Soldering procedures/ orthodontic assistant training

SOLDERING
PROCEDURES
INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com

INTRODUCTION

SOLDERING - DEFINITIONS
GPT- 7
To unite bring into or restore to a firm
union the act of uniting two pieces of metal
by the proper alloy of metals

In general soldering can be defined as
joining of metals by the medium of filler
that has lower fusion temperature than
that of parent metals to be joined.

NEED FOR SOLDERING
Dimensional change of the long span
FPD when fabricated as single piece
casting.
AESTHETICS

Schiffleger et al. (1985) have reported that
the accuracy of fit of one-piece castings
decreases as the number of units
increases.39 Four unit bridges and larger
restorations exhibit unacceptable levels of
marginal opening. Furthermore, when
such bridges were sectioned, the fit of
each individual unit on its die improved,
indicating that the investment expansions
required for individual units are different
from those required to relate one unit to
another

Gegauff and Rosensteil, 1989, reported
on the improved seating of four unit
castings following soldering, as opposed
to one-piece casting

TECHNIQUES FOR
SOLDERING
Depending on the degree of precision to
which the components are to be joined.
FREEHAND SOLDERING
JIG SOLDERING
INVESTMENT SOLDERING

Depending on the heat source
TORCH SOLDERING
OVEN SOLDERING
INFRARED SOLDERING

Depending on the application of ceramic
PRECERAMIC SOLDERING
POST CERAMIC SOLDERING

SOLDER JOINT GAP AND
CONFIGURATION
Size shape of the completed solder must
satisfy the requirements of prostheses for
strength aesthetics and hygiene.
Larger the buccolingual dimension and
occlusogingival dimensions , stronger the
joint will be. Occlusogingival dimensions
is particularly significant.

0.3

0.31mm of gap between the
component parts is considered to be
the optimum
RYGE AND STACKHOSE – 0.13mm
WILLIS L.M ,NICHOLIS – 015mm
BUTSON etaL – 0.2mm

Soldering technique
This involves several critical steps:
(1) cleaning and the surfaces to be joined,
(2) assembling the parts to be joined,
(3) preparing and fluxing the gap surfaces
between the parts,

4) maintaining the proper position of the
parts during the procedure,
(5) controlling the proper temperature,
and
(6) controlling the time to ensure
adequate flow of solder and complete
filling of the solder joint.

FREE HAND SOLDERING

Objectives
l To use the
principles of
flame
soldering to
properly
construct the
soldered
triangle andwww.indiandentalacademy.com

Materials
l .036 round wire
l Flux
l Silver wire
solder
lOrthodontic torch or Blazer torch Metal polishingwww.indiandentalacademy.com

l When solder flows properly it
spreads quickly over the metal
surfaces and penetrates small
openings, following points of contact
by capillary action. The parts to be
joined must be perfectly clean and
remain free of oxides during the
actual heating process
Soldering Stainless Steel

When do you apply the solder?
l First, flux bubbles as the excess water
is driven off
l Then it dries becoming hard, white and
crusty
X Finally as it gets even hotter, it melts
into a molten, glistening film.
– This indicates that the metals are hot
enough for the solder to flow toward them if
held in close proximity

What Happens If . . .
l The metal is under heated?
– the solder will ball up due to decreased
surface tension
l The metal is too hot?
– it will begin to glow cherry red, a sign that it
has become annealed
l The surface of the metal is blackened?
– indicates oxidation and the solder will not
flow until the surface is cleaned and flux
reappliedwww.indiandentalacademy.com

Tips
l Adjust height of flame to 1- 1.5 inches
– the smaller the flame the more intense the
heat
l Adjust the air until a barely audible hiss
is heard
l Use the tip of the middle cone to solder
l Mix the contents of the flux in the cap,
to avoid flux being too watery

Step One
l Dip end of .036 auxiliary wire into flux so that
a small portion adheres to tip

Step Two
l Holding the fluxed end into the proper portion
of the flame, feed enough solder from the coil
to make a 2-3 mm ball of solder and flux

Step Three
l Evaluate the amount of solder on auxiliary
wire
l Using a pair of pliers remove the flux which
will appear a greenish color due to the borax
glass
– the borax glass will prevent the flame from
reaching the solder
l After cleaning and evaluating and
determining that there is an adequate
amount of solder reapply flux to the tip of the
auxiliary wirewww.indiandentalacademy.com

