Dental Amalgam Chapter 5 Quiz
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Questions and Answers

What percentage of copper is found in high copper amalgam alloys?

  • No copper
  • Less than 6%
  • More than 6% (correct)
  • Exactly 6%

    • Which metal in dental amalgam primarily increases strength and decreases creep?

  • Mercury
  • Zinc
  • Tin
  • Copper (correct)

    • Which property of amalgam is primarily decreased by silver content?

  • Workability
  • Strength
  • Setting time
  • Creep (correct)

    • What role does zinc play in dental amalgam?

    <p>Prevents oxidation</p> Signup and view all the answers

    Which corrosion product is associated with silver in dental amalgam?

    <p>AgCl and AgS</p> Signup and view all the answers

    How does tin affect the setting time of an amalgam restoration?

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

    What is a primary advantage of using dental amalgam as a restorative material?

    <p>High compressive strength and hardness</p> Signup and view all the answers

    What effect does mercury have on the properties of dental amalgam?

    <p>Decreases strength if in excess</p> Signup and view all the answers

    What is the main constituent of dental amalgam?

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

    What is the approximate percentage of liquid mercury in dental amalgam?

    <p>43 to 54%</p> Signup and view all the answers

    What is formed during the amalgamation reaction?

    <p>A hard restorative material</p> Signup and view all the answers

    Why has dental amalgam remained popular for over 150 years?

    <p>It offers ease of manipulation and low cost</p> Signup and view all the answers

    What kind of reaction occurs when mercury is mixed with an alloy in dental amalgam?

    <p>Amalgamation reaction</p> Signup and view all the answers

    Which of the following elements is NOT typically found in the alloy powder used for dental amalgam?

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

    What color is dental amalgam typically described as?

    <p>Silvery-gray</p> Signup and view all the answers

    What is a primary concern regarding the use of dental amalgam?

    <p>Mercury toxicity</p> Signup and view all the answers

    What is the term for the change in volume of amalgam due to temperature changes?

    <p>Dimensional change</p> Signup and view all the answers

    What percentage of strength does amalgam reach after one hour of placement?

    <p>40 to 60%</p> Signup and view all the answers

    What is a key disadvantage of using dental amalgam?

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

    How does creep affect the properties of amalgam?

    <p>It leads to gradual dimensional change under load.</p> Signup and view all the answers

    What can happen if an amalgam filling expands excessively?

    <p>It could protrude from the cavity.</p> Signup and view all the answers

    What phenomenon is characterized by a chemical reaction between amalgam and its environment that affects only the surface?

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

    What effect does contact with a gold restoration have on an amalgam filling?

    <p>Accelerates corrosion</p> Signup and view all the answers

    What is considered an objectionable effect of dental amalgam related to its appearance?

    <p>Amalgam tattoo</p> Signup and view all the answers

    How does the coefficient of thermal expansion for amalgam compare to that of dentine?

    <p>It is about three times greater.</p> Signup and view all the answers

    What potential issue can arise from the thermal expansion of amalgam?

    <p>Microleakage around the fillings.</p> Signup and view all the answers

    What is the most critical responsibility of the dental specialist with regard to amalgam?

    <p>Correct preparation and use of amalgam.</p> Signup and view all the answers

    What happens if the amalgam mix contains greater quantities of mercury?

    <p>It becomes ‘wetter’ and is used with hand mixing.</p> Signup and view all the answers

    What is the optimal final mercury content in amalgam for lathe-cut materials?

    <p>About 45%.</p> Signup and view all the answers

    What is a known effect of certain mercury compounds on human health?

    <p>They can harm the central nervous system.</p> Signup and view all the answers

    What does trituration refer to in the manipulation of amalgam?

    <p>Mixing the alloy with mercury.</p> Signup and view all the answers

    What allergic reaction is usually associated with amalgam fillings?

    <p>Contact dermatitis.</p> Signup and view all the answers

    What is the main advantage of using a mechanical amalgamator for trituration?

    <p>It allows for a more uniform and reproducible mix.</p> Signup and view all the answers

    What is the optimal mercury content in set amalgam?

    <p>44-48%</p> Signup and view all the answers

    What is the most significant risk if condensation is delayed after trituration?

    <p>It becomes too hard to carve and may chip.</p> Signup and view all the answers

    Which of the following instruments is primarily used for condensing amalgam?

