Heat treatment of glass ionomer, silicate, zinc phosphate and zinc polycarboxylate cements.

The compressive strength and erosion resistance of glass ionomer, silicate, zinc phosphate or zinc polycarboxylate cements, submitted to heat treatments at 50 degrees or 70 degrees C after mixing, have been assessed. Zinc phosphate cement specimens showed a marked reduction in compressive strength properties and erosion resistance, while minor improvements in compressive strength were observed for various brands of the other types of cements. For silicate cement a considerable improvement in erosion resistance was noted. One brand showed a reduction in the release of phosphate amounting to approximately a factor of 20. The various improvements observed may be clinically exploited by exposing the restoration after insertion to radiation from an external heat source which deposits radiation energy in the surface or bulk of the restoration.