Step Four
l Score the main wire to determine the exact
placement of the auxiliary wire
– Carbon (lead pencil) is an ANTIFLUX
l Using the prepared auxiliary wire as a
carrying device, simultaneously hold the
larger arch wire in the flame and draw the
soldered end toward the flame

OHHH, AHHH!
l The solder will flow towards the flame
lYou must hold the wires in position for a brief moment after

Completed Solder Joint
l should be triangular in shape and
symmetrical
l should be free of pits, voids and irregularities
l the main wire should not be annealed
lsolder should encircle the underside of the main wire
(remember mechanical retention)

Completed Solder Joint
l the auxiliary wires should be at 90o to the
main wire the completed project should lie flat
and conform to the handout

Flame Soldering
The Triangle

Process is Similar
l Finished triangle will have 3 solder
joints that are butt joints

If You Can’t Make It Fine...
Make it Shine
l Carefully trim any excess solder using
stones or discs
– do not polish away mechanical retention
l Smooth solder joints using rubber
wheels
– intraorally prevents plaque build up
l Polish surface using metal polish
(tripoli/rouge)
– increases resistance to tarnish and
corrosion

Performance Criteria
l The completed product conforms to the
diagram An adequate amount of solder
encircles the wire ( a triangle of solder)
The wire adjacent to the solder joint has
not been annealed The surface of the
solder joint(s) are free from pits, voids,
and irregularities The solder joints are
finely polished and have a smooth
surface

INVESTMENT SOLDERING

PROCEDURE
OCCLUSAL
SOLDERING INDEX
INVESTING
WAX REMOVAL AND
PREHEATING
SOLDERING

An intraoral plaster or ZOE impression is
made of the occlusal surfaces of the
FPD to capture the relative relationship
of the individual FPD components and
transfer this to the laboratory This
procedure can also be performed in the
laboratory if the the individual
components are seated completely on
an accurate master cast.
Occlusal Soldering Index

Advantage
After the soldering procedure has been
completed, the FPD can be reseated in
the index and soldering accuracy can be
verified (sometimes a small amount of
plaster must be removed in the area
where the solder has been added to
ensure seating).

James A. Stackhouse Jr. B.Sc., D.D.S.,
M.S.[1967] did a study to stimulate in the
laboratory a clinical technique for bridge
assembly and to measure the influence
each of following procedures had upon
changes in crown position. The accuracy
of the plaster index technique was easily
established, as was the minimal distortion
of the assembly caused by transfer to the
soldering investment.

The interferences drawn were:
1. The plaster index was an accurate means of
transferring the crowns from the model to the
investment.
2. The changes in crown position caused by the
setting expansion of the refractory soldering
investment were small and unrelated to those
caused by soldering.
3. The individual crowns in the soldered assemblies
often demonstrated that axial, rotational, and linear
changes in position had occurred.
4. The symmetry of the soldering investment
influenced the accuracy of the assembly. An even
configuration was generally superior to an
asymmetrical soldering block.

• Grind the
connector
surfaces of the
finished castings
with a stone to
remove surface
oxides. Then fully
seat the castings
on the working
cast or in the
mouth.

Post ceramic
application joints are
best indexed
intraorally after the
contour and
appearance have
been perfected.
If necessary, the
soldering gap can be
adjusted at this time
(gap distance 0.25 –
o.31

Make an impression plaster registration
in a small tray or on a sheet of base
plate wax for the occlusal index.

3. Trim the index to fully expose the
margins before investing.

Investing
Seat each casting into the index and lute
it to place with sticky wax.
Flow wax into the connector area to
prevent the investment from entering

To create a space that will help the solder
spread, adapt sprue wax gingival to the solder
joint. Burying the units completely in the
investment makes soldering difficult because
the unnecessary bulk of the investment
prevents rapid heating of the castings.

Protect any glazed porcelain from
contacting the investment by coating it
with wax before investing. To protect
regular gold margins from the soldering
flame, they should be embedded in the
investment; otherwise, they may
become overheated and melt. For the
same reason, all margins should be
embedded in the investment before
preceramic application soldering.

Box the assembly with a suitable sheet wax,
Mix the investment carefully and flow it into
the castings without trapping any air. Only
slight vibration is used so the castings will not
be displaced from the index.

Allow the invested block to bench set before
removing the wax and preheating.

