SOLDERING
DEFINITION

Soldering involves joining two
components of metal with an
intermediate metal whose melting
temperature is lower than the parent
metal.
REQUIREMENTS OF A
SOLDER





Fuse safely below the sag or creep
temperature of the parent alloy.
Resist tarnish and corrosion.
Non pitting.
Free flowing.
Match the color of the parent metal.
COMPOSITION OF SOLDERS






Gold
Silver
Copper
Tin
Zinc
Gold solders are designated by
fineness.
SOLDERING FLUX
 Flux
means flow.
 Improve the flow of a metal
 Chemicals that limit the flow of metals
are called antifluxes
FUNCTIONS OF A FLUX
PROTECTOR
It covers the metal surface and prevents oxide
formation.
 REDUCER
It helps to reduce the oxides present on the
metal surface.
 SOLVENTS
It dissolves any oxide presence and removes it.

COMPOSITION OF A FLUX
 Borax
glass
 Boric acid
 Silica
ANTIFLUX
 Used
to control the flow of the metal.
 Most common anti-fluxes used is
graphite.
 Better fluxes like Rouge in chloroform
can be used.
SOLDERING
INVESTMENT
This are silica –bonded investments
that fused quartz.
 Fused quartz is used because it is the
lowest thermally expanding form of
silica.

SOLDERING FOR METAL
CERAMIC RESTORATION
It is usually done prior to ceramic
application hence it is also known as
pre ceramic soldering.
 Post ceramic materials are also
available.


Pre ceramic soldering is done at a
temperature of 1075 to 1120 degree
celsius whereas post ceramic soldering
should be done at a temperature of
920 degree celsius because ceramic
may begin to sag at higher
temperatures.
Post ceramic soldering should be done
after ceramic firing.
 Ceramic portions should be finished
only afetr soldering.

ADVANTAGES OF PRE
CERAMIC SOLDERING
The metal framework can be soldered
and tried in prior to ceramic build up.
 Minor casting errors can also be
patched up during ceramic build up.

DISADVANTAGES OF PRE
CERAMIC SOLDERING
 Difficult
to build ceramic on
already soldered units.
ADVANTAGES OF POST
CERAMIC SOLDERING
 Porcelain
can be properly build up
due to better access.
DISADVANTAGES OF POST
CERAMIC SOLDERING



The metal and porcelain may sag at high
soldering temperatures.
It is more technique sensitive.
The solder should be re-glazed and re-fired.
OVEN SOLDERING
 Performed under vacuum or air.
 A piece of solder is placed in the joint
space and it is heated to a standard
temperature in the furnace.
 Superior joint strength.
DISADVANTAGES
 The parent metal will sag or melt
if heated for o long time.
TORCH SOLDERING
Soldering is done under direct flame.
 A gas air torch is used for this purpose.
 The torch flame has two parts – the
reducing part (is at a higher
temperature) and the soft brush part.




The solder should be melted using the soft
brush flame.
The flame should be constantly swiped
over the solder for a period of 4 -5
minutes.
At no point of time the flame should be
held in a stationary position.
INFRARED SOLDERING
Used for low fusing connectors.
 Good accuracy.
 Similar strength as conventional
soldering.
 Protective eyewear is necessary.

LASER WELDING




Done to join Ti components of dental
crowns, bridges and partial denture frame
works.
Pulsed high power Neodymium lasers are
used.
Low thermal influence preferred in
dentistry.
Superior joint strength.
SOLDERING TECHNIQUE
The design of the connector is
determined while fabricating the wax
pattern.
All the solder connectors require about
0.25mm parallel spaced between the
parent components.
The smaller units are inserted
separately in the mouth.
A thick mix of quick setting plaster is
molded over the inserted units.
Once the plaster sets, it is removed
along with the inserted units.
Plaster index is inverted.
Components of the prosthesis will be
visible.
A triangular piece of utility wax should
be placed to index restoration inorder
to shape the soldering assembly.
The units are invested and the
investment is allowed to bench set.
Invested wax is eliminated using
boiling water or chloroform.
Area of the restoration surrounding the
joint should be coated with anti-flux.
After coating the flux and the anti-flux,
the assembly is preheated in a burnout
furnace.
Connectors are soldered using a torch
or a furnace.
DISADVANTAGES
Not economical.
CERAMIC/ACRYLIC
VENEERING
• The ceramic or acrylic veneers in metal
resin or metal ceramic restorations are
usually added after soldering.
• Ceramic veneering is done in 3 steps
1. METAL PREPARATION.
2. PORCELAIN APPLICATION.
3. PORCELAIN FIRING.
METAL PREPARATION
• Any minor casting defects in the cut back
area should be corrected.
• Recovery includes sand-blasting and
ultrasonic cleaning.
• The gingival surface of the pontic should be
reduced.
• Gingival surface of the pontic should always
be covered with porcelain.
PORCELAIN APPLICATION



After preparing the metal, an opaque
layer of porcelain should be applied over
the metal surface.
Gingival surface of porcelain is coated
with cervical porcelain.
Layer of cervical, body and incisal
porcelains should be used to build up the
facial surface.


Porcelain in the interdental area should
be sectioned to demarcate junction of
the two units.
A separating liquid is applied over the
edentulous ridge prior to building up the
gingival surface of the pontic.
PORCELAIN FIRING
•Next the porcelain is fired as per the
manufacture’s instruction.
•After firing the core porcelain, glaze
porcelain is added and fired as usual.
ACRYLIC VENEERS
•Similar to ceramic veneering except for
a few differences.
•Major difference is that only
mechanical bonding exists between
the metal and resin.
•Bond strength is considerably less.
PROCEDURE
• Mechanical undercuts can be created by
sprinkling plastic retentive pearls over the
wax pattern before casting.
• The surface of the cast metal can be
roughened using Al2O3 air abrasive unit.
• A small quantity opaque resin is added onto
the metal surface. Body shade resin is
added over the opaque resin and contoured
using a modelling instrument.
•The resin should be polymerised under
pressure in a warm water bath. Light
cure resins are also available.
•Resin core should be carved to remove
excess material. Space should be
provided to accommodate incisal
shade resin.
•Finally incisal shade resin is added and
contoured.
•After polymerization, the restoration is
finished and polished
THANKING YOU