Fixed Prosthodontics Quiz
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Questions and Answers

What is the primary function of opaque porcelain in a metal-ceramic restoration?

  • To bond with the metal surface and mask its color (correct)
  • To decrease the strength of the ceramic material
  • To add translucency to the restoration
  • To create a natural tooth color

    • What is the purpose of glazes in a metal-ceramic restoration?

  • To add color to the restoration
  • To increase the strength of the ceramic material
  • To create a natural tooth shape
  • To achieve a high-gloss finish (correct)

    • What is the term used to describe the process of creating a wax pattern, investing, and casting in metal-ceramic restorations?

  • Casting technique
  • Waxing technique
  • Lost wax technique (correct)
  • Investment technique

    • What is the purpose of dentin porcelain in a metal-ceramic restoration?

    <p>To achieve a natural tooth color</p> Signup and view all the answers

    What is the term used to describe the layers of ceramic material used in a metal-ceramic restoration?

    <p>Ceramic layers</p> Signup and view all the answers

    What is the primary function of the body porcelain in a metal-ceramic restoration?

    <p>To build up the ceramic material</p> Signup and view all the answers

    What is the term used to describe the process of adding color to a metal-ceramic restoration?

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

    What is the primary function of the metal coping in a metal-ceramic restoration?

    <p>To add strength to the restoration</p> Signup and view all the answers

    What is the term used to describe the process of creating a metal substructure in a metal-ceramic restoration?

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

    Study Notes

    Lost Wax Technique

    • The lost wax technique is used in fixed prosthodontics to create a metal framework for a dental restoration.

    Waxing Up

    • Waxing up is the process of rebuilding a prepared tooth on a die using wax.
    • Wax is used because it can be conveniently manipulated and precisely shaped by heating, and it can be completely eliminated from the mold after investing.
    • Inlay casting wax is a type of wax used in forming the pattern for cast restorations.

    General Requirements of Wax

    • The wax should have the following properties:
      • Color: should be suitable for the specific application
      • Flow: should be able to flow easily
      • Carving: should be able to be carved accurately
      • Addition: should be able to be added to without distorting the pattern
      • Residue: should leave minimal residue after removal
      • Compensation: should compensate for metal shrinkage
      • Strength and rigidity: should have sufficient strength and rigidity after cooling

    Step-by-Step Process

    • Modification of the master cast
    • Addition of wax layers
      • Dipping the first layer, followed by anatomical buildup of the wax pattern by addition
    • Evaluation
      • Axial contours
      • Occlusal morphology
      • Margins

    Removable of Wax Pattern

    • Remove the pattern from the die using extreme caution not to distort it

    Spruing

    • A sprue is a channel in the investment material through which molten wax can escape during the burnout process, and molten metal can reach the mold cavity.
    • Requirements for a sprue:
      • Allow molten wax to escape from the mold
      • Enable molten metal to flow into the mold
      • Molten metal inside the sprue must remain molten slightly longer than metal that had filled the mold
    • Types of sprue formers:
      • Wax
      • Plastic
      • Metal

    Properties of Sprue

    • Diameter: should be thicker than the thickest portion of the pattern
    • Location: should be attached to the bulkiest non-critical part of the pattern, away from margins and occlusal contacts
    • Angulation: should be at an angle (45°) to allow the incoming molten metal to flow freely to all portions of the mold
    • Length: should be according to the investment used, with a minimum of 6-8 mm for gypsum-bonded investment and 3-4 mm for phosphate-bonded investment
    • Venting: small auxiliary sprues or vents improve casting of thin patterns and help gases escape during casting

    Casting

    • Done using a centrifugal casting machine or air pressure casting machine
    • Molten metal is cast into the mold

    Casting Defects

    • Can be attributed to poor casting technique and failure to adhere to casting laws
    • Types of defects:
      • Rough casting
      • Large nodules
      • Small nodules
      • Fins
      • Incomplete casting
      • Marginal discrepancy

    Cleaning the Casting

    • After solidification, the ring is removed and quenched in water
    • Divesting: removal of the casting from the investment mold
    • Pickling: process of removing oxides and tarnish from the surface of the casting using an acid

    Porcelain Build-up

    • Ceramic layers are built up on a metal coping
    • Types of porcelain:
      • Opaque porcelain
      • Body porcelain
      • Incisal porcelain

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    Related Documents

    Waxing Up, Spruing, Investing, Casting, and Porcelain Build-Up PDF

    Description

    Test your knowledge on fixed prosthodontics, including metal framework, porcelain build-up, and laboratory steps.

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