Biomechanical Behavior of All-On-4 Concept and Alternative Designs Under Different Occlusal Load Configurations for Completely Edentulous Mandible: A 3-D Finite Element Analysis

Abstract

Abstract Background In edentulous patients, the number of implants, the area where the implant will be placed, the presence and length of the cantilever in the prosthesis and the occlusion type can be challenging. The aim of this study was to evaluate the effect of the All-on-4 design and 4 alternative implant-supported fixed prosthesis designs on stress distribution in implants, peri-implant bone, and prosthetic framework in the edentulous mandible under different loading conditions using three-dimensional finite element analysis (3D-FEA). Methods Five different experimental finite element models (Model A (unsplinted 6), Model B (splinted 6), Model C (All-on-4), Model D (axial; 2 anterior, 2 posterior), Model E (4 interforaminal) were created. Porcelain substructure, Co-Cr framework, titanium abutments and implants were modeled, and three different loading conditions were applied (canine loading, unilateral I-loading, unilateral II-loading). The highest minimum (Pmin) and the maximum (Pmax) principal stress values were acquired for cortical and trabecular bones; the highest von Mises (mvM) stress values were obtained for implants and metal frameworks. Results Model B and Model D showed the most favorable stress distribution. The All-on-4 design (Model C) also showed acceptable stress values close to Model B and Model D in the cortical and trabecular bone. The lowest stress values measured in the implants and Co-Cr framework in Model B and Model D, in accordance with the stress values in the bone structure. The highest stress values in all structures were measured for the unilateral loading- II, while the lowest values were found for canine loading. The use of angled (30º) implants did not affect the stress values as much as the length of the cantilever, splinting and configuration of the occlusal load. Conclusion It was concluded that Model B and Model D experimental models showed better biomechanical performance in the implant, peri-implant bone, and prosthetic framework. Furthermore, the use of splinted framework, avoiding the cantilevers, results in lower stress transmission. On the other hand, canine loading and unilateral loading-I exhibited the best loading conditions. Although the forces on the cantilever region were attenuated in unilateral loading-II, it generated considerably higher stress distribution.