Dental Material Lecture 9: Abrasion and Polishing
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Questions and Answers

What happens when a hard, rough surface slides along a softer surface?

  • Polishing occurs
  • Corrosion occurs
  • Abrasion occurs (correct)
  • Erosion occurs
  • What is the type of abrasion where abrasive particles are bonded to the instrument?

  • Air-particle abrasion
  • Two-body process (correct)
  • Erosion
  • Three-body process
  • What is the main reason why restorations and prostheses need further trimming, smoothing, and polishing?

  • To remove any imperfections from the processing stage (correct)
  • To make it stronger and more durable
  • To make it more resistant to corrosion
  • To make it aesthetically pleasing
  • What is the primary factor that determines the rate of abrasion of a given material by a given abrasive?

    <p>Hardness of the abrasive</p> Signup and view all the answers

    What is the term for the material being abraded?

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

    What is the process of material removal achieved by air-pressure propelled abrasives?

    <p>Air-particle abrasion</p> Signup and view all the answers

    What may happen if a restoration or appliance is not polished before being placed in the mouth?

    <p>Food and debris may cling to it, making it unhygienic</p> Signup and view all the answers

    What is the definition of abrasion?

    <p>The wearing away of a substance or structure through a mechanical process</p> Signup and view all the answers

    What is the primary difference between an abrasive agent and a polishing agent?

    <p>The particle size of the agent</p> Signup and view all the answers

    What is the maximum amount of material removed during polishing?

    <p>0.005mm</p> Signup and view all the answers

    Which of the following is a non-abrasive method of polishing?

    <p>Application of a glaze layer</p> Signup and view all the answers

    What is the optimal speed for polishing compared to abrading?

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

    What is the purpose of blasting in abrasion?

    <p>To remove investment from castings</p> Signup and view all the answers

    What is the primary purpose of proximal stripping in abrasion?

    <p>To remove enamel</p> Signup and view all the answers

    What is the main characteristic of polishing abrasives that distinguishes them from finishing abrasives?

    <p>They have finer particle sizes and are less hard.</p> Signup and view all the answers

    What is the primary use of cleansing abrasives?

    <p>To remove soft deposits from tooth enamel or restorative materials.</p> Signup and view all the answers

    Which type of abrasive is most commonly used in a white stone instrument?

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

    What is the main advantage of synthetic diamond abrasives over natural diamond abrasives?

    <p>They have a consistent shape and size.</p> Signup and view all the answers

    What is the result of reducing the particle size of an abrasive sufficiently?

    <p>The scratches become extremely fine and may disappear entirely.</p> Signup and view all the answers

    Which type of abrasive is used for fine grinding of tooth enamel and metal alloys?

    <p>Arkansas stone</p> Signup and view all the answers

    What is the definition of polishing?

    <p>The production of a smooth mirror-like surface without much loss of any external form.</p> Signup and view all the answers

    Why are synthetic abrasives preferred over natural abrasives?

    <p>They have more predictable physical properties.</p> Signup and view all the answers

    What is the effect of larger, coarse abrasive particles on a surface?

    <p>They abrade a surface more readily and leave coarser scratches.</p> Signup and view all the answers

    Why do sharp, irregular shaped particles abrade a surface more rapidly?

    <p>Because they have a larger surface area</p> Signup and view all the answers

    What is the effect of increasing speed and pressure on the rate of abrasion?

    <p>It is directly proportional to the rate of abrasion.</p> Signup and view all the answers

    What is the primary purpose of lubricants during abrasion?

    <p>To reduce heat buildup and wash away debris</p> Signup and view all the answers

    What type of abrasive instrument design involves adding a paste or a water soluble medium to a non-abrasive instrument?

    <p>Non-bonded abrasives</p> Signup and view all the answers

    What is the characteristic of finishing abrasives?

    <p>They are hard and coarse</p> Signup and view all the answers

    Why do bonded abrasives tend to disintegrate rapidly?

    <p>Because the particles detach with time</p> Signup and view all the answers

    What determines the types of abrasive grits?

    <p>Particle size</p> Signup and view all the answers

    Study Notes

    Importance of Polishing

    • A restoration or appliance should be highly polished before being placed permanently in the mouth to prevent discomfort, food accumulation, and tarnish and corrosion.

    Abrasion

    • Defined as the wearing away of a substance or structure through a mechanical process, such as grinding, rubbing, or scraping.
    • Types of abrasion: two-body (e.g., diamond bur on enamel) and three-body (e.g., pumice with a bristle brush) processes.
    • Factors affecting the rate of abrasion: hardness, particle size, particle shape, speed, and pressure.

    Abrasives

    • Defined as a hard substance used for grinding, finishing, or polishing a less hard surface.
    • Substrate: the material being abraded.
    • Types of abrasives: finishing, polishing, and cleansing abrasives.
    • Examples of abrasives: Arkansas stone, chalk, corundum, diamond, and synthetic alpha aluminum oxide.

    Abrasive Instrument Design

    • Abrasive grits: coarse, medium, and fine particle sizes derived from crushed and filtered materials.
    • Bonded abrasives: abrasive particles bonded to a grinding tool, which tend to disintegrate rapidly.
    • Non-bonded abrasives: paste or water soluble medium added to a non-abrasive instrument.

    Polishing

    • Defined as the production of a smooth, mirror-like surface without much loss of external form.
    • Difference between abrasion and polishing: particle size, speed, and material removal.
    • Methods of polishing: abrasive process, non-abrasive polishing (e.g., application of a glaze layer, electrolytic polishing, and burnishing).

    Methods of Abrasion

    • Manual abrasion: proximal stripping of enamel using abrasive strips.
    • Rotary instruments: burs, wheels, cups, discs, cones, etc.
    • Blasting: using a steady stream of abrasive to remove investment of castings.

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    Description

    This quiz covers the importance of polishing restorations and prostheses before placing them in the mouth, and the process of trimming, smoothing, and polishing. It is part of a Prosthetic Dental Technology course.

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