Effect of Hand Files, Rotary Protaper Universal and Protaper Retreatment Files on Crack Formation in Dentin: an in Vitro Study

Background: The aim of the study was to compare the effect of hand files, rotary protaper universal files and protaper retreatment files on crack formation in dentin. Methods: Eighty mandibular premolar teeth with single canals are selected and mounted on resin blocks with simulated periodontal ligaments. The teeth were divided into four groups of twenty samples in each group. Un-instrumented group serves as control group while group two and three consists of hand file and rotary protaper universal file system respectively. Group 4 consists of retreatment group consisting of two sub groups of ten samples in each group. Subgroup 4a consist of samples prepared with hand file while subgroup 4b consist of samples prepared with rotary protaper universal system. Thereafter, retreatment is performed with protaper retreatment file system in both the sub groups. All the roots were sectioned perpendicular to the long axis at 4mm from apex using a low speed saw (Isomet) under water cooling. Digital images of each sections were captured at 25X magnification using a digital camera attached to a stereomicroscope and cracks were noted. Results: Although the result is statistically non significant, hand files show less number of cracks as compared to rotary protaper universal file