandentalacademy.com 119
  120. 120. CLASSIFICATION OF DENTAL CERAMICS • Different types of dental ceramics are available These include core ceramic, liner ceramic, margin ceramic, opaque dentin (also, body or gingival) ceramic, dentin ceramic, enamel (incisal) ceramic, stain ceramic, glaze ceramic, and addition ceramic www.indiandentalacademy.com 120
  121. 121. • These products can be classified in several possible ways according to their: (1) use or indications (anterior, posterior, crowns, veneers, post and cores, FPDs, stain ceramic, and glaze ceramic); www.indiandentalacademy.com 121
  122. 122. • (2) composition (pure alumina, pure zirconia, silica glass, leucitebased glass-ceramic, and lithiabased glass-ceramic • (3) processing method (sintering, partial sintering and glass infiltration ,CAD-CAM, and copymilling); www.indiandentalacademy.com 122
  123. 123. • Microstructure (glass, crystalline, and crystal-containing glass); • Translucency (opaque, translucent, and transparent); Fracture resistance; or Abrasiveness www.indiandentalacademy.com 123
  124. 124. Based on the method of fabrication 1. Condensation porcelains using condensation and sintering 2. Castable ceramics –Dicor-Dentsply 3. Pressable ceramics 4. Machinable ceramics 5. Infiltrated ceramics 6. Injection molded ceramics –Cerestore www.indiandentalacademy.com 124
  125. 125. Classification (Mclean) 1) Regular feldspathic porcelain 2) Aluminous porcelain 3) Metal bonding porcelain. www.indiandentalacademy.com 125
  126. 126. Based on their fusion temperature (Phillips,1982) type Fusing temperature range uses High fusing porcelains- 1288 to 1371 C 1200-1400 used for manufacturing denture teeth . Medium fusing Porcelains- 1093 to 1260 C 1050-1200 for all ceramic restorations and prefabricated pontics. Low fusing porcelains- 871 to 1066 C for metal ceramic and all 800-1050 www.indiandentalacademy.com ceramic. Both are similar in composition and microstructure. 126
  127. 127. METAL SUB STRUCTURE DESIGN. • Majority of the porcelain-to-metal bond failures occur as a direct result of improper substructure design • Errors in the preparation of the metal ceramic sub-structure frequently go unnoticed until the brittle porcelain veneer fails in service. www.indiandentalacademy.com 127
  128. 128. METAL SUB STRUCTURE DESIGN. • TYPES • FUNCTIONS. • DESIGN. www.indiandentalacademy.com 128
  129. 129. Types of metal ceramic system. • A. Cast metal ceramic alloys: • 1.Noble-metal alloy systems: • High gold - a) Gold platinum palladium. • Low gold - b) Gold palladium silver. • Gold free - c) Palladium silver. • 2.Base metal alloys systems: • Nickel chromium alloy. • Cobalt chromium alloys ( rarely used in ceramic bonding). www.indiandentalacademy.com 129
  130. 130. • B. • Foil copings: • a) Bonded platinum foil coping. • b) Swaged gold alloy foil coping. www.indiandentalacademy.com 130
  131. 131. a) Bonded platinum foil coping: • Another method of bonding porcelain to metal is the use of tin oxide coatings on platinum foil. • The method consists of bonding aluminous porcelain to platinum foil copings. • Attachment of the porcelain is secured by electroplating the foil with a thin layer of tin and then oxidizing it in a furnace. www.indiandentalacademy.com 131
  132. 132. • The objective of this type of restoration is to improve esthetics. • The thicker cast metal coping that is normally used is replaced by a thinner platinum foil, thus allowing more space for the porcelain. www.indiandentalacademy.com 132
  133. 133. b) Swaged Gold Alloy Foil Coping: • A laminated gold alloy supplied in fluted shape is also used as an alternative to the cast metal coping. • The foil is swaged onto the die and flame sintered to form a coping. • An “interfacial alloy” powder is applied and fired and the coping is then veneered with porcelain. www.indiandentalacademy.com 133
  134. 134. Primary functions:• The casting provides fit of the restoration to the prepared tooth. • The metal forms oxides that bond chemically to the dental porcelain. www.indiandentalacademy.com 134
  135. 135. • The coping serves as a rigid foundation to which the brittle porcelain can be attached for increased strength & support. • The sub structure restores the tooth's proper emergence profile. www.indiandentalacademy.com 135
  136. 136. Secondary functions. • Metal occlusal & lingual articulating surfaces generally less destructive to the enamel of the opposing natural tooth. • Fabrication of the restoration with minimal occlusal clearance has more potential for the success with metal substructure than all ceramic alloys. www.indiandentalacademy.com 136
  137. 137. • Occlusal surfaces can be easily adjusted & repolished intraorally. • The metal axial walls can support the removable partial denture. www.indiandentalacademy.com 137
  138. 138. Metal sub structure design • Majority of the porcelain-to-metal bond failures occur as a direct result of improper substructure design • Errors in the preparation of the metal ceramic sub-structure frequently go unnoticed until the brittle porcelain veneer fails in service. www.indiandentalacademy.com 138
