Dental Alloys Properties
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Questions and Answers

What is the primary reason for documenting the use of dental alloys?

  • To comply with medical device regulations (correct)
  • To ensure the alloy's composition is known
  • To track the cost of the alloy
  • To compare with other dental materials
  • What is the purpose of taking metal shavings from intraoral restorations?

  • To analyze the alloy's composition (correct)
  • To evaluate the alloy's esthetics
  • To test the alloy's corrosion resistance
  • To determine the alloy's strength
  • What is the primary method of corrosion in dental alloys?

  • Mechanical wear and tear
  • Electrochemical reaction (correct)
  • Chemical reaction with saliva
  • Thermal decomposition
  • Why is corrosion of dental alloys a concern from a biocompatibility standpoint?

    <p>Because it releases elements that can affect surrounding tissues</p> Signup and view all the answers

    What is a common method for measuring corrosion in dental alloys?

    <p>Observing the alloy for surface deterioration</p> Signup and view all the answers

    What is the significance of identifying and quantifying released elements in dental alloys?

    <p>To assess the alloy's biocompatibility</p> Signup and view all the answers

    What is the purpose of EDX analysis in dental alloys?

    <p>To characterize the alloy's composition</p> Signup and view all the answers

    What is the accuracy of analyzing dental alloys using scanning microscopy and EDX?

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

    What is an alloy typically composed of?

    <p>Two or more metals or non-metals</p> Signup and view all the answers

    What is a characteristic of dental alloys?

    <p>They are composed of at least four metals</p> Signup and view all the answers

    Why has the composition of dental alloys evolved over time?

    <p>Due to the increase in price of gold and palladium</p> Signup and view all the answers

    What is a challenge in understanding the biocompatibility of dental alloys?

    <p>The complexity and diversity of the alloys</p> Signup and view all the answers

    How many elements from the periodic table are used in today’s dental alloys?

    <p>Over 25 elements</p> Signup and view all the answers

    What is the most common way to express the composition of dental alloys?

    <p>Weight percentage (wt.%)</p> Signup and view all the answers

    Why is atomic percentage a better predictor of an alloy’s biological properties?

    <p>Because it better predicts the number of atoms available to be released</p> Signup and view all the answers

    What is a key difference between weight percentage and atomic percentage?

    <p>Weight percentage and atomic percentage may be substantially different from one another</p> Signup and view all the answers

    What is a necessary condition for an alloy to have adverse biological effects?

    <p>The alloy releases elements</p> Signup and view all the answers

    What influences the biological response to an alloy?

    <p>The biological effects of released elements, the quantities released, and the duration of tissue exposure</p> Signup and view all the answers

    What is a factor that influences the corrosion of dental alloys?

    <p>The surface structure of the alloy</p> Signup and view all the answers

    What is true about elemental release and corrosion from alloys?

    <p>It occurs in all alloys, regardless of type or composition</p> Signup and view all the answers

    What influences the lability of an element?

    <p>The electronic structure of the element</p> Signup and view all the answers

    What is the primary consequence of thermal treatment on a ceramic alloy?

    <p>A 2-3.5-fold increase in copper and zinc release</p> Signup and view all the answers

    What is the role of metal oxides generated during the firing process?

    <p>They increase the attachment between ceramic and alloy</p> Signup and view all the answers

    What can modify the lability of an element?

    <p>The presence of other elements around it</p> Signup and view all the answers

    What reduces the lability of copper in dental alloys?

    <p>The presence of palladium</p> Signup and view all the answers

    Why may exposed oxides at the crown margin increase the toxicity of the alloy?

    <p>Because they promote elemental release</p> Signup and view all the answers

    What reduces the lability of titanium?

    <p>The formation of TiO2 on the surface of titanium</p> Signup and view all the answers

    What is the consequence of recasting base metal alloys?

    <p>A significant increase in the release of elements and cytotoxicity</p> Signup and view all the answers

    What is the problem with placing a gold surface coating on a nickel-based or cobalt-based alloy?

    <p>It enhances corrosion</p> Signup and view all the answers

    Why should gold surface coating of nickel-based or cobalt-based alloys be discouraged?

    <p>Because of the significant problems with the integrity of the long-term bonds between coatings and the alloys</p> Signup and view all the answers

    What happens to the release of ions from alloys over time?

