Stress distribution in a mandibular premolar after separated nickel-titanium instrument removal and root canal preparation: a three-dimensional finite element analysis

Abstract

Objective: This study used finite element analysis (FEA) to assess the von Mises stresses of a mandibular first premolar after removing a separated instrument with an ultrasonic technique. Methods: FEA models of the original and treated mandibular first premolar were reconstructed, and three models (the original canal, size 30/taper 0.04 canal, and separated instrument removal canal) were created. Two-direction (vertical and lateral) loading patterns were simulated with a 175-N force. The maximum von Mises stresses of the models within the roots from the apex to the cervical region were collected and summarized. Results: Under vertical and lateral loads, all maximal values in the three models were localized in the straight-line access region. Compared with the original model (model 1), the treated models (models 2 and 3) had greater maximum stress values from the apex to the cervical region. Greater differences in the maximum von Mises stresses between models 2 and 3 were present in the straight-line access region. Conclusions: Separated instrument removal caused changes in stress distribution and increases in stress concentration in the straight-line access region of roots.