Auto polymerizing Resin Soldering Index.
A plaster or ZOE occlusal index is less
suitable for the registration of anterior
restorations.
The thinness of the incisal edges of these
units makes them less stable, and
accurate repositioning is more difficult.

For this reason, auto
polymerizing resin is
recommended, although the
resin burns off during the
procedure. Therefore, the
accuracy of the soldering
procedure can only be verified
intraorally. Join the completed
units together with auto
polymerizing resin. The resin
will later burn out, leaving no
residue that could interfere
with the casting.

Apply the resin with a bead
technique. This will minimize the
distortion from polymerization
shrinkage. Excessive bulk of
resin reduces the accuracy of the
technique but sufficient material
must be present to ensure that
the components do not break
(because they cannot then be
accurately reseated in the index).
The resin should extend onto the
incisal edges of the retainers.

When the resin has fully hardened,
carefully loosen the prosthesis from the
abutments, Then replace it and check
whether distortion has occurred. This is
done in the same way as the try in of a
finished FPD. It must be stable with no
marginal discrepancies

Investing
Warm a sheet of wax and push
the cervical aspect of the
restorations through it. Then
seal it along the axial wall with a
warmed instrument. This will
protect the porcelain from
contact with the soldering
investment.
Fill the castings with soldering
investment and blot excess
water from the remaining
investment, forming it into a
patty on a slab or tile.

Seat the
restorations on the
patty. When a joint
is to be oven-
soldered, the
restoration should
be angled forward
so that the solder
can be placed
above the joint
before the block is
set inside the
furnace.

Wax Removal and Preheating
If a plaster or ZOE index was used, remove it
after the investment has fully set. This is most
effectively accomplished after removing the wax
with boiling water. The joint space must be free of
investment.

Flowing a little flux into the joint space while the
soldering block is still warm from wax removal
is recommended. This will prevent small
particles from inadvertently falling into the gap.
Be aware that many special soldering
investments have low strength, and the
assembly is easily broken at this stage.

Preheat the investment in a burnout
furnace to 650' C (for low-heat soldering)
or 850' C (for preceramic soldering)
(12202' ~ or 1562' F).

Acrylic resin indexes are removed by heating
slowly to 300' C (5720 F), at which time Most of
the resin will have burned away
Heat the block to 650' C (1202' F) until all
traces of wax and resin have vaporized and
then transfer it to the soldering stand or
porcelain furnace.

Torch Soldering
An oxygen-gas or an air-gas torch is the
preferred means of applying heat for
dental soldering procedures because
(1) access and visibility are maximal
throughout the procedure;
(2) the laboratory technician can apply
heat differentially to the work, that is, to
some areas more than others.

3) oxidation and reduction reactions can
be controlled directly;
(4) heat can be removed immediately
after solder flow;
(5) the addition of solder to the partially
completed joint can be made readily.

Disadvantages
(1) the uneven distribution of heat
created during soldering can warp or
damage portions of the prosthesis;
(2) the overall control of temperature is
imprecise; that is, the laboratory
technician must assess the procedure
without the benefit of a thermocouple or
temperature gauge; and
(3) a pressurized supply of the
necessary gases must be available.

Torch Soldering (Low
Heat)
Transfer the
assembly to a
soldering stand with a
Bunsen flame
underneath and place
a piece of solder
above the gap.

Adjust the gas-air torch
give a sharp blue cone
(as for casting) and then
reduce the air for a
softer "brush" flame. The
reducing zone of the
flame is used to heat the
investment block. The
flame is directed at the
lingual aspect of the
block rather than at the
casting.

Heat evenly and slowly, moving the tip of
the flame constantly. This is particularly
important in post ceramic
Quickly move the flame to the facial. When
the solder "spins" in the joint, remove the
flame.

Extinguish the flame and let the
soldered prosthesis cool for 4 or 5
minutes before quenching (unless there
is porcelain on the restoration, in which
case it should cool to room
temperature). Earlier quenching may
lead to distortion, whereas prolonged
bench cooling increases the brittleness
of the joint.

Torch Soldering (High Heat)
Wear dark glasses for eye protection .
Gas-oxygen torches for high-heat
preceramic soldering use a miniature
needle tip so that the flame can be
pinpointed on the joint space.

