Characterization of the differential efficacy of austenitic vs martensitic NiTi rotary files in non-surgical root canal retreatment: a micro-CT analysis

Aim: Our study aims to characterize the differen-tial efficacy of martensitic and austenitic files in root canal retreatment regarding defiling ability, debris management and morphometric features. Materials and methods: A total of 10 human premolar teeth with two separate fully formed roots were selected, prepared with BioRace system (BR) up to a size BR2 (0.04/25). Root canals were filled and then divided according to the file type into two groups (n = 10). Two geometrically identical files have been used with the only difference between them is heat treatment; One Curve (OC) martensitic and One Shape (OS) austenitic. Preoperative and postoperative Micro-CT scans were done for all the samples, and the percent volume of residual fill-ing materials was calculated. Canals reshaping and remain-ing debris in the canals were assessed by calculating the vol-ume of the canals before and after retreatment using Micro-CT software. Results: The percentages of removed filling materials were similar between both groups (97.2% OC vs 97.8% OS). OS was significantly faster than OC (P < 0.05). Retreatment procedure did not significantly change volume, structure model index, surface area, and canal cur-vature. OS group transported the canals more than OC at the apical third (P < 0.05). There were no significant dif-ferences between both groups concerning un-instrumented surface area and accumulated hard tissue debris (AHTD) (P > 0.05). Conclusion: Under the circumstances of this study, neither file systems could completely remove the fill-ing materials. However, OC resulted in less transportation than OS in the apical one third (P < 0.05). Also, OC re-sulted less AHTD than OS but with no statistical difference.