Finite Elements Analysis of Biomechanical Behavior of the Bracket in a Gradual Horizontal Periodontal Breakdown—A Comparative Analysis of Multiple Failure Criteria

Abstract

This study assessed the stress distribution (in eighty-one 3D models of the second lower premolar) in a stainless-steel bracket and enamel crown under 0.5 N of intrusion, extrusion, rotation, translation, and tipping during a horizontal periodontal breakdown of 0–8 mm. The FEA simulations (totaling 405) employed five failure criteria and assessed the adequacy and accuracy of Von Mises (VM), Tresca (T), Maximum Principal (S1), Minimum Principal (S3), and Hydrostatic Pressure. T and VM criteria showed no change in stress display areas during the periodontal breakdown, seeming to be more correct and adequate than the other three (with unusual stress displays). Both VM and T (found to be more adequate) generated maximum stress areas on the attachment side and the entire base of the bracket, confirming the non-homogenous stress distribution areas and the risks of bond failure. Rotation, translation, and tipping were the most stressful movements and showed slightly lower quantitative values for 8 mm bone loss when compared with the intact periodontium, while intrusion and extrusion showed the opposite behavior (slight increase). Periodontal breakdown did not influence the stress display in the bracket and its surrounding enamel area during the five orthodontic movements.

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

“…In dental field, the numerical studies' results are regarded with care since they often contradicted clinical knowledge and displayed various results from one report to another . This issue was not addressed, except for our previous research [5,6,9,10,16,48].…”

“…The material of bracket (i.e., stainless steel) is a ductile material that can deform under loads and recover its initial shape when the loads ceased [7][8][9].…”

“…From a mechanical point-of-view (according to the material failure theory), a ductile material (e.g., steel and rubber) can suffer from various elastic deformations (higher tensile resistance) before its failure and could return to its original form when the force ceased. On the other hand, a classical brittle material (e.g., concrete and glass), when subjected to loads, suffers from limited deformations, closely followed by cracking and fracture, but with a higher compression resistance [9,10].…”

“…FEA accuracy depends on the selection of proper failure criteria which are suitable for the analyzed material, anatomically correct models, and proper boundary conditions. Our previous studies [5,6,9,10,16,48] reported that since dental tissues are ductile-like materials (with a certain brittle flow mode) only a failure criterion specially designed for ductile materials is suitable (i.e., Von Mises overall stress and Tresca shear stress). Moreover, for validation, the quantitative results must be correlated with MHP, while qualitative results with acknowledged clinical data.…”

“…Moreover, for validation, the quantitative results must be correlated with MHP, while qualitative results with acknowledged clinical data. Despite many FEA studies 49,50] investigating PDL and bone-implant interface, none approached these vital issues, thereby supplying questionable and contradictory results [5,6,9,10,16,48]. Only one older numerical FEA study [30] was found to make a limited distinction between brittleness and ductileness for the root canal filling, but without further development.…”