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2. DEFINITIONS SOLDERING: It’s defined as the joining of metals by the
fusion of filler metal between them, at a temperature below the solidus
temperature of the metals being joined and below 450°C.
3. BRAZING: It’s a term used industrially. Soldering operations at or above
450°C is generally termed brazing. Most dental soldering procedures are
actually brazing, but the names are used interchangeably in dentistry.
Brazing is defined as joining of metals by the fusion of a filler metal
between them, at a temperature below the solidus temperature of metals
being joined and above 450°C.
4. LIQUIDUS TEMPERATURE: the temperature at which metals of an alloy
system begin to solidify on cooling or become totally liquid on cooling.
SOLIDUS TEMPERATURE: the temperature at which metals of an alloy
system become completely solidified on cooling or start to melt on heating.
5. WELDING: The joining of two or more metal parts by applying heat,
pressure or both, with or without a filler metal, to produce localized union
across the interface through fusion or diffusion.
6. CAST JOINING Another type of metal joining procedure in dentistry. It is
the process of combining two components of a fixed partial denture by
means of casting molten metal into interlocking region between invested
components. This is preferred for base metal alloys because of technique
sensitivity of brazing or soldering these alloys.
7. Soldering / Brazing : The diff. is between the liquidus temp. of the filler
metal. Soldering & Brazing / Welding : Possible absence of the filler metal
& the partial fusion of the parts joined by welding.
8. SOLDERING HISTORY The soldering technique has been known to
man for hundreds, maybe thousand years. However, with the industrial
revolution in Europe as well as North America, the need for higher
temperatures and more user-friendly tools emerged. The old methods of
heating metals with coal fires etc. were no longer practical. It was
discovered that when the vapor from heated alcohol was ignited over a
burning wick, it burnt with a very concentrated flame of high temperature
very suitable for different heating purposes. Many different designs
emerged using this technique and these heating tools were generally
called blow pipes. The first known patent is from France and is dated
January 7, 1791.
9. During the early 1900`s, a great variety of blow lamps specially designed
for different purpose and applications came on the market. After the
Second World War, the propane gas emerged as a cleaner and safer fuel
for different heating purposes. The introduction of propane caused a lot of
changes in the blow lamp industry world-wide.
10. The first appliances used had a metal frame work. The attachment of
axillaries to bring about the different type of tooth movements required
soldering of these parts. Welding in orthodontics became popular after the
arrival of spot welders. It became popular because of the short time
required, the ease of welding and the absence of elaborate equipments
11. Soldering is often used in construction of dental appliances. Large
partial dentures are frequently cast in parts that are soldered together after
carefully fitting them to master cast. In orthodontics soldering is used for
joining wires, bands springs etc The soldering process involves the
substrate or the parent metals to be joined, soldering filler metal (usually
called solder), a flux, and a heat source. All are equally important and the
role of each must be taken in to consideration to solder metal components
successfully .
12. COMPONENTS OF SOLDERED JOINT Parent metal Solder/filler
metal Fluxes and Anti fluxes
13. PARENT METAL The parent metal is the metal or alloy to be joined.
This is also known as a substrate metal or base metal. Soldering operation
is the same for any substrate metal, but the ease of soldering is not same
for any substrate metal. The composition of parent metal determines-
Melting range Oxide that forms on the surface during heating Wettability of
the substrate by the molten solder. Soldering should take place below the
solids temperature of the parent metal.
14. Composition of alloy determines the oxides that form on its surface
during heating. The flux used should be able to reduce these oxides, inhibit
further oxidation and facilitate its removal. Composition of alloy determines
the wettability of the substrate by the molten solder alloy. The solder
chosen must wet the metal at as low a contact angle as possible to ensure
wetting of the joint area. Manufacturer of the alloy should provide guidance
and instruction regarding the flux to be used with that alloy. A low temp
soldering is preferred rather than the high temp soldering for Stainless
steel wire to prevent carbide precipitation and to prevent an excessive
softening of the wire. So silver solders are generally preferred.
15. FLUX In Latin flux means “to flow” . Purpose of flux is to remove any
oxide coating on the substrate metal surface when the filler metal is fluid
and ready to flow into place. They protect the alloy surface from oxidation
during soldering and dissolve metallic oxides as they are formed. The
resulting solution of oxides or other extraneous matter in flux constitutes
“slag”.
16. CLASSIFICATION OF FLUX 1.According to their primary purpose /
activity Surface protection type: - This type of flux covers the metal surface
and prevents access to oxygen, so that no oxides can form. Reducing
agent type: - This type reduces any oxides present and exposes clean
metal. Solvent type: - This type dissolves any oxides and drives them
away. The composition of most commercial fluxes is formulated to
accomplish two or more of these purposes.
17. 2.According to their composition Borax fluxes Fluoride fluxes 3.
According to the pH of the flux Acidic fluxes – SiO2 Basic fluxes – CaO,
lime CaCO3 LIMESTONE Neutral – Fluorspar (Ca.F2),Borax (Na2B4O2)
18. BORAX FLUXES Borax from Persian burah Also called sodium borate ,
or sodium tetraborate , or disodium Tetraborate. They are based on boric
or borate compounds such as boric acid/boric anhydrate and borax. It is
usually a white powder consisting of soft colorless crystals that dissolve
easily in water. Borax has a wide variety of uses:- It is a component of
many detergents, cosmetics, and enamel glazes. It is also used to make
buffer solutions in biochemistry as a fire retardant as an insecticide as a
flux in metallurgy They act as protective fluxes and reducing fluxes for low
stability. oxides such as copper oxide. And are used for noble metal alloys.
19. BORAX
20. They are available in Liquid form : Solution of borax/boric acid in water.
Indicated for soldering of orthodontic appliances and bridges in which
minimum amount of flux is required. Paste form : Formed by mixing borax
with petroleum jelly. Required when fluxes are needed in large quantity.
Powder form : Contains a mixture of borax, basic acid, silica flour and finely
divided charcoal. Charcoals reducing agent and silica holds molten flux in
surface of hot metal. This is usually used for casting operation.
21. FLUORIDE FLUXES Composition:- Potassium fluoride – 50-60% Boric
acid – 25-35% Borax glass - 6-8% Potassium carbonate – 8-10% As the
choice of flux is dictated by the type of alloys to be soldered, the fluoride
flux is used with alloys containing base metals even if a gold/silver solder is
used. Some fluoride containing fluxes involve toxic fluorides when heated,
so inhalation of fumes should be avoided.
22. POTASSIUM FLUORIDE The chemical compound with the formula KF.
After hydrogen fluoride, KF is the primary source of the fluoride ion for
applications in manufacturing and in chemistry. It is an alkali metal halide
and occurs naturally as the rare mineral carobbiite(potassium-67.30% +
fluorine-32.70%) is a colorless cubic mineral. It is found at Monte Somma,
Somma-Vesuvius Complex, Province of Naples, Campania, Italy. It was
discovered in 1956 . Aqueous solutions of KF will etch glass due to the
formation of soluble fluorosilicates.
23. SUPER FLUX A combination of high melting salts is used as fluxes to
combine the good characteristics of each ingredient and create superior
flux. A formula for efficient flux is Borax glass – 55 parts Boric acid – 35
parts Silica - 10 parts The ingredients may be fused together and then
crushed to fine powder.
