Biomechanical behavior of functionally graded S53P4 bioglass-zirconia dental implants: Experimental and finite element analyses

Abstract Objectives The aim of this work was to evaluate the biomechanical behavior of one-piece zirconia implants with a functionally graded bioglass (BG) layer as compared to monolithic implants and BG-coated implants, using the finite elements method (FEM). Methods Zirconia disks were infiltrated with bioglass S53P4 and then morphologically inspected by scanning electron microscopy followed by mechanical assays on micro-indentation tests for further biomechanical validation using the finite element method (FEM). On modeling, zirconia dental implants anchored into the mandibular bone were simulated on occlusal loading as recorded under mastication. Three types of implants were simulated: i) free of BG coating, ii) with 100 μm or 150 μm thick conventional BG coatings; and c) with graded BG coatings involving 3 different chemical composition distributions. The stress state at both implant and bone were evaluated using the FEM. The mechanically-induced bone remodeling was analyzed through the bone strain results. Results Infiltration of BG into a zirconia structure resulted in a ∼100 μm thick layer with an exponential-like gradation of chemical composition and properties. Regarding the FEM calculations, the BG coating induced up to 30% decrease on stress in the implant body in comparison to the control implant, while the gradient of chemical composition also improved the stresses’ distribution. The stresses distribution towards to the BG-coatings were significantly high and could lead to failure. Stresses on the bone were recorded down to its strength threshold, with insignificant influence of the coating layer. The bone strain values on all models indicates further bone remodeling although BG-coated and BG-graded implants showed the highest strain magnitude that may enhance the mechanical stimulation for bone maintenance. Significance Graded BG-zirconia dental implants showed enhanced overall biomechanical behaviour as compared to the BG-coated or monolithic zirconia dental implants. Also, such biomechanical improvements seen for the BG-graded system should be considered in combination with the well-known osseointegration benefits of bioactive glasses.