Computer Simulation of the Mechanical Behavior of the 'Zygomatic Bones-Implants-Splinting Bar-Removable Overdenture' Dental Structure Under Operational Loads.

Background/Objectives: When solving the problems of installing zygomatic implants after partial or full maxillectomy with subsequent attachment of a removable overdenture (ROD), computer simulation based on the finite element method (FEM) is an effective tool for treatment planning. In this study, stress-strain states of the 'zygomatic bones-implants-splinting bar-ROD' dental structure were evaluated under various loading conditions. Methods: A 3D FEM computer simulation was carried out to estimate stress-strain states of the elements of the dental structure and to study the effect of redistribution of the loads transferred from the ROD to the zygomatic bones through four implants. Results: That successive insertion and removal of the ROD caused identical stresses in the elements of the dental structure. Given the accepted level of critical stress of about 13 MPa, their values may be exceeded in the zygomatic bones during both processes. In the ROD, the equivalent stresses did not exceed the critical levels upon alternate loading of 50 N on the posterior teeth (both molars and premolars) under all biting and mastication. Taking into account the linear dependence of the applied load and the stresses in the ROD, it can be stated that its integrity is maintained until 118 N (or the generally accepted typical value of 100 N). Under the 90° biting angle, the equivalent stresses are below the critical level in all the studied cases; thus, the acceptable value increases to 213 N, but it is only 63 N at a biting angle of 45°. Conclusions: It has been established that the equivalent stresses in the zygomatic bones can exceed the critical stress level of 13 MPa. In addition, some practical recommendations and prospects of the study have been formulated.