Efficacy of the ProTaper Retreatment system in removing Thermafil, GuttaCore or vertically compacted gutta-percha from curved root canals assessed by micro-CT

Abstract

Aim

To evaluate ex vivo the efficacy of ProTaper Universal Retreatment files (Dentsply Sirona, Ballaigues, Switzerland) in removing Thermafil, GuttaCore (both Dentsply Sirona) or vertically compacted gutta-percha from curved root canals using micro-CT.

Methodology

Sixty curved molar roots with the same mean canal curvatures and radii in two directions were prepared using ProFile instruments (Dentsply Maillefer) to size 30 with 0.04 taper and obturated with either Thermafil, GuttaCore or vertically compacted gutta-percha and AH Plus (n = 20). Specimens were retreated using the ProTaper Universal Retreatment files D1, D2 and D3 to working length and root canal preparation was completed with ProTaper Next (Dentsply Sirona) to size X4. Percentages of residual filling material and dentine removal were assessed using micro-CT imaging. Working time and procedural errors were recorded. Statistical analysis was perfomed using Kruskal-Wallis and Wilcoxon tests.

Results

No significant differences between carrier-based and warm vertical compaction regarding residual filling material (14.2-19.3%) and dentine removal (2.7-3.2 mm³) were detected (P > 0.05). Time to reach working length was significantly faster for canals filled with GuttaCore than that observed for Thermafil and warm vertical compaction (P < 0.05). Five lateral perforations with the D3 file occurred during retreatment, one in the Thermafil and four in the vertical compaction group.

Conclusions

Remaining filling material and dentine removal was similar for all canal filling techniques. Regaining working length was significantly faster for GuttaCore compared to Thermafil and vertically compacted gutta-percha. Procedural errors occured during retreatment of severely curved root canals with the ProTaper Universal Retreatment files in 5 out of 60 canals (8%).

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