Dental Casting and Soldering Alloys.pptx

Presented By:
Akanksha
MDS 1st year
Department of Prosthodontics and Crown & Bridge
Dental Casting Alloys

•Twentieth century generated substantially new changes
to dental prosthetic materials
Economy Performance Aesthetics
Anusavice KJ. Phillip’s Science Of Dental Materials. Eleventh Edition, Elsevier Pub. Chapter 19. Dental Casting and Soldering Alloys. 563-620.

• Alloys continue to be used as the principal material for
prosthetic restorations and will likely be the principal
material for years to come.
• No other material has the combination of strength,
modulus, wear resistance, and biologic compatibility
that a material must have to survive long term in the
mouth
John R. Agar, Thomas D. Taylor, Fixed prosthodontics , Dental Clinics of North America , Volume 48, Issue 2,2004

DESIRABLE REQUIREMENTS OF
DENTAL CASTING ALLOYS

BIOLOGICAL REQUIREMENTS
Biocompatible
Resistance to tarnish
and corrosion
Anusavice KJ. Phillip’s Science Of Dental Materials. 12 Edition, Elsevier Pub. Chapter 16. Dental Casting and Joining Alloys. 367-95.

Biocompatibility
• Must tolerate oral fluids
• Not release any harmful products in oral environment
Components of
alloys released
Toxic or
allergic
reactions

Tarnish and Corrosion Resistance
Corrosion resistance can be derived from :
• Material components being too noble to react in the
oral environment
Examples:
• gold and palladium

• Ability of one or more of the metallic elements to form
an adherent passivating surface film, which inhibits any
subsurface reaction
Examples :
• Chromium in Ni-Cr and Co-Cr alloys
• Titanium in commercially pure titanium [CP Ti] and in Ti-
6Al-4V alloy.

FUNCTIONAL REQUIREMENTS
High strength and hardness
High modulus of elasticity
High toughness
High ductility
High sag resistance
For all metallic
prostheses

FUNCTIONAL REQUIREMENTS
Porcelain bonding
Melting temp. of metal >
firing temp. of porcelain
 Of metal >  of porcelain
High modulus of elasticity
For metal-ceramic
prostheses

WORKING REQUIREMENTS
Ease of casting
Ease of soldering
Ease of burnishability

Castability
Molten metal should
• Completely wet the investment mold material
• Flow freely into the most intricate regions of investment
mold.

FUNCTIONAL MECHANICAL
PROPERTIES OF CASTING ALLOYS

Elastic modulus
• Proportional constant between stress and strain during
elastic deformation
• Rigidity and stiffness
• For dental prosthesis, it is equivalent to flexure
resistance

Loading of pontic
Lift the mesial and
distal aspect of
prosthesis
Prosthesis flexes
Mesiodistal bending moment
exerted on the abutment teeth
Dislodging
force

The overlying brittle porcelain will fail catastrophically
when the metal substructure flexes beyond the flexural
strength limit of the ceramic

• Enough rigidity to prevent flexure
during placement and function of
the prosthesis.
• Resistance to flexure also allows
clasps to fit into areas of minimal
undercuts and still provide
adequate retention.

Fatigue Resistance
• Occurs when a material is subjected to repeated
loading and unloading below its elastic limit.
• Determined experimentally by subjecting a material to
a cyclic stress between two values and determining
the number of cycles required to produce failure.

When a removable partial
denture is inserted and
removed daily
clasps are strained
elastically
(as they slide over the undercuts of
abutment teeth)

CLASSIFICATION OF DENTAL
CASTING ALLOYS

Dental
casting alloys
General
classification
Mechanical
properties
Specific use

Alloy Classification by Noble Metal Content
American Dental Association (1984)

Alloys for
specific
use
For all metal
prostheses
For metal-ceramic
prostheses
For frameworks
of RPD

Why alloys for all metal restorations cannot be used for
metallic ceramic restoration ??
The alloys may not
form thin, stable
oxide layers to
promote atomic
bonding to porcelain
Their melting range
may be too low to
resist sag
deformation or
melting at porcelain-
firing temperatures
Their thermal
contraction
coefficients may not
be close enough to
those of commercial
porcelains

