In vitro evaluation of working time during endodontic retreatment

Abstract

Aim: The aim of this in vitro study was to evaluate the working time for gutta-percha and sealer removal using different instrumentation techniques. Methodology: The root canals of seventy-two extracted single-rooted straight premolars were prepared using BioRaCc rotary instruments and crown-down technique, before filling with laterally condensed gutta-percha and AH Plus" sealer. After 30-day storage at 37°C and 100% humidity, teeth were randomly allocated to 3 groups (n = 24) depending on retreatment instrumentation tech­nique: ProTaper Universal Retreatment System (PTUS); D-RaCe System and Hedstrom hand files. Stopwatch was used for measuring the working time. Measuring included the time required to reach the working length, time to complete the filling material removal and total re­treatment time. The criteria for complete filling material removal was absence of gutta-percha or scaler remnants during irrigation or attached to the files. Time required for gutta-percha removal, irrigation, working length meas­urement, instruments changing and cleaning was consid­ered as a total retreatment time. Data were analysed using one-way ANOVA and Scheffe's post-hoc test. Results: No significant difference between groups was demonstrated when comparing the time required to reach the working length. Complete removal of filling material was the fastest in PTUS group and the slowest in Hedstrom group. Significant differences were found between each group (p < 0.0001). After measuring the total retreatment time, significant differences were found when compar­ing both rotary systems to Hedstrom group (p < 0.0001), but no significant difference was found when comparing PTUS to D-RaCe, although the procedure was the fastest in PTUS group. Conclusion: Usage of rotary NiTi instruments for the re­moval of root filling material during retreatrnent proce­dure is less time-consuming comparing to hand files. No significant difference was recorded between two tested rotary systems.