Dental Amalgam Composition
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Questions and Answers

What is the primary role of mercury in the composition of amalgam?

  • It increases the strength of the amalgam
  • It acts as a scavenger for oxides
  • It facilitates the reaction due to its affinity to Hg (correct)
  • It decreases the corrosion of the amalgam

    • What is the effect of copper on the amalgam?

  • It increases the strength and hardness of the amalgam (correct)
  • It increases the corrosion of the amalgam
  • It has no effect on the properties of the amalgam
  • It decreases the strength and hardness of the amalgam

    • What is the primary function of zinc in the composition of amalgam?

  • It decreases the setting time of the amalgam
  • It acts as a scavenger for oxides (correct)
  • It increases the flow and creep of the amalgam
  • It improves the corrosion resistance of the amalgam

    • What is the effect of palladium on the amalgam?

    <p>It improves the corrosion resistance and mechanical properties of the amalgam</p> Signup and view all the answers

    What is the classification of alloys based on the number of alloyed metals?

    <p>Binary, ternary, quaternary alloys</p> Signup and view all the answers

    What is the advantage of spherical particles in amalgam?

    <p>They require less mercury to wet the alloy particles</p> Signup and view all the answers

    What is the result of the initial reaction between mercury and alloy particles in Lathe-cut Low Copper Alloys?

    <p>Formation of Ag2Hg3 and Sn7–8Hg3</p> Signup and view all the answers

    What is the characteristic of the conventional alloy based on copper content?

    <p>It has a low copper content of 2-6%</p> Signup and view all the answers

    What is the term used to describe alloys containing palladium, gold, or platinum?

    <p>Nobel metal alloys</p> Signup and view all the answers

    What is the range of zinc content in zinc-containing alloys?

    <p>0.01-1%</p> Signup and view all the answers

    What is the term used to describe the silver mercury phase in the setting reaction of amalgam?

    <p>Ag2Hg3</p> Signup and view all the answers

    What is the difference in the reaction between Lathe-cut Low Copper Alloys and Admixed High Copper Alloys?

    <p>The reaction occurs in two phases in Low Copper Alloys and one phase in High Copper Alloys</p> Signup and view all the answers

    What is the purpose of removing the Hg rich layer of each increment before packing the next increment?

    <p>To increase adaptation and density of amalgam</p> Signup and view all the answers

    When should carving of amalgam start?

    <p>When a slight resistance of carver movement is felt</p> Signup and view all the answers

    What is the direction of carving?

    <p>From the tooth structure towards the bulk of amalgam</p> Signup and view all the answers

    What is the purpose of pre-carving burnishing?

    <p>To increase adaptation and density of amalgam</p> Signup and view all the answers

    What instrument is used for supplemental grooves and removal of overhanged margins of restoration?

    <p>Fine tipped probe</p> Signup and view all the answers

    What can result from early carving of amalgam?

    <p>Both A and B</p> Signup and view all the answers

    What is the primary purpose of leaving sufficient Hg during condensation?

    <p>To ensure cohesion of the mix during condensation</p> Signup and view all the answers

    What is the purpose of mechanical mulling?

    <p>To reduce the mixing time by 1-2 seconds</p> Signup and view all the answers

    What is the primary aim of condensation?

    <p>To achieve a homogenous packing of the freshly triturated amalgam into the cavity</p> Signup and view all the answers

    What is the characteristic of a condenser that provides better force during condensation?

    <p>It is serrated</p> Signup and view all the answers

    What is the technique used to fill the cavity during condensation?

    <p>Filling the cavity increment by increment starting from the auxiliary cavity</p> Signup and view all the answers

    What is the indication that the increment is fully condensed during condensation?

    <p>The surface of the increment becomes soft and a squeezing sound is heard</p> Signup and view all the answers

    What is the purpose of carving the gingival margin?

    <p>To check for any overhanged margins of amalgam</p> Signup and view all the answers

    What direction should the removal of the matrix be done in?

    <p>Buccal or lingual direction</p> Signup and view all the answers

    What is the purpose of post-carve burnishing?

