Frequency of morphological defects produced on the active surface of continuous and reciprocating rotation instruments after repeated use

Resumo

Root canal preparation is essential for the adequate sanitization of dentinal tubule systems, allowing favorable conditions for sealing in the cervical-apical direction. Objective: To analyze the frequency of morphological defects produced in continuous and reciprocating rotation instruments after repeated uses by scanning electron microscopy (SEM). Material and methods: Forty-five replicates of prototyped lower molars were randomly assigned to three groups according to the system used: G1. Biorace®, G2. V-File®, or G3. Protaper Next®. After root canal preparation, all the instruments were washed in an ultrasonic vat and subsequently analyzed by SEM to visualize the morphological defects (dullness of the edges, grooves, microcavities, and cracks) in images obtained with a magnification of 50x to 1500x. To determine defects on each instrument’s surface, the active part was divided into 14 parts, with segments on the two sides from 1 to 7. The relationship between the number of defects observed in the different instruments was assessed using chi-square tests. Results: Defects were observed in all tested instruments, with statistically significant differences between the systems (P<0.05). BioRace® system was associated with a significant higher number of defects, than V-File® (P><0.05) but was not significantly different from ProTaper Next® (P>0.05). No significant difference was observed between V-File® and ProTaper Next® groups (P>0.05). Conclusion: All the analyzed instruments showed defects in the active surface after repeated use.