  139. 139. Sub structure design (contd) • Hence necessary to understand the essentials of proper substructure design, since it will help to ensure the longevity of the final prosthesis. www.indiandentalacademy.com 139
  140. 140. Principles of substructure design. • Are the occlusal contacts to be in metal or porcelain? www.indiandentalacademy.com 140
  141. 141. • Occlusion in metal requires less tooth reduction (1 to 1.5 mm). • Approximately 2 mm of occlusal reduction is necessary for posterior teeth and 1 to 1.5 mm for anterior teeth requiring porcelain on occluding surfaces. www.indiandentalacademy.com 141
  142. 142. • Metal surfaces can be more easily adjusted and repolished at chair side without adversely affecting the restoration. • On the other hand, removing the glaze of a metal ceramic restoration during intraoral adjustments weakens the porcelain greatly www.indiandentalacademy.com 142
  143. 143. • 2. Are the centric occlusal contacts 1.5 to 2mm from the porcelain-metal junction? www.indiandentalacademy.com 143
  144. 144. • occlusal contacts when placed directly on or close to the porcelainmetal junction, there is an increased likelihood the porcelain will chip or fracture at that point of contact . • Porcelain is strongest under compression and weakest under tension, so situations that induce tensile stresses in the ceramic during function are more apt to promote bond failures www.indiandentalacademy.com 144
  145. 145. • A substructure should be designed so the functional incisal or occlusal contacts are located at least 1 .5 mm and perhaps as much as 2 mm from the metal-porcelain junction. www.indiandentalacademy.com 145
  146. 146. • When the anterior teeth contact in the incisal region,it is often necessary to consider a design with lingual surface in porcelain to avoid functioning on or over the porcelain metal junction. www.indiandentalacademy.com 146
  147. 147. • Do not design the sub structure so contact occurs at the porcelain metal junction. www.indiandentalacademy.com 147
  148. 148. • When the anterior teeth occlude in the gingival half of the maxillary teeth or when the lingual tooth reduction is less than 1mm it is best to design the sub structure with occlusion in the metal. www.indiandentalacademy.com 148
  149. 149. • 3.Are the interproximal contacts to be restored in metal or porcelain? www.indiandentalacademy.com 149
  150. 150. • The inter proximal contact areas of anterior teeth, and at least the mesial contacts of posterior teeth, are frequently restored in porcelain • with porcelain inter proximal contact areas would be more esthetic, particularly with anterior teeth. www.indiandentalacademy.com 150
  151. 151. • It is important to provide proper metal support to a porcelain marginal ridge in the substructure design to prevent possible fracture • However, the distal inter proximal contacts of posterior teeth may be restored in either metal or porcelain because these areas are not as critical esthetically. www.indiandentalacademy.com 151
  152. 152. • 4.Are the cusp tips (or incisal edges )adequately supported by the metal substructure with no more than 2mm of unsupported porcelain? www.indiandentalacademy.com 152
  153. 153. • The ultimate goal of any substructure is to support an even thickness (1mm minimum, 2 mm maximum) of the porcelain veneer. • If this maximum thickness is exceeded, the ceramic layer may no longer be properly supported, resulting in a catastrophic failure at the cusp tip or incisal edge www.indiandentalacademy.com 153
  154. 154. • 5. Is the substructure thick enough to provide a rigid foundation for the porcelain veneer? www.indiandentalacademy.com 154
  155. 155. • Areas to be veneered with porcelain must be at least 0.3 mm thick. • with base metal alloys, the coping can be reduced to 0.2 mm or less and still be strong enough to support the porcelain www.indiandentalacademy.com 155
  156. 156. How does dental porcelain bond to metal? (1) van der Waals forces (Lacy, 1977), • (2) mechanical retention, • (3) compression bonding, and • (4) direct chemical bonding (Lacy, 1977; McLean, 1980; www.indiandentalacademy.com 156
  157. 157. van der Waals forces • The attraction between charged atoms that are in intimate contact yet do not actually exchange electrons is derived from van der Waals forces. • These secondary forces are generated more by a physical attraction between charged particles • Van der Waalsforces are generally weak. www.indiandentalacademy.com 157
  158. 158. www.indiandentalacademy.com 158
  159. 159. • The better the wetting of the metal surface, the greater the van der Waals forces. • porcelain's adhesion to metal can be diminished or enhanced by alterations in the surface character (texture) of the porcelain-bearing surface on the substructure www.indiandentalacademy.com 159
  160. 160. • van der Waals forces are only minor contributors to the overall attachment process. www.indiandentalacademy.com 160
