soldering and welding in orthodontics

soldering and welding 1

A VERY GOOD MORNING

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DEPARTMENT OF ORTHODONTICS AND

DENTOFACIAL ORTHOPAEDICS

TOPIC-SOLDERING AND WELDING

UNDER THE GUIDANCE OF –DR. MOHAMMAD MUSHTAQHEAD OF THE DEPARTMENT

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“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”.

PARACELSUS

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“Necessity is the mother of all inventions”

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.

Nuts and bolts Adhesives

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5

METAL JOINING OPERATIONS

Are divided into three categories

• SOLDERING

• BRAZING

• WELDING

soldering and welding31.07.2012


SOLDERINGHISTORY

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.

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.

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.

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The appliance had a metal framework. The attachment of axillaries to bring about the different type of tooth movements required soldering of these parts.

Welding in orthodontics became popular because of the short time required, the ease of welding and the absence of elaborate equipments

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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.

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.

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COMPONENTS OF SOLDERED JOINTS

The soldered joint consists of the following components:

A). Parent metalB). Fluxes and anti- fluxesC). Solder or filler metal

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PARENT METAL

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: melting range oxide that forms on the surface during

heating wetablitly of the substrate by the molten

solder

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FLUX

In Latin the word 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

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CLASSIFICATION OF FLUXES

i. According to their primary purposeTYPE I – surface protectionTYPE II – reducing agentTYPE III – solvent

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ii. According to pH of the fluxAcidic flux – SiO2

Basic flux – CaO, Lime CaCO3, limestone

Neutrals – fluorspar (CaF2,), Borax (NaBO2)

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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 flux

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BORAX FLUXES

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.

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They are available in different forms such as- 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, 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 operations

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FLUORIDE FLUXES

Composition of fluoride fluxes is- 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 is used. Some fluoride containing fluxes involve toxic fluorides when heated, so inhalation of fumes should be avoided.

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POTASSIUM FLOURIDE

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%).

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SUPERFLUX

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 Borax glass- 55 parts Boric acid – 35 parts Silica – 10 parts

The ingredients may be fused tighter and then crushed to a fine powder.

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APPLICATION OF FLUX:

The following points are to be considered - Painted on the substrate metal at the junction of pieces

to be joined. Fused on the surface of the parent metal strip. Whatever is the technique used the most important

thing to be considered is the amount of flux to be used. Too little of flux burns off and tends to be ineffective. Excess flux remains trapped in the filler metal and

weakens the joint. Flux combined with metal oxide forms glass that is

difficult to remove complete

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ANTI- FLUX

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.

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 case whiting CaCO3 in alcohol and water suspension is used.

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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 structure

being joined. Resistance to tarnish and corrosion. Acceptable color to give an inconspicuous

joint. Resistance to pitting during heating.

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FLOW TEMPERATURE

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.

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CLASSIFICATION OF SOLDERS

SOFT SOLDERS AND HARD SOLDERS

PRECIOUS METAL SOLDERS AND NON – PRECIOUS METAL SOLDERS

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GOLD SOLDERS

Has good tarnish and corrosion resistance.

Extensively used for crown and bridge applications. Composition: Gold – 45-81 wgt% Silver – 8-30 wgt% 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.

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SILVER SOLDERS

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: Silver – 10 – 80% Copper – 15 -30% Zinc – 4 – 35% With small amounts of cadmium, tin, phosphorus.

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HEAT SOURCE

The most common instrument used as heat source is gas- air or gas oxygen torch.

Fuels used are- Hydrogen- low heat content, so heating is slow Natural gas – heat content is 4 times that of hydrogen. 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.

Propane – is the best choice. It has the highest heat & good flame temperature.

Butane – has similar flame temperature and heat content. Both are readily available. Uniform in quality, virtually water free and burn clean.

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FLAME

The flame has been divided into four zones. (picture) Cold mixing zone ( unburned gas) Partial combustion zone (oxidizing) Reducing zone 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.

