Biomechanical Stress Analysis of Overdentures Supported and Retained by Peek Implants and Attachments Using Different Designs : A 3D Finite Element Analysis Study

Background: Analysis of stresses induced by using poly ether ether ketone (PEEK) implants and prosthetic attachments for implant supported mandibular complete overdenture. Methods: 3D finite element model was made for lower complete overdenture, supported by implants (4 mm in diameter, 12 mm in length) and retained by ball attachments. Linear static stress analysis was carried out by ANSYS 2020. Three model cases were created. Model 1 supported by two Ti implants in canine region, Model 2 supported by three PEEK implants (2 in canine region, 1 in midline), Model 3 supported by 4 PEEK implants bilaterally in canine and premolar region. Same material either titanium alloy or PEEK was used in modelling all prosthetic components in each case model. Application of force (120 N) bilaterally was carried out 3 times for each model case (vertical, oblique and lateral). Results: Model 3 showed the highest maximum and minimum principal stresses, in peri-implant cortical bone and exceeded its tensile and compressive yield strength after lateral loading. In model 2 Cortical bone Maximum and minimum principal stresses did not exceed its yield strength, in the three loading scenarios. However, cortical bone tensile stresses labial to midline implant in model 2 showed low safety factor. Conclusions: Model 2 design can be promising biomechanically, if used in normal density bone, but with caution against the critical high tensile stresses at the cortical bone labial to midline implant. While model 3 design could result in excessive high stresses leading to yielding and resorption of cortical bone.