Soldering Process and Techniques
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Questions and Answers

What are the components involved in the soldering process?

  • Solder alloy, Flux and Antiflux, Heat source
  • Metals to be joined, Flux and Antiflux, Heat source
  • Metals to be joined, Solder alloy, Heat source
  • Metals to be joined, Solder alloy, Flux and Antiflux, Heat source (correct)

    • What determines the composition of the 'parent metals' in soldering?

  • Their melting range (correct)
  • Their color
  • Their strength properties
  • Their corrosion resistance

    • What is a desirable quality of an ideal solder alloy?

  • Poor resistance to tarnish and corrosion
  • Low strength properties
  • Ability to wet the parent metal with sufficient flow (correct)
  • High melting point

    • What is the lead-tin eutectic alloy commonly known as?

    <p>Plumber Solder</p> Signup and view all the answers

    What are hard solders known for?

    <p>Higher melting temperature, high strength, and hardness</p> Signup and view all the answers

    What is the purpose of using low fusing solder in dentistry?

    <p>To avoid carbide precipitation and structural changes</p> Signup and view all the answers

    What is the role of flux in soldering?

    <p>To facilitate the flow of solder</p> Signup and view all the answers

    What is the role of boric acid flux?

    <p>Used with gold alloys to permit the solder alloy to wet and spread over the metal surface</p> Signup and view all the answers

    What happens to the setting expansion of gypsum products when the water-to-powder ratio is increased?

    <p>It increases</p> Signup and view all the answers

    What is the effect of allowing setting gypsum to set under water?

    <p>It increases the setting expansion by more than double</p> Signup and view all the answers

    What is the purpose of zinc in gold alloys?

    <p>To improve castability and fluidity of the alloy</p> Signup and view all the answers

    What is the primary factor controlling hygroscopic expansion in gypsum products?

    <p>Time of immersion in water</p> Signup and view all the answers

    What is the role of indium and tin in gold alloys?

    <p>To produce oxides that help bonding with porcelain</p> Signup and view all the answers

    What is a characteristic of gypsum products in terms of strength?

    <p>They are brittle materials with strength that increases rapidly as the material hardens</p> Signup and view all the answers

    What is the effect of accelerators on the rate of solubility of hemihydrate?

    <p>They increase the rate of solubility</p> Signup and view all the answers

    What is the classification of gold alloys based on?

    <p>Carat and Fineness</p> Signup and view all the answers

    What is the difference between carat and fineness in gold alloys?

    <p>Carat refers to the parts of pure gold in 24 parts of alloy, while fineness refers to the parts of pure gold per thousand parts of alloy</p> Signup and view all the answers

    What is the most commonly used accelerator in gypsum products?

    <p>Potassium sulphate</p> Signup and view all the answers

    Why is the use of carat or fineness classification not suitable in dentistry?

    <p>Because it does not determine the other metals which may have a pronounced effect over the properties</p> Signup and view all the answers

    What is the effect of a high water/powder ratio on the setting time of gypsum products?

    <p>It retards the setting time</p> Signup and view all the answers

    What is the effect of temperature on the setting time of gypsum products at 20°C-50°C?

    <p>It accelerates the setting time</p> Signup and view all the answers

    What is the gold content in economy gold alloys?

    <p>42-58%</p> Signup and view all the answers

    What is the critical ratio between palladium and silver-copper in dental gold alloys?

    <p>1% palladium for every 3% silver</p> Signup and view all the answers

    What occurs if the silver-copper ratio is not carefully balanced in dental gold alloys?

    <p>Tarnish of the alloy</p> Signup and view all the answers

    What is the purpose of sprue attachment?

    <p>To permit smooth flow of the alloy</p> Signup and view all the answers

    What is the function of crucible former?

    <p>To act as a base of ring</p> Signup and view all the answers

    What is the purpose of liner?

    <p>To allow expansion space</p> Signup and view all the answers

    What is the cause of distortion?

    <p>Release of internal stresses</p> Signup and view all the answers

    What is the purpose of wetting agent?

    <p>To increase wax pattern wetting</p> Signup and view all the answers

    What are the causes of surface porosity?