    <p>To smoothen the amalgam surface</p> Signup and view all the answers

    What is checked using pressure sensitive articulating paper?

    <p>Any premature contact of the tooth</p> Signup and view all the answers

    What is the advantage of not using the restored side for 24 hours?

    <p>To prevent cracking or fracturing of the restoration</p> Signup and view all the answers

    What is the primary aim of finishing and polishing?

    <p>To remove any premature contact and provide a lustrous homogenous amalgam surface</p> Signup and view all the answers

    Study Notes

    Properties of Dental Amalgam Alloys

    • Facilitates reaction due to affinity to Hg
    • Increases flow and creep
    • Decreases setting expansion, strength, and corrosion (forms most corrodible phase)

    Composition of Amalgam

    • Copper:
      • 0-6% by weight in low-copper alloys
      • 6-30% by weight in high-copper alloys
      • Increases strength, hardness, and corrosion resistance
      • Decreases creep and flow, tarnish, and corrosion
    • Zinc:
      • About 0-2% by weight
      • Acts as scavenger for oxides
      • Causes delayed expansion when contaminated with moisture or saliva
      • Decreases strength and setting expansion
    • Palladium and Indium:
      • Palladium (0-1% by weight): improves corrosion resistance and mechanical properties
      • Indium (0-4% by weight): decreases mercury evaporation and amount of mercury required to wet alloy particles

    Classification of Dental Amalgam Alloys

    • According to number of alloyed metals:
      • Binary alloy (e.g., silver, tin)
      • Ternary alloy (e.g., silver, tin, copper)
      • Quaternary alloy (e.g., silver, tin, copper, zinc)
    • According to particle size:
      • Micro-cut
      • Fine-cut
      • Coarse-cut
    • According to particle shape:
      • Conventional lathe cut (irregular)
      • Spherical (smooth surfaced spheres)
      • Spheroidal (spherical with irregular surface)
    • Advantages of spherical particles:
      • Requires less Hg
      • Less condensation force
      • Higher strength
      • Easy amalgamation
      • Smooth surface finishing
    • According to copper content:
      • Low-copper (2-6% copper)
      • High-copper (6-30% copper)
    • According to zinc content:
      • Zinc-free alloy (<0.01% zinc)
      • Zinc-containing alloy (0.01-1% zinc)
    • According to addition of noble metals:
      • Nobel metal alloys (e.g., palladium, gold, or platinum)

    Setting Reaction of Amalgam

    • For lathe-cut low-copper alloys:
      • Mercury reacts with tin and silver to form two products (silver-mercury phase and tin-mercury phase)
      • Formation of ɣ2 phase and ɣ1 phase
    • For admixed high-copper alloys:
      • Reaction occurs in two phases
      • Hg-rich layer of each increment should be removed before packing the next increment

    Amalgam Manipulation

    • Carving:
      • Aims: reproduce normal tooth anatomy, ensure efficient mastication and tooth function, and remove superficial Hg-rich layer
      • Timing: when amalgam starts initial setting
      • Direction: from tooth structure towards bulk of amalgam, parallel with cavo-surface outline of cavity
      • Instruments: burnisher, large spoon, discoid or cleoid excavator, amalgam carver, fine-tipped probe
    • Condensation:
      • Definition: forcible packing of fresh amalgam mix into prepared cavity details to slightly overfill it
      • Aims: homogenous packing, improve adaptation, eliminate voids, and express Hg-rich layer
      • Instruments: amalgam carrier, condenser (smooth or serrated, manual or mechanical)
      • Technique: fill increment by increment, apply condensation force, and remove excess Hg
    • Post-carve burnishing:
      • Done with light pressure until surface acquires a homogenous stain or velveteen appearance
      • Advantage: smoothens amalgam surface
    • Finishing and polishing:
      • Aims: remove premature contact, marginal flashes, or marginal overhangs, and provide a lustrous homogenous amalgam surface

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    Description

    This quiz assesses knowledge of dental amalgam composition, including the effects of mercury, copper, and zinc on various properties of amalgam.

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