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Related Experiment Videos

Composition of clinically aged amalgam restorations.

D B Boyer1, J W Edie

  • 1College of Dentistry, University of Iowa, Iowa City.

Dental Materials : Official Publication of the Academy of Dental Materials
|July 1, 1990
PubMed
Summary

Clinically aged dental amalgams show altered phase distribution compared to new ones. Low-copper amalgams decrease gamma phases, while high-copper amalgams show enlarged reaction rings after years of use.

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Area of Science:

  • Dental Materials Science
  • Materials Engineering
  • Metallurgy

Background:

  • Dental amalgam remains a widely used restorative material.
  • Understanding the long-term behavior of amalgam in vivo is crucial for clinical practice.
  • Previous studies have focused on the initial composition and properties of amalgam.

Purpose of the Study:

  • To investigate the changes in elemental and phase composition of clinically aged dental amalgams.
  • To compare the aged phase distribution in low-copper and high-copper amalgams.
  • To correlate clinical aging with microstructural alterations in dental restorative materials.

Main Methods:

  • Analysis of 25 clinically aged amalgam restorations (2-25 years) from five subjects.
  • Electron microprobe analysis for bulk elemental and phase composition.
  • Point-counting on back-scattered electron micrographs to determine phase volume fractions.

Main Results:

  • Aged amalgams showed minimal bulk elemental variation, with minor chloride contamination.
  • Phase compositions were similar to new amalgams, but with significant internal amalgamation of gamma particles.
  • Low-copper amalgams exhibited decreased gamma, gamma-1, and gamma-2 phases, with increased beta-1 and tin-chloride.
  • High-copper amalgams showed decreased gamma, increased beta-1, and enlarged reaction rings (gamma-1 and eta').

Conclusions:

  • Clinical aging significantly alters the phase distribution within dental amalgams.
  • Low-copper amalgams undergo degradation, favoring tin-chloride formation.
  • High-copper amalgams demonstrate microstructural changes, including enlarged reaction zones, indicating ongoing reactions over time.

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