Comparison of hand and rotary instrumentation for removing gutta-percha from previously treated curved root canals: a microcomputed tomography study

AimTo compare the efficacy of hand and rotary nickel-titanium (NiTi) instruments in removing filling material from curved root canals of root filled teeth with unknown preparation parameters. MethodologyNinety mandibular molars with root fillings in curved root canals and homogenous root canal filling extending to 0-2mm short of the radiographic apex were selected. Root canal curvatures and radii were measured in two directions and microcomputed tomography (micro-CT) scans were used to determine preoperative volumes of the filling material. Subsequently, the teeth were assigned to two identical groups (n=14). The root fillings were removed with Hedstrom files or FlexMaster NiTi rotary instruments. Postoperative micro-CT imaging was used to assess the percentage of residual filling material as well as the amount of dentine removal. Working time and procedural errors were recorded. Data were compared using analysis of covariance and analysis of variance procedures. ResultsRoot canals retreated with Hedstrom files were associated with less remaining filling material compared with FlexMaster instruments (P<0.05). Both retreatment techniques removed similar amounts of dentine with no significant differences (P>0.05). FlexMaster instruments were significantly faster than Hedstrom files (P<0.05). No procedural errors were detected in the Hedstrom group, whilst three instruments fractured in the FlexMaster group. ConclusionsHand instrumentation resulted in significantly less residual filling material than retreatment with rotary NiTi instruments. Dentine removal was not significantly different for both techniques. FlexMaster NiTi rotary files were significantly faster than Hedstrom files, but were associated with a higher risk of instrument fracture.