ALLOYS FOR ALL-METAL
PROSTHESES
High noble metal, noble metal, predominantly base metal

High Noble and Noble Alloys
• For prosthetic dental applications,
it is necessary to incorporate various elements in gold
to produce alloys with suitable properties

Alloy element Function
PLATINUM
• Increases the hardness and elasticity of
gold
• Raises the melting temperature of the alloy
COPPER
• Renders heat treatable
• gives reddish colour to alloy
PALLADIUM
• Improves tarnish and corrosion
• Increases the biocompatibility
SILVER
• Neutralises reddish colour of copper
• gives white colour to Pd based alloys

Alloy element Function
ZINC • Acts as oxygen scavenger during
melting and casting
INDIUM • Promotes gold like colour in Pd-Ag
based alloys
IRIDIUM OR RUTHENIUM • Grain refiners
• Improves yield strength

GOLD-BASED ALLOYS
Alloy Clinical Use
Type 1 Designed for inlays supported by teeth not
subjected to significant masticatory forces
Type 2 Widely used for inlays
Type 3 For constructing crowns and onlays for high
stress
Type 4 High stress areas such as bridges and partial
denture frameworks

CLASSIFICATION OF GOLD ALLOYS FOR ALL
METAL PROSTHESES
• Type 1: Low strength—For castings subjected to very slight
stress (e.g., inlays), the minimum yield strength (0.2% offset) is
80 MPa, and the minimum percent elongation is 18%
• Type 2: Medium strength—For castings subjected to
moderate stress (e.g., inlays, onlays, and full crowns), the
minimum yield strength (0.2% offset) is 180 MPa, and the
minimum percent elongation is 10%.

• Type 3: High strength—For castings subjected to high
stress (e.g., onlays, thin copings, pontics, crowns, and
saddles), the minimum yield strength (0.2% offset) is 270
MPa, and the minimum percent elongation is 5%.
• Type 4: Extra-high strength—For castings subjected to
very high stress (e.g., saddles, bars, clasps, thimbles, certain
single units, and partial denture frameworks), the minimum
yield strength (0.2% offset) is 360 MPa, and the minimum
percent elongation is 3%.

Mechanical Property Requirements Proposed in ISO Draft
International Standard 1562 for Casting Gold Alloys (2002)
Type Descriptor Yield strength
(Mpa)
Elongation
(%)
1 Low 80 18
2 Medium 180 10
3 Hard 270 5
4 Extra hard 360 3

HEAT TREATMENT
• gold alloys can be significantly hardened if the alloy contains a
sufficient amount of copper
• The actual mechanism of hardening is probably the result of several
different solid state transformations
• the criteria for successful hardening are time and temperature
• Type III and Type IV gold alloys that can be hardened (strengthened
from the quenched as-cast condition) can, of course, also be softened

Heat
treatment of
gold alloys
Softening
heat
treatment
Hardening
heat
treatment
Solution heat
treatment
Age
hardening

casting Quenched
in water
Electric furnace
700˚ C (1292˚ F)
10 min
All intermediate phases
are changed to a
disordered solid solution
Prevents ordering
from occurring
during cooling

Effect
Ductility Tensile
strength
Proportional
limit
hardness

Indications
Adjusting Burnishing Polishing
• for structures that are to be ground, shaped, or
otherwise cold worked, either in or out of the
mouth

casting Quenched
in water
Electric furnace
200 °C and 450 °C
15 to 30 minutes
AGE HARDENING

Effect
Tensile
strength
Proportional
limit
Hardness
Ductility

Indications
•As oral restoration delivered to the patient
Metallic
partial
denture
saddles FPD’s

• Ideally, before the alloy is age-hardened, it should be subjected to a
softening heat treatment to relieve all residual strain hardening
before the alloy is hardened again by heat treatment to produce a
disordered solid solution
• If not done, there will not be proper control of the hardening process
because the increase in strength, proportional limit, and hardness
and the reduction in ductility are controlled by the amount of
possible solid-state transformations

