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Effect of three different rotary instrumentation systems on crack formation in root dentin: An in vitro study

Introduction: Biomechanical preparation (BMP) of root canal damages the root dentin which becomes a gateway to dentinal cracks and thereby causing failure of the treatment. Therefore, there is a need of best instruments to minimize the failure of endodontic treatment. Aims and Objective: The objective of this study is to compare the incidence of cracks observed in the root dentin after root canal preparation with three different rotary instrument systems. Material and Methods: Seventy-five freshly extracted permanent maxillary incisors were randomly selected. Teeth were divided into five groups (n = 15), Group 1 – Untreated (negative control group), Group 2 – BMP done with nickel–titanium K-files (positive control group), Group 3 – BMP done with ProTaper Universal files, Group 4 – BMP done with ProTaper Next files, and Group 5 – BMP done with HyFlex EDM files. Roots were sectioned horizontally at 2 mm, 4 mm, and 6 mm from the apex. All slices were then viewed under stereomicroscope. All findings were analyzed using Chi-square test. Observations and Results: In the apical third, Group 5 had maximum number of fracture cases while Group 4 had lesser number and Group 3 had the least. In the middle third, Group 3 had maximum number of fracture cases while Group 4 and Group 5 showed lesser number of fractures. In the cervical third, Group 3 and Group 4 showed equal and maximum number of fracture cases. Group 5 showed no fracture cases. Group 1 and Group 2 showed no fracture cases in all the root sections. Conclusion: Conventional hand instrumentation is the best as compared to rotary instrumentation. However, rotary systems render various benefits with an acceptable success in comparison to the conventional hand instrumentation. In our study, we found that HyFlex EDM rotary system was the best with least number of fracture as compared to other systems used.