Impact of Canal Taper and Access Cavity Design on the Lifespan of an Endodontically Treated Mandibular Molar: A Finite Element Analysis

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Introduction: This study investigated the impact of different canal tapers and access cavity designs

on the lifespan of endodontically treated mandibular first molar using the finite element method.

Methods: Finite element analysis was performed on simulated models with three access cavity

designs (traditional, conservative and truss). The mesial canals were prepared to either constant tapers

of 25/.04 and 25/.06, or variable taper corresponding to the cumulative canal preparation shapes of

TruNatomy Prime and ProTaper Gold F2. The distal canals in all models had a 40/.04 preparation. Using occlusal fingerprint analysis, all models were subjected to cyclic occlusal loading until model failure. The number of cycles until failure, location of failure, stress distribution patterns and maximum von Mises stresses were assessed.

Results: The traditional access models showed a lower lifespan than the conservative and truss models regardless of the canal taper, while there was not a notable difference in the conservative and truss models. The stresses migrated apically along the root surface, remarkably on the mesial aspect of the mesial root and the furcation area's outer surface. After root canal preparation with different tapers, there were no evident changes in pattern and magnitude of stresses distributed along the root surface.

Conclusions: The lifespan of the tooth is affected more significantly by the access cavity design than the root canal preparation taper. As stress patterns migrate apically rather than concentrate in the pericervical area, crack initiation and propagation might occur anywhere on the root surface.