Place the solder above the gap and
concentrate the reducing zone of the
flame on the joint space.
When the solder melts, draw it into t1he
joint and quickly "chase" it around with
the flame . The preceramic solder may
have a melting point close to that of the
parent metal, and there is danger of
melting a thin framework unless the
flame is concentrated on the joint space

Soldering in an oven offers the following
advantages:
(1) temperatures are more nearly uniform
throughout the work,
(2) temperatures are known at any point during
the procedure,
(3) application of vacuum can control oxidation,
and
(4) close monitoring of the procedure is feasible
if the work is visible in the furnace. Although
equivalent.
Oven Soldering

Prepare a piece of solder by dipping it in
liquid flux and melting it in a Bunsen flame
to form a ball. The size of the ball will be
determined by the connector size and the
joint gap.
Leave a short tail attached to the ball to
help position it above the joint space. As
an alternative, the solder can be fed into
the joint area

Put the assembly in the furnace and
increase the temperature to fuse the
solder. A vacuum is not needed for
oven soldering of noble metal alloys. Air
firing is preferred by some technicians
because in a vacuum there is always
the chance of drawing entrapped gases
to the surface of glazed porcelain,
causing localized swelling or bloating.

Infrared Soldering
Infrared soldering can be used
for low -fusing connectors as
well as preceramic soldered
joints. A specially designed
unit that uses an infrared light
as its heat source is used. The
connector area of the soldering
assembly must be positioned
precisely relative to the focal
point of the reflector that
concentrates the heat.

The operator observes the soldering
procedure through a dark screen and
cuts off the electrical supply when
solder flow is observed. Good accuracy
is possible with the system .
The joints have similar strength to
conventional soldering, although weaker
joints have been reported with infrared
presoldering of gold platinum-palladium
alloys.

Lower the protective
shield to prevent eye
injury, and activate the
heat source. When a
complete connector
has formed after the
fusing point of the
solder is reached, the
heat source is shut off,
and the assembly is
removed from the
soldering platform.

Louly AC, Mora AF, Moore BK, Andres CJ, Goodacre CJ
(1991).
Authors investigated on tensile strength of preceramic
solder joints.
Infrared soldering was compared to gas-oxygen torch
soldering by testing specimens made from each of the
following four classes of metal ceramic alloys: gold
platinum-palladium, gold-palladium, palladium- silver,
and nickel-chromium-beryllium.
There was no significant difference between infrared
and torch soldering for the gold-palladium, palladium-
silver, and base metal alloy specimens.
However, infrared soldering of the gold-platinum-
palladium alloy samples produced significantly weaker
joints than those produced by torch soldering.

Cattaneo G, Wagnild G, Marshall G,
WatanabeL(1992) conducted a comparative
study on two different techniques of the
joining.
This study compared soldering by a
conventional torch procedure with an
infrared soldering technique.
Comparisons were made for tensile
strength, porosity, and time efficiency
between the two methods. No significant
difference was found in ultimate tensile
strength between the two types of solder
joints

Cheng AC, Chai JY, Gilbert J, Jameson LM
(1993)13 conducted study on joints joined
by torch soldering and infrared technique.
The ultimate tensile strength and
percentage elongation of solder joints of
three alloy systems were tested.
Solder joints were formed using either an
infrared soldering machine or gas-oxygen
torch.

For high noble and noble alloy solders, there
were no significant differences in ultimate tensile
strength of joints made with either method.
For base metal alloy solder, the ultimate tensile
strength of joints made with the infrared
technique was significantly higher than that
made with the gas-oxygen torch technique.
The infrared technique can be used as an
alternative to the gas-torch technique for
soldering high-noble and noble alloys. It is
superior to the gas-torch technique for soldering
a cobalt-chromium alloy.

Post ceramic soldering
ADVANTAGES
Good access to finish
the margins on both
the wax pattern and
the casting prior to
soldering. Adjacent
units do not
compromise any
access.

The size and
position of each
joint can be
easily checked
unhindered by
the presence of
adjacent units.

There is good access
for finishing the
porcelain margins.
Porcelain can be
wrapped beneath the
joint
for finishing proximal
porcelain

Individual units can
be tried in the mouth
for marginal fit . There
is, therefore, no
temptation to accept a
long-span bridge with
one unit not fitting as
well as it should.
for porcelain
contouring.

