Effects of ProTaper Universal, Mtwo, and HyFlex Instruments on Crack Formation in Dentin

Abstract

Objective: The purpose of the present study was to evaluate the incidence of cracks in root dentin after root canal shaping procedures performed with the newly introduced HyFlex instruments compared with the ProTaper Universal and Mtwo instruments

Methods: One hundred extracted single-rooted mandibular premolars with mature apices and straight root canals (<5°) were selected and kept in distilled water. External root surfaces were meticulously inspected for defects using an LED.D, and radiovisiographs were taken to exclude teeth with multiple canals. The teeth were sectioned under water cooling, covered in wax, and set in an acrylic block. Light body silicon-based material was used to simulate the periodontal ligament. The samples were randomly divided into four groups: Group 1 (negative control, uninstrumented), Group 2 (ProTaper Universal), Group 3 (HyFlex), and Group 4 (Mtwo). The results were expressed as the number and percentage of cracked roots, and statistical analysis was performed using a chi-square test at a 95% confidence level (P = .05).

Results: No cracks were observed in the negative control group. Vertical root fractures were absent in all groups. The incidence of dentinal cracks varied significantly among the instrumented groups: Mtwo and HyFlex instruments induced fewer cracks (12% and 8%, respectively), whereas ProTaper Universal instruments showed a higher incidence of cracks (48%) (p < .05).

Conclusion: This study concluded that Instrumentation of root canals with Hyflex CM, Mtwo, and ProTaper could cause damage to root canal dentin.  Hyflex CM has a tendency to cause less dentinal cracks as compared with other files.