  161. 161. Mechanical retention • The porcelain-bearing area of a metal casting contains many microscopic irregularities into which opaque porcelain may flow when fired. • Air abrading the metal with aluminum oxide is believed to enhance mechanical retention further by eliminating surface irregularities (stress concentrations) www.indiandentalacademy.com 161
  162. 162. Mechanical retention's contribution to bonding may be relatively limited. • Dental porcelain does not require a roughened area to bond to metal but some surface roughness is effective in increasing bonding forces • www.indiandentalacademy.com 162
  163. 163. www.indiandentalacademy.com 163
  164. 164. www.indiandentalacademy.com 164
  165. 165. Compression bonding • Dental porcelain is strongest under compression and weakest under tension; hence, if the coefficient of thermal expansion of the metal substrate is greater than that of the porcelain placed over it, the porcelain should be placed under compression on cooling www.indiandentalacademy.com 165
  166. 166. • the metal contracts faster than the porcelain but is resisted by the porcelain's lower coefficient of thermal expansion. • This difference in contraction rates creates tensile forces on the metal and corresponding compressive forces on the porcelain. www.indiandentalacademy.com 166
  167. 167. Chemical bonding • The single most significant mechanism of porcelain-metal attachment is a chemical bond between dental porcelain and the oxides on the surface of the metal substructure www.indiandentalacademy.com 167
  168. 168. • The two hypothesis that explains chemical bonding are • 1, The sandwich theory the oxide layer is permanently bonded to the metal substructure on one side while the dental porcelain remains on the other www.indiandentalacademy.com 168
  169. 169. • The oxide layer itself is sandwiched in between the metal substructure and the opaque porcelain. This "sandwich" theory is undesirable in that a thick oxide layer might exist that would weaken the attachment of metal to porcelain www.indiandentalacademy.com 169
  170. 170. • The second, and more likely, theory suggests that the surface oxides dissolve, or are dissolved by, the opaque layer. The porcelain is then brought into atomic contact with the metal surface for enhanced wetting and direct chemical bonding so metal and porcelain share electrons. (McLean, 1980; Yamamoto, 1985) www.indiandentalacademy.com 170
  171. 171. • Chemical "bonding" is generally accepted as the primary mechanism in the porcelain-metal attachment process www.indiandentalacademy.com 171
  172. 172. www.indiandentalacademy.com 172
  173. 173. www.indiandentalacademy.com 173
  174. 174. The oxidation (degassing) process • After the cast metal ceramic castings have been properly finished with uncontaminated carbide burs or ceramic abrasives the castings are heat-treated in a porcelain furnace (in air or a vacuum) to a designated temperature for a specified period of time (Naylor, 1986). www.indiandentalacademy.com 174
  175. 175. • The heat-treatment process allows specific oxides to form on the metal surface. These oxides are responsible for the chemical porcelain- metal "bond." www.indiandentalacademy.com 175
  176. 176. • A high-gold-content alloy contains oxidizable trace elements such as tin, indium, and iron to produce an adherent oxide layer. Because elements like gold and the other noble metals do not oxidize, it is often necessary to hold these castings at temperature for several minutes to permit the non noble trace elements to form the oxide layer www.indiandentalacademy.com 176
  177. 177. • The base metal alloys readily oxidize, but trace elements are still added in an effort to form a particular type of oxide for a stable bond . • The oxidation procedure may be carried out in a vacuum to minimize the amount of oxidation, and the hold time is often reduced or omitted. www.indiandentalacademy.com 177
  178. 178. • Allowing certain base metal alloys to oxidize in air, or to remain at temperature, could lead to over oxidation. An excessively thick and non-adherent oxide layer is often responsible for porcelain bond failures www.indiandentalacademy.com 178
  179. 179. www.indiandentalacademy.com 179
  180. 180. • A properly oxidized casting often has a distinctive appearance in terms of color and character (texture, thickness, etc). • That appearance of a properly oxidized metal substructure differs among alloy systems and may also differ among alloys within the same system. www.indiandentalacademy.com 180
  181. 181. www.indiandentalacademy.com 181
  182. 182. • Some manufacturers do not recommend an oxidation/ degassing step; instead, they advocate minimizing the number of firings to which the casting is subjected. www.indiandentalacademy.com 182
  183. 183. Removing the oxide layer • Two principal methods for removing oxides are – Acid treatment (chemical method) – Nonacid treatment (mechanical method). www.indiandentalacademy.com 183
  184. 184. Acid treatment (chemical method) • Different types of acids are used to reduce or eliminate surface oxides, including hydrofluoric, hydrochloric, and dilute sulfuric acid. • The potential hazards of these acids require that they be stored and used in clearly marked, resealable plastics bottles. • It is advisable to wear protective rubber gloves and eye protection during all handling procedures. www.indiandentalacademy.com 184