It is easy to modify colour and contour of
porcelain on individual units.
It enables units made from ceramic and
non-ceramic gold castings to be used with
the same prosthesis. Any tooth movement
occurring during the period of fabrication
will not influence the final fit of the
framework, as relationships between units
are not finalized until the indexing stage.
The tensile strength of the joint is as great
as that of the parent cast metal

Disadvantages
Cracking or bubbling of porcelain may
occur, but this is unlikely if the porcelain
is well condensed and fired and provided
there are no internal flaws present before
soldering
Greater risk of cloudy or dull porcelain if
the units have had multiple firings, due to
devitrification caused by extended firing
during soldering.

Additional clinical stage - indexing is required.
Mobile teeth can create difficulties - movement
during the indexing can influence the tooth
relationships or the occlusion.
Pontics can be difficult to locate - always cast a
pontic integral with a retainer so that it is soldered
only at one end.
Since the pontic is an extension of the retainer,
any small rotations of the retainer or abutment will
be magnified at the other end of the pontic and
may result in unaesthetic embrasures.

Procedure
1) The crowns are tried in the mouth one at a
time and checked for fit, shade and contour.
2) All units are then inserted and the contacts
checked, these should be passive.
If one crown is displaced by another or by a
tooth, adjustment is made to the contact areas
3) The occlusion is checked for gross errors.
4) The shape of the crowns is altered as
necessary with a fine diamond bur.
5) The surface is characterised and polished

6) Minor occlusal errors are corrected.
7) Small amounts of surface stain are
added if necessary.
8) The crowns are glazed and to be re-
checked in the mouth.
9) They are then cemented with a
temporary cementation . The object of this
temporary cementation is to replicate the
effect of the luting cement on inter crown
relationships.

10) The crown relationships are checked.
When, prior to soldering, two or more
pontic units are cantilevered from one
retainer, the adjacent retainer should
incorporate a slot to house an extension
from the pontic . This prevents the pontic
from rotating about the abutment from
which it is cantilevered. Small rotations can
lead to large discrepancies which spoil the
aesthetics and alter the occlusion.

11) Undercuts on
crowns and the
areas beneath the
handling tags on
the crowns are
blocked out with
syringe material
hydrocolioid.

12) The occlusal surfaces of
the crowns and pontics are
coated with a thin layer of
Vaseline.
(DuraLay powder and Super C
liquid (or DuraLay 11) are
beaded onto each occlusal
surface, ensuring that the resin
does not flow across joints,
and that the covering over
each crown remains discrete .
A one piece of DuraLay index
is not used since some
polymerisation shrinkage may
occur, also the resin has a high
thermal coefficient of
expansion and may, therefore,
change dimension with a
change in mouth to room and
room temperature.)

A,, For patients who
salivate excessively,
and require
restorations in the
lower jaw, it may be
necessary to prescribe
oral propantheline
hydrochloride, 30 mg
(Pro-Banthine), one
hour prior to the
appointment.

16) Plaster is mixed
and is applied in a
'runny' state to the
DuraLay to lock the
individual units
together.
17) The plaster can
be applied either by a
small spatula, from a
5ml syringe or via a
Beauty wax tray
contoured to the arch
form from a study
cast.

18) Once set the index formed by the stone and
DuraLay coverings is removed. Any crowns
which do not come out with the index are
removed from their abutments.
19) Any crowns retained by the index are
removed, since the joint areas must be prepared
in the laboratory.
20) The crowns are then carefully replaced in
the index and checked for positive fit. There
must not be any rocking of retainers when finger
pressure is applied.. The rigid DuraLay assists
in the location. Furthermore, if the crowns are
removed the DuraLay will not crack and the
index can be used again.

24) Following soldering, the units are retried in
the mouth.
25) Any rocking of the bridge between
abutments is unacceptable. In such cases, the
bridge is sectioned with a very thin diamond disc
and re-indexed. Although cementation with a
soft temporary cement may allow some tooth
movement to occur and may even eliminate the
rock, there is no evidence that the tooth will
have moved to ensure full seating of the crown
margins around the entire periphery of the
crown, this technique is not acceptable.

Cho GC, Chee WW (1995) did an
investigation on the different soldering
indexing materials. Multiple-unit fixed
partial dentures routinely require an
intraoral index to ensure accurate fit. One
of the most commonly used materials is
Duralay acrylic resin, which has yielded
satisfactory clinical results, but one
disadvantage has been a prolonged
setting time.