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Fig: zones of the flame

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METHODS OF SOLDERING

OVEN (FURNACE) SOLDERING

INFRA- RED SOLDERING

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OVEN (FURNACE) SOLDERING

A furnace with enough wattage to provide heat required to raise the temperature of the filler metal to its flow point is used.

Advantages of oven (furnace) soldering are:1. Uniform temperature2. Close monitoring is possible3. Temperature is known4. Application of vaccum control oxidation.

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INFRA - RED SOLDERING

The unit uses light from a 1000 watt Tungsten.

Quartz – iodine bulb which is mounted at the primary focal point of a gold pointed elliptical reflector is used.

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.

This is used for high temperature soldering.

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TECHNIQUES OF SOLDERING

INVESTMENT SOLDERING

FREE HAND SOLDERING

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INVESTMENT SOLDERING

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.

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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.

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SOLDER JOINT 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 and porosities by the incomplete flow of the filler metal.

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STEPS IN SOLDERING

Cleaning and preparing the surface 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 &

complex filling of the solder joint.

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CORRECT MANNER TO HOLD THE SOLDERING TORCH

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SELECTION OF A SOLDER JOINT

Fig: Point contact offers inadequate strength

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Fig: Wrapping the wire around gives the best type of joint

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Fig: Longer areas of joint help increase the joint strength

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SOLDERING OF THINNER WIRE TO THICKER WIRE

Fig : thin wire is wound around the thick wire first of all

Fig : the joint before and after soldering31.07.2012


ORTHODONTIC SOLDERING

In orthodontic application 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.

The work should be held 3 mm beyond the tip of the blue cone in the reducing zone of the flame.

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It is recommened that while soldering the rest of the appliance should be covered with a damp cloth.

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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”.

Flux must cover all the areas to be joined before heat is applied.

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


MICROSTRUCTURE OF SOLDERED JOINTS

When the solder has fused properly and has

not been overheated, a well – defined boundary forms between the solder and the soldered parts.

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RADIOGRAPHIC ANALYSIS OF SOLDERED JOINT QUALITY

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


APPLICATION OF SOLDERING IN DENTISTRY

Soldering in dentistry is used for various purposes,

Inlays Crowns Fixed bridgework Removable partial dentures Orthodontic appliances

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SOLDERING APPLICATIONS IN ORTHODONTICS

Wire to wire Tube can be soldered to the bridge of the

Adam’s clasp. Attachment of springs to arch wire, the

solder must be gold solder with a melting point below 800° C.

Soldering lingual arch or palatal arch.

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CORROSION OF SOLDERED JOINTS

A concentration of the composition of silver solder reveal that any material containing up to about 20% zinc & 20- 30% copper with additions in some cases of low cadmium & tin content 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 the soldered joint.

The silver solders react readily to chemical attack. The breakdown reaction between the silver soldered

stainless steel joints is an electrochemical process with no initial evidence of gross macroscopic corrosion.

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After a time, many silver – soldered joints exhibit a change in appearance such as darkening to resemble a tarnished – corroded surface.

Laboratory studies on corrosion indicate that some of the precious metal substitutes may corrode while in service.18

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SOLDERING FAILURES

Soldering failures are seen due to variety of reasons-

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 are factors for increasing the incidence of failure of soldered joints.

Creep, corrosion, crack stress corrosion, fatigue and corrosion erosion. Are other failures encountered

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BIOCOMPATIBILTY

Besides the deterioration of the soldered joints, concern must also be given to the released – corroded agents.

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.

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.

It is believed that possible allergies to non – toxic metals released from dental alloy may be formed.

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Metabolic and bacteriologic participation can also occur in response to corroded metallic agents. Furthermore penetration & staining of hard dental tissues due to the release of metallic ions from solder or any biomaterial are definitely to be avoided.

Laboratory tests indicate that silver – soldered stainless steel joints degrade in a saliva substitute and the prepared solutions.

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 & in toothpaste for oral antiseptics, need careful appraisal for resistance to the degradation and corrosion of dental materials.

