Comparative evaluation of root dentin defects produced by commercially available rotary endodontic single-file systems used in two different motions: an in-vitro study

Introduction
Optimal preparation of the root canal system allows establishment of the essential ‘three-dimensional seal’. Overzealous preparation of root canals may cause dentinal cracks and fractures; leading to endodontic failure. Recent evidence iterates that vertical root fractures (VRFs) are probably caused by propagation of these smaller, less pronounced dentinal defects and not by force practiced during preparation. OBJECTIVES: The aim of the study was to evaluate and compare the presence of dentinal defects after root canal preparation using two endodontic single file systems, One Curve and WaveOne Gold (WOG) with two different working motions, continuous rotary and reciprocating motion, respectively.

Material and methods
Twenty single-rooted teeth were selected and divided into three groups: Group 1, control (n = 4); group 2, continuous rotary One Curve single-file system (n = 8), and group 3, reciprocating WOG single-file system (n = 8). Root canal preparation was performed in groups 2 and 3, followed by root sectioning in all the three groups at 3, 6, and 9 mm from apical end, and observed under stereo-microscope (40× magnification) for the presence of any dentinal defects. Intra-group samples were compared for mean defect scores using analysis of variance (ANOVA), and Tukey’s post-hoc test was applied for pairwise comparisons.

Results
All groups recorded the presence of dentinal defects. The recorded dentinal defects were 8.3%, 25%, and 12.5% in group 1, group 2, and group 3, respectively. Continuous rotary One Curve single-file system showed an increased number of dentinal defects compared with reciprocating WOG single-file system. Overall, craze line defects were more commonly observed when compared with incomplete and complete dentin cracks. Most of the defects were observed at the middle section, followed by the coronal and apical sections.

Conclusions
The current research show that dentinal defects can lead to vertical root fracture, compromising the prognosis. Detailed knowledge regarding instruments’ kinematics and proper chemico-mechanical preparations are imperative in successful treatment.