Root Canal Preparation Does Not Induce Dentinal Microcracks In Vivo

Introduction: This in vivo study aimed to evaluate the development of dentinal microcracks after root canal preparation of contralateral premolars with rotary or hand instruments using micro-computed tomographic technology. Methods: Sixty contralateral intact maxillary and mandibular premolars in which extraction was indicated for orthodontic purposes were selected and distributed into positive (n = 6, teeth with induced root microcracks) and negative (n = 6, intact teeth) control groups as well as 2 experimental groups (n = 24) according to the instrumentation protocol: ProTaper rotary (PTR) or ProTaper hand (PTH) systems (Dentsply Maillefer, Ballaigues, Switzerland). After root canal preparation, teeth were extracted using an atraumatic technique and scanned at a resolution of 17.18 mu m. A total of 43,361 cross-sectional images of the roots were screened for the presence of dentinal microcracks. The results were expressed as the percentage and number of root section images with microcracks for each group. Results: All roots in the positive control group showed microcracks at the apical third, whereas no cracks were observed in the specimens of the negative control group. In the PTR group, 17,114 cross-sectional images were analyzed, and no microcrack was observed. In the PTH group, dentinal microcracks were observed in 116 of 17,408 cross-sectional slices (0.66%) of only 1 specimen. These incomplete microcracks extended from the external root surface into the inner root dentin at the area of reduced dentin thickness. Conclusions: Root canal instrumentation with PTR and PTH instruments of contralateral maxillary and mandibular premolars did not result in the formation of dentinal microcracks in vivo.