Abstract
AIM: Ex vivo study to evaluate the efficacy of ProTaper Universal Retreatment instruments in removing Thermafil, GuttaCore and vertically compacted gutta-percha from curved root canals using micro-CT. METHOLOGY: 60 curved root canals were divided into 3 groups with similar average curvatures and radii in two dimensions. All canals were prepared using ProFile instruments to size 30/.04 and then filled with either Thermafil, GuttaCore or vertically compacted warm gutta-percha (n=20). All roots were scanned using the micro-CT before retreatment. Retreatment was performed using ProTaper Universal Retreatment and ProTaper Next instruments to size 40/.06 before all roots were scanned in the micro-CT once more. Efficacy was evaluated by residual root canal filling and dentine removal, both assessed by the micro-CT images, and needed working time and procedural errors, both recorded during the retreatment. Statistical analysis was performed using Kruskal-Wallis and Wilcoxon tests. RESULTS: No significant differences regarding the percentages of residual filling (14.2-19.3%) and the amount of dentine removed (2.7-3.2mm³) were detected (p > 0.05). Time to reach working length and total time for the retreatment were significantly faster for canals filled with GuttaCore than Thermafil or vertically compacted gutta-percha (p < 0.05). Procedural errors in form of lateral perforations occurred in four vertically compacted specimens and in one Thermafil specimen. CONCLUSIONS: residual filling occurred in all examined specimens. The amount did not differ significantly between the three groups. The amounts of dentine removed were also similar. Time to reach working length and complete retreatment was significantly faster for GuttaCore compared with Thermafil and vertically compacted gutta-percha. Lateral perforations occurred in 5 of 60 canals.
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