• Under normal clinical conditions, cast gold restorations are
cemented on prepared teeth using the alloy in the softened
condition
• It has been found that significant aging of a commercial Type
IV gold alloy takes place slowly over a 2-week period at
intraoral temperature
• The accompanying dimensional changes in the gold alloy
castings do not have clinical significance

SILVER-PALLADIUM ALLOYS
• White
• Predominantly silver in composition
• Palladium
• Provides nobility
• Increases tarnish resistance

Disadvantage
• greater potential for tarnish and corrosion
• Poor castability – because of lower density of alloy and
propensity of dissolving oxygen in molten state

Base Metal Alloys
• They are substitutional solid solution alloys which do
not contains any noble metal
• Substitutes for gold alloys Type III and Type IV
• Rely on Chromium for corrosion resistance

Base metal
alloys
Ni-Cr
alloys
With
Be
Without
Be
Co-Cr
alloys
• improves castability
• promotes the formation of a
stable metal oxide for porcelain
bonding
Beryllium

Role of each element
Element Function
Cobalt Increases strength, hardness, modulus of
elasticity
Nickel Increases strength, hardness, modulus of
elasticity and ductility
Chromium Increases tarnish and corrosion resistance
Molybdenum Increases corrosion resistance & strength
Decreases coefficient of thermal expansion

Element Function
Beryllium Grain refiner and reduces fusion temperature
Manganese and
silicone
Improves castability
Carbon Increases hardness and strength
Decreases ductility
Aluminium Forms nickel aluminium compounds which
increases both tensile and yield strength
Nitrogen Improves the overall castability

Titanium and Titanium Alloys
applications
All metal
prostheses
Metal-ceramic
prostheses
Implants and
removable partial
dentures

• High melting point (1668 °C)
• High rate of oxidation above 900 °C
• Derives its corrosion protection from a thin
passivating oxide film (approximately 10 nm thick),
which forms spontaneously with surrounding oxygen.

• Requires a special casting machine with arc-melting
capability and an argon atmosphere along with a
casting investment consisting of oxides, such as MgO,
ZrO2, or Y2O3
• Special surface modifications of cast titanium, using
caustic NaOH based solutions or silicon nitride
coatings, have been employed to improve the bond
between cast CP Ti and dental porcelain

Commercially Pure Titanium
According to the American Society for Testing and Materials
(ASTM F-67)
four unalloyed grades of CP Ti based on the concentration
of impurities

Allotropic
transformation
882.3° C
 Phase
HCP structure
 Phase
BCC structure
More stronger
More ductile

Incorporating 
and/or 
microstructural
stabilizers

Near- 
-


Alloying elements
Alpha-phase
stabilizers
aluminium
Carbon
Nitrogen
Gallium
Beta-phase
stabilizers
vanadium
Molybdenum
Cobalt
nickel
The most widely used
titanium alloy in dentistry is
Ti-6Al-4V, which is an α–β
alloy

ALLOYS FOR METAL-CERAMIC
PROSTHESES

Low tensile
strength
Low shear
strength
Chief objection to the use of dental porcelain as a
restorative material is:
To minimize this disadvantage:
bond the porcelain with a cast alloy substructure made to fit the
prepared teeth provided that a strong bond is attained between the
porcelain veneer and the metal.