  185. 185. • A rubber-tipped instrument should be used to place oxidized castings into the acid appropriate for the alloy. • Place the covered container in an ultrasonic unit for the time recommended by the alloy manufacturer. • Remove the casting and thoroughly rinse it under tap water. For the final cleaning step, put the coping in a container of distilled water and clean it ultrasonically for 10 to 15 minutes. www.indiandentalacademy.com 185
  186. 186. Nonacid treatment (Mechanical method) • Castings can be air-abraded with pure, 50um aluminum oxide (Al2o3) that is nonrecycled. • Steam clean or ultrasonically clean the casting in distilled water for 10 to 15 minutes before applying the opaque porcelain. www.indiandentalacademy.com 186
  187. 187. Porcelain-metal bond failures • Metal ceramic alloys, whether noble or base metals, all oxidize differently because of variations in their composition. • If the oxidation process is not performed properly, the subsequent porcelain-metal bond may be weak and may lead to bond failure. www.indiandentalacademy.com 187
  188. 188. www.indiandentalacademy.com 188
  189. 189. Porcelain delamination • With base metal alloys, the separation of the porcelain veneer from the metal substrate can be more a loss of the "attachment" of the oxide layer that is either too thick or is poorly adherent to the metal substructure. www.indiandentalacademy.com 189
  190. 190. www.indiandentalacademy.com 190
  191. 191. Porcelain delamination contd • Overoxidation has been a particular problem with the heavily oxidizing base metal alloys and has been linked to their increased tendency for bond failures . www.indiandentalacademy.com 191
  192. 192. • Bond failures are not caused by a loss of the chemical bond between the ceramic and the oxide layer • on the contrary, the porcelain might remain visibly attached to the oxides but the oxide layer may be so thick that the bond is lost through it . • This particular problem is caused by the formation of a thick and poorly adherent oxide layer. www.indiandentalacademy.com 192
  193. 193. www.indiandentalacademy.com 193
  194. 194. www.indiandentalacademy.com 194
  195. 195. Classification of bond failures in metal-ceramics. • (Given by O’ Brien (1977). • 1) Metal – Porcelain: • Fracture leaves a clean surface of metal. Seen when metal surface is devoid of oxides. May also be due to contaminated or porous metal surface. Usually occurs in high gold alloys. www.indiandentalacademy.com 195
  196. 196. • 2) Metal oxide – Porcelain: • Porcelain fractures at metal oxide surface, leaving oxide firmly attached to metal .Seen more often in base metal alloy systems. • 3) Metal – Metal Oxide: • Metal oxide breaks away from the metal and is left attached to the porcelain. Seen commonly in base metal alloy systems due to over production of chromium and nickel oxides. www.indiandentalacademy.com 196
  197. 197. • 4) Metal Oxide –Metal Oxide: • Fracture occurs through the metal oxide. Results from overproduction of oxide causing sandwich effect between metal and porcelain. Occurs during the usage of nickel-chromium alloys. • 5) Cohesive within Metal: • More common in bridges where the joint area breaks. Rarely seen in single crowns. www.indiandentalacademy.com 197
  198. 198. • 6) Cohesive within Porcelain: • Tensile failure within porcelain. Bond strength exceeds strength of porcelain. Seen in high gold content alloys. www.indiandentalacademy.com 198
  199. 199. • Excessive absorption of oxides by the porcelain can lower the porcelain's coefficient of thermal expansion, alter the final shade (cause a graying or bluing), or do both (Naylor, 1986 www.indiandentalacademy.com 199
  200. 200. • Changes in the shade of the porcelain may not be noticeable with posterior restorations, particularly if a greater thickness of porcelain masks the dark oxides www.indiandentalacademy.com 200
  201. 201. Incompatible materials • Further more, bond failures are not always attributable to improper oxidation but may actually be caused by a physical incompatibility between the porcelain and the metal substructure. The difference in the coefficient of thermal expansion of the veneering porcelain and the metal ceramic alloy may be slight yet sufficient to be responsible for cracking of the ceramic veneer or substantial enough to result in porcelain debonding. www.indiandentalacademy.com 201
  202. 202. www.indiandentalacademy.com 202
  203. 203. Overoxidation/underoxidation • The oxidation procedure varies for alloys of different compositions. • Careful processing followed by an assessment of the postoxidation appearance of each casting will ensure that the procedure was accomplished correctly. • Castings that are either overoxidized or underoxidized should be reprocessed accordingly until a uniform oxide of the desired color and thickness recommended for the alloy involved has formed. www.indiandentalacademy.com 203