    <p>Under packaging, sandy or sticky stage, increase the monomer</p> Signup and view all the answers

    What are the causes of gaseous porosity?

    <p>Rapid heating and decrease thermal conductivity</p> Signup and view all the answers

    What is the purpose of vacuum investing?

    <p>To decrease the porosity</p> Signup and view all the answers

    What are the types of rings?

    <p>Metallic, rubber, and split metal</p> Signup and view all the answers

    What is the purpose of gradual heating of investment?

    <p>To become ready for molten and to avoid undersized restoration</p> Signup and view all the answers

    What is the reason for holding the impression firmly against the vibrator?

    <p>To remove bubbles and encourage flow into impression details</p> Signup and view all the answers

    What is the result of excess water (free water) evaporation?

    <p>Porosity</p> Signup and view all the answers

    What is the advantage of using mechanical mixers under vacuum pressure?

    <p>It gives the gypsum superior properties</p> Signup and view all the answers

    What is the correct sequence of manipulation steps for gypsum?

    <p>Proportioning, mixing, pouring</p> Signup and view all the answers

    What is the term for the time needed for the reaction to be completed?

    <p>Setting time</p> Signup and view all the answers

    Study Notes

    Soldering Process

    • The components involved in the soldering process are:
      • Metals to be joined (parent metals)
      • Solder alloy
      • Flux and Antiflux
      • Heat source

    Parent Metals

    • The composition of the parent metals in soldering is determined by their melting range.

    Ideal Solder Alloy

    • Desirable qualities of an ideal solder alloy include:
      • Ease of flow at low temperature
      • Ability to wet the parent metal with sufficient flow
      • High strength properties compatible with that of the structure being soldered
      • Acceptable color
      • High resistance to tarnish and corrosion

    Solder Alloys

    • Types of solder alloys:
      • Soft Solders (lower melting point, 260°C)
      • Hard Solders (higher melting temperature, high strength, and hardness)
    • Specific examples of solder alloys include:
      • Lead-tin eutectic alloy (commonly known as Plumber Solder)
      • Gold solder (fusion temperature range: 700°C to 900°C)
      • Silver solder (formation of silver-copper eutectic alloy responsible for low melting range)

    Flux and Antiflux

    • The role of flux in soldering is to:
      • Facilitate the flow of solder
      • Dissolve any oxides present on the surface and protect the surface from oxidation during heating, providing a clean and non-oxidized metal surface
    • The role of antiflux in soldering is to prevent the flow of solder

    Other

    • Low fusing solder is used in dentistry to avoid carbide precipitation and structural changes.
    • The fineness or carat of the gold solder should be slightly less than the carat or fineness of the parts being joined.

    Crown and Bridge Alloys

    • Crown and bridge alloys are made of silver-palladium alloys.
    • Copper is avoided in Type IV systems when gold is not present.

    Gypsum

    • Manipulation steps for gypsum include:
      • Proportioning
      • Mixing
      • Pouring
    • Vigorously mixing gypsum increases powder wetting and removes air bubbles.
    • Mechanical mixers under vacuum pressure give gypsum superior properties.

    Impression

    • The impression should be held firmly against the vibrator to remove bubbles and encourage flow into impression details.
    • Stone should be added from one side slowly to allow small amounts to flow from tooth to tooth around the arch until all teeth are filled.

    Setting Time

    • Setting time is the time needed for the reaction to be completed.
    • Mixing time is the time taken from the addition of the powder to water until a homogeneous workable mix is obtained.
    • Working time is the time available to use a workable mix with even consistency.
    • Initial setting time is the time elapsed from the beginning of mix until partial setting occurs.
    • Final setting time is the time elapsed from the beginning of mix until complete setting.

