Assessment of the Effect of the Degree of Root Canal Taper on the Fracture Resistance of Endodontically Treated Teeth: An In Vitro Study

Objective: To evaluate and compare the fracture resistance of endodontically treated mandibular premolars using two different root canal preparation tapers. Methods: Eighty extracted single canal mandibular premolars were used. The specimens were sectioned for 13-mm roots. Then, all samples were randomly divided into four root canal preparation groups (n=20). Group 1 (n=20): Unprepared (control group). Group 2: A. (n=10) and B.(n=10), preparations with RACE EVO (FKG Dentaire SA, La Chaux de Fonds, Switzerland) rotary instruments up to size 30 taper 0.04, and size 30 taper 0.06, respectively, without obturation. Group 3 (n=20) and Group 4 (n=20): preparations with RACE EVO rotary instruments up to size 30 taper 0.04 and size 30 taper 0.06, respectively, then obturated with AH plus sealer by single cone obturation technique. Mechanical vertical compression testing with a universal testing machine exposed the samples to axial forces. Testing continued at 1 mm/min until samples shattered. The results were statistically analyzed by One-way ANOVA (p<0.05). Results: Different root canal taper preparations did not alter the fracture resistance of endodontically treated teeth in this study. G 1 had the strongest fracture resistance (898.00 N), whereas G 4 had the lowest (763.00 N). The groups did not vary statistically (P > 0.05). Conclusions: Root fracture resistance was unaffected by root canal preparation tapers. Conversely, the taper 0.06 preparations group had the least fracture resistance. The most unrepairable type III fractures were in taper 0.06 preparations.