  204. 204. • Contamination – castings that demonstrate some form of contamination may not have to be remade but by simply refinishing a substructure's porcelain-bearing surface may be all that is necessary when surface debonding becomes evident. Uncontaminated finishing materials are used to prevent this. www.indiandentalacademy.com 204
  205. 205. www.indiandentalacademy.com 205
  206. 206. • Simply refinishing this casting removed the surface and subsurface contamination and resulted in an appropriate porcelain-metal bond. www.indiandentalacademy.com 206
  207. 207. Applying Porcelain to the Metal Substructure • The application of dental porcelain to the metal substructure is the single most demanding procedure in the fabrication of a metal ceramic restoration. • As a rule, the skills needed for this particular process require the most effort to perfect. www.indiandentalacademy.com 207
  208. 208. Instruments and equipment • Brushes • A variety of brush sizes and styles are available in porcelain instrument kits, the most important of which are the brushes used for building or stacking porcelain. . The size range varies from a no. 4 to a no. 8. Sable brushes are the standard because they permit easy manipulation of the porcelain. www.indiandentalacademy.com 208
  209. 209. • Another frequently used instrument is a large no.10 brush, often referred to as a whipping brush • A basic instrument kit should also include flat brushes with relatively stiff bristles. These large- and small-sized brushes should be kept dry because they are used exclusively to remove porcelain particles from non porcelain-bearing areas and from inside the substructure prior to firing. www.indiandentalacademy.com 209
  210. 210. • Very small no. 0 to no. 000 sable brushes are required for the placement of stains or small increments of porcelain. These brushes are useful anywhere maximum control is necessary www.indiandentalacademy.com 210
  211. 211. Carving Instruments • Porcelain carving instruments, designed for shaping and carving porcelain buildups. • Carving instruments serve two principal functions. • 1.Those with a serrated handle can be used to condense wet porcelain. • 2.Instruments with blades, as well as the small discoid carver, can be used to build (stack) porcelain, shape the buildup, and carve the porcelain. www.indiandentalacademy.com 211
  212. 212. Spatula • Small, flexible, metal spatula is used to dispense and mix porcelain. • Any small metal fragments generated during mixing can then be introduced into the wet porcelain as contaminants. www.indiandentalacademy.com 212
  213. 213. • This metal debris can dramatically discolor the mix as well as the fired porcelain restoration. With careful use, however, the metal mixing spatula need not be abraded. • But for added safety, a glass mixing rod is often substituted for the metal spatula to avoid this problem altogether. www.indiandentalacademy.com 213
  214. 214. Razor knives • Another necessity in the basic set of instruments is some type of razor knife, equipped with a thin, flexible blade for carving the porcelain buildup. www.indiandentalacademy.com 214
  215. 215. Hemostat • A small, straight or curved hemostat is needed to hold the work during the opaquing process and during porcelain additions and condensation. • Hemostats can be modified to hold the metal substructure securely without damaging the metal margins. However, an 18-gauge handle added to the lingual collar provides a convenient, safe, yet secure grip for removing the restoration from the working cast and holding it during condensation www.indiandentalacademy.com 215
  216. 216. Glass or ceramic mixing slab • Finally, either a glass slab, ceramic tile, or ceramic tray can serve as a plate for mixing and storing the porcelain during the buildup procedure. Initially, a small mixing slab will suffice (Fig 8-9a). www.indiandentalacademy.com 216
  217. 217. • As modifiers are added and more complex buildups are attempted,a larger working surface will be required to accommodate all the different porcelain mixtures www.indiandentalacademy.com 217
  218. 218. PORCELAIN CONDENSATION. • Condensing dental porcelain actually refers to any procedure that results in the unfired porcelain particles being tightly packed on to themselves. • As the particles moves closer together, the air and moisture previously occupying the space between the individual particles move to the surface of the buildup. www.indiandentalacademy.com 218
  219. 219. • Any liquid or air that remains trapped in the unfired porcelain will form voids in the unfired ceramic. • The presence of porosity in fired porcelain weakens the restoration and impairs its esthetic qualities. www.indiandentalacademy.com 219
  220. 220. • In well-condensed porcelain there is reduction in the amount of firing shrinkage. • Methods of porcelain condensation. • 1) capillary action. • 2) vibration • 3) spatulation • 4) whipping • 5) dry powder addition. www.indiandentalacademy.com 220
