Evaluation of the effect of various canal preparation thechniques on root crack formation

Abstract

Root fracture is not an instant event but a result of gradual propagation of tiny, less pronounced craze lines in tooth structure. Recent studies have shown that canal instrumentation has the potential to cause dentinal cracks. Aim: The purpose of this study was to compare the Protaper rotary system and hand instrumentation regarding formation of dentinal cracks. Method and materials: Fifty seven mandible incisor teeth were selected for the study. The teeth were decoronated. The roots were examined to exclude cracked samples. A standard model for PDL simulation was used. The teeth were randomly divided into 2 experimental and one control groups. The teeth in group 1 and 2 were prepared using hand and Protaper rotary instrumentation respectively. The teeth in control group left unprepared. The teeth were then sectioned horizontally 3 and 6mm from the apex and the presence of various dentinal defects was observed under microscope. The differences between groups were analyzed with Chi-square test. Result: Considering all types of defects, hand group demonstrated significantly more defects than control group (P=0.001).However, there was no significant difference between rotary and control or hand and rotary groups (p>0.05).Considering the fractures there was also no significant difference between groups (P>0.05). Conclusion: Protaper rotary system when used according to the manufacture instructions tends to produce less dentinal defects than hand instrumentation.