Failure of Amalgam Restoration: Excessive Discolouration

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In this article of Amalgam Failure, we discuss another type of failure which is Severe or excessive discolouration. We will explain the major causes, clinical picture and treatment.

Excessive Discolouration

Causes

  1. Tarnish.
  2. Corrosion.
  3. Amalgam Blues.

 

Cause 1: Tarnish

Tarnish : Loss of Amalgam Lister

Tarnish : Loss of Amalgam Lister

  • Formation of a surface film of discolouring oxides and sulphides leading to loss of amalgam luster.
  • This is enhanced by: Excess Hg, under trituration, improper condensation, Lack of finishing, moisture contamination, and bad oral hygiene.

Cause 2: Corrosion

  • Its the actual disintegration of the bulk of amalgam.
  1. Chemical corrosion: due to Lack of polishing and food stagnation which may lead to halogenation and sulfurization.
  2. Electric corrosion: Setting of electromotive force between two different electrodes of different electric potential through an electrolyte.This occurs between two dissimilar metallic restorations, as:
    • Old and new similar metallic restoration.
    • Polished and unpolished areas of the same restoration.
    • The same restoration but heterogeneous in structure.
  3. Concentration cell corrosion
  • It is a type of electric corrosion resulting from accumulation of certain types of food on a site of restoration making it different in its electric potential from other sites of amalgam. It is increased with rough surfaced amalgam and bad oral hygiene.
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Freash and Shiny amalgam Filling

Freash and Shiny amalgam Filling

Corrosion leading to Amalgam Surface Pitting

Corrosion leading to Amalgam Surface Pitting

Amalgam Showing through because of thin remaining Enamel

Amalgam Showing through because of thin remaining Enamel

Cause 3: Amalgam blues

This type of discolouration is by the amalgam being seen through the enamel, It is mainly due to:

  • Thin or undermined enamel that shows dark blue discoloration of amalgam.
  • Penetration of metallic ions and corrosive products of amalgam through the dentinal tubules.

 

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Clinical Picture

  • Tarnish: Loss of surface luster.
  • Corrosion: Rough pitted amalgam surface.
  • Amalgam blues:  Dark bluish discolouration.

Treatment

  • Tarnish: requires re-polishing.
  • Corrosion: may require removal of old restoration followed by bleaching and correct replacement.
  • Amalgam blues: are prevented with application of cavity varnish to seal dentinal tubules from penetration of metallic ions.

 

 

 


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About Author

Dr. Mohsen Saeed Ozaibi

A Dentist, Professional Blogger and Owner on OziDent.com. Graduated in 2009 with a Bachelor Degree in Dental Science from Misr International University. A Pioneer in Digital Dental Content Publishing.

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