24. APPLICATION OF FLUX Painted on to the substrate metal at the
junction of pieces to be joined. Fused on to the surface of the filler metal
strip. Whatever be the technique used the most important thing to consider
is the amount of flux used. Too little flux tends to burn off and will be
ineffective. Excess flux remains trapped within filler metal and cause a
weakened joint. Flux combined with metal oxides forms a glass during
soldering process that is difficult to remove completely. A two step method
for removing residual flux Blast joint immediately after removal from
investment with alumina abrasive particles followed by boiling in water for
about 5 minutes.
25. ANTI FLUX Materials used to restrict flow of solder are known as anti
flux. It is applied on the surface of specific area where the solder should
flow into. It is applied before applying flux or solder. E.g.: Graphite in the
form of lead pencil. Disadvantage of graphite is that it can burn off on
prolonged heating at high temperature. In such cases whiting (CaCO3 in
alcohol and water suspension) is used.
26. FILLER METAL/SOLDER Qualities of an ideal solder Ease of flow at
relatively low temperature. Sufficient fluidity to freely flow when melted.
Ability to wet substrate metal. Strength compatible with that of the structure
being joined. Resistance to tarnish and corrosion . Acceptable colour to
give an inconspicuous joint. Resistance to pitting during heating.
27. FLOW TEMPERATURE The temperature at which the filler metal wets
and flows on the substrate metal and produces a bond. It is usually higher
than the liquidus temperature. ISO 9333 requires that the flow temperature
of the filler metal should be lower than the solidus temperature of the
substrate metals. A rule of thumb is that flow temperature of the filler metal
should be 56°C (100°F) lower than the solidus temperature of the substrate
metal. If the flow point of the filler metal is close to or above the solidus of
either substrate alloying can take place. An alloy formed through diffusion
can have properties different from filler metal and substrate metal.
28. CLASSIFICATION OF SOLDERS l . Soft solders Hard solders II.
Precious metal solders Non precious metal solders
29. SOFT SOLDERS They are lead- tin eutectic alloy with a low melting
point. Sometimes called as plumbers solder. They have low fusion range of
about 260°C or less. Soft solders lack corrosion resistance, so they are
impractical for dental use. HARD SOLDERS Hard solders have higher
meting temperature & possess greater hardness and strength. Heating is
done with gas torch or special devices. Two types of hard solders are used
in dentistry
30. Gold solders Has good tarnish and corrosion resistance Extensively
used for crown and bridge applications. Composition Gold – 45-81 wt %
Silver - 8-30 wt % Copper -7-20 wt % with small amounts of Tin, Zinc and
Phosphorus to modify fusion temperature and flow qualities. They are high
fusing with a fusion temperature range of 750- 900° C.
31. Silver solders Used in orthodontic appliances They are low fusing –
fusion temp-600-750°C Used with stainless steel or other base metal alloys
Resistance to tarnish and corrosion is not as good as gold solders But
have strength comparable to gold solders Composition Silver -10-80 %
Copper -15-30% Zinc -4-35% with small amounts of cadmium, tin and
phosphorus. The formation of silver-copper eutectic is responsible for the
low melting range of silver solder.
32. SILVER SOLDER
33. HEAT SOURCE The most common instrument used as heat source is
gas- air or gas- oxygen torch. The type of torch depends on the type of
fuel. The fuels used are :- Hydrogen -low heat content, so heating is slow.
Natural gas - heat content is four times that of hydrogen.
34. Acetylene - high flame temperature, but variation in temperature from
one part of the flame to the other part is more than 100°C. So positioning of
the torch is critical. It is chemically unstable gas, decompose to carbon and
hydrogen. carbon can get incorporated in to nickel and palladium alloys.
Propane - is the best choice. Have highest heat content& good flame
temperature. Butane - has similar flame temperature and heat content.
Both are readily available. Uniform in quality, virtually water free and burn
clean.
35. FLAME The flame can be divided in to four zones Cold mixing zone
(unburned gas) Partial combustion zone (oxidizing) Reducing zone
Oxidizing zone (burned gas). The portion of the flame that is used to heat
the soldering assembly should be the neutral or slightly reducing part,
because this produces the most efficient burning process and most heat.
Improperly adjusted torch or improperly positioned flame can lead to
oxidation of the substrate or filler metal and result in a poorly soldered joint.
If unburned portion of flame is used carbon may be introduced to the
substrate or filler. To prevent oxide formation the flame should not be
removed once it has been applied to the joint area until soldering process
has been completed.
36.
37. OVEN (FURNACE) SOLDERING A furnace with enough wattage to
provide heat required to raise the temperature of the filler metal to its flow
point. Advantages: Uniform temperature Close monitoring is possible
Temperature is known Application of vacuum control oxidation
38. INFRARED SOLDERING The unit uses light from a 1000 watt
Tungsten filament quartz- iodine bulb which is mounted at the primary focal
point of a gold plated elliptical reflector. The material to be soldered is
placed at the reflectors secondary focal point at which the reflected infrared
energy of Tungsten light source is focused. This is used for high
temperature soldering.
39. TECHNIQUES OF SOLDERING Investment soldering Free hand
soldering
40. INVESTMENT SOLDERING Used when very accurate alignment of
parts to be joined is needed. The parts are placed on the master cast with
a gap of at least 1mm. The parts are fastened with sticky wax before
placing soldering investment. Anti flux is applied to confine the flow of
solder. The investment is preheated to eliminate moisture. Flux can be
applied before or after heat treatment. Soldering is carried out with
reducing flame at 750- 870°C. The investment is cooled 5 min before
quenching. Flux will cool to a glass which is removed by pickling.
41. FREE HAND SOLDERING Free hand soldering is used for soldering
orthodontic appliances. Orthodontic torches can be placed on a bench so
that both hands can be used to hold the parts in position.
42. SOLDER JIONT GAP If the gap is too great the strength will be
controlled by the strength of the filler. If the gap is narrow the strength will
be limited by the flux inclusions& porosities by the incomplete flow of the
filler, metal.
43. STEPS IN SOLDERING Cleaning and preparing the surfaces to be
joined Assembling the parts to be joined Preparation and fluxing of the gap
surfaces between the gaps Maintaining the proper position of the parts
during procedure. Control of proper temperature Control of time to ensure
adequate flow of the solder& complete filling of the solder joint
44. ORTHODONTIC SOLDERING In orthodontic applications low
temperature soldering is used to prevent carbide precipitation and to
prevent excessive softening of the wire. Low fusing silver solders are used
with a soldering temperature range of 620-655°C. Fluoride fluxes are used
for orthodontic stainless steel and other base metal alloys. Free hand
soldering technique is employed with a needle like non luminous gas air
flame is used.
45. The work should be held 3mm beyond the tip of the blue cone in the
reducing zone of the flame. Soldering should be observed in a shadow,
against a black back ground, so that the temperature can be judged by the
color of the work. The color should never exceed a dull red. Flux must
cover all the areas to be joined before heat is applied. As soon as the flux
fuses solder is added and heating is continued until metal flows around the
joint. The work is then removed from the heat and quenched in water .
