Detecting Dentinal Microcracks Using Different Preparation Techniques: An In Situ Study with Cadaver Mandibles Paymon Bahrami, DDS, MSD,* Raymond Scott, DDS, MS,* Johnah C. Galicia, DMD, MS, PhD,* Ana Arias, DDS, PhD,* † and Ove A. Peters, DMD, MS, PhD* Abstract Introduction: This study assessed the frequency of dentinal microcracks using a cadaver mandible model in teeth instrumented with TRUShape (TS; Dentsply Si- rona, York, PA), WaveOne Gold (WO, Dentsply Sirona), or K-files (KF) compared with an uninstrumented control group (CG). Methods: Fifteen human mandibles with 95 single-rooted teeth were randomly distributed into the following groups: CG (no preparation, n = 11), TS (n = 28), WO (n = 28), and KF (step-back preparation with K-Flex-o-files [Dentsply Sirona], n = 28). Teeth were prepared to apical sizes of #25/.06 or #25/.07; overlying bone was removed, and then teeth were lifted out of the socket and sectioned at 3, 6, and 9 mm from the apex using a low-speed saw. Resulting slices were photographed at 20Â and 25Â magnification. Three in- dependent and blinded evaluators assessed the images for the presence of dentinal microcracks and their exten- sion, direction, and location. The chi-square test was used for statistical analysis (P < .05). Results: In the final sample of 83 teeth for the 4 groups, microcracks were found in 10 of 33, 13 of 66, 16 of 69, and 21 of 81 sections for CG, TS, WO, and KF, respectively. There were no significant differences in the frequency of microcracks among the CG, TS, WO, or KF instruments overall or when comparing section levels (3 mm [P = .9], 6 mm [P = .18], or 9 mm [P = .69], respectively, from the apex). There were also no significant differ- ences in the extension, direction, or location of the dentinal microcracks among all groups (P > .05). Conclusions: There was no difference in the frequency of microcracks among the experimental groups instru- mented with TS, WO, and KF or uninstrumented controls. (J Endod 2017;-:1–4) Key Words Dentinal microcracks, in situ model, rotary instrumentation C urrently, there ap- pears to be a contro- versy whether the fracture of root-filled teeth is attrib- uted to the loss of struc- ture or other contributing factors (1). One of the re- ported causes for extraction of an endodontically treated tooth is vertical root fracture (VRF) (2). VRF can be caused by root canal preparation (3). Some studies (4–7) suggest that dentinal microcracks may be created in root canal preparations by different rotary systems versus using hand filing techniques. Additionally, authors reported that dentinal microcracks, sometimes also labeled dentin defects or dentinal damage, are formed regardless of the file kinematics such as rotary movement or reciprocation (8, 9). Other authors suggested that file kinematics or preparation techniques had no effect on crack formation but implicated the length to which the canals were prepared (10–12). However, most of these studies were performed in vitro using extracted teeth with no bone and periodontal ligament (PDL), which likely alters internal forces received both during access cavity preparation and instrumentation of the root canal system. The PDL acts to absorb much of the forces introduced into teeth clinically (13). Although several other studies attempted to simulate the PDL (7,10–12,14,15), no artificial material was found to completely reproduce the viscoelastic properties of the PDL and the overlying periodontal tissue. In addition, there could be potential trauma and damage to the tooth during the extraction procedure, which may influence the outcomes of studies based on sectioning of extracted teeth. At the same time, studies using micro–computed tomography assess- ment have shown that dentinal microcracks observed postinstrumentation were frequently already present in the corresponding preoperative images (14–16), confirming the limitation of the use of extracted teeth for the assessment of dentinal microcracks induced by root canal preparation. However and despite the current evidence, many articles are still being published on the topic using extracted teeth and advising of the risk of microcrack induction when using rotary instruments (17, 18). In a previous study (19), a human cadaver model was used to overcome these shortcomings by preparing the teeth in situ and carefully separating the teeth from the mandible afterward for observation. In that study, no evidence of further dentinal damage was shown when comparing preparation with WaveOne or GT hand files (Dentsply Sirona, York, PA) compared with uninstrumented controls. However, that From the *Department of Endodontics, University of the Pacific, Arthur A. Dugoni School of Dentistry, San Francisco, California; and † Department of Conservative Dentistry, School of Dentistry, Complutense University, Madrid, Spain. Address requests for reprints to Dr Ove A. Peters, Department of Endodontics, Arthur A. Dugoni School of Dentistry, 155 5th St, San Francisco, CA 94103. E-mail address: opeters@pacific.edu 0099-2399/$ - see front matter Copyright ª 2017 American Association of Endodontists. http://dx.doi.org/10.1016/j.joen.2017.07.008 Significance In an in situ model, various canal preparation tech- niques (hand preparation, WaveOne Gold recipro- cation, and rotary TRUShape) did not create additional dentinal microcracks. Basic Research—Technology JOE — Volume -, Number -, - 2017 Detecting Dentinal Microcracks 1