RESUMO
With the use of an extracted human tooth as in vitro model, this study measured temperature changes in the surface of gutta-percha while it was being ultrasonically thermoplasticized. Two sources of ultrasonic oscillation were used: a Cavitron 2001 ultrasonic unit with a file in a PR-30 insert and an ENAC ultrasonic unit with a plugger or file. Temperature elevation in the apical third of the tooth was minimal with either instrument (1.66 degrees C to 3.74 degrees C). The temperature rise in the middle third was higher with the ENAC unit, although probably still within clinically acceptable limits (range, 6.35 degrees C to 19.10 degrees C). The time taken for each unit to thermoplasticize the gutta-percha and reach a predetermined distance in the experimental model was recorded and defined as instrument efficiency. The Cavitron unit that had the PR-30 insert with a No. 25 file required 0.48 sec/mm, whereas the ENAC unit with a No. 25 file required 10.83 sec/mm and the ENAC unit with a plugger required 8.38 sec/mm. It appears that the Cavitron unit with a PR-30 insert was more than 22 times as efficient as the ENAC unit for thermoplasticizing gutta-percha under the experimental conditions used in this study.
