Jeronimo CAREAGA, Ana Flávia Almeida BARBOSA, Graziela Dos Santos MASSA, Carolina O. LIMA, Erick M SOUZA, Ricardo Tadeu LOPES, Jorge N.R. MARTINS, Francisco Manuel BRAZ-FERNANDES, Marco A. VERSIANI, Luciana Moura SASSONE, Emmanuel JNL SILVA
European Endodontic Journal - 2026;11(5):196-206
Objective: This study aimed to assess the shaping ability of 2 preparation systems with similar designs but different heat treatments during the progressive enlargement of severely curved mesiobuccal and mesiolingual canals in mandibular molars. Methods: Twenty-two mandibular molars with mesial canals curved >25º were scanned, pair-matched and divided into 2 groups (n = 11) for preparation using austenitic (Genius) or martensitic (Genius Proflex) heat-treated instruments. Phase transformation temperatures of the instruments were determined via differential scanning calorimetry. Mesiobuccal and mesiolingual canals were first instrumented with a 17/.05 file and then sequentially enlarged using instruments sized 25/.04-40/.04, with scans taken after each enlargement step. Pre- and postoperative datasets were analysed for volume, surface area, unprepared canal areas, removed dentine volume, transportation and dentine thickness reduction. Statistical analyses included Student's t-test, Generalized Linear Model (GLM) multivariate model and independent t-tests (significance: P < .05). Results: Genius displayed an austenitic structure, while Genius Proflex exhibited an R-phase structure at both 20ºC and 36ºC. Instrument size increase (P = .001) and heat treatment (P < .001) significantly affected shaping outcomes without interaction effects (P = .882). Size increases impacted canal volume (P = .023), unprepared areas (P = .005), removed dentine (P < .001) and dentine thickness reduction (P < .001), but not surface area (P = .390). Heat treatment significantly influenced unprepared canal areas (P < .001). Martensitic instruments caused less transportation (P < .05) and preserved more distal dentine (P < .001) compared to austenitic instruments. Conclusions: In severely curved mesial canals of mandibular molars, martensitic instruments result in fewer unprepared areas, reduced transportation and better dentine preservation at the distal root canal wall compared with austenitic instruments.
