Biomechanical behavior of implant retained prostheses in the posterior maxilla using different materials: A finite element study

Abstract

Abstract Background: In this study, the biomechanical behavior of the mesial and distal off-axial extensions of implant-retained prostheses in the posterior maxilla with different prosthetic materials were investigated using FEA. Methods: 3D finite element models with three implant prosthetic designs: fixed-fixed, mesial cantilever, and distal cantilever were designed depending upon cone beam CT images of an intact maxilla of an anonymous patient. The 3D modeling software Mimics Innovation Suite (Mimics 14.0 / 3-matic 7.01; Materialise, Leuven, Belgium) was used. All the models were imported into the FE package Marc/Mentat (ver. 2015; MSC Software, Los Angeles, Calif). The material properties of the implant, bone, monolithic zirconia, and polyetherketoneketone polymer (PEKK) were taken from literature. Then, individual models were subjected to separate axial loads of 300 N. Stress values were computed for the prosthesis, bone, and implant under axial loading. Results: Distal off-axial extension designs generated the maximum von Mises stresses (105 MPa) while the fixed-fixed designs generated the minimum von Mises stresses (35 MPa). The zirconia distal cantilever model yielded the most elevated levels of von Mises stresses within the prosthesis (105 MPa), with concentrated patterns at the implant prosthesisinterface near the offset extension. The von Mises stresses were highest in the implant (112 MPa) and compact bone (100 MPa) for the PEKK distal cantilever model. On the other hand, the zirconia fixed-fixed model exhibited the minimum von Mises stresses in the implant (49 MPa) and compact bone (20 MPa). Conclusions: The fixed-fixed prosthetic design showed the lowest von Mises stresses. In clinically challenging conditions Mesial cantilever design together with a rigid prosthetic material is suggested as a second alternative with acceptable biomechanical behavior.