46. SOLDERING APPLICATIONS IN ORTHODONTICS Wire to wire
Tubes can be soldered to the bridge of the Adams clasp. Attachment of
springs to arch wire. When soldering an auxiliary spring to arch wire, the
solder must be a gold one with a melting point below 800°C. Soldering
lingual arch or palatal arch: to hold the arch during soldering position it on
the model and place a blob of wet pumice over the middle portion of the
model. Water is immediately soaked on to the cast leaving dried pumice
which is firm enough to secure the arch during soldering.(F.G. Thompson,
JCO 1969 April)
47. SOLDERING FAILURES Are due to: Failure to clean the parts to be
joined Improper fluxing Poor flow of solder Over heating of the solder can
lead to pitted joint of low strength Besides porosities and brittleness from
oxides, gases, or foreign matter resulting from the soldering procedures as
factors for increasing the incidences of failure of soldered joints. Creep,
corrosion, stress corrosion cracking, corrosion-fatigue, and corrosion-
erosion. Gas embitterment can also be generated by gases formed from
electrochemical processes. Hydrogen embitterment from corrosion is a
very well-known phenomenon that occurs with some material-solution
combinations and at temperatures comparable to physiologic conditions.
48. CORROSION OF SOLDERED JOINTS A consideration of the
composition of silver solders reveals that any material containing up to
about 20 percent zinc and 20 to 30 percent copper with additions in some
cases of low cadmium and tin cannot remain inactive to physiologic
solutions. Weak corrosion-prone micro structural phases composed mainly
of copper and zinc has been shown to occur within the solder itself. It is
known that corrosion occurs when an electrolyte comes into contact with a
soldered joint. The silver solders react readily to chemical attack. The
breakdown reaction between silver-soldered stainless steel joints is an
electrochemical process with no initial evidence of gross macroscopic
corrosion. After a time, many silver-soldered joints exhibit a change in
appearance such as darkening to resemble a tarnished, corroded surface.
49. BIOCOMPATIBILITY Besides the deterioration of the soldered joint,
concern must be given to the toxicological importance of the released
corroded agents. For Cadmium -containing solders, because of Cadmium's
toxicity, a continual appraisal must be made regarding Cadmium's fate
biologically. The release of Cadmium from dental alloys has been the
subject of several reports. Even in the case of such nontoxic elements as
Zinc, Copper, Tin, and Silver , the introduction of higher concentrations of
these elements via soluble corrosion products can alter their behaviour
Causing biologic imbalances with further biologic consequences .
50. It is believed that possible allergies to nontoxic metals released from
dental alloys may be formed. Metabolic and bacteriologic participation can
also occur in response to corroded metallic agents. Furthermore, the
penetration and staining of hard dental tissues due to the release of
metallic ions from solders or any biomaterial are definitely to be avoided.
Laboratory tests indicate that silver-soldered stainless steel joints degrade
in a saliva substitute and other prepared solutions. Corrosion products
containing oxides, hydroxides, and chlorides of zinc, copper, tin, and
cadmium can be easily identified. Silver is also attacked Besides the oral
physiologic fluids, additional chemical agents contained in mouth rinses
and in toothpastes for oral antiseptic, need careful appraisal for resistance
to the degradation and corrosion of dental materials. Many commercial
mouth rinses contain active chlorides and additional components. The
chlorides are notorious for their depassivation tendencies of metallic
materials.
51. NEWER SILVER SOLDERS For joining stainless steel, additional
alloys with improved corrosion resistance classifications of silver soldering
alloys (referred to here as brazing alloys), including BAg-18 and BAg-21
(American Welding Society), can be used very effectively. These silver
soldering alloys have silver contents at about the same level as the solder
products presently employed, but they have slightly higher copper
contents, with additions of up to about 10 percent tin for wetting stainless
steels and up to about 3 percent nickel for immunity to crevice corrosion.
The important fact is that both cadmium and zinc are removed from these
alloys. The soldering (brazing) temperature range is between 700 and
900°C, in some instances about 200°C higher than the presently employed
products. Because of the non-free-flowing characteristics of these
proposed soldering alloys for dental applications, familiarization with their
properties and handling characteristics is advisable .
52. WELDING Welding is the process by which the surfaces of metals are
joined by mixing, with or without the use of heat. Cold welding is done by
hammering or pressure. An example of cold welding is the gold foil filling.
Hot welding uses heat of sufficient intensity to melt the metals being joined.
The heat source is usually an oxyacetylene flame or high amperage
electricity.
53. TYPES OF WELDING SPOT WELDING PRESSURE WELDING
LASER WELDING PLASMA WELDING
54. LASER WELDING
55. PLASMA WELDING
56. PRESSURE WELDING
57. SPOT WELDER
58. THEORY Orthodontic spot welders employ the electrode technique and
are used instead of soldering in cases where the heating cycle must be
very short, in order to prevent changes in the physical properties of the
components being joined. Orthodontic welding is achieved by passing a
large amount of current for a very short duration through an area of high
resistance. Heat is generated of a magnitude great enough to cause
melting at the interface in contact. Copper electrode - Low resistence As
sufficient heat is generated at the weldmate interface, the stainless steel
components soften, flow and fuse together under the influence of
mechanical pressure, forming a weld nugget
59. In spot welding the following three properties of the metal are
favorable: A comparatively low melting point (approximately 1370° C.), high
electric resistance, And low conductivity of heat.
60. VARIABLES AND THEIR APPLICATION Welding of stainless steel
depends on the proper use of each of the following three variables: 1. The
current flowing through the circuit. 2. The time during which the current is
allowed to flow. 3. The mechanical pressure applied at the welding head.
61. The improper application of these variables can result in either over- or
under welding UNDER WELDING - Insufficient current - The current
passed for an insufficient amount of time - Pressure applied inadequate in
approximation. OVER WELDING - Yield weak a joint as under welding. -
Progressive corrosion. This occurs when chromium is precipitated at the
grain boundaries of each crystal. This process is known as weld decay . A
satisfactory welded joint is one which is strong, has not undergone
oxidation (blackening), and has not been over compressed during fusion.
62. CLINICAL APPLICATION The use of the spot welder in orthodontics is
so common that it is almost a reflex. 1.The welding surfaces should be
clean of all debris materials and oxides. 2.The surface of each electrode
must be smooth, flat, and perpendicular to its long axis. When the
electrodes are together, they should be in total contact. If not, they should
be filed until total contact is achieved. Sparking and localized over welding
will result if interface contact is not uniform. 3.Adjust the welder to settings
recommended by the manufacturer .
63. 4. Select the proper electrode for the thickness or shape of the material
to be welded. A broad electrode should be used for thin material and a
narrow one for thick material. This will allow sufficient heat to reach the
weld area, but not over weld or oxidize the weldmates. If too narrow an
electrode is used in welding a bracket (thick) to a band (thin), localized
over welding will occur in the thin material and under welding in the thick
material Proper electrode selection— a broad electrode for thin material in
conjunction with a narrow electrode for the thicker material— will result in
an even distribution of the weld nugget
64. 5.Insert the weldmates between the electrodes, close them together,
and depress the weld button. If sparking is observed, localized over
welding has occurred. The electrodes should be checked for size and/or
contact. If black areas are seen at the points where the electrodes
contacted the weldmates, over welding has occurred. (JCO-Volume, 1976
Feb Orthodontic welding-Robert E. Binder. DMD)
65. A CHECKLIST FOR SUCCESSFUL WELDING Mount the electrodes
correctly in the welder and adjust with parallel, precision filing to eliminate
gaps. Weld together only wires of the same material. Place the thinner wire
in the groove of the lower electrode. Use 1540 Newtons of pressure. Set
the voltage according to the operating instructions. Use a single electrical
impulse.
