Effect of simulated pulpal blood flow rate on the rise in pulp chamber temperature during direct fabrication of exothermic provisional restorations.

Abstract

To evaluate exvivo the effect of several simulated pulpal blood flow rates on the change in pulp chamber temperature during direct fabrication of a provisional restoration using a polymethylmethacrylate (PMMA) resin. Fifteen noncarious human premolars were prepared for complete coverage restorations. A curved needle connected to a peristaltic pump simulated the pulp blood flow. Two K-type thermocouples connected to a digital thermometer were placed in the pulp chamber, and the assembly was placed in an incubator at 37°C. Three provisional crowns were made for each specimen using no water flow (group 1), a 1-mLmin-1 flow rate (group 2) and a 0.5-mL/min-1 flow rate (group 3). The pulp chamber temperature was recorded continuously during polymerization until the temperature increase peaked and started to decrease and reached the baseline temperature (37°C). The temperature increase was measured for the three water flow conditions. Data were analysed statistically using descriptive statistics, repeated measures one-way analysis of variance (anova) with Greenhouse-Geisser correction and Bonferroni tests. The level of significance was set at P<0.05. All of the groups were associated with an increased pulp chamber temperature. Groups with flow rates at 1 and 0.5mLmin-1 had a significantly lower temperature rise when compared to the group without water flow (P<0.001). Direct fabrication of provisional restorations can cause a critical increase in pulp chamber temperature. However, in the presence of simulated pulpal blood flow rates of 1 or 0.5mLmin-1 , the increase in pulp chamber temperature did not exceed the critical threshold (5.6°C).