  221. 221. Capillary action. • The technique of blotting a wet built up with absorbent paper uses surface tension. www.indiandentalacademy.com 221
  222. 222. Vibration. • Is created by passing a serrated instrument over the neck of a hemostat in which the restoration is held. • Vibration is a means to mechanically draw additional moisture to the surface where it can then be removed by blotting paper. www.indiandentalacademy.com 222
  223. 223. Spatulation. • A spatula is used to apply , then rub the porcelain built up to force the liquid to the surface. www.indiandentalacademy.com 223
  224. 224. Whipping. • A no. 10 sable brush is rapidly moved over the porcelain surface with a whipping motion. The whipping motion brings the liquid to the outer surface for blotting. www.indiandentalacademy.com 224
  225. 225. Dry powder addition. • Requires dry porcelain powder be sprinkled on an area of wet porcelain, using the existing liquid to moisten the powder addition. www.indiandentalacademy.com 225
  226. 226. Opaquing the metal substructure • The areas of the substructure that will be veneered with porcelain must not be touched and should be protected from dust, oils from the skin, and any other forms of contamination www.indiandentalacademy.com 226
  227. 227. www.indiandentalacademy.com 227
  228. 228. Applying opaque porcelain— glass rod technique • First wet the oxidized metal substructure to be veneered with distilled water and gently vibrate the casting to thoroughly wet the surface. • A wet surface makes porcelain application easier and reduces the possibility of trapping air between the porcelain and the metal. The thin film of water also will draw the opaque particles onto the metal www.indiandentalacademy.com 228
  229. 229. www.indiandentalacademy.com 229
  230. 230. Glass rod technique. • Use the pointed end of the glass rod to apply the opaque porcelain. Begin by opaquing the most convex portion of the coping Move the opaque toward the porcelain-metal junction from one interproximal area to the other and cover the incisal edge. www.indiandentalacademy.com 230
  231. 231. www.indiandentalacademy.com 231
  232. 232. • Then move the opaque over the incisal edge to cover the porcelain-bearing surface on the lingual aspect. Once the porcelain-bearing areas are completely covered, lightly tap the hemostat and the porcelain will settle into any concavities www.indiandentalacademy.com 232
  233. 233. www.indiandentalacademy.com 233
  234. 234. • If, during the opaque application, areas of opaque appear rough and irregular, lightly tap the hemostat handle or move the serrations on a carver across the hemostat in a sawing motion. • The vibrations created by either of these procedures will act to condense the wet porcelain into a more uniform layer. • www.indiandentalacademy.com 234
  235. 235. www.indiandentalacademy.com 235
  236. 236. • Excess moisture should be removed before the opaque is applied to the metal. Gently blend the opaque at the porcelainmetal junction. • Lightly tap the hemostat and dry the opaque by placing it in front of an open porcelain furnace muffle. www.indiandentalacademy.com 236
  237. 237. www.indiandentalacademy.com 237
  238. 238. • Dry the opaque layer by exposing it to the heat radiating from the porcelain muffle. www.indiandentalacademy.com 238
  239. 239. www.indiandentalacademy.com 239
  240. 240. • A properly fired (sintered) opaque layer should have a sheen or eggshell glisten. www.indiandentalacademy.com 240
  241. 241. • If a second application of opaque porcelain is required, lightly wet the opaqued surface with opaque liquid. • Apply the second opaque porcelain layer in the same manner as the first. • Keep this second layer as thin and uniform as possible. www.indiandentalacademy.com 241
  242. 242. www.indiandentalacademy.com 242
  243. 243. www.indiandentalacademy.com 243
  244. 244. Applying opaque porcelain— brush technique • Simply mix the opaque porcelain .Use the tip of porcelain brush to lift a portion of the mixed opaque www.indiandentalacademy.com 244
  245. 245. • Apply the porcelain on the most convex part of the oxidized coping. Repeat the process several times until the porcelain-bearing area is completely covered with porcelain. www.indiandentalacademy.com 245
  246. 246. www.indiandentalacademy.com 246
  247. 247. www.indiandentalacademy.com 247
  248. 248. Mixing dentin porcelains – The technique for mixing body porcelains is same as that used to mix opaque porcelains in that a glass rod is preferred to a metal spatula and the liquid is carefully added to the powder to prevent the entrapment of air. www.indiandentalacademy.com 248
  249. 249. • Mix the body powders (dentin and enamel) with the recommended liquid (Vita VMK 68 porcelain and modeling liquid ) www.indiandentalacademy.com 249
  250. 250. • When properly mixed, dentin porcelain should have a smooth,cream consistency. www.indiandentalacademy.com 250
  251. 251. • If too much liquid is added to the mix, use a tissue or blotting paper to remove excess liquid until the proper consistency is achieved. www.indiandentalacademy.com 251
