Comparison of dentinal crack incidence by using two different tapers of rotary systems: RaCe and Hyflex CM before and after lateral compaction obturation technique

Abstract

Introduction: Root canal preparation is one of the most important steps in root treatment, which is carried out with the aid of different instruments. Research results suggest that files used in the canal preparation stage may create several cracks in the dentin but the results vary by the file tapers. The present study is an attempt to analyze the effects of using different tapers and different rotary devices in canal preparation on dentinal cracking and to study the difference between tapers in creating microcracks following the adoption of the lateral obturation method.

Materials and Methods: A total of 204 mesiobuccal roots of extracted maxillary first molars with only one apical foramen were selected and classified into the following 17 categories: the control group consisting of 12 teeth (unprepared teeth); 8 groups including roots prepared with 4% taper and apical size of no #30 using RaCe and Hyflex CM files, roots prepared with 4% taper and apical size of no #25 using RaCe and Hyflex CM files, roots prepared with 6% taper and apical size of no #30 using RaCe and Hyflex CM files, roots prepared with 6% taper and apical size of no #25 using RaCe and Hyflex CM files; and 8 groups that were prepared with the same methods used in the previous groups and were obturated with lateral compaction technique. Following the preparation and obturation phases, the teeth were cut into three 3, 6 and 9 mm sections and the sections were examined under a stereomicroscope with X63 magnification by two observers. The presence or absence of cracks in each section was calculated for each group, and the results were compared using the chi-square test and Fisher's Exact Test. Results: The crack formation in the two system types before and after obturation were similar in the 9 and 6 sections but in the 3 mm section in the RaCe system was significantly higher than the Hyflex CM system (especially with an increase in the final apical size). In final apical size off 30 and 0.06 taper in the 9 and 3 sections, crack formation in the RaCe system before and after obturation was higher than the Hyflex CM system. Conclusion: According to the results of this study, in the RaCe system with increasing the size of the canal preparation causes more cracks in the 9 and 3 area of the tooth, while in the Hyflex CM group, which is made of special type of alloy, apical size, taper and obturation forces make no difference in crack formation. The lowest crack formation was sees in 3 sections of Hyflex CM.