66. CONCLUSION The choice of solder material has extreme importance
in determining the properties of the soldered joints. In orthodontics, silver
solders are popular because of their lower fusion temperatures and easy-
handling characteristics. It is also rationalized that both fixed and
removable orthodontic appliances are not meant to be permanent;
therefore, solders with properties inferior to some of the higher-fusing
solders can be tolerated. Soldering is still a useful and needed procedure
for the joining of metallic parts. The choice of whether free-hand or
investment, torch or oven, or pre or post ceramic soldering techniques are
used, as well as variations in gap distance and high- or low-fusing
soldering alloys, is in many instances up to the discretion of the
orthodontist and technician. The breakage of soldered components is one
of the pitfalls associated with this joining procedure. Even though following
guidelines should theoretically prevent them from occurring, solder failures
are not rare.
67. Spot welding is suitable only when the thickness of the band or flange
more or less corresponds to that of the sheet to which it is to be welded,
and should not be used to join auxiliary springs and arch wires. One kind of
electrode is ample for spot welding in the construction of orthodontic
appliances. Although welding is one of the technical procedures most
commonly used by orthodontists, the process is usually poorly understood
and not employed efficiently. In the final analysis, however, the
combination of techniques which offer optimum mechanical, physical, and
chemical properties or offer the desired property with the most favorable
must be selected.
68. REFERENCE Phillip’s science of dental materials- Anusavice dental
materials –A programmed review of selected topics- W.J.O’Brien Dental
Materials – Craig. removable appliances – PC Adams American journal of
orthodontics 1937 may American journal of orthodontics 1982 February
journal of clinical orthodontics 1969 April journal of clinical orthodontics
1969 November journal of clinical orthodontics1976 February journal
clinical orthodontics 1987 September journal of clinical orthodontics 1991
January journal of clinical orthodontics 2000 may
1. 31.07.2012 soldering and welding 1
2. TOPIC- SOLDERING AND WELDING UNDER THE GUIDANCE OF –
DR. MOHAMMAD MUSHTAQ HEAD OF THE DEPARTMENT31.07.2012
soldering and welding 2
3. “Never must the physician say the disease is incurable. By that
admission he denies GOD , our creator ; he doubts Nature with her
profuseness of hidden powers and mysteries”. PARACELSUS31.07.2012
soldering and welding 3
Adhesives31.07.2012 soldering and welding 4 Nuts and bolts 4. Since it
is not always possible to create a metal device in one piece, such as by
casting, it is necessary assemble it from separately prepared parts. In
dentistry, the fabrication techniques used are either soldering or welding.
5. Are divided into three categories • SOLDERING • BRAZING •
WELDING31.07.2012 5 soldering and welding
After the second world war, the PROPANE gas emerged as a cleaner and
safer fuel for different heating purposes. The introduction of propane
caused a lot of changes in the blow lamp industry world –wide.31.07.2012
soldering and welding 6 It was discovered that when the vapor from
heated alcohol was ignited over a burning wick, it burnt with a very
concentrated flame of high temperature very suitable for different heating
purposes. The soldering technique has been known to man for hundreds
may be thousands of year. However , with industrial revolution in Europe
as well as North America , the need for higher temperature and more user
friendly tools emerged. 6.
Welding in orthodontics became popular because of the short time
required, the ease of welding and the absence of elaborate
equipments31.07.2012 soldering and welding 7 The appliance had a
metal framework. The attachment of axillaries to bring about the different
type of tooth movements required soldering of these parts.7.
The American National Standards Institute (ANSI) currently is considering
a proposal to call all joining operations in dentistry as brazing rather than
soldering. Thus brazing may be the predominant term in the
future.31.07.2012 soldering and welding 8 SOLDERING is defined as the
joining of metals by the fusion of filler metal between them, at a
temperature below the solidus temperature of the metals being joined and
below 450° C. 8.
9. The soldered joint consists of the following components: A). Parent
metal B). Fluxes and anti- fluxes C). Solder or filler metal31.07.2012
soldering and welding 9
wetablitly of the substrate by the molten solder31.07.2012 soldering and
welding 10 oxide that forms on the surface during heating melting range
10. The parent metal is the metal or alloy to be joined. It is also known as
substrate metal or base metal. Soldering operation is the same for any
substrate metal. The composition of parent metal determines:
Purpose of flux is to remove any oxide coating on the substrate metal
surface when the filler metal is fluid and ready to flow into place. They
protect the alloy surface from oxidation during soldering and dissolve
metallic oxides as they are formed. The resulting solution of oxides or other
extraneous matter in flux constitutes31.07.2012 soldering and welding 11
In Latin the word flux means “to flow” 11.
i. According to their primary purposeTYPE I – surface protectionTYPE II –
reducing agentTYPE III – solvent31.07.2012 soldering and welding 1212.
13. ii. According to pH of the flux Acidic flux – SiO2 Basic flux – CaO, Lime
CaCO3, limestone Neutrals – fluorspar (CaF2,), Borax (NaBO2)31.07.2012
soldering and welding 13
iii. Based on boric or borate compounds TYPE I – protective fluxes by
forming a low- temperature glass TYPE II – reducing fluxes low stability
oxides such as copper oxides TYPE III – fluoride flux31.07.2012 soldering
and welding 1414.
15. Also called as sodium borate, or sodium tetraborate or disodium
tetraborate. They are based on boric or borate compounds such as boric
acid, boric anhydrate and borax. It is usually a white powder consisting of
soft colorless crystals that dissolve easily in water.31.07.2012 soldering
and welding 15
Powder form- contains a mixture of borax, silica flour and finely divided
charcoal. Charcoal is reducing agent and silica holds molten flux in surface
of hot metal. This is usually used for casting operations31.07.2012
soldering and welding 16 Paste form- formed by mixing borax with
petroleum jelly. Required when fluxes are needed in large quantity.
Liquid form- solution of borax/boric acid in water, indicated for soldering of
orthodontic appliances and bridges in which minimum amount of flux is
required. 16. They are available in different forms such as-
Potassium carbonate – 8-10% As the choice of flux is dictated by the type
of alloys to be soldered, the fluoride flux is used with alloys containing base
metals even if a gold/silver is used. Some fluoride containing fluxes involve
toxic fluorides when heated, so inhalation of fumes should be
avoided.31.07.2012 soldering and welding 17 Borax glass – 6-8% Boric
acid – 25-35% Potassium fluoride – 50-60% 17. Composition of fluoride
fluxes is-
18. The chemical compound with the formula KF. After hydrogen fluoride.
KF is the primary source of the fluoride ion for appliances in manufacturing
and in chemistry. It is an alkali metal halide and occurs naturally as the rare
mineral carbobite (potassium -67.30% + fluorine -32.70%).31.07.2012
soldering and welding 18
Silica – 10 parts The ingredients may be fused tighter and then crushed to
a fine powder.31.07.2012 soldering and welding 19 Boric acid – 35 parts
Borax glass- 55 parts 19. A combination of high melting salt is used as
fluxes to combine the good characteristics of each ingredient and create
superior flux. A formula for effective flux is
Flux combi Excess flux remains trapped in the filler metal and weakens
the joint. Too little of flux burns off and tends to be ineffective.
