Micro-computed tomographic assessment of dentinal microcrack formation in straight and curved root canals in extracted teeth prepared with hand, rotary and reciprocating instruments.

Abstract

To compare microcrack formation in roots of extracted teeth after the shaping of straight and curved root canals with hand, rotary and reciprocating files using micro-computed tomographic (micro-CT) analysis. Thirty straight mandibular incisors and 30 severely curved mesial roots of mandibular molars were randomly divided into 6 experimental groups (n=10) according to the systems used for the root canal preparation and the root canal curvature: ProTaper Universal for Hand Use (Dentsply Sirona, Ballaigues, Switzerland), HyFlex EDM (Coltene-Whaledent, Altstätten, Switzerland) and Reciproc Blue (VDW, Munich, Germany) files used in mandibular incisors (straight canals) and mesial roots of mandibular molars (curved canals). The roots were imaged with micro-CT scanning at an isotropic resolution of 14μm before and after root canal preparation, and the cross-sectional images generated were assessed to detect microcracks. All dentinal defects identified after root canal preparation were already present before instrumentation, and no new microcracks were detected. Dentinal microcracks were present in 19% (ProTaper Universal for Hand Use), 11% (Hyflex EDM) and 23% (Reciproc Blue) of the cross-sections when the instrumentation was performed in mandibular incisors. Instrumentation of mandibular molars revealed microcracks in 15% (ProTaper Universal for Hand Use), 16% (Hyflex EDM) and 17% (Reciproc Blue) of the cross-sections. Preparation of straight and curved root canals with ProTaper Universal for Hand Use, HyFlex EDM and Reciproc Blue systems did not produce microcracks in extracted teeth when evaluated with micro-CT.