Original metal-ceramic alloys
• contained 88% gold
• too soft for stress-bearing restorations such as fixed
partial dentures
• No chemical bond between these alloys and dental
porcelain
Mechanical retention and undercuts were used

•Bond strength of the porcelain to this type of alloy was less
than the cohesive strength of the porcelain itself.
•Failure occurred at the metal-porcelain interface
Addition of 1% iron, indium and tin
•oxide forming elements
•The bond strength increased by factor of 3
•Iron also increases the proportional limit and strength of
the alloy by forming an FePt3 precipitate with platinum

Common features of principal chemical elements
potential to bond
to dental
porcelain
Possess
coefficients of
thermal
contraction
compatible with
those of dental
porcelains
Their solidus
temperature is
sufficiently high
to resist
softening during
sintering of
porcelain

Porcelain Bonding to Metals
• addition of a small quantity of base metal to noble and high
noble alloys promotes oxide formation on the surface
• For base metal alloys, some oxides may be poorly adherent
oxide to the metal substructure, which can result in
porcelain delaminating from the metal substrate

Coefficient of Thermal Contraction
The coefficients of thermal expansion (CTE) tend to have a reciprocal
relationship with the melting points of alloys (because of an inverse
dependence on the relative strength of interatomic bonding), as well as
the melting range of alloys; that is, the higher the melting
temperature of a metal, the lower its CTE

Coefficient of Thermal Contraction
The thermal contraction differential between metal alloys and
dental porcelains may, under certain conditions, contribute to
high levels of stress in porcelain, which can induce cracking of
porcelain or delayed fracture

Solidus temperature
alloy is heated
close to its solidus
temperature
become
susceptible to
flow under its
own mass
(creep)
• size of the prosthesis
• number of firings that are required for porcelain veneering

All metal-ceramic alloys should have a solidus temperature
that is significantly higher than the sintering temperature of
the porcelain so as to minimize creep deformation

Sag deformation in a
fixed dental prosthesis
(FDP)
framework

If sag deformation has occurred
The FPD can be sectioned and soldered to
obtain an acceptable fit on theprepared dies
Cast-joining of the bridge sections can be
performed
A remake of the cast structure with a sag-
resistant alloy

How can certain differences in thermal contraction
between a metal and its veneering ceramic either
increase or decrease the resistance to cracking or
fracture of the veneer?
Why must a metal for metal-ceramic prostheses have its
thermal contraction coefficient slightly higher than that
of its veneering ceramic?

THERMAL COMPATIBILITY OF METAL-CERAMIC SYSTEMS
• When a metal-ceramic prosthesis is cooled from the sintering
temperature, the metal and its veneering ceramic contract at
different rates because of differences in their thermal contraction
coefficients
• Chemical bond between the metal and the porcelain prevents the
two components from separating

the component that contracts more will be stretched by the
adjacent component; at the same time, the material that
contracts less will be compressed by the other
Such changes in dimensions can be controlled by certain stresses
Transient stress
Residual stress

• The instantaneous stress at a given temperature during the cooling
cycle is termed transient stress
• The stress distribution, which exists at room temperature, is called
the residual stress
• When the prosthesis is cooled, the tensile stress that develops in the
porcelain is of concern.
• If the transient tensile stresses that develop during cooling are
insufficient to cause immediate cracking of the porcelain or delayed
cracking after cooling to room temperature, the combination of a
metal-porcelain system is considered thermally compatible

Effect of Metal-Ceramic Contraction Mismatch
• A slight thermal contraction mismatch (produced with a higher
contraction of the metal) is recommended to develop residual
compressive hoop and axial stresses in porcelain, which are
protective in nature
• Significant higher mismatches may lead to porcelain cracking or bond
failure because of development of tensile stress, which exceeds the
tensile strength of porcelain

When the porcelain is under compression in hoop and axial
(tangential) directions, the porcelain in the radial direction
(oriented toward the center of the crown and perpendicular
to the facial surface) is pulled outward by tensile stress in the
radial direction
Residual stress in the porcelain veneer of a metalceramic crown for a case in which
the coefficient of thermal contraction for the porcelain is less than that for the metal.