Whatever is the technique used the most important thing to be considered
is the amount of flux to be used. Fused on the surface of the parent metal
strip. Painted on the substrate metal at the junction of pieces to be
joined. 20. The following points are to be considered - ned with metal
oxide forms glass that is difficult to remove complete31.07.2012 soldering
and welding 20
In such case whiting CaCO3 in alcohol and water suspension is
used.31.07.2012 soldering and welding 21 E.g. Graphite in the form of
lead pencil. Disadvantage of graphite is that it can burn off on prolonged
heating at high temperature. 21. Materials used to restrict flow of solder
are known as anti-flux. It is applied on the specific area where the flux
should flow into. It is applied before applying flux or solder.
Resistance to pitting during heating.31.07.2012 soldering and welding 22
Acceptable color to give an inconspicuous joint. Resistance to tarnish
and corrosion. Strength compatible with that of structure being joined.
Ability to wet substrate metal. Sufficient fluidity to freely flow when
melted. Ease of flow at relatively low temperature. 22. Qualities of an
ideal solder:
A rule of thumb is that flow temperature of the filler metal should be 56°
C(100° F) lower than the solidus temperature of the substrate metal. If the
flow temperature of the filler metal is above or close to solidus temperature
if the substrate an alloying can take place. An alloy formed through
diffusion can have properties different from the filler as well as substrate
metal.31.07.2012 soldering and welding 2323.
PRECIOUS METAL SOLDERS AND NON – PRECIOUS METAL
SOLDERS31.07.2012 soldering and welding 24 SOFT SOLDERS AND
HARD SOLDERS 24.
Copper – 7-20 wgt% Small amounts of tin, zinc and phosphorus are added
to modify fusion temperature and flow qualities. They are high fusing with a
fusing temperature range of 750°C - 900°C.31.07.2012 soldering and
welding 25 Silver – 8-30 wgt% Gold – 45-81 wgt% 25. Has good
tarnish and corrosion resistance. Extensively used for crown and bridge
applications. Composition:
With small amounts of cadmium, tin, phosphorus.31.07.2012 soldering
and welding 26 Zinc – 4 – 35% Copper – 15 -30% Silver – 10 – 80%
26. They are used in orthodontic appliances. White solders are usually
required for stainless steel and chromium – based alloys foe color
matching. Their formulation is very similar to gold solders, with the
omission of the gold11. They are low fusing temperature 600 - 750° C.
They are used with stainless steel or other base metal alloys. Their
resistance to tarnish and corrosion is not as good as gold solders. But they
have strength comparable to gold solders. Composition:
Propane – is the best choice. It has the highest heat Acetylene - high
flame temperature, but variation in temperature from one apart of the flame
to the other part is more than 100° C. so, positioning of torch is critical. It is
chemically unstable gas, decomposes to carbon and hydrogen. Carbon
can get incorporated in to nickel and palladium alloy. Natural gas – heat
content is 4 times that of hydrogen. Hydrogen- low heat content, so
heating is slow 27. The most common instrument used as heat source is
gas- air or gas oxygen torch. Fuels used are- & Butane – has similar
flame temperature and heat content. Both are readily available. Uniform in
quality, virtually water free and burn clean.31.07.2012 soldering and
welding 27good flame temperature.
Oxidizing zone ( burned gas) The portion of the flame used for heating the
soldering assembly should be neutral or slightly reducing part. Because
this produces the most efficient burning and the critical heat. Improperly
positioned flame or improperly adjusted torch can lead to oxidation of the
substrate or filler metal and result in poorly soldered joint. If unburned part
of flame is used it may lead to incorporation of the carbon in the filler or the
substrate. To prevent oxide formation flame should not be removed once
its applied to the joint that is to be soldered until the soldering process is
complete.31.07.2012 soldering and welding 28 Reducing zone Partial
combustion zone (oxidizing) Cold mixing zone ( unburned gas) 28. The
flame has been divided into four zones. (picture)
Fig: zones of the flame31.07.2012 soldering and welding 2929.
INFRA- RED SOLDERING31.07.2012 soldering and welding 30 OVEN
(FURNACE) SOLDERING 30.
Advantages of oven (furnace) soldering are: 1. Uniform temperature 2.
Close monitoring is possible 3. Temperature is known 4. Application of
vaccum control oxidation.31.07.2012 soldering and welding 3131. A
furnace with enough wattage to provide heat required to raise the
temperature of the filler metal to its flow point is used.
This is used for high temperature soldering.31.07.2012 soldering and
welding 32 The material to be soldered is placed at the reflectors
secondary focal point at which reflected infra red energy of Tungsten light
source is focused. Quartz – iodine bulb which is mounted at the primary
focal point of a gold pointed elliptical reflector is used. 32. The unit uses
light from a 1000 watt Tungsten.
FREE HAND SOLDERING31.07.2012 soldering and welding 33
INVESTMENT SOLDERING 33.
34. It is used when very accurate alignment of parts to be joined is needed.
The parts are placed on the master cast with a gap of at least 1mm. The
parts are fastened with sticky wax before placing soldering investment. The
investment is preheated to eliminate moisture. Soldering is carried out with
reducing flame at 750 – 870 ° C. The investment is cooled 5 minutes
before quenching. Flux will cool to a glass which is removed by
pickling.31.07.2012 soldering and welding 34
35. Free hand soldering is used for soldering orthodontic appliances.
Orthodontic torches can be placed on a bench so that both hands can be
used to hold the parts in position.31.07.2012 soldering and welding 35
If the gap is narrow, the strength will be limited by the flux inclusions and
porosities by the incomplete flow of the filler metal.31.07.2012 soldering
and welding 36 If the gap is too great the strength will be controlled by the
strength of the filler. 36.
Control of time to ensure adequate flow of the solder Control of proper
temperature. Maintaining the proper position of the parts during
procedure. Preparation and fluxing of the gap surfaces between the
gaps. Assembling the parts to be joined. Cleaning and preparing the
surface to be joined. 37. & complex filling of the solder joint.31.07.2012
soldering and welding 37
38. 31.07.2012 soldering and welding 38
39. Fig: Point contact offers inadequate strength31.07.2012 soldering and
welding 39
40. Fig: Wrapping the wire around gives the best type of joint31.07.2012
soldering and welding 40
41. Fig: Longer areas of joint help increase the joint strength31.07.2012
soldering and welding 41
42. Fig : thin wire is wound around the thick wire first of all Fig : the joint
before and after soldering31.07.2012 soldering and welding 42
The work should be held 3 mm beyond the tip of the blue cone in the
reducing zone of the flame.31.07.2012 soldering and welding 43 Free
hand soldering technique is employed with a needle like non- luminous gas
air flame is used. Fluoride fluxes are used for orthodontic stainless steel
and other base metal alloys. Low fusing silver solders are used with a
soldering temperature range of 620 - 655° C. In orthodontic application
low temperature soldering is used to prevent carbide precipitation and to
prevent excessive softening of the wire. 43.
