Assessment of the Best FEA Failure Criteria (Part II): Investigation of the Biomechanical Behavior of Dental Pulp and Apical-Neuro-Vascular Bundle in Intact and Reduced Periodontium

Abstract

The aim of this study was to biomechanically assess the behavior of apical neuro-vascular bundles (NVB) and dental pulp employing Tresca, Von Mises, Pressure, S1 and S3 failure criterions in a gradual periodontal breakdown under orthodontic movements. Additionally, it was to assess the accuracy of failure criteria, correlation with the maximum hydrostatic pressure (MHP), and the amount of force safe for reduced periodontium. Based on cone-beam computed tomography, 81 3D models of the second lower premolar were subjected to 0.5 N of intrusion, extrusion, rotation, tipping, and translation. A Finite Elements Analysis (FEA) was performed. In intact and reduced periodontium apical NVB, stress (predominant in all criteria) was significantly higher than dental pulp stress, but lower than MHP. VM and Tresca displayed identical results, with added pulpal stress in translation and rotation. S1, S3 and Pressure showed stress in the apical NVB area. 0.5 N seems safe up to 8 mm periodontal breakdown. A clear difference between failure criteria for dental pulp and apical NVB cannot be proved based only on the correlation quantitative results-MHP. Tresca and VM (adequate for ductile materials) showed equivalent results with the lowest amounts of stress. The employed failure criteria must be selected based on the type of material to be analyzed.

Investigating the Ability of the Tooth and Surrounding Support Tissues to Absorb and Dissipate Orthodontic Loads during Periodontal Breakdown—Finite Elements Analysis

“…This numerical FEA analysis is part of a larger step-by-step research project [2,3,5,6,9,10,16,48] (with clinical protocol no. 158/02.04.2018) investigating the FEA methodology to improve the accuracy of numerical study results and to assess the biomechanical behavioral changes in dental tissues produced by the periodontal breakdown.…”

“…It must be emphasized that, from a biomechanical point-of-view, linear elasticity and isotropy assumptions are correctly employed only if the applied forces are up to 1 N, and the non-homogeneity of materials is considered and addressed using the Tresca criterion. There is no available data on the above issues for higher applied forces in dental tissues and no studies, except for our previous studies [2,3,5,6,9,10,16,48], acknowledged and addressed these issues.…”

“…Some of the stresses are absorbed and dissipated through these components, and only a part reaches other tissular components (i.e., periodontal ligament, PDL; neuro-vascular bundle, NVB; dental pulp; cortical and trabecular bone). This absorptiondissipation ability is theoretically and clinically recognized, but not yet quantified or sufficiently studied [1][2][3][4].…”

“…Dental pulp and neuro-vascular bundle (NVB) are ductile-like materials [2], being highly vascularized tissues, with NVB being more sensitive to circulatory disturbances due to its topographical position in the apical third PDL [2,5].…”

“…Cementum (which resembles a ductile material) has similar physical properties to dentine and ensures the support and absorption-dissipation of both tissues [1,2,10,11,14].…”