Thermally compatible metal ceramic system αM > αP

Thermally incompatible metal-ceramic system αP > αM

When the contraction coefficient of the porcelain is much lower
than that of the metal (αP << αM)
• porcelain cracking or metal-ceramic bond failure can occur near the
metal– porcelain interface
• This incompatibility failure is likely caused by the development of
radial tensile stresses that exceed the tensile strength of porcelain

OTHER CAUSES OF PREMATURE FAILURES IN
METAL-CERAMIC PROSTHESES
• Delayed cracks in porcelain caused by the interaction of moisture
and the relatively high residual tensile stresses within porcelain at the
conclusion of the glazing cycle
• Delayed failure of this type is attributed to stress corrosion

DISCOLORATION OF PORCELAIN BY SILVER
• Colloidal dispersion of silver atoms entering body and
incisal porcelain or the glazed surface from vapor
transport or surface diffusion
• cause color changes
green, yellow-green, yellow-orange,
orange, and brown hues
Greening
(discoloration
phenomenon)

• Porcelains with higher sodium contents
exhibit a more intense discoloration because of more
rapid silver diffusion in sodium-containing glass
• Intensity of discoloration increases near cervical
region

Extent of discoloration can be increased by
Higher silver content alloys
Lighter shades of porcelain
Multiple firing procedure
Higher temperatures
Body porcelain in direct contact
with alloy
Vacuum firing procedure

High Noble and Noble Alloys for
Metal-Ceramic Prostheses

GOLD-PLATINUM-PALLADIUM ALLOYS
• first successful metal-ceramic restorations
• Platinum increased their melting temperature
• Rhenium (Re) is added to some alloys as a grain refiner to
increase hardness
• Iron, is added to form a bonding oxide

GOLD-PLATINUM-PALLADIUM ALLOYS
adequate elastic
modulus,
strength,
hardness and
elongation
Low sag
resistance
Use limited to
crowns and
three-unit FDPs

GOLD-PALLADIUM-SILVER ALLOYS
• economical alternatives to the Au-Pt-Pd or Au-Pd-Pt alloys
Resistance to
tarnish and
corrosion
Improved sag
resistance
Discolouration
due to silver
vapour release

GOLD-PALLADIUM ALLOYS
• Olympia(Heraeus Kulzer), was introduced in 1977 by
J.F. Jelenko & Co
• White in colour
• overcome the porcelain discoloration effect ( silver
free alloy)

• Aesthetic capability
• provide an alloy with a lower thermal contraction
coefficient than that of either the Au-Pd-Ag or Pd-Ag
alloys
• castability, corrosion resistance, and adherence to
porcelain are excellent

PALLADIUM-GOLD ALLOYS
• free of silver
• do not contribute to porcelain discoloration
• physical properties are generally similar to those of
the Au-Pd alloys

PALLADIUM-GOLD-SILVER ALLOYS
• Similar to the Au-Pd-Ag types of alloys in their potential for
porcelain discoloration
• Gold contents ranging from 5% to 32%
• Silver contents varying between 6.5% and 14%
• Range of thermal contraction coefficients that increase
with an increase in silver content

PALLADIUM-SILVER ALLOYS
• first gold-free noble alloy
Palladium
Silver
• Raises melting temperature
• Lowers thermal expansion coefficient of
the alloy
• Lowers melting temperature
• Raises thermal expansion coefficient of
the alloy

Internal oxide formation and creep-induced nodule formation
in a Pd-Ag alloy for metal-ceramic restorations

•Silver discoloration is most severe
•Low specific gravity
•Low intrinsic cost
•Easier to burnish, grind and polish
Gold metal conditioners or Ceramic coating agents

PALLADIUM-COPPER-GALLIUM ALLOYS
• very popular in the 1990s
• Dark brown or black oxide formed during oxidation
and subsequent porcelain firing cycles
Masking with thick opaque porcelain layer

PALLADIUM-GALLIUM-SILVER ALLOYS
•Most recent
•Slightly lighter coloured oxides than Pd-Cu alloys
•Low thermal coefficient and are more compatible with
lower expansion porcelain

Base Metal Alloys for Metal-
Ceramic Prostheses

• Higher hardness and elastic modulus (stiffness)
this enables the coping to be 0.1 to 0.2 mm thick without risking significant
deformation under mastication stress or sagging of the metal framework at the
porcelain firing temperature
make the alloys more difficult to cast and presolder than Au-Pd or
Pd-Ag alloys