Many commercial mouth rinses contain active chlorides & additional components. The chlorides are known for their depassivating tendencies of metallic materials.

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Nickel as an allergen

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).

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Nickel alloys have the special problem of being a common allergen, with as many as 6% of the female population & 20% of the male population being sensitive to them.17 (CRAIG, O ‘BREIN,POWERS, Dental material properties & manipulation, 6th edition, chapter 11 gold and non- precious alloys, page 321)

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.

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Signs & symptoms of the nickel allergy

Intraoral symptoms Stomatitis from mild to severe erythema Perioral rash Loss of taste or metallic taste Numbness Burning sensation Soreness at the side of tongue Angular chielitis Severe gingivitis in the absence of plaque Extraoral symptoms Generalized urticaria Widespread eczema Flare-up of allergic dermatitis

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Pictures showing nickel allergy

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Treatment approach to patients with nickel allergic contact dermatitis

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.

Preventive strategies Avoidance of nickel Antiperspirants

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Therapeutic strategies Oral doxepin (10–25 mg at night in

adults) 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.

Binding agents and barrier creams ethylene diamine tetra-acetic acid (ETDA)

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COMMERCIAL MATERIALS

Tru- Chrome Solder And Flux,

Formula No. 6 Silver Solder,

Unitek Flux

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WELDING

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.

Pioneer work in this field was done was Friel and Mc Keag

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PRINCIPLE OF WELDING

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.

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PARTS OF A WELDER

Electric transformer Copper electrodes Pressure mechanism TimingThe heat generated is calculated using the formula H ∞ I2 RT H = heat in joulesI = current in amperesR = resistance in ohmsT = duration of current in seconds fig : showing circuit diagram of

welder

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COLD WELDING – is done by hammering or pressure. An example is cold welding of 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.

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TYPES OF WELDING

SPOT WELDING

PRESSURE WELDING

LASER WELDING

OXY-ACETYLENE (OA)

ARCH WELDING

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SPOT WELDING

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


Applications of spot welding in Orthodontics

Spot welding may be used as method of fusing-

Stainless steel strip for making bands. Securing attachments to the bands Attaching springs to a rigid bow wire, or to

bands. It is used more in the construction of fixed

appliances than removable appliances.

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PRESSURE WELDING

Gold foil, mat, or powdered gold) restorations are pressure welded by hand or mechanical foil condensers

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LASER WELDING

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 solidification

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OXY-ACETYLENE (OA)

oxy-acetylene flame burns at 6000 F, ͦ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.

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Advantages of Oxy-Acetylene Welding : It's easy to learn. The equipment is cheaper than most other types of welding rigs

(e.g. TIG welding) The equipment is more portable than most other types of

welding rigs (e.g. TIG welding) OA equipment can also be used to "flame-cut" large pieces of

material.

Disadvantages of Oxy-Acetylene Welding : OA weld lines are much rougher in appearance than other kinds

of welds, and require more finishing if neatness is required. OA welds have large heat affected zones (areas around the

weld line that have had their mechanical properties adversely affected by the welding process)

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ARCH WELDING

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.

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WELDING ORTHODONTIC MATERIAL

Wires should not be parallel to each other

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Instead the should be placed perpendicular to each other in a groove.

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VARIABLES AND THEIR APPLICATIONS

Welding of stainless steel depends upon the proper use of the following three variables-

The current following through the circuit The time during which the current is allowed

to flow. The mechanical pressure applied at the

welding head. The improper application of these variable may

result in under welding or over welding.

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UNDER WELDING Insufficient time. Insufficient amount of time for which the current

is passed. Pressure applied is insufficient for approximation.

OVER WELDING Yields as weak joint as under welding Joint is more prone to corrosion This occurs when chromium is precipitated at the

grain boundary of each crystal. This process is known as weld decay

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“A satisfactorily welded joint is the one which is strong, has not undergone oxidation(blackening), and has not been over compressed during fusion”

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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.

