Effect of framework in immediate loading implant-supported full-arch fixed bridge: 3D-finite element analysis

Background: Reducing the risk of overloading is mandatory to achieve a predictable osseointegration in immediate loading protocols. Purpose: The aim of this study was to analyse through a three-dimensional Finite Element Analysis (3D-FEA) stress distribution on four implants supporting a full-arch implant-supported fixed bridge (FFB) using different prosthesis design. Materials and Methods: A 3-D edentulous maxillary model was created using a customized computer software. Four implants were virtually placed into the maxilla and splinted with a FFB of 12 masticatory units. 3 different configurations were evaluated: (1) full acrylic resin prosthesis without framework, (2) acrylic resin veneering material with cast metal framework, (3) acrylic resin veneering material with a carbon fibre framework. An occlusal load of 150 N was applied on the left most distal portion of the bridge and stresses transmitted into peri-implant bone, to the implants and to the prosthodontic components were recorded. Results: 3D-FEA revealed higher stresses on the implants (up to +58,27%), on peri-implant bone (up to +56,93%) and in the prosthesis (up to +91,43%) when the full-acrylic denture was simulated. Conclusions: FEA simulating a maxillary rehabilitation revealed that FFBs endowed with a stiff framework decrease stresses on implants, prosthesis and on the peri-implant bone providing a better load distribution compared with all-acrylic prostheses. Keywords: Dental implants, Framework, Dental materials, Finite Element Analysis, In vitro study, Prosthodontics