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

    What is the effect of solders on dental alloys?

    <p>They increase the corrosion of dental alloys</p> Signup and view all the answers

    What is the primary factor influencing the accumulation of elements locally around dental alloys?

    <p>Rate of release of elements at the implantation site</p> Signup and view all the answers

    What is unique about the corrosion properties of brass in the mouth?

    <p>It is extremely corrosion-prone</p> Signup and view all the answers

    In which tissue have elevated copper levels been demonstrated in dogs adjacent to crowns composed of brass?

    <p>Gingival tissues</p> Signup and view all the answers

    What is the significance of the study on patients with inflamed gingiva adjacent to various dental alloys?

    <p>It showed that alloy components are present in gingiva and mucosa</p> Signup and view all the answers

    What is the general trend observed in the levels of alloy components in human gingival tissues adjacent to dental alloys?

    <p>The levels are generally low</p> Signup and view all the answers

    What is the main reason why elements released from nonamalgam dental alloys do not contribute significantly to the systemic body burden of elements?

    <p>The amounts released are far below those taken in as part of the diet</p> Signup and view all the answers

    What is the primary source of metal intake in the body?

    <p>Daily dietary intake</p> Signup and view all the answers

    What is the significance of Table 8.3 in the context of dental alloys?

    <p>It compares the amounts of elements released from dental alloys to daily dietary intake</p> Signup and view all the answers

    Study Notes

    Basic Material Properties

    • An alloy is a mixture of two or more metals or non-metals (elements).
    • Dental alloys typically contain at least four metals and often six or eight different metals, making them metallurgically complex.
    • Alloy compositions are diverse and have evolved over the past 20 years, with many types of alloys emerging that were unknown just a few years ago.
    • Most dental alloys were previously based on gold, but today's alloys may be based on silver, gold, palladium, nickel, cobalt, or titanium.

    Alloy Composition

    • The composition of dental alloys can be expressed in two ways: weight percentage (wt.%) or atomic percentage (at.%).
    • Weight percentage is the most common way to describe an alloy's composition, but atomic percentage is better for predicting the number of atoms available to be released.
    • The wt.% and at.% of an alloy may be substantially different from one another.

    Analysis of Dental Alloys

    • Dental alloys are classified as medical devices, and their use must be documented by the dentist and laboratory technician.
    • Information about an alloy's composition is available in the literature or from manufacturers.
    • Metal shavings can be taken from intraoral restorations and analyzed using scanning microscopy and energy-dispersive x-ray (EDX) analysis to determine the alloy's composition.

    Corrosion and Release of Elements

    • Corrosion is the primarily electrochemical process of alloys involving the ionization of elements that are released into the environment.
    • Elements that are initially uncharged lose electrons and become positively charged ions as they are released into solution.
    • Corrosion is a chemical property of an alloy that influences other properties, including esthetics and strength.
    • The release of elements from an alloy is necessary for an alloy to have adverse biological effects such as toxicity, allergy, or mutagenicity.
    • Factors that influence the corrosion of dental alloys include:
      • Composition of the alloy (particularly at the surface)
      • Phase structure of the alloy
      • Surface structure (roughness, presence of oxides)
      • Crevices, pits
      • Thermal treatment/history
      • Combinations of alloys (gold coating, soldering)
      • Time in service

    Factors Influencing Element Release

    • The composition of an alloy is a fundamental factor that influences element release.
    • Certain elements, such as copper, zinc, and nickel, have higher tendencies to be released than elements such as gold and palladium.
    • The lability of an element may be substantially modified by other elements around it.
    • The phase structure of the alloy and thermal treatment can also influence element release.

    Clinical Practice Advice

    • Gold surface coating of nickel-based or cobalt-based alloys should be discouraged because the combination of the alloys and their permanent contact may enhance corrosion rather than retard it.
    • Only those solders or alloy combinations should be used that have a low tendency for corrosion.

    Nonimplanted Dental Alloys

    • Elements released from nonimplanted dental alloys may or may not gain access into the body.
    • There is some evidence that elements from dental crowns and other alloys gain access to local gingival tissues or the oral mucosa.
    • However, there is little evidence to demonstrate that elements released from nonamalgam dental alloys contribute significantly to the systemic body burden of elements.

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    Description

    Learn about the composition and properties of dental alloys, including their metallurgically complex nature and diverse compositions.

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