The effect of different separated file retrieval strategies on the biomechanical behavior of a mandibular molar: a finite element analysis study

Document Type

Article

Publication Date

Winter 1-1-2025

Abstract

Introduction: This study addresses the impact of different approaches for managing separated files (SF) on the biomechanical behavior and fatigue life of endodontically treated teeth (ETT) by finite element analysis (FEA).

Methods: Six FE models were created; IT: The intact tooth model, SF: The model simulates a scenario where the apical 3 mm of a nickel-titanium file (size 30/.04) is separated and retained at the middle root third, US360: simulated circumferential ultrasonic troughing done to the full length of the SF, US180: simulated troughing of 180⁰ at the inner wall of the root canal to the full length of the SF, TD: simulated application of a trephine drill to expose 1 mm of the SF, and P: simulated iatrogenic perforation sealed using MTA. Occlusal loading followed the occlusal fingerprint of the tooth before maximum von Mises (vM), maximum principal stresses (MPS), safety factor, and number of cycles (NCF) till failure were determined and compared for all models. Two Areas of interest (AOI) were chosen for deeper analysis: the cervical region of the teeth (AOI-C) as well as the mid-root sections including the separated file and 1 mm above and below the separated file (AOI-F).

Results: The intact tooth recorded the highest NCF (8.360 x 106) and safety factor (1.412). All other models showed a very narrow range of variation in all aspects of comparisons. The lowest NCF was recorded by the P model (5.779 x 106), while the highest NCF following the IT model was the SF (5.941 x 106). The highest vM recorded was (66.2 MPa) and was recorded at the mesiobuccal line angle of the P model near its cervical margin, while the lowest was 40.36 MPa at the same region of the IT model. To facilitate comprehension of MPS results, the node showing maximum VMS at both AOI-C & AOI-F were tracked and the value of MPS was registered and demonstrated in Figure 3.

Conclusion: Under the limitation of this study, various management strategies for file retrieval do not affect the biomechanical behavior of the tooth despite the variability in radicular dentin removal. Clinicians may try file retrieval by removing the surrounding root dentin material around the file fragment within the amounts of general guidelines.

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