    <p>Amalgam condenser</p> Signup and view all the answers

    Why is polishing of amalgam fillings typically delayed for 24 hours?

    <p>To allow for the restoration to harden and gain mechanical strength.</p> Signup and view all the answers

    Which factor is crucial for achieving optimal mechanical properties in set amalgam?

    <p>Adequate adaptation to the cavity.</p> Signup and view all the answers

    What should be done soon after condensing amalgam?

    <p>Carve away the surface layer rich in mercury.</p> Signup and view all the answers

    What generally requires lower forces during the condensation of amalgam?

    <p>Spherical particle amalgams.</p> Signup and view all the answers

    Study Notes

    Introduction to Dental Amalgam

    • Dental amalgam has been a standard restorative material for over 150 years, primarily for posterior restorations.
    • Its popularity is due to its ease of manipulation, cost-effectiveness, and longevity.
    • Although there are concerns regarding mercury toxicity, dental amalgam is generally considered to present an acceptable risk-to-benefit ratio when used properly.

    Composition of Dental Amalgam

    • Dental amalgam consists of mercury combined with an alloy of silver, tin, copper, and sometimes zinc or other trace metals.
    • An amalgamation reaction occurs when the alloy is mixed with mercury, resulting in a hard, silvery-gray restorative material.

    Alloy Composition and Properties

    • Common composition for conventional amalgam alloy includes:
      • Silver (Ag): 40-60%
      • Tin (Sn): 27-30%
      • Copper (Cu): 13-30%
      • Zinc (Zn): up to 2%
      • Mercury (Hg): 3%
    • Each metal serves distinct roles:
      • Silver enhances strength and expansion, minimizes creep.
      • Tin increases reactivity and corrosion but decreases strength.
      • Copper improves strength and corrosion resistance.
      • Zinc adds plasticity and prevents oxidation.

    Classification of Amalgam

    • Amalgam can be classified based on several criteria:
      • Number of alloyed metals
      • Shape of the particles
      • Copper content: low (<6%) vs. high (>6%)
      • Zinc content: zinc-containing (>0.01%) vs. zinc-free (<0.01%)
      • Unmixed vs. admixed types

    Advantages and Disadvantages

    • Advantages:
      • High compressive strength and durability.
      • Ease of handling and manipulation.
      • Excellent wear resistance and distinction from tooth structure.
      • Cost-effective restoration option.
    • Disadvantages:
      • Aesthetic concerns due to silver color.
      • Potential mercury exposure and related health hazards.
      • Possible occurrence of amalgam tattoos and lack of insulation.

    Properties Affecting Amalgam Restorations

    • Dimensional Changes: Proper dimensioning is critical; large contractions can lead to gaps, while expansions may cause sensitivity.
    • Strength: Amalgam gains strength over time. It reaches 90% strength within 24 hours and is weaker shortly after placement.
    • Creep: Amalgam may undergo plastic deformation under stress.
    • Corrosion & Tarnish: Corrosion affects mechanical properties and is accelerated in contact with other metals; tarnish primarily affects the surface.
    • Thermal Properties: Amalgam has a higher thermal conductivity than dentine, leading to potential issues with microleakage.
    • Biological Properties: Mercury compounds may impact the nervous system, and allergic reactions might occur.

    Manipulation of Amalgam

    • Key steps for amalgam manipulation include:
      • Proportioning & Dispensing: Ratio of alloy to mercury typically ranges from 5:8 to 10:8. Optimal final mercury content is under 50%.
      • Trituration: Mixing can be done mechanically or manually, with mechanical being more common for consistency and efficiency.
      • Condensation: Proper condensation ensures ideal adaptation within the cavity and reduces porosity.
      • Carving: Carving after condensation must be timely to avoid hardening.
      • Polishing: Polishing is performed after achieving adequate strength to enhance aesthetics and resistance to corrosion; usually requires a 24-hour delay post-placement.

    Conclusion

    • The dental professional is responsible for the correct use and preparation of amalgam to ensure quality restorations.
    • Proper handling and preparation are critical to avoiding faulty restorations that may jeopardize tooth integrity.

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    Chapter 5 Dental Amalgam PDF

    Description

    This quiz covers the key concepts of dental amalgam, focusing on its history, uses, and safety considerations. Explore the reasons behind its long-standing popularity and the current debates regarding mercury toxicity. Test your understanding of dental therapeutics and its implications.

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