Zahra Sadat Madani - Assistant Professor, Department of Endodontics, Faculty of Dentistry, Babol University of Medical Sciences, Babol, Iran
Akam Saeidi - Assistant Professor, Department of Endodontics, Faculty of Dentistry, Babol University of Medical Sciences, Babol, Iran
Ali Bijani - Assistant Professor, Social Determinant of Health Research Center, Health Research Institute, Babol University of Medical Sciences, Babol, Iran
Hanif Allahbakhshi - Assistant Professor, Department of Prosthodontics, Faculty of Dentistry, Kashan University of Medical Sciences, Kashan, Iran
Azadeh Hesarkhani - Assistant Professor, Department of Endodontics, Faculty of Dentistry, Kashan University of Medical Sciences, Kashan, Iran

Background:One of the main reasons for extraction of endodontically treated teeth is vertical root fracture (VRF). Some factors such as root canal treatment are involved in vertical root fracture because of their potential to weaken the tooth structure. Therefore, this study aimed to investigate the effect of combining different obturation materials and rotary systems on the fracture resistance of treated teeth. Methods:Eighty extracted maxillary central incisors were selected. The coronal portions of all teeth wereremoved at the cemento-enamel junction leaving the root segment of nearly ۱۳ mm length. Roots were randomly divided into۲ groups according to the system used in root canal preparations, Group I: ProTaper, Group II: Wave ۱. Each main group was further subdivided into ۲ equal subgroups according to the obturation system being used, Subgroup A: ProTaper, AH۲۶ obturator, Subgroup B: ProTaper, Bioceramic, Subgroup C: Wave ۱, AH۲۶ obturator and Subgroup D: Wave ۱, Bioceramic. Fracture resistance of each sample was measured by loading in universal testing machine. The results were analyzed with two-way ANOVA followed by multiple comparison Tukey HSD test. Results: The highest mean fracture resistance value (۲۵۶.۷N) was associated with Soft-Core/AH۲۶ obturation and wave one (subgroup C), while the lowest value (۲۳۹.۸ N) was for Bioceramic sealer and Wave ۱ (subgroup D); however, there was no statistical significant difference (P>۰.۰۵) among all tested subgroups. Conclusion: All instrumentation techniques caused weakening of the root structure and made them susceptible to fracture without any significant difference and therefore alternative strategies should be considered to reinforce endodontically treated roots.

fracture, Resistance, Root Canal Preparation, Endodontic Obturation