Sang Won Kwak1, Jung-Hong Ha2, Ya Shen3, Markus Haapasalo3, Hyeon-Cheol Kim4. 1. Department of Conservative Dentistry, School of Dentistry, Dental and Life Science Institute, Dental Research Institute, Pusan National University, Yangsan, Korea. 2. Department of Conservative Dentistry, School of Dentistry, Kyungpook National University, Daegu, Korea. 3. Division of Endodontics, Department of Oral Biological and Medical Sciences, Faculty of Dentistry, The University of British Columbia, Vancouver, British Columbia, Canada. 4. Department of Conservative Dentistry, School of Dentistry, Dental and Life Science Institute, Dental Research Institute, Pusan National University, Yangsan, Korea. Electronic address: golddent@pusan.ac.kr.
Abstract
INTRODUCTION: This study aimed to compare the torque generated by four different files in root canals with four different curvature angles. METHODS: Four brands of nickel-titanium (NiTi) endodontic files were selected: WaveOne Primary, WaveOne Gold Primary, ProTaper Universal F2, and ProTaper Next X2. A tempered steel block containing artificial canals with four different canal curvatures (15°, 25°, 35°, and 45°) was constructed. Each file was used according to the manufacturer's instructions in the dynamic model, with an added 15 axial up-and-down movements of 4 mm at the end of the canal. The generated torque was recorded, and the total and maximum torque values were measured. A two-way analysis of variance and Duncan's post-hoc comparison were performed at a significance level of 95%. RESULTS: A significant correlation between the curvature angle and the type of file system was observed (P < .05). As the degree of canal curvature increased, the generated total and maximum torque increased. At 15° and 25°, the NiTi files with reciprocating motion generated a higher total and maximum torque than files with continuous rotation. ProTaper Universal of conventional NiTi alloy showed the steepest increase in the generated total and maximum torque with the increasing curvature angle. ProTaper Next file had the lowest torque values at the higher canal angles of 35° and 45° (P < .05). CONCLUSIONS: Despite the study limitations, it can be concluded that root canal curvature, design, and heat-treatment of NiTi files, and file kinematics affect the generated torque during instrumentation.
INTRODUCTION: This study aimed to compare the torque generated by four different files in root canals with four different curvature angles. METHODS: Four brands of nickel-titanium (NiTi) endodontic files were selected: WaveOne Primary, WaveOne Gold Primary, ProTaper Universal F2, and ProTaper Next X2. A tempered steel block containing artificial canals with four different canal curvatures (15°, 25°, 35°, and 45°) was constructed. Each file was used according to the manufacturer's instructions in the dynamic model, with an added 15 axial up-and-down movements of 4 mm at the end of the canal. The generated torque was recorded, and the total and maximum torque values were measured. A two-way analysis of variance and Duncan's post-hoc comparison were performed at a significance level of 95%. RESULTS: A significant correlation between the curvature angle and the type of file system was observed (P < .05). As the degree of canal curvature increased, the generated total and maximum torque increased. At 15° and 25°, the NiTi files with reciprocating motion generated a higher total and maximum torque than files with continuous rotation. ProTaper Universal of conventional NiTi alloy showed the steepest increase in the generated total and maximum torque with the increasing curvature angle. ProTaper Next file had the lowest torque values at the higher canal angles of 35° and 45° (P < .05). CONCLUSIONS: Despite the study limitations, it can be concluded that root canal curvature, design, and heat-treatment of NiTi files, and file kinematics affect the generated torque during instrumentation.