Stress analysis of simulated maxillary first molar prepared with three rotary nickel ⁃ titanium instruments

Abstract

Objective To compare the differences in the stress distribution in simulated first molars prepared with three rotary nickel⁃titanium instruments. Methods Four simulated first molars were prepared without instruments and with Reciproc, WaveOne and Protaper. Before and after preparation, each simulated molar was scanned by Micro ⁃CT. The data were imported to Mimics 16.0 software to establish three⁃dimensional models. Finite element analysis was pro⁃ cessed with Abaqus 6.14 software under conditions of longitudinal and lateral load. Results Under vertical load condi⁃ tions, the maximum von Mises stress of the enamel increased by 1.36%, 21.48% and 20.99% in the Reciproc, WaveOne and Protaper groups, respectively, after preparation, while the maximum von Mises stress of the cementum increased by 55.98% , 41.18% and 33.04% , respectively, and the maximum von Mises stress of the alveolar bone increased by 45.55%, 40.37% and 24.09%, respectively. Under 45° lateral load conditions, the maximum von Mises stress of the enamel increased by 1.79%, ⁃4.58% and 3.82% in the Reciproc, WaveOne and Protaper groups, respectively, after prep⁃ aration, while the maximum von Mises stress of cementum increased by 16.33%, 7.58% and 4.32%, respectively, and the maximum von Mises stress of the alveolar bone increased by 46.82%, 36.40% and 8.29%, respectively. Under the same conditions, the von Mises stresses of the cementum and alveolar bones of the simulated molars were higher after preparation than before preparation, especially under lateral load conditions. The stress was focused on the border be⁃ tween the crown and the root. The von Mises stress of the cementum and alveolar bones increased much more in the Re⁃ ciproc group than in the other two groups under both conditions. Conclusion The von Mises stress of simulated molars was greater after preparation than before preparation. The von Mises stress of the cementum and alveolar bones in⁃ creased much more in the Reciproc group than in the other two groups.

Keywords

• Root canal preparation
• Nickel⁃titanium instruments
• Stress
• Single files
• Micro⁃computed tomog⁃ raphy
• Finite element analysis