Difficulties of base metal alloys after casting
Removal of investment materials as well as oxides from casting
Grinding and polishing of fixed restoration require more time
Removal of defective restoration require more time
Potential hazard of dust generation

• solidification shrinkages are greater than those of gold base alloys,
which represents a challenge for technicians to obtain acceptable-
fitting base metal castings
Using type V die stone for dies and enhancing the expansion
of the investment mold during setting of the investment are
the most common practices to improve the fit of prostheses

Comparative Properties of High Noble Alloys and Base Metals
for Metal-Ceramic Prostheses

ALLOYS FOR REMOVABLE
PARTIAL DENTURE

• Co-Cr
• Ni-Cr
• Co-Cr-Ni
• Co-Cr-Mo
• Fe-Cr
• Type IV gold
• CP Ti
• Ti-6V-4Al

Base Metal Alloys for Removable Partial Denture
• Cobalt-chromium-molybdenum alloy has been the primary
metal for partial denture prostheses
• Cobalt increases the elastic modulus and strength
• Molybdenum and manganese improve the alloy’s corrosion
resistance

• Inclusion of greater than 30% of chromium by weight makes the alloy
difficult to cast and forms the brittle σ phase
• Carbide formation is essential for high yield strength and hardness in
the alloy, but it lowers ductility
• Co-Cr clasps are reported to be too retentive initially and that they
slowly lose this retention because of plastic deformation of the clasp
from repeated seating and removal of the appliance.

Titanium- Based Alloys for Removable Partial
Dentures
• Commercially pure titanium and titanium alloys
excellent
biocompatibility
outstanding
corrosion
resistance
mechanical
properties

• Because of the connector’s low elastic modulus, its rigidity is often
improved by increasing its thickness or changing its design
• Increasing the rigidity is beneficial in reducing debonding between
resin and the metal framework
• On the other hand, the lower yield strength and tensile strength and
higher percent elongation of CP Ti suggest that cast clasps may be
more easily adjusted.

• casting of titanium remains a challenge, since internal porosity within
the clasp assemblies can lead to clasp fracture
• The reaction layer on the surface must be removed chemically with
hydrofluorosilicic acid or mechanically by grit blasting and rotary
instruments
high electrostatic binding
capacity of the titanium
surface oxides
higher plaque adherence
to titanium frameworks

• A clinical survey of RPDs revealed gradual discoloration of titanium
alloy frameworks, while those made with CP Ti and other base metal
alloys do not discolor
• An in vitro study has also revealed that exposing titanium alloys to
alkaline denture cleansers (pH greater than 11) causes discoloration
• Laser welding of titanium has facilitated repair of titanium
frameworks because of the low thermal conductivity of titanium and
localized heating during laser welding.
It is hypothesized that aluminium segregates from the
titanium alloy during casting and corrodes during service

ALTERNATIVE
TECHNOLOGIES
FOR FABRICATING
PROSTHESES

Sintering of burnished metal foil
CAD-CAM processing of
metal blocks
Copy milling of metal blocks
Electroforming of metal
copings
Three-dimensional printing
with metal powder followed
by sintering.

SINTERING OF BURNISHED FOIL
• most commonly used commercial foil system, Captek is used for
making copings or frameworks for metal-ceramic prostheses

Captek
Captek P and Captek G
Capcon and Capfil
Captek Repair paste
and Capfil

• Captek P and Captek G are used to fabricate crown copings
and fixed dental prosthesis abutments
• Capcon and Capfil, which are used to connect copings
• Captek Repair paste and Capfil, which are used to add
material to Captek structures

Captek copings
• contain, by weight, 88.2% Au, 9.0% platinum-group metals
(including 4% Pt), and 2.8% Ag
• made with a thickness of 0.25 mm for anterior crowns and
0.35 mm for posterior crowns

The inner and outer gold-rich layers are approximately 25 μm
in thickness, and the middle layer is made of a Au-Pt metal.

