Evaluation of Dentinal Microcrack Formation with Endodontic Retreatment Files using Scanning Electron Microscope: An in vitro Study

Aim: The aim of this study is to evaluate the incidence of dentinal defects after root canal retreatment with ProTaper Universal retreatment (PTUR) and Hyflex remover file system using scanning electron microscope. Materials and Method: Sixty extracted single-rooted human teeth were selected and divided into 4 groups of 15 teeth each. In negative control group, teeth were left unprepared. In positive control group, teeth were prepared with ProTaper Next and obturated with no further retreatment. In PTUR and Hyflex groups, teeth were prepared and obturated followed by removal of the filling material with PTUR and Hyflex instruments, respectively. 3 mm of roots were then sectioned at 3 mm from the apex and observed under a scanning electron microscope to detect defects. Results: PTUR group showed significantly higher (p value <0.05) incidence of defects than the other groups. No significant differences were observed between Hyflex and the positive control group. Conclusion: Within the limitations of the present study it was concluded that all retreatment instruments used in this study created defects in the root dentin. PTUR instruments showed a significantly higher association with creating dentinal defects than Hyflex remover. Key words: Dentinal defects, Hyflex remover, PTUR files, Retreatment