Temperature changes in thermoplasticized gutta-percha: a comparison of two ultrasonic units

Ultrasonic condensation of gutta-percha: the effect of power setting and activation time on temperature rise at the root surface - an in vitro study

AIM

To determine the effect of power setting and duration of activation on the temperature rise at the root surface during root canal obturation by ultrasonic condensation of gutta-percha.

METHODOLOGY

A human maxillary canine was used in an in vitro split tooth model to allow repeated obturation of the root canal system using an ultrasonic device to thermocompact gutta-percha. Combinations of power settings (1, 3 and 5) and durations of activation (4, 10 and 15 s) were used to test their effect on temperature rise at the root surface using eight K-type thermocouples at the mid-root and apical levels. At the end of each obturation, the tooth was disassembled to remove the gutta-percha in preparation for the next obturation (n = 10 for each combination). Multiple linear regression models were used to investigate the effects of power setting, duration of activation and thermocouple location on the maximum temperature rise recorded.

RESULTS

Only one combination of power setting (5) and duration of activation (15 s) resulted in temperature rise in excess of 10 degrees C. The maximum temperature rise at the mid-root level was significantly (P < 0.001) greater than that recorded apically. It is also significantly affected by the combination of power setting and duration of activation.

CONCLUSIONS

Temperature rises at the root surface during ultrasonic condensation of gutta-percha in excess of 10 degrees C were evident in only one combination of power (5) and time (15 s) settings at the mid-root level.

Residue of gutta-percha and a glass ionomer cement sealer following root canal retreatment

A previous report indicates that root canals obturated with a new glass ionomer cement endodontic sealer (Ketac-Endo, Espe, Germany) and laterally condensed gutta-percha can be retreated by ultrasonic instrumentation. To address the possibility of Ketac-Endo being used without condensation of gutta-percha, the purpose of this study was to evaluate the efficacy of ultrasonic retreatment in canals obturated with single-cone gutta-percha and Ketac-Endo. Thirty root canals were prepared in a standardized way to ISO size 40 and obturated with gutta-percha and Ketac-Endo. Either a size 40 gutta-percha cone was used with and without lateral condensation, or a size 25 single cone, without condensation. After 14 days, the canals were retreated using chloroform and ultrasonic instrumentation. The roots were split vertically, and the amount of residual debris on the canal walls was assessed by three examiners using a dissecting microscope. Debris was recorded in the apical, middle and coronal canal levels according to a preset evaluation scale. The mean scores for each group were compared by ANOVA and Mann-Whitney U-test, with a 5% level of significance. In the roots obturated with lateral condensation the amounts of residual debris in the coronal and middle canal levels was lower than in the other two groups, whereas in the apical level it was higher. Statistically, only the differences in the apical level were significant (P < 0.03). It was concluded that ultrasonic retreatment may be performed effectively in root canals obturated with single-cone gutta-percha and Ketac-Endo.