Finite element assessment of cement thickness effects on stress distribution in implant-supported ceramic–metal crowns

The durability of implant-supported dental restorations depends heavily on the layer of cement that bonds the prosthetic crown to the framework. However, the influence of cement thickness on the distribution of mechanical stresses within the implant-prosthesis system remains poorly understood. The aim of this study is to evaluate the effect of cement layer thickness on the biomechanical behavior of a metal-ceramic implant-supported restoration. A three-dimensional finite element model of a mandibular segment, incorporating cortical and cancellous bone, a titanium implant and abutment, and a metal-ceramic crown, was developed using SolidWorks software. Three thicknesses of cement were considered: 20, 40, and 60 µm. Static loads were applied to the crown in three directions: axial (100 N), buccal-lingual (50 N), and mesio-distal (23.4 N). The equivalent Von Mises stresses were evaluated at the level of the peri-implant bone, the cement layer, the crown, and the implant-abutment-frame interfaces in order to analyze the influence of cement thickness on stress distribution. The increase in cement thickness led to a decrease in maximum stresses in the peri-implant bone, from 12.32 MPa (20 µm) to 10.49 MPa (60 µm) in cortical bone, and from 2.51 to 1.88 MPa in cancellous bone, as well as a reduction in stresses in the cement layer from 9.74 to 8.47 MPa under axial load. In contrast, stresses in the crown increased with cement thickness, reaching 65.24 MPa for 60 µm. No significant variation in stresses was observed at the implant-abutment-frame interface. The thickness of the cement layer significantly influences the distribution of stresses in implant-supported restorations. A greater thickness protects the peri-implant bone by dissipating loads, but increases the stresses in the crown. Optimizing the thickness of the cement is therefore a key parameter for improving the clinical longevity of implant restorations.