It is recommened that while soldering the rest of the appliance should be
covered with a damp cloth.31.07.2012 soldering and welding 4444.
As soon as the flux fused solder is added, heating is continued until metal
flows around the joint. The work is then removed from the heat and
quenched in water.31.07.2012 soldering and welding 45 Flux must cover
all the areas to be joined before heat is applied. Soldering should be
observed in a shadow, against a black background, so that the
temperature can be judged by the color of the work. The color should be
“dull red”. 45.
46. When the solder has fused properly and has not been over- heated, a
well – defined boundary forms between the solder and the soldered
parts.31.07.2012 soldering and welding 46
47. A simplest method is to lay the structure on an unexposed piece of
intraoral radiographic film and expose the film with an x-ray beam, using an
accelerating voltage of 90 kV and a current of 10mA for 1second. Another
film should be exposed after rotating the appliance at a 90 degree angle to
the initial orientation. One can clearly see the radiolucent voids at certain
area that is soldered.31.07.2012 soldering and welding 47
Orthodontic appliances31.07.2012 soldering and welding 48 Removable
partial dentures Fixed bridgework Crowns Inlays 48. Soldering in
dentistry is used for various purposes,
Soldering lingual arch or palatal arch.31.07.2012 soldering and welding
49 Attachment of springs to arch wire, the solder must be gold solder with
a melting point below 800° C. Tube can be soldered to the bridge of the
Adam‟s clasp. Wire to wire 49.
A concentration of the composition of silver solder reveal that any material
containing up to about 20% zinc50. & 20- 30% copper with additions in
some cases of low cadmium & The breakdown reaction between the silver
soldered stainless steel joints is an electro- chemical process with no initial
evidence of gross macroscopic corrosion.31.07.2012 soldering and
welding 50 The silver solders react readily to chemical attack. Weak
corrosion prone micro structural phases composed mainly of copper and
zinc has been shown to occur within the solder itself. It is known that
corrosion occurs when an electrolyte comes into contact with the soldered
joint. tin content remain inactive to physiologic solutions.
Laboratory studies on corrosion indicate that some of the precious metal
substitutes may corrode while in service.1831.07.2012 soldering and
welding 51 After a time, many silver – soldered joints exhibit a change in
appearance such as darkening to resemble a tarnished – corroded surface.
51.
Creep, corrosion, crack stress corrosion, fatigue and corrosion erosion.
Are other failures encountered31.07.2012 soldering and welding 52
Besides porosities and brittleness from oxides, gases or foreign matter
resulting from the soldering procedures are factors for increasing the
incidence of failure of soldered joints. Over heating of the solder can lead
to pitted joint of low strength. Poor flow of solder Improper fluxing
Failure to clean the parts to be joined. 52. Soldering failures are seen due
to variety of reasons-
It is believed that possible allergies to non – toxic metals released from
dental alloy may be formed.31.07.2012 soldering and welding 53 Even in
case of such non – toxic elements as zinc, copper, tin and silver, the
introduction of higher concentrations of these elements via soluble
corrosion products can alter their behavior. Causing biological imbalances
and further biologic consequences. For cadmium containing solders,
because of cadmium toxicity, a continual appraisal must e made regarding
cadmium‟s fate biologically. The release of cadmium from dental alloys has
been the subject of several reports. Besides the deterioration of the
soldered joints, concern must also be given to the released – corroded
agents. 53.
Metabolic and bacteriologic participation can also occur in response to
corroded metallic agents. Furthermore penetration54. & Corrosion
products containing oxides, hydroxides and chlorides of zinc, copper and
sodium can be easily identified. Silver is also attacked. Besides the oral
physiologic fluids, additional chemical agents contained in mouth rinses
Laboratory tests indicate that silver – soldered stainless steel joints
degrade in a saliva substitute and the prepared solutions. staining of hard
dental tissues due to the release of metallic ions from solder or any
biomaterial are definitely to be avoided. & Many commercial mouth rinses
contain active chloridesin toothpaste for oral antiseptics, need careful
appraisal for resistance to the degradation and corrosion of dental
materials. & additional components. The chlorides are known for their
depassivating tendencies of metallic materials.31.07.2012 soldering and
welding 54
Dermatitis due to contact with nickel was first reported at the end of
nineteenth century in 1925. Nickel allergy is rarely written down when filling
out patient history prior to seeing the dentist, even though so many dentist
items do contain nickel. Nickel has been used in dentistry for more then
eighty years in both restorative work (fillings, crowns, bridges, partial
dentures) and Orthodontic appliances (wires, bands,
brackets ,etc).31.07.2012 soldering and welding 5555.
Nickel alloys have the special problem of being a common allergen, with
as many as 6% of the female population56. & 20% of the male
population being sensitive to them.17 (CRAIG, O „BREIN,POWERS,
Dental material properties & Patho - physiology of nickel allergy: it arises
as a result of two essential,stages: an induction phase, which primes and
senitize the immune system for an allergen, and the elicitation phase, in
which this response is triggered. As such it is a type IV delayed
hypersensitivity re action involving a cell – mediated response.31.07.2012
soldering and welding 56manipulation, 6th edition, chapter 11 gold and
non- precious alloys, page 321)
Se Angular chielitis Soreness at the side of tongue Burning sensation
Numbness Loss of taste or metallic taste Perioral rash Stomatitis
from mild to severe erythema 57. Intraoral symptoms Flare-up of allergic
dermatitis31.07.2012 soldering and welding 57 Widespread eczema
Generalized urticaria vere gingivitis in the absence of plaque Extraoral
symptoms
58. 31.07.2012 soldering and welding 58
Antiperspirants31.07.2012 soldering and welding 59 Avoidance of nickel
Preventive strategies Diagnosis of nickel allergy A dermatologist should
confirm the diagnosis by patch testing using 5 per cent nickel sulfate in
petroleum jelly. Other tests done are Dimethylglyoxime spot test, Finger
test. 59.
Binding agents and barrier creams ethylene diamine tetra-acetic acid
(ETDA)31.07.2012 soldering and welding 60 Steroids In adults
prednisone in a single morning dose of 40 to 60 mg can be prescribed and
tapered over 2 to 3 weeks, as symptoms resolve. Oral doxepin (10–25
mg at night in adults) Therapeutic strategies 60.
Unitek Flux31.07.2012 soldering and welding 61 Formula No. 6 Silver
Solder, Tru- Chrome Solder And Flux, 61.
Pioneer work in this field was done was Friel and Mc Keag31.07.2012
soldering and welding 6262. Welding is the fusion of two pieces of similar
metal under pressure without the introduction of third material. The metal
must be softened by heat as well as compressed to achieve this. Or It may
also be defined as process of fusing two or more metal parts through the
application of heat, pressure or both without using filler metal to produce a
localized union between two parts.