    Sprue

    • Sprue is used to create a channel and act as a reservoir.
    • Rules for sprue attachment include:
      • Attaching to the thickest portion
      • Attaching at a 45° angle to the proximal surface
    • Sprue materials include:
      • Wax
      • Plastic
      • Metal filled with sticky wax

    Crucible Former

    • Crucible former functions as a base of the ring and increases input concentration.
    • Types of rings include:
      • Metallic
      • Rubber
      • Split metal

    Liner

    • Liner functions include:
      • Allowing expansion space
      • Providing water for gypsum to undergo hygroscopic expansion
      • Allowing easy removal

    Distortion

    • Distortion is due to the release of internal stresses.
    • Distortion is affected by time and temperature.

    Wetting Agent

    • A wetting agent is used to increase wetting of the wax pattern.

    Vacuum Investing

    • Properties of vacuum investing include:
      • Low porosity
      • Smoother surface
      • Increased mechanical properties

    Melting and Casting

    • Melting and casting requires:
      • Heat source
      • Casting pressure
    • Underheating or overheating of the investment can cause problems.

    Casting Machines

    • Types of casting machines include:
      • Centrifugal casting machine
      • Air pressure machine
      • Both centrifugal and air pressure vacuum machine

    Porosity

    • Causes of surface porosity include:
      • Under packaging
      • Sandy or sticky stage
      • Increased monomer
      • Decreased separating medium
    • Causes of gaseous porosity include:
      • Rapid heating
      • Decreased thermal conductivity of the investment
    • Shape and location of surface porosity:
      • Irregular shape
      • Surface location
    • Shape and location of gaseous porosity:
      • Round, regular, uniform shape
      • Covered with a thin layer of skin investment
      • Bulkiest portion location

    Non-Metalic Denture Base

    • Presentation and proportioning of non-metalic denture base:
      • Powder/liquid or gel form
      • 3/1 ratio
    • Effects of increasing or decreasing the powder/liquid ratio:
      • Insufficient wetting or granular cured
      • Flowy mix, polymerization shrinkage, porosity
    • Stages of mix:
      • Sandy
      • Sticky
      • Dough
      • Rubbery
      • Stiff

    Separating Medium

    • Rules of separating medium:
      • Prevent passage of water from gypsum to resin
      • Decrease passage of monomer to plaster
      • Decrease porosity
      • Ease separation of flask
    • Mould requirements:
      • Over-filled
      • Dough stage
      • Sufficient pressure
    • Effects of early or delayed packaging:
      • Decreased viscosity or increased porosity
      • Increased viscosity or fracture and movement of the tooth

    Curing Cycles

    • Curing cycles:
      • 74°C for 8 hours
      • 74°C for 1 hour
    • Effects of increasing or decreasing temperature or curing time:
      • Gaseous porosity
      • Inferior properties, porosity, denture stomatitis

    Polishing

    • Methods for stone removal and acrylic excess removal:
      • Shell blasting
      • Acrylic burs
    • Polishing method:
      • Wet polishing wheel and slurry of pumice in water

    Gold Alloys

    • Functions of zinc in gold alloys:
      • Improves castability and fluidity of the alloy
    • Functions of indium and tin in gold alloys:
      • Produces oxides in porcelain alloys, which help bonding with porcelain
    • Classification of gold alloys based on gold content:
      • Carat and Fineness
    • Difference between carat and fineness:
      • Carat refers to the parts of pure gold in 24 parts of alloy
      • Fineness refers to the parts of pure gold per thousand parts of alloy
    • Use of carat or fineness classification in dentistry:
      • Not suitable, as it only refers to the amount of gold and does not determine the other metals which may have a pronounced effect on properties
    • Description of yellow and white colored alloys:
      • Yellow colored alloys have a prominent yellow color
      • White colored alloys have a prominent yellow gold color
    • ADA requirements for dental gold alloys:
      • Not less than 75% noble metal content
    • Economy gold alloys:
      • Gold content: 42-58%
      • Comparable to Type III and Type IV gold alloys
    • Replacement for reduction in gold in dental gold alloys:
      • Palladium, silver, and other metals
    • Critical ratio between palladium and silver-copper:
      • 1% palladium for every 3% silver
    • Effects of unbalanced silver-copper ratio:
      • Tarnish of the alloy

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    Description

    This quiz covers the basics of the soldering process, including the components involved, composition of parent metals, and desirable qualities of a solder alloy.

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