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SOME IMPORTANT CONSIDERTAIONS

The welding surfaces should be free of all the debris and oxides. The surface of 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.

Adjust the welder to the setting recommended by the manufacturer.

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.

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.

If sparking is observed, localized over welding has occurred. If black areas are seen where the electrodes contacted the metal, over welding has occurred

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BIOCOMPATIBILTY

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.

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.

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.

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POINTS TO BE KEPT IN VIEW FOR A SUCCESSFUL WELDING

Mount the electrodes correctly in the welder and adjust with parallel precision to eliminate gaps.

Weld together the wires of same material Place the thinner wire in the groove of

lower electrode Use 1540 Newton of pressure Set the voltage according to the operator

instructions Use single electric impulse

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COMMERCIAL SPOT WELDERS

506- A DIAL- A – WELDrocky mountain/denver,Colorado

80217

Multi Purpose Orthodontic Welderunitek,

Monrovia, California 80217

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BRAZING

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.

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.

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.

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Electrolytic polishing

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.

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http://en.wikipedia.org/wiki/Electrochemical


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 min

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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.

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COMPARSION welding soldering brazing

1 No third metal is introduced Third metal is introduced Third metal is introduced

2 Temperature required can range up to 3800°C

Temperature required is upto 450° C

Temperature required is above 450° C

3 Work pieces are heated up to their melting points

They are not heated upto melting point

Work pieces are heated but below their melting point

4 Mechanical properties may change of the metal due to such high temperatures that are used.

Change in mechanical properties of the parent metal is negligible

Change in mechanical properties of the parent metal is negligible

5 High skill level is required Cost and skill involvement is low Both cost and skill level involvement is in between the two

6 No preheating is required Preheating is required if good quality joints are desired

Preheating is desirable.

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CONCLUSION

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.

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.

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Both soldering and welding can cause a deterioration in properties if the wire is overheated or under heated.

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.

Welding is the most commonly used procedure by an Orthodontist. It is so common that it is almost a reflex.

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“ 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”

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REFERENCES

1. B.W.DARVELL, Materials Science For Dentistry, Chapter 22 soldering and welding, 9 th edition, page 486. 2. KENNETH J. ANUSAVICE & PAUL CASCONE, Chapter 19 Dental Casting And Soldering Alloys, Phillips’ Science Of Dental

Materials 11th Edition, page 608,612,613,614,615,616 3. STEPHEN T. RASMUSSEN, O’BREIN & RYGE, an outline of dental materials & their selection, chapter 26 soldering and

welding, page 320,326,328 4. CRAIG’S DENTAL MATERIALS, chapter 15noble dental alloys and solders, page 378,379 5. RICHARD VAN NOORT, Introduction To Dental Materials, Chapter Stainless Steel, 3 rd edition, page 295, 296 6. S.I. BHALAJHI, Orthodontics the Art and Science, chapter 39 lab procedures, page 474.475476 7. SRIDHAR PREMKUMAR, Orthodontics Exam Preparatory Manual For Undergraduates, Chapter 17 Materials Used In

Orthodontics, 2nd edition, page 314, 315. 8. C. PHILIP ADAMS & 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 9. TC WHITE, J H GARDINER, B C LEIGHTON, Orthodontics For Dental Students, 3 rd Edition, Chapter Appliance Therapy In

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http://dx.doi.org/10.1046/j.1365-2133.2002.04852.x



http://linkinghub.elsevier.com/retrieve/pii/S1567-5769(01)00173-4


http://dx.doi.org/10.1016/S1567-5769(01)00173-4



http://www.blackwell-synergy.com/openurl?genre=article&sid=nlm:pubmed&issn=0007-0963&date=2001&volume=145&issue=6&spage=877


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Thank you….

Dr. Sneh Kalgotra 1st year post graduate student Deptt. Of Orthodontics and Dentofacial

Orthopaedics, Govt. Dental College & Hospital,

Srinagar

31.07.2012

soldering and welding in orthodontics

Education

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