63. Welds are made by passing an electric current through the pieces to be
joined which are pressed together tightly. The resistance offered by
stainless steel to an electric current of high ampereage generates enough
heat to soften it.31.07.2012 soldering and welding 63
Timing The heat generated is calculated using the formula H ∞ I2 RT H =
heat in joules I = current in amperes R = resistance in ohms T = duration of
current in seconds fig : showing circuit diagram of welder31.07.2012
soldering and welding 64 Pressure mechanism Copper electrodes
Electric transformer 64.
HOT WELDING – uses heat of sufficient intensity to melt the metals being
joined. The heat source is usually an oxyacetylene flame or high amperage
electricity.31.07.2012 soldering and welding 65 COLD WELDING – is
done by hammering or pressure. An example is cold welding of gold foil
filling. 65.
ARCH WELDING31.07.2012 soldering and welding 66 OXY-
ACETYLENE (OA) LASER WELDING PRESSURE WELDING SPOT
WELDING 66.
67. Typical values for the pulse are 2 to 6 volts for 1/25 – 1/50th of a
second at 250 to 750 amperes. Fig : a spot welder.31.07.2012 soldering
and welding 67
It is used more in the construction of fixed appliances than removable
appliances.31.07.2012 soldering and welding 68 Attaching springs to a
rigid bow wire, or to bands. Securing attachments to the bands
Stainless steel strip for making bands. 68. Spot welding may be used as
method of fusing-
69. Gold foil, mat, or powdered gold) restorations are pressure welded by
hand or mechanical foil condensers31.07.2012 soldering and welding 69
70. A laser generates a coherent, high intensity impulse of light that can b
focused. By selecting the duration and the intensity of impulse metals can
be melted in small regions without extensive micro structural damage to
the metal. Owing to the expansion from the local high temperature and the
change of state, the two liquid surfaces contact and form a weld on
solidification31.07.2012 soldering and welding 70
71. oxy-acetylene flame burns at 6000 YF, and is the only gas flame that is
hot enough to melt all commercial metals. Oxy-acetylene welding is simple
in concept - two pieces of metal are brought together, and the touching
edges are melted by the flame with or without the addition of filler
rod.31.07.2012 soldering and welding 71
OA welds have large heat affected zones (areas around the weld line that
have had their mechanical properties adversely affected by the welding
process)31.07.2012 soldering and welding 72 OA weld lines are much
rougher in appearance than other kinds of welds, and require more
finishing if neatness is required. OA equipment can also be used to
"flame-cut" large pieces of material. Disadvantages of Oxy-Acetylene
Welding : The equipment is more portable than most other types of
welding rigs (e.g. TIG welding) The equipment is cheaper than most
other types of welding rigs (e.g. TIG welding) Its easy to learn. 72.
Advantages of Oxy-Acetylene Welding :
73. The fusing of two or more pieces of metal together by using the heat
produced from an electric arc welding machine. The arc is like a flame of
intense heat that is generated as the electrical current passes through a
highly resistant air gap.31.07.2012 soldering and welding 73
Wires should not be parallel to each other31.07.2012 soldering and
welding 7474.
Instead the should be placed perpendicular to each other in a
groove.31.07.2012 soldering and welding 7575.
The mechanical pressure applied at the welding head. The improper
application of these variable may result in under welding or over
welding.31.07.2012 soldering and welding 76 The time during which the
current is allowed to flow. The current following through the circuit 76.
Welding of stainless steel depends upon the proper use of the following
three variables-
This occurs when chromium is precipitated at the grain boundary of each
crystal. This process is known as weld decay31.07.2012 soldering and
welding 77 Joint is more prone to corrosion Yields as weak joint as
under welding Pressure applied is insufficient for approximation. OVER
WELDING Insufficient amount of time for which the current is passed.
Insufficient time. 77. UNDER WELDING
78. “A satisfactorily welded joint is the one which is strong, has not
undergone oxidation(blackening), and has not been over compressed
during fusion”31.07.2012 soldering and welding 78
79. Strength of the welded joint In engineering applications, spot and
pressure welds have strengths comparable to other forms of joining metals
such as soldering or arc welding. Laser welds are comparable to soldered
joints. Corrosion resistance of the welded joint welds in general are more
susceptible to corrosion than the surrounding metal. Spot welding in
dentistry has been confined to temporary appliances, where the results
have been satisfactory.31.07.2012 soldering and welding 79
The surface of The welding surfaces should be free of all the debris and
oxides. 80. If sparking is observed, localized over welding has occurred.
If black areas are seen where the electrodes contacted the metal, over
welding has occurred31.07.2012 soldering and welding 80 If narrow
electrode is used to weld a bracket (thick) to a band(thin), localized over
welding will occur in the thin material and under welding will occur in the
thick material. Select the proper electrode of the proper thickness or
shape of the material to be welded. A broad electrode should be used for
thin material and a narrow electrode should be used for thick material. This
will allow sufficient heat to reach the weld area but not allow oxidation of
the material. Adjust the welder to the setting recommended by the
manufacturer. each electrode should be smooth, flat and perpendicular to
its long axis. Sparking and localized over welding would result if the contact
is not uniform.
Exposure to infrared radiation (IR), produced by the electric arc and other
flame cutting equipment may heat the skin surface and the tissues
immediately below the surface.31.07.2012 soldering and welding 81
Ultraviolet radiation (UV) is generated by the electric arc in the welding
process. Skin exposure to UV can result in severe burns, in many cases
without prior warning. Ozone is a highly active form of oxygen and can
cause great irritation to all mucous membranes. Symptoms of ozone
exposure include headache, chest pain, and dryness of the upper
respiratory tract. 81.
Use single electric impulse31.07.2012 soldering and welding 82 Set the
voltage according to the operator instructions Use 1540 Newton of
pressure Place the thinner wire in the groove of lower electrode Weld
together the wires of same material Mount the electrodes correctly in the
welder and adjust with parallel precision to eliminate gaps. 82.
Multi Purpose Orthodontic Welderunitek, Monrovia, California
8021731.07.2012 soldering and welding 83 506- A DIAL- A – WELDrocky
mountain/denver,Colorado 80217 83.
The American National Standards Institute (ANSI) currently is considering
a proposal to call all joining operations in dentistry as brazing rather than
soldering. Thus brazing may be the predominant term in the
future.31.07.2012 soldering and welding 84 Brazing is defined as joining
of metals by the fusion of filler metal between them, at a temperature below
the solidus temperature of metals being joined and above 450° C. It‟s a
term used industrially. Soldering operations at and above 450° C is
generally termed brazing. Most dental soldering procedures are actually
brazing but the terms are used interchangeably in dentistry. 84.
