The Ability of Different Nickel-Titanium Rotary Instruments to Induce Dentinal Micro-cracks during Root Canal Preparation

Abstract

Abstract Objective The aim of this study was to investigate the incidence of cracks in root dentin after root canal preparation with SmartTrack files, ProTaper Next files, and HyFlex CM files. Materials and Methods Sixty extracted single-rooted human mandibular premolars with one canal were used for the study. Fifteen teeth were left unprepared and served as control; another 15 were instrumented with SmartTrack files up to 30/0.06, and the remaining 30 were shaped with ProTaper Next till X3 and HyFlex CM files up to 30/0.04. After root canal preparation, all the roots were sectioned perpendicular to the long axis at 2, 4, and 6 mm from the apex, and the sections were then observed under a stereomicroscope. The absence or presence of cracks was recorded. Results No cracks were observed in the control group. There was presence of cracks at all the levels in all the experimental groups. There was a significant difference in crack formation when the groups were compared whereas this difference was not significant when the levels were compared (p > 0.05). In the SmartTrack group, there was crack in 73% samples whereas in HyFlex CM and ProTaper Next, the number of samples with cracks was 27% and 53%, respectively. In the apical region, the number of samples that shows cracks was 29% whereas the number of cracks in the middle and coronal regions was 20%. Conclusion Within the limitations of this study, root canal preparation with rotary nickel-titanium (Ni-Ti) instruments can cause crack formation in root canal dentin. The ProTaper Next and HyFlex instruments have a tendency to cause fewer dentinal cracks compared with the SmartTrack instruments.