Objective - To compare the incidence of dentinal cracks caused by rotary NiTi instruments using ProTaper Next, 2 Shape (2S) and Neolix systems after root canal preparation. Materials and Method – Forty five freshly extracted mandibular premolars were obtained and randomly divided into three experimental groups (n=15).Group I- BMP done with ProTaper Next (PTN) files; Group II – BMP done with 2Shape (2S); Group III – BMP done with Neolix files. The roots were then sectioned horizon tally at 3mm (coronal), 6mm (middle) and 9mm (apical) from the apex. The slices were viewed under stereomicroscope. The presence of dentinal defects was noted. Data were analysed using non parametric Chi square testand Kruskal-Wallis test. Result –There was statistically significant difference amongst the three groups (p ≤ 0.05) when compared in apical third, with maximum number of cracks in Group III. In middle third, maximum cracks were seen in Group III followed by Group II and Group I. The difference was statistically non-significant (p>0.05). In coronal third non-significant (p>0.05) difference was observed between Group II and Group III with more cracks in the latter. No cracks were observed in Group I group for coronal third. Conclusion- 2 Shape files show lesser cracks then Neolix & more than PTN system. Pro Taper Next system showed least cracks and was found to be better than other file systems.