85. Electropolishing, also known as electrochemical polishing or electrolytic
polishing , is an electrochemical process that removes material from a
metallic workpiece PURPOSE OF ELECTROPLOSHING Electropolishing
improves corrosion resistance by reducing surface area, eliminating
occlusions, reducing free iron, and producing a passivating film of a
corrosion resistant chromium oxide.31.07.2012 soldering and welding 85
86. Orthophosphoric acid 10-75%by vol Sulfuric acid 25%by vol Density at
room temperature 1.74-1.82 g/cm3 Temperature 50-85°c Voltage 8-20 V
(power supply 20 Volt Exposure time 0.5-30 min31.07.2012 soldering and
welding 86
87. The electropolishing process removes the nickel and the iron
preferentially, leaving a surface rich in chromium. This phenomenon
imparts the important property of “passivation” to electropolished
surfaces.31.07.2012 soldering and welding 87
88. welding soldering brazing1 No third metal is introduced Third metal is
introduced Third metal is introduced2 Temperature required can
Temperature required is upto 450° Temperature required is above range
up to 3800°C C 450° C3 Work pieces are heated up to They are not
heated upto melting Work pieces are heated but their melting points point
below their melting point4 Mechanical properties may Change in
mechanical properties of Change in mechanical change of the metal due to
the parent metal is negligible properties of the parent metal such high
temperatures that is negligible are used.5 High skill level is required Cost
and skill involvement is low Both cost and skill level involvement is in
between the two6 No preheating is required Preheating is required if good
Preheating is desirable. quality joints are desired 31.07.2012 soldering and
welding 88
Soldering is still useful and needed procedure for joining of metallic parts.
The choice metal joining procedure is in many instants up to the discretion
of the Orthodontist and the technician.31.07.2012 soldering and welding
89 The choice of soldering materials has extreme importance in
determining the properties of the soldered joints. In Orthodontics silver
solders are popular because of their low fusion temperature and easy
handling characteristics. It is also rationalized that both removable and
permanent Orthodontic appliances are not meant to stay for life, therefore
solders with properties inferior to high fusing solders can be tolerated. 89.
Welding is the most commonly used procedure by an Orthodontist. It is so
common that it is almost a reflex.31.07.2012 soldering and welding 90 In
the final analysis, however the combination of techniques which offer
optimum mechanical, physical and chemical properties or offer desired
properties which are most favorable must be selected. Both soldering
and welding can cause a deterioration in properties if the wire is
overheated or under heated. 90.
91. “ Nothing is good or bad in the world, our perception makes it so, what
seems like congestion in the train becomes atmosphere in the night
club”31.07.2012 soldering and welding 91
2. KENNETH J. ANUSAVICE 1. B.W.DARVELL, Materials Science For
Dentistry, Chapter 22 soldering and welding, 9th edition, page 486. 92.
REFERENCES & 3. STEPHEN T. RASMUSSEN, O‟BREINPAUL
CASCONE, Chapter 19 Dental Casting And Soldering Alloys, Phillips‟
Science Of Dental Materials 11th Edition, page 608,612,613,614,615,616
& RYGE, an outline of dental materials & 8. C. PHILIP ADAMS 7.
SRIDHAR PREMKUMAR, Orthodontics Exam Preparatory Manual For
Undergraduates, Chapter 17 Materials Used In Orthodontics, 2nd edition,
page 314, 315. 6. S.I. BHALAJHI, Orthodontics the Art and Science,
chapter 39 lab procedures, page 474.475476 5. RICHARD VAN NOORT,
Introduction To Dental Materials, Chapter Stainless Steel, 3rd edition, page
295, 296 4. CRAIG‟S DENTAL MATERIALS, chapter 15noble dental
alloys and solders, page 378,379 their selection, chapter 26 soldering and
welding, page 320,326,328 & 13. PHILLIP‟S, Skinner‟s Science Of Dental
Materials, Chapter 33 Gold Alloy Solders, Soldering Procedur 12.
HARCOURT, ASIA, SAUNDERS, PILILLIP‟S, Science Of Dental Materials
10th Edition, Page, 628,629 11.LYMAN 3RD edition, Metals Handbook.
Cleveland : American Society For Metals. 1948 10. ROBERT E BINDER,
DMD, JCO VOL 1976 Feb, Orthodontic Welding 9. TC WHITE, J H
GARDINER, B C LEIGHTON, Orthodontics For Dental Students, 3rd
Edition, Chapter Appliance Therapy In General, page 182,183 W. JOHN
S. KERR, the design construction and use of removable orthodontic
appliances, appendix c, welding and soldering for orthodontic appliance
construction, page 173,175 14. ROBERT G. CRAIG, JOHN M. POWERS,
JON C. WATAHA, Dental materials and propertiese, Page 563 &
manipulation, 8th edition, chapter 11, dental casting alloys & 15. ROBERT
G. CRIG, Restorative Dental Materials, Chapter Castsolders, page 413 &
17.CRAIG, O „BREIN,POWERS, Dental material properties 16.
PHILLIP‟S, Elements Of Dental Materials, Chapter 25, Miscellaneous
Materials, 3rd edition, page 341 Wrought Alloys 11th edition, page 447 &
18. WRIGHT PSG, Dental Materials In Clinical Dentistry, Post- Graduate
Dental Handbook, Chapter 9, Non – Precious Ceramic Metal Alloys,
volume 11, page 20731.07.2012 soldering and welding 92manipulation,
6th edition, chapter 11 gold and non- precious alloys, page 321
31.07.2012 soldering and welding 93 32. Rietschel RL (1997).
"Mechanisms in irritant contact dermatitis". Clin. Dermatol. 15 (4):557–9.
31.DermNet dermatitis/contact-allergy 30.. www.skinchannel.com.
Retrieved 31 March 2011. 29.Bourke J, Coulson I, English J (2001).
"Guidelines for care of contact dermatitis". Br. J. Dermatol. 145 (6): 877–
85. doi:10.1046/j.1365-2133.2001.04499.x. PMID 11899139. 28. Kimber
I, Basketter DA, Gerberick GF, Dearman RJ (2002). "Allergic contact
dermatitis". Int. Immunopharmacol. 2 (2–3): 201–11. doi:10.1016/S1567-
5769(01)00173-4.PMID 11811925. 27.Morris-Jones R, Robertson SJ,
Ross JS, White IR, McFadden JP, Rycroft RJ (2002)."Dermatitis caused by
physical irritants". Br. J. Dermatol. 147 (2): 270–5. doi:10.1046/j.1365-
2133.2002.04852.x. PMID 12174098. 26.Irritant Contact Dermatitis, at
DermNetNZ, http://www.dermnetnz.org/dermatitis/contact- irritant.html
25.Matsumoto, Kazuyuki; Fujimoto, Masao; Ito, Kazuo; Tanaka, Hitoshi;
Hirono, Iwao (1990). "Comparison of the effects of bilobol and 12-O-
tetradecanoylphorbol-13-acetate on skin, and test of tumor promoting
potential of bilobol in CD-1 mice". The Journal of Toxicological Sciences 15
(1): 39– 46. doi:10.2131/jts.15.39. PMID 2110595. 24.Menz, J; Rossi,
ER; Taylor, WC; Wall, L (1986). "Contact dermatitis from Grevillea Robyn
Gordon". Contact dermatitis 15 (3): 126–31. PMID 2946534. 23
C.Michael Hogan (2008) Western poison-oak: Toxicodendron
diversilobum, GlobalTwitcher, ed. Nicklas Stromberg [1] 22. "DermNet
NZ: Contact Dermatitis". Retrieved 2006-08-14. 21. European Society of
Contact Dermatitis. "What is contact dermatitis". 20. G.F. Vander Voort,
ed., "Chemical and Electrolytic Polishing," ASM Handbook, Vol. 9:
Metallography and Microstructures, ASM International, 2004, p 281-293,
ISBN 978-0-87170-706-2 93.
