ORIGINAL RESEARCH Untouched canal areas and debris accumulation after root canal preparation with rotary and adaptive systems Rosa Maria Vianna Lopes, DDS, MSc 1 ; Fernanda Cunha Marins, DDS 1 ; Felipe Gonçalves Belladonna, DDS, MSc 2 ; Erick Miranda Souza, DDS, MSc, PhD 3 ; Gustavo De-Deus, DDS, MSc, PhD 2 ; Ricardo Tadeu Lopes, DDS, MSc, PhD 4 ; and Emmanuel Jo~ ao Nogueira Leal Silva, DDS, MSc, PhD 1 1 Department of Endodontics, School of Dentistry, Grande Rio University (UNIGRANRIO), Duque de Caxias, Rio de Janeiro, Brazil 2 Department of Endodontics, Fluminense Federal University (UFF), Niter oi, Rio de Janeiro, Brazil 3 Department of Dentistry II, Federal University of Maranh~ ao, S~ ao Luis, Maranh~ ao, Brazil 4 Nuclear Engineering Program, Federal University of Rio de Janeiro (UFRJ), Rio de Janeiro, Rio de Janeiro, Brazil Keywords debris, micro-computed tomography, shaping ability, untouched canal areas. Correspondence Emmanuel Jo~ ao Nogueira Leal da Silva, Department of Endodontics, School of Dentistry, Grande Rio University (UNIGRANRIO), Rua Herotides de Oliveira, 61/902, Icara  ı, Niter oi, RJ, Brazil. Email: nogueiraemmanuel@hotmail.com doi: 10.1111/aej.12237 (Accepted for publication 8 August 2017.) Abstract This study assessed the percentage of untouched canal areas and the amount of debris accumulation after canal preparation with ProTaper Next (PTN) and Twisted File Adaptive (TFA) systems using micro-computed tomographic (mi- cro-CT) imaging. Twenty isthmus-containing mesial roots of mandibular molars were anatomically matched through micro-CT evaluation and ran- domly assigned to one of the two experimental groups (n = 10), according to the system used for canal preparation: PTN (X1 and X2 files using rotary motion) and TFA (SM1 and SM2 files using adaptive motion). After canal preparation up to ISO size 25, the specimens were then scanned and the matched images of the mesial canals, before and after preparation, were exam- ined from the furcation level to the apex to quantify the untouched surface canal areas and to evaluate the amount of accumulated debris. An indepen- dent samples t-test and a Mann–Whitney test were used, respectively, to com- pare these variables between the groups with a significance level set at 5%. Root canals prepared with either PTN or TFA systems were found to present similar untouched canal surface areas (P = 0.52) and hard-tissue debris accu- mulation (P = 0.39). Both systems produced a suboptimal and similar mechan- ical preparation of the mesial canals of mandibular molars and were not able to yield root canals completely free from packed hard-tissue debris. Introduction Development of new nickel–titanium (NiTi)-based root canal preparation systems has been primarily based on changes in the instrument design, alloy and kinematics. These modifications continue evolving with the core aim to optimise outcomes related to the shaping ability of the instruments. Despite the improvement of file sys- tems, several studies continuously report the observa- tion of large amounts of untouched canal walls (1,2) and accumulation of hard-tissue debris in fins, isth- muses and irregularities, which are considered as highly undesirable effects/limitations of mechanical prepara- tion (3–5). In infected root canal systems, untouched canal walls and accumulated hard-tissue debris may conceal bacteria and serve as a cradle for maintaining root canal infection (5). Recently, a new M-Wire NiTi rotary system (ProTaper Next (PTN); Dentsply Maillefer, Baillaigues, Switzerland) was introduced into the market with the claim by the manufacturer to improve canal-shaping effectiveness. It is designed with progressive and regressive percentage tapers, a unique off-centred rectangular design for supe- rior strength and a novel asymmetric rotary motion (6,7). Moreover, its offset design is indicated as a novel feature to maximise auguring debris out of the canal (8). Using a patented unique kinematics technology, Twisted File Adaptive (TFA; SybronEndo, Orange, CA, USA) is another new system recently launched. It is driven by a dedicated motor (Elements Adaptive motor; SybronEndo) © 2017 Australian Society of Endodontology Inc 260 Aust Endod J 2018; 44: 260–266