Temperature change in pulp cavity in vitro during the polymerization of provisional resins.

Objectives: To measure the temperature change in the pulp cavity of an extracted tooth during the polymerization of provisional resins within impression putty and polyethylene matrices. The effect of pre-cooling the putty matrix was also evaluated.

Methods: A freshly extracted premolar tooth had putty impressions recorded prior to crown preparation. Putty matrices were stored at room temperature, 4 and -12 degrees C prior to use. A thermocouple placed in the pulp chamber recorded the temperature change every 15s for a 10-min duration during polymerization of three resins using putty and clear polyethylene matrices. Five recordings were made with each material at each storage temperature.

Results: There is a temperature rise of 3.4-5.5 degrees C when the resins were autocured in a putty matrix. When the polyvinyl matrix was used the temperature rise increased to 4.0-8.2 degrees C (P<0.001). The temperature rise was reduced to zero when the putty had been pre-cooled in the fridge (P<0.001) and reduced further following pre-cooling in the freezer (P<0.001).

Significance: The use of a polyvinyl matrix allows higher pulp temperature rises to occur due to the exotherm from provisional resins. Lower temperatures were recorded when putty was used. The temperature rise could be eliminated when the putty was cooled at 4 degrees C prior to reinsertion.