The Effects of Different Endodontic Cavities on the Fracture Resistance of Endodontically Treated Mandibular First Molars- A Three-dimensional Finite Element Analysis

Abstract Objectives: The purpose of this study was to predict the fracture resistance of endodontically treated mandibular first molars (MFMs) with diverse minimally invasive endodontic access cavities using finite element models.Materials and Methods: Based on microcomputed tomographic data of an MFM, five three-dimensional finite element models representing a natural tooth (NT) and 4 endodontically treated MFMs were generated using finite element analysis software (HyperWork 14.0, Altair, USA). Treated MFM models were with a traditional endodontic cavity (TEC) and minimal invasive endodontic (MIE) cavities, including a computer-aided designed guided endodontic cavity (GEC), contracted endodontic cavity (CEC) and truss endodontic cavity (TREC). Three loading conditions were applied, simulating a maximum bite force of 600 N vertically and a normal masticatory force of 225 N vertically and laterally. The distributions of von Mises (VM) stress and peak VM stress were calculated.Results: The peak VM stresses of the NT model were the lowest under normal masticatory forces. In endodontically treated models, the distribution of VM stress in GEC model under all loads was the most similar to NT model. The peak VM stresses of the GEC and CEC models under different forces were lower than those of TREC and TEC models. The peak VM stresses of the GEC were lower than those of the CEC under normal masticatory loads but higher under maximum bite load. Under two vertical loads, the peak VM stresses of the TREC model were the highest, while under the lateral load, the peak VM stress of the TEC model was the highest. However, the VM stress in most part of the TEC model was higher than that in TREC model under all loads. Conclusions: Compared with TEC, GEC and CEC could better improve the fracture resistance of teeth. TREC may have a limited effect on fracture resistance enhancement when compared to GEC and CEC.Clinical Relevance: Our data demonstrated that compared with TEC and TREC, GEC and CEC access could better improve the fracture resistance of endodontically treated teeth, which may be an alternative balancing biomechanical properties and clinical convenience.