Biomechanical behavior of cantilevered 3-unit implant-supported prostheses made of PEKK and monolithic zirconia: A finite element study

Objective: To evaluate the biomechanical performance of various designs of cantilevered three-unit implant-supported prostheses, using two distinct prosthetic materials and under different loading conditions.

Method: Three mandibular models were created with varying implant positions to support a 3-unit prosthesis using two materials (Zirconia and PEKK), resulting in three different designs: distal cantilever (M1), fixed-fixed (M2), and mesial cantilever (M3). The geometric model was created by segmenting a CBCT scan of an edentulous mandible using Mimics software, followed by refinement in 3-Matic to generate a trabecular bone core encased by a 2 mm-thick cortical shell and a 1 mm-thick mucosal layer. Implant CAD files were integrated, and the models were processed in SolidWorks to finalize solid geometries. These were then imported into ANSYS for mesh generation and finite element analysis, with materials assumed to be isotropic and elastic. Models underwent 3 different static loading protocols (Vertical 100 N, 30° Oblique 50 N, 45° Oblique 50 N). Von Mises stress and total deformation were calculated.

Results: Model 2 demonstrated the best performance. Under vertical loading, PEKK prostheses showed lower stress than zirconia in the prosthetic body (10-45 %) and the cortical bone (3-40 %), but higher stresses in the implant (4-10 %). Compared to vertical loading, oblique loading generated higher stress but remained within a safe range without compromising function.

Conclusion: The fixed-fixed design showed optimal biomechanical performance. The mesial cantilever was more favorable than the distal for stress distribution. Zirconia provided superior stress dissipation, while PEKK showed reduced stress in the prosthetic body but increased stress I the implant and bone.

Clinical significance: The study provides prosthodontists with evidence recommending design and materials for 3-unit implant-supported prostheses. Zirconia is ideal for cantilevered designs, resisting high bending forces and minimizing implant stress, while PEKK is more suitable for fixed-fixed designs with lower stress levels.