A comparative study of root canal preparation with HERO 642 and Quantec SCrotary Ni-Ti instruments

Aim The purpose of this study was to compare several parameters of root can al preparation using two different rotary nickel-titanium instruments: HERO 642 (MicroMega, Besancon, France) and Quantec SC (Tycom, Irvine, CA, USA). Methodology Fifty extracted mandibular molars with root canal curvatures be tween 20 degrees and 40 degrees were imbedded into a muffle system. All roo t canals were prepared to size 45 (Quantec SC), or 40 (HERO 642), respectiv ely. The following parameters were evaluated: straightening of curved root canals, postoperative root canal diameter, safety issues (file fractures, p erforations, apical blockages, loss of working length), cleaning ability, a nd working time. Results Both Ni-Ti-systems maintained curvature well: the mean degree of st raightening was 2.3 degrees for Quantec SC and 1.6 degrees for HERO 642. Mo st procedural incidents occurred with Quantec SC instruments (five fracture s, three apical blockages, eight cases of loss of working length), HERO 642 preparation resulted in three blockages and one perforation. Following pre paration with HERO 642, 63% of the root canals showed a round, 24% an oval, and 17% an irregular diameter; Quantec SC preparations resulted in a round diameter in 24% of the cases, oval shape in 29%, and irregular cross-secti on in 47% of the cases. Mean working time was shorter for HERO 642 (52 s) t han for Quantec (117 s). Cleanliness of the root canal walls was investigat ed under the SEM using a five-score system for debris and smear layer. For debris HERO 642 achieved better results (80% scores 1 and 2) than Quantec S C (76%). The results for smear layer were similar: cleaner root canal walls were found after preparation with HERO 642 (53% scores 1 and 2), followed by Quantec SC (41%). Conclusions Both systems respected original root canal curvature well and s howed good cleaning ability; Quantec SC showed deficiencies in terms of saf ety.