Dental Amalgam (Delayed Expansion)
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Dental Amalgam (Delayed Expansion)

Amalgams

Dental Material

Dental Amalgam (Delayed Expansion)

Zinc containing low copper/ high copper amalgam usually show Delayed Expansion.

During trituration/condensation if the Zinc containing amalgam is contaminated with moisture, delayed expansion can take place.

H2O + Zn → ZnO + H2 (gas)

The hydrogen released does not combine with amalgam but accumulated within the restoration there by increasing the pressure and expansion of mass.

This is usually observed after 3-5 days of condensation and may continue for months together reaching values > 400 µm (4%).

This increase in pressure may lead to:

  1. Protrusion of restoration out of cavity
  2. Increased microleakage
  3. Pitter surface
  4. Corrosion
  5. Increased creep
  6. Dental Pain
  7. Fracture of tooth/restoration
  8. Recurrence of caries.
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