This study compared the setting times of
two auto polymerizing resins, Duralay and
G. C. Pattern resin. The dimensional
accuracy of these materials was also
compared with one light-cured resin, G.C.
Unifast light-cure resin. All three materials
were suitable to relate castings with
clinically acceptable outcomes, and
chairside time could be saved with the use
of recently introduced indexing materials.

Adding proximal contacts
The addition of solder to a proximal
contact area is done to build up a contour
that may be deficient for any number of
reasons.
It can easily be done freehand on a single
restoration. A fixed partial denture must be
invested before the addition.

. The area to be soldered must be wider
than the contact. It should extend across
the entire proximal surface, just apical to
the marginal ridge. The periphery of this
new bulk will be blended into the contours
of the crown, rather than being a pimple
on the side of the crown.

Bend one tip of a pair of
locking soldering
pliers so that a crown
can be held by its
axial wall without the
pliers touching the
margin

Grasp the crown with
the locking soldering
pliers. The bent beak
should be inside the
casting, and there
should be no contact
at any other point.
Wrap a wet paper
towel around the
handle of the soldering
pliers.

Warm the casting slightly and place a
small drop of soldering flux on the contact
to be soldered, staying within the pencil
outline. Dip a piece of solder (depending
on the size of the casting) into the flux.

Place the solder on
the proximal surface .
Holding the soldering
pliers with the wet
towel, place the
casting over the
burner, keeping the
casting in the blue
reducing tip of the
flame

Keep it there until the casting glows a
bright red, allowing the solder to melt and
adapt itself to the casting.
Remove the casting from the flame.

. Allow a gold alloy casting to cool until the
metal loses its glow and then quench it in
water.
Air abrade it with 50 pm aluminum oxide.
If the casting is made of a base metal
alloy, allow it to cool for at least 5 minutes
before quenching it.
Clean it with aluminum oxide abrasive.
Then finish it to the proper contour and
return it to the mouth for final adjustment
of the contact area.

Repairing Casting Voids
Deficiencies in casting that can be
repaired by soldering are
"Blow holes" or voids extending all the
way through a casting on an axial surface,
Pits that do not extend all the way
through, are candidates for solder repairs.

Solder should not be used to repair:
Deficient margins- It is impossible to get
an acceptably adapted margin by adding
solder.
Occlusal holes -Holes in the occlusal
surface cannot be successfully soldered
because of the risk of solder running over
the entire surface. Aside from the
technique difficulties, the presence of a
hole on the occlusal surface of a crown is
usually symptomatic of inadequate
occlusal reduction in the preparation.

To repair a pit:
outline the area around it with a no. 2
pencil.
Grasp the crown with the modified locking
soldering pliers, the handle of which is
wrapped in a wet paper towel.
Warm the casting slightly and put a dab of
flux into the pit.

Stick a corner of a triangular-shaped piece
of solder, 1 x 2 mm, into the pit.
Hold the casting over the Bunsen burner
until the solder flows, remove it from the
flame, let it cool, and then quench it,
Air abrade it with 50 pm aluminum oxide,
wash it, and finish down the newly
soldered area,

To repair a hole that extends all the way through a
crown,:
Mark the die through the hole with a very fine
lead.
Remove the casting and place a small piece of
platinum foil over the mark on the die.
Reseat the crown over the foil and apply a bead
of sticky wax to the hole.
When it has cooled, remove the casting from the
die.
The small piece of foil should be stuck to the
inside of the casting. It will serve as a matrix over
which the solder can flow.
Fill the casting with investment and set it down in
a small patty of investment.

When the investment has set, pick off the
bead of sticky wax over the hole to be
repaired.
Antiflux the area around the hole with a no.
2 pencil.
Place the casting on a tripod and warm it
slightly.
Apply a small amount of flux to the hole
and the foil visible through the hole.
Continue heating the casting and add a
square of solder slightly larger than the
hole.

Heat the casting, not the solder. When the solder
flows, remove the flame.
Put the invested casting in a casting well or on a
heat-safe bench top.
if it is a gold casting, wait 2 or 3 minutes to
quench. Then air abrade it with 50 micron
aluminum oxide.
Wash the casting and finish the outward-facing
surface of the axial wall, The platinum foil will be
stuck to the inside of the casting. If it is left there,
it will prevent the casting from seating
completely. Use a no. 2 round bur to remove it.

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Soldering procedures/ orthodontic assistant training

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