Comparison between all-on-four and all-on-six treatment concepts and framework material on stress distribution in atrophic maxilla: A prototyping guided 3D-FEA study

We evaluated two treatment concepts for the rehabilitation of moderate atrophic maxilla with dental implants (all-on-four and all-on-six) and the effect of framework material on the stress distribution of implant-support system. A three-dimensional finite element model based on a prototype was built to simulate an entirely edentulous maxilla with moderate sinus pneumatization that was rehabilitated with a full-arch fixed dental prosthesis. Four standard implants were positioned according to the all-on-four concept and four standard implants and two short implants were placed according to the all-on-six concept Three framework materials were evaluated: cobalt-chrome (CoCr), titanium (Ti) and zirconia (Zr), totalizing six groups. A unilateral oblique force of 150 N was applied to the posterior teeth. The von Mises (sigma(VM)), maximum (sigma(max)) and minimum (sigma(min)) principal stress and displacements were obtained. All-on-six showed smaller sigma(min), sigma(vm) and sigma(max) values on the cortical bone, implants and trabecular bone, respectively. All-on-four exhibited higher displacement levels. Ti presented the highest stress values on the cortical bone, implants, abutments, prosthetic screws and displacement levels. In conclusion, the all-on-six approach and framework stiffer materials showed the most favorable biomechanical behavior. However, the stress values did not exceed the bone resistance limits for both treatment concepts. (C) 2016 Elsevier B.V. All rights reserved.