00. Soldering

7/28/2019 00. Soldering

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SOLDERING

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DEFINITION

Soldering involves joining two

components of metal with an

intermediate metal whose meltingtemperature is lower than the parent

metal.

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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.

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COMPOSITION OF SOLDERS

Gold

Silver

Copper

Tin

Zinc

Gold solders are designated by

fineness.

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SOLDERING FLUX

Flux means flow.

Improve the flow of a metal

Chemicals that limit the flow of metalsare called antifluxes

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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.

SOLVENTSIt dissolves any oxide presence and removes it.

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COMPOSITION OF A FLUX

Borax glass

Boric acid

Silica

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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.

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SOLDERING

INVESTMENT

This are silica –bonded investments

that fused quartz.

Fused quartz is used because it is thelowest thermally expanding form of

silica.

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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.

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Pre ceramic soldering is done at a

temperature of 1075 to 1120 degree

celsius whereas post ceramic solderingshould be done at a temperature of

920 degree celsius because ceramic

may begin to sag at highertemperatures.

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Post ceramic soldering should be done

after ceramic firing.

Ceramic portions should be finishedonly afetr soldering.

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ADVANTAGES OF PRE

CERAMIC SOLDERING

The metal framework can be soldered

and tried in prior to ceramic build up.

Minor casting errors can also bepatched up during ceramic build up.

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DISADVANTAGES OF PRE

CERAMIC SOLDERING

Difficult to build ceramic on

already soldered units.

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ADVANTAGES OF POST

CERAMIC SOLDERING

Porcelain can be properly build up

due to better access.

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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.

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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.

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DISADVANTAGES

The parent metal will sag or melt

if heated for o long time.

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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.

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The solder should be melted using the softbrush flame.

The flame should be constantly swipedover the solder for a period of 4 -5minutes.

At no point of time the flame should beheld in a stationary position.

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INFRARED SOLDERING

Used for low fusing connectors.

Good accuracy.

Similar strength as conventional

soldering.

Protective eyewear is necessary.

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LASER WELDING

Done to join Ti components of dentalcrowns, bridges and partial denture frame

works. Pulsed high power Neodymium lasers are

used.

Low thermal influence preferred in

dentistry.

Superior joint strength.

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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.

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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.

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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.

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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.

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DISADVANTAGES

Not economical.

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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.

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METAL PREPARATION

•Any minor casting defects in the cut back

area should be corrected.

•Recovery includes sand-blasting andultrasonic cleaning.

•The gingival surface of the pontic should be

reduced.

•Gingival surface of the pontic should always

be covered with porcelain.

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PORCELAIN APPLICATION

After preparing the metal, an opaquelayer 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 thefacial surface.

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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.

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PORCELAIN FIRING

•Next the porcelain is fired as per the

manufacture’s instruction.

•After firing the core porcelain, glazeporcelain is added and fired as usual.

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ACRYLIC VENEERS

•Similar to ceramic veneering except for

a few differences.

•Major difference is that onlymechanical bonding exists between

the metal and resin.

•Bond strength is considerably less.

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PROCEDURE

• Mechanical undercuts can be created bysprinkling plastic retentive pearls over the

wax pattern before casting.

• The surface of the cast metal can beroughened using Al2O3 air abrasive unit.

• A small quantity opaque resin is added onto

the metal surface. Body shade resin isadded over the opaque resin and contouredusing a modelling instrument.

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•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 incisalshade resin.

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•Finally incisal shade resin is added and

contoured.

•After polymerization, the restoration isfinished and polished

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THANKING YOU

00. Soldering

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