  252. 252. Appling dentin porcelain. • The dentin porcelain buildup procedure is to apply and condense enough porcelain to create a restoration that is 10% to 15% large than normal. www.indiandentalacademy.com 252
  253. 253. • This overbuilding will accommodate the enamel veneer that will be placed over the dentin layer and help to compensate for shrinkage of the porcelain. A high quality sable brush is preferred to create the porcelain buildup www.indiandentalacademy.com 253
  254. 254. The dentin built up technique. • Return the cleaned, opaqued coping to the master cast. www.indiandentalacademy.com 254
  255. 255. • To minimize the entrapment of air in the porcelain, move the tip of the pointed brush through the mixed dentin porcelain and remove the brush with the dentin porcelain captured on the brush www.indiandentalacademy.com 255
  256. 256. • Apply the porcelain to the most convex surface (midfacial area) on the restoration. www.indiandentalacademy.com 256
  257. 257. • Coax the porcelain toward the interproximal and incisal areas. Add more porcelain to the facial surface and use a light tapping motion to move the porcelain along the porcelain-metal junction. www.indiandentalacademy.com 257
  258. 258. • Move the porcelain down to the incisal edge and lightly blot the buildup to condense the porcelain on the substructure. place the additional dentin porcelain in the incisal region and move it from one interproximal area to the other. www.indiandentalacademy.com 258
  259. 259. • Control the flow of the material and condense the buildup by periodically blotting the wet porcelain with the tissue. use light gingival-toincisal strokes on the facial surface to create the desired facial contour. www.indiandentalacademy.com 259
  260. 260. • Add additional porcelain to the incisal aspect of the incisal edge. www.indiandentalacademy.com 260
  261. 261. • Add additional porcelain to complete the mesial and distal corners. www.indiandentalacademy.com 261
  262. 262. Cutting back the dentin buildup • With the buildup complete, dentin porcelain as to be removed from those areas of the crown where you would like to have enamel porcelain. The procedure of removing dentin porcelain for enamel placement is referred to as the "dentin cutback." www.indiandentalacademy.com 262
  263. 263. If dentin porcelain is overbuilt(A), the amount of dentin remaining after the cutback may also be incorrect. www.indiandentalacademy.com 263
  264. 264. When the restoration has the correct anatomical contours and is slightly overbuilt(A) by 10% to 15%, the dentin cutback will also be correct. www.indiandentalacademy.com 264
  265. 265. Dentin cut back technique • With a razor knife cut back the incisal edge from between 1 to 1.5 mm. www.indiandentalacademy.com 265
  266. 266. • Remove dentin porcelain at the mesial interproximal line angle. Extend the cut to the junction of the middle and gingival one thirds for younger patients. www.indiandentalacademy.com 266
  267. 267. • Cut across the middle one third. Stop the cut back at the distal interproximal area. www.indiandentalacademy.com 267
  268. 268. • At the distal interproximal line angle, make a cut from the incisal edge toward the gingival one third as far as required for the esthetics .Then cut back the middle one third of the facial surface as necessary. www.indiandentalacademy.com 268
  269. 269. • Examine the restoration from an incisal view for symmetry and adequacy of the cutback. www.indiandentalacademy.com 269
  270. 270. • Smooth the cutback areas with the porcelain brush so the transitions from dentin to enamel porcelain are gradual. www.indiandentalacademy.com 270
  271. 271. • For younger patients ,develop mamelons.With a pointed brush ,create two depressions on the facial surface with vertical strokes from incisal to gingival. www.indiandentalacademy.com 271
  272. 272. Mixing the enamel porcelain. www.indiandentalacademy.com 272
  273. 273. • Glass rod is used to mix the powder and liquid .The enamel mix is slightly wetter than the dentin mix to facilitate its addition to a previously applied and condensed dentin layer. www.indiandentalacademy.com 273
  274. 274. • The mixed enamel porcelain should have a consistency that permits it to be readily picked up by a properly pointed porcelain brush. www.indiandentalacademy.com 274
  275. 275. • With a pointed brush, apply enamel porcelain to one corner of the cutback. www.indiandentalacademy.com 275
  276. 276. • Add more enamel porcelain and move it across the facial surface in the incisal one third. Push the wet mix toward the middle one third of the crown and work it into the opposite interproximal line angle. www.indiandentalacademy.com 276
  277. 277. • Blend the enamel porcelain at the junction of the middle and gingival one thirds and begin to establish the incisal edge and condense the porcelain by blotting periodically. www.indiandentalacademy.com 277
  278. 278. • With additional enamel porcelain, complete the incisal edge length and the mesialincisal line angle. Work your way along the incisal edge to create more of a distalincisal line angle. www.indiandentalacademy.com 278
