Warm vertical compaction sequences in relation to gutta-percha temperature

The aim of this study was to analyze warm vertical compaction sequences in relation to the temperature variations of gutta-percha. Twenty-four maxillary incisors were obturated according to two different instrumentation techniques: Compaction and heating were performed with either the monomanual classical or bimanual method. To evaluate gutta-percha temperature, thermocouples (TC) were introduced into channels bored through the dentin into the root canal system or fixed on the root surface at 8 (TC8), 4 (TC4), 2 (TC2), and 0 mm (TC0) from the apex. Maximal temperature was 118 degrees C for TC8, 52 degrees C for TC4, and 44 degrees C for TC2 and TC0. At TC0, the temperature remained above 42.9 degrees C for 10 +/- 5 s. These results show the importance of heating down to a distance of 7 mm to ensure a significant increase in apical gutta-percha temperature. They further indicate that the last compaction should last more than 15 s to avoid detrimental cooling and dimensional variations. The principal differences between the monomanual and bimanual methods were the compaction time (5.07 +/- 0.2 min vs 4.02 +/- 0.3 min) and the number of compactions (8 +/- 1 vs 12 +/- 2).