Stress Distribution in Peri-implant Bone of Implants Restored with Screw, Cement, and Cement-Screw Retained Crowns Using Three Crown Materials: a Three-dimensional Finite Element Analysis.

Aim: To comparatively evaluate stress distribution in the peri-implant bone in three-dimensional finite element (3D FE) models of titanium implants with different crowns-Metal Ceramic, Zirconia, Poly Ether Ether Ketone (PEEK) retained by three methods-screw, cement, cement-screw under functional load.

Settings and design: An implant crown can be retained by screw, cement or a combination of the two-cement-screw. Materials for fabricating implant restorations vary which distribute stress differently in the peri-implant bone.

Materials and methods: Nine 3D FE models depicting the restoration-implant-bone complex in the mandibular premolar region were constructed using CAD Solidworks software. The Altair pre-processor was used for model meshing. Young's modulus and Poisson's ratio were allotted to each material. Occlusal loading (100N) in vertical and oblique (30°) directions was performed on the 3D FE models and von Mises stresses generated in the peri-implant bone were visualised, evaluated according to colour code, numerically recorded, assessed and compared.

Results: For the vertical and inclined force models, stress distribution in peri-implant bone was higher in all screw retained models and lower for all cement retained and cement-screw retained models. Peri-implant bone stresses were comparable for cement retained and cement-screw retained prosthesis.

Conclusion: Any of the nine combinations of crown materials-Metal Ceramic, Zirconia, PEEK and retention methods-screw retained, cement retained, cement-screw retained can be used clinically as they have stress varying for less than 10% across all models.