RESUMO
AIM: To compare the efficacy of conventional and new retreatment instruments when removing gutta-percha root fillings in curved root canals. METHODOLOGY: A total of 56 curved molar roots were instrumented with ProFile instruments and filled using system B and Obtura II. The root fillings were removed with manual K-files and Hedström files (Dentsply Maillefer), ProFile (Dentsply Maillefer), R-Endo (Micro-Mega) or ProTaper Universal retreatment files (Dentsply Maillefer). Eucalyptol was used as a solvent with all techniques. Bucco-lingual and proximal radiographs of the roots were exposed and the percentage area of the remaining material was calculated by dividing the area of remaining filling material by the area of canal wall. Data were statistically analysed with Kruskal-Wallis and Mann-Whitney U tests (P = 0.05). RESULTS: None of the techniques completely removed the root filling materials. No significant differences were found amongst the coronal, middle and apical thirds in both radiographic projections (P > 0.05). In the bucco-lingual direction, the remaining filling material was significantly less following manual instrumentation than R-Endo and ProTaper instrumentation (P < 0.05). In the proximal view, it was significantly less following manual and ProFile instrumentation than R-Endo (P < 0.05). Complete removal of filling material occurred only in three specimens (with manual instruments). Manual instruments were significantly faster than R-Endo and ProFile (P < 0.05). More procedural errors (five fractured instruments and two perforation) were noted when using ProTaper (P < 0.05). CONCLUSIONS: In this laboratory study in curved molar roots, ProTaper Retreatment and R-Endo instruments were less effective in removing filling material from canal walls than manual and ProFile instruments.
