Bending resistance and quantitative transportation assessment after multiple uses of a reciprocating instrument

Aim: This study assessed the ability of Reciproc R25 instruments in maintaining the original profile of root canal anatomy in simulated curved canals (SCC) after multiple uses. The bending resistance of R25 before and after each use was evaluated. Materials and methods: Fifty SCC manufactured in clear resin blocks and ten R25 instruments were used. Each instrument prepared five SCC with four reuses, without intermediate sterilization. The flexibility of each instrument was determined by 45-degree bending tests before and after reuse. Colour stereomicroscopic images from each block were taken at the same position before and after instrumentation. All image processing and data analysis were performed with Fiji program. Evaluation of canal transportation was obtained for straight and curved canal regions. Univariate analysis of variance and Tukey's test were used (P 0.05). Results: No significant difference was observed in bending resistance before and after multiple uses (P > 0.05). There was no difference in canal transportation resulting from utilizing R25 instruments after five multiple uses (P > 0.05). However, canal transportation was more severe in curved canal portions than straight portions (P 0.05). Conclusions: Bending resistance and the final shape obtained in plastic blocks following R25 instrument use did not vary significantly between the first and the fifth use. Keywords: dental instruments, root canal preparation, transportation