Evaluation of surface defects in the root canal dentin after preparation with two types of NiTi rotary files

Vertical root fracture (VRF) is one of the incidents that can happen during root canal therapy, either during preparation or canal obturation, eventually resulting in tooth loss. Several new rotary systems have been introduced in recent years. The aim of this study was to evaluate surface defects in the root canal dentin after preparation with two different NiTi rotary file systems. In this experimental study, 75 mandibular single canal premolars were selected and divided into three equal groups: group 1 samples were prepared with ProTaper system; group 2 samples were prepared with Mtwo system; and group 3 samples were not prepared (control) (n=25). Each root canal was irrigated with 12 mL of 2% NaOCl solution. Distilled water was used as the final rinse. The samples were sectioned at 3-, 6- and 9-mm distances from the apex and evaluated under ×12 magnification. The defects were categorized in 3 groups: no defects, fractured and defective. Data were analyzed with chi-squared and Fisher’s exact tests (α=0.05). The greatest defects were detected in groups 1 and 2. There were significant differences between ProTaper and Mtwo groups on one hand and the control group on the other (p value = 0.022). There was no significant differences between ProTaper and Mtwo systems (p value = 0.001). Under the limitations of the present study, the Mtwo and ProTaper rotary systems exhibited no differences in inducing microcracks and defects on the canal wall dentin during root canal preparation.