  279. 279. • Blend the enamel porcelain into the gingival one third on the facial surface. Re-create the interproximal contours and line angles. www.indiandentalacademy.com 279
  280. 280. • Shape the mesialincisal corner as required for each case. Examine the builtup from an incisal view and evaluate the overall shape. Make certain the restoration is slightly over built. www.indiandentalacademy.com 280
  281. 281. • Condense the built up. www.indiandentalacademy.com 281
  282. 282. • Use your thin razor knife to cut and shape the mesial and distal interproximal areas. This procedure also removes any unwanted porcelain below the interproximal contact areas. www.indiandentalacademy.com 282
  283. 283. • Carefully remove the crown from the master cast. Add enamel porcelain to the small dimples in each interproximal contact area. www.indiandentalacademy.com 283
  284. 284. • Remove excess porcelain from the porcelain-metal junction and clean the facial metal collar of any porcelain with a small brush or your pointed porcelain buildup brush. www.indiandentalacademy.com 284
  285. 285. Firing procedure. • The large bulk need more time to dry and pre-heat. • Adhere to manufacturers recommended drying time. • A properly fired porcelain body bake should have a pebbly or “orange peel appearance”. www.indiandentalacademy.com 285
  286. 286. Adjusting and finishing the metal ceramic restoration. • Applying and firing the porcelain veneer to a metal substructure only approximates the shape, contour, occlusion, and surface finish restoration. • The porcelain application process requires slight overbuild of the ceramic, this results in a bulky restoration. www.indiandentalacademy.com 286
  287. 287. • Consequently, the fired porcelain requires additional adjustments to reduce any overcontouring and recreate a lifelike ceramic surface finish before the characterizing (staining) and glazing stages. • Adjusting , contouring, and finishing procedures for metal ceramic restorations play a critical role in achieving both proper function and optimal esthetics. www.indiandentalacademy.com 287
  288. 288. Armamentarium. • 1. Equipment – Handpiece with speeds of 50,000 rpm or below. • 2. Instruments – Iwanson metal caliper. • 3. Materials – Diamond abrasives, Prepolish wheels, diamond disks. www.indiandentalacademy.com 288
  289. 289. • The iwanson metal calipers can be used for thickness measurements of metal or metal and porcelain. www.indiandentalacademy.com 289
  290. 290. • Diamond abrasive instruments. www.indiandentalacademy.com 290
  291. 291. • Porcelain prepolish wheel .Designed for smoothening and polishing ceramic surfaces. www.indiandentalacademy.com 291
  292. 292. • Diamond disks • For adjusting and contouring interproximal areas. www.indiandentalacademy.com 292
  293. 293. Procedures in adjusting and finishing the metal ceramic restoration. • 1. To ensure the casting completely seats on the die. www.indiandentalacademy.com 293
  294. 294. 2.Adjusting the interproximal contacts. • a) Mark the mesial interproximal contact using thin double – sided marking film. www.indiandentalacademy.com 294
  295. 295. • b) Marking identifies the location and intensity of contact. www.indiandentalacademy.com 295
  296. 296. • Adjustments in the contact area with pre-polish wheel. www.indiandentalacademy.com 296
  297. 297. • The thickness of the restoration is periodically checked to ensure that it is not over contoured. www.indiandentalacademy.com 297
  298. 298. • The desired characterization is marked and with an abrasive the appropriate shape is created with desired effect. www.indiandentalacademy.com 298
  299. 299. Staining and glazing. • After a restoration has been adjusted and finished, it is necessary to make color corrections or additions and create a lifelike surface luster. www.indiandentalacademy.com 299
  300. 300. • Surface stains should be applied with a small sable brush. www.indiandentalacademy.com 300
  301. 301. • Stain is placed in area where the characterization is intended. Blend or dilute the effect of the stain www.indiandentalacademy.com 301
  302. 302. • The glaze is picked up with a staining brush and applied to the ceramic surface where desired. www.indiandentalacademy.com 302
  303. 303. • Dry the restoration in the porcelain furnace. www.indiandentalacademy.com 303
  304. 304. • The restoration is fired according to the porcelain manufacturers direction. www.indiandentalacademy.com 304
  305. 305. • Typically glazed restoration. www.indiandentalacademy.com 305
  306. 306. Mechanical polishing. • Mechanical polishing of the restoration after glazing gives the restoration a natural life like appearance. www.indiandentalacademy.com 306
  307. 307. A diamond polishing paste. www.indiandentalacademy.com Pumice flour 307
  308. 308. • After mechanical polishing. A life like luster is created in the ceramic yet the surface characterizatio n remains. www.indiandentalacademy.com 308
  309. 309. www.indiandentalacademy.com Leader in continuing dental education www.indiandentalacademy.com 309

×