• The Captek P layer is adapted first to the die and fired at a
temperature of 1075 °C.
• During this firing cycle, the adhesive and binders are
eliminated, and the Pd and Pt particles become
interconnected by sintering to form a three-dimensional
network of capillary channels.
• Captek G, which contains 97% gold by weight plus binders,
which is applied over the Captek P coping.

• The Captek G metal is drawn by capillary action into the
network structure of the Captek P coping.
• Captek G is provided in two thicknesses, one for anterior
copings and one for posterior copings.
• A 0.35-mm-thick layer of porcelain is applied to the coping,
which may or may not require the Capbond bonding agent.

Advantage of Captek Crowns
• Very low thickness
ensures minimal tooth reduction or improved aesthetics
compared with conventional metal ceramic crowns made with
cast metal copings

CAD-CAM PROCESSING
• alternative method to produce metal, ceramic, or composite
restorations without the need for processes that require
two or more patient appointments for a given type of
restoration or prosthesis
• developed in the early 1980s to produce ceramic inlays and
crowns during one chair-side appointment

• electronically or digitally records surface coordinates of the prepared
tooth and stores these retrieved data in the memory of a computer
• The image data can be retrieved immediately to mill or grind a metal,
ceramic, or composite prosthesis by computer control from a solid
block of the chosen material
• Within minutes, the prosthesis can be fabricated and placed in a
prepared tooth and bonded or cemented in the mouth of the patient
in a period ranging from 10 min to 1 hr

COPY MILLING
based on the principle of tracing the surface of a pattern that
is then replicated from a blank of ceramic, composite, or
metal that is ground, cut, or milled by a rotating wheel whose
motion is controlled by a link through the tracing device
cutting a key blank using a tracing of a master key

CELAY
(Mikrona Technologies,Spreitenbach,
Switzerland)
• use since 1991
• The pattern to be traced is
made from a blue-colored
resin-based composite
(Celay-Tech; 3M ESPE)

ELECTROFORMING
• A master cast of the prepared tooth (teeth) is prepared and
coated with a special die spacer to facilitate separation of
the duplicating material
• dies are duplicated with a gypsum product

• After applying a conductive silver layer to its surface, the die
is connected to a plating head and connected to a power
source and then placed in a plating solution
• After a sufficiently thick layer of gold or other metal is
deposited, the gypsum is removed and the coping is
sandblasted
• The coping is then coated with a bonding agent during the
wash bake, and subsequent ceramic layers are condensed
and sintered in a conventional way.

THREE-DIMENSIONAL PRINTING
• form of additive manufacturing technology
• three-dimensional object is created by depositing successive
layers of material
• objects are made using liquid resins curable by ultraviolet or
laser irradiation.

BIOLOGICAL HAZARDS OF
BASE METAL ALLOYS

Leached from an
alloy into the oral
environment by
dissolution
Released to the
environment by
airborne particulates
during grinding and
polishing
Propagated by
vapour during
casting

RISKS FOR DENTAL LABORATORY TECHNICIANS
• Risk of beryllium vapor exposure in the absence of an
adequate exhaust and filtration system
• Physiological responses vary from contact dermatitis
to severe chemical pneumonitis
• Symptoms range from coughing, chest pain, and
general weakness to pulmonary dysfunction

• Airborne levels of beryllium can be controlled with a
local exhaust system
• Good ventilation and exhaust facilities should be
employed whenever any material is ground.

POTENTIAL PATIENT HAZARDS
• Exposure to nickel
Anusavice KJ. Phillip’s Science Of Dental Materials. 12 Edition, Elsevier Pub. Chapter 7. Biocompatibility.111-47.

Anusavice KJ. Phillip’s Science Of Dental Materials. 12 Edition, Elsevier Pub. Chapter 7. Biocompatibility.111-47.

How to minimize exposure of metallic dust in
patients and dentist ??
High speed evacuation system during grinding operation
Patients informed about potential allergic effects of nickel
Thorough medical history of patients
Evidence of previous allergic response
Patch testing for sensitivity of metals

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Dental Casting and Soldering Alloys.pptx

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