Influence of Progressive vs. Minimal Canal Preparations on the Fracture Resistance of Mandibular Molars: A Finite Element Analysis
Date of Award
Master of Science (MS)
INTRODUCTION: Several file systems have been recently introduced with the objective of preserving coronal dentin. There is limited research comparing the role of canal shaping on preservation of pericervical dentin and its role in fracture resistance. The aim of this study is to investigate the effect of minimal canal taper on residual tooth strength and stress distribution after root canal treatment. Methods: Two pre-accessed mandibular molar TruTeeth (Acadental Endo 3DP, Lenexa, KS) were subject to simulated endodontic treatment in this study. One tooth was instrumented with ProTaper Gold (Dentsply, Tulsa, OK) to F2 (25/0.08v progressive taper) in the mesial canals and F3 (30/0.09v progressive taper) in distal canals using manufacturer protocol. The other tooth was instrumented with V-Taper 2H (SSWhite Dental, Lakewood, NJ) to 25/0.06v (minimal taper) in mesial canals and 30/0.06v (minimal taper) in the distal canals. The two teeth were scanned using microcomputed tomography (micro-CT,) and STL (stereolithography) surface meshes were developed for Finite Element Analysis (FEA). Four models were evaluated assessing the type of instrumentation and presence of resin access filling. The results of the FEA provided quantitative and qualitative measurements for Von Mises (VM) stress distribution and total deformation. Results: Under a 200-N multipoint load, the maximum VM stress was greater in the Pro-Taper Gold prepared models than in the V-Taper 2H prepared models. The models without an access restoration had higher total deformation values than the models with a resin filled access. In all models, total deformation values were highest in the clinical crown on the buccal aspect of the tooth. The greatest stress values were found in the pericervical dentin, and stresses decreased apically through the root. Conclusions: Within the limitations of this study, it can be concluded that the maximum stress values within the tooth prepared by ProTaper Gold were higher than those in the tooth prepared by V-Taper 2H. The minimally invasive instrumentation of the V-Taper 2H system preserves more pericervical dentin which may increase the resistance to fracture.