Changes in root surface temperatures with in vitro use of the system B heatsource

The purpose of this study was to measure root surface temperatures while using the System B HeatSource at various temperature settings. A split-tooth model of a human maxillary central incisor was prepared with 10 thermocouples to record root surface temperatures at 1-mm increments from the root apex. A System B HeatSource model 1005 was used to warm and compact gutta-percha to within 3 mm of the working length using the Buchanan technique. Twenty obturations were recorded at each of the following temperature settings: 250°, 300°, 350°, 400°, 450°, 500°, 550°, and 600°C. Examination of the mean temperatures recorded for each position and at each temperature setting revealed that the thermocouple 5 mm from the apex (T5) detected the highest increases in root surface temperatures. Only this site exceeded the 10°C rise in temperature for one full minute that could cause damage to the supporting structures. The range of instantaneous temperatures at this site was 8.85 to 12.06°C, with a mean of 10.62 ± 0.93°C. The results of this in vitro study indicate that any temperature setting of the System B HeatSource at or above 250°C has the potential to cause the root surface temperature to rise 10°C. Whether this occurs in vivo or if it does is maintained long enough to cause any tissue damage remains to be determined.