Implant-supported resin-matrix ceramic crowns with polyetheretherketone coping: a new rehabilitation system proposal

To evaluate the ideal resin cement layer (CL) and the polyetheretherketone coping (PEEKcop) occlusal thickness in implant-supported resin-matrix ceramic (RMC) crowns in the posterior region of an atrophic mandible (3:1 crown-to-implant ratio), under normal and traumatic occlusion.

Twenty-four finite element models were created according to CL (30, 50, and 70 μm), no presence of coping (7 mm RMC), coping thickness (1.4, 2.0, and 3.5 mm), and occlusion (normal; traumatic). Mohr-Coulomb stress ratio (σ_{MC ratio}), maximum shear stress, von Mises stress (σ_vM), displacement, minimum principal stress (σ_min), and failure risk were evaluated under a 200 N load.

Traumatic occlusion resulted in higher average stress values than normal occlusion in all groups. The 70 μm cement layer had the lower average stress distribution in both occlusion conditions. PEEKcop thickness 3.5 showed the lowest crown σ_{MC ratio}, reducing it by 19 % and 87 % under normal and traumatic occlusion, respectively. The PEEKcop thickness of 3.5 had the lowest values for coping, abutment (displacement), and implant (σ_vM) at normal occlusion and in coping, abutment, and implant (displacement) under traumatic occlusion. In cortical bone, there was an increase in the σ_min using PEEKcop thickness 3.5 under traumatic occlusion, while stress values were similar between groups under normal occlusion. Also, PEEKcop thickness 3.5 with 70 μm CL showed the lowest failure risks.

PEEKcop thickness 3.5 with CL 70 μm resulted in the lower average stresses in implant-supported RMC crowns in the posterior region of an atrophic mandible among all groups in both occlusion conditions.