The effect of heat-treated single-file systems on dentinal crack formation.

Objectives The aim of this study was to compare the formation of dentinal crack after root canal preparation performed with different heat treated single-file systems. Materials and Methods Forty mandibular premolar teeth were randomly divided into four groups according to the file system to be used during the preparation (n = 10): Group 1: Reciproc Blue; group 2: One Curve; group 3: HyFlex EDM; group 4: (control group) hand files. During the cleaning and shaping, irrigation was performed with a total of 10 ml of 5.25% sodium hypochlorite and 2 mL of distilled water. Then sections were taken from the roots (3, 6 and 9 mm). Sections were examined on a stereomicroscope to determine the presence of cracks. Chi-square test was used for data analysis. Results There was a significant difference between the groups in dentinal crack frequency (P 0.05). A statistically higher mean value was obtained in the control group compared to the other groups in terms of working time (P < 0.001). Conclusions All the files used during root canal preparation formed dentin crack. Hy-Flex EDM caused less dentinal cracks than other file systems. The flexibility of nickel-titanium instruments because of heat treatment seems to have a significant influence on dentinal crack formation.