Towards Enhanced Osteointegration: A Comparative and In-Depth Study of the Biocompatibility of an Innovative Calcium-Doped Zirconia Coating for Biomedical Implants

Innovation in oral implantology is constantly on the move, with a constant search for new biomaterials to overcome many of the limitations of the biomaterials used in current implantable medical devices. This study explores the biocompatibility of an innovative 5% calcium-to-zirconia (Ca-SZ) coating deposited by PVD on TA6V substrates for use in oral implantology. In order to determine the contribution of the Ca-SZ coating, an in vitro biocompatibility study was carried out to assess the potential influence of the Ca-SZ coating (1) on the viability and proliferation of saos-2 and HaCaT cells over a short-term exposure period of 96 h, (2) on the synthesis of pro-inflammatory cytokines, and (3) on the synthesis of osteogenic differentiation markers over a long-term exposure period of 21 days, in comparison with reference biomaterials. The sampling consisted of n = 3 biological replicates, and a p-value of <0.05 was used as the threshold for statistical significance. Viability and proliferation kinetics to WST-1 and CyQUANT NF, respectively, showed improved viability/proliferation of Ca-SZ exposed to both cell lines independently. The TNF-alpha and IL-6 assays revealed reduced levels of cytokines compared with the reference biomaterials, including the control groups. In parallel, in Saos-2 cells exposed to Ca-SZ for 21 days under osteogenic conditions increased expression of osteogenic markers, such as the synthesis of soluble collagens, alkaline phosphatase (ALP), osteopontin, and osteocalcin, reflecting dynamic and facilitated osteoblastic differentiation, which was supported by the formation of hydroxyapatite (HA) crystals observed by SEM micrograph and confirmed by EDS mapping. In conclusion, Ca-SZ demonstrates an overall better biocompatibility compared with reference biomaterials, linked to a bioactive interaction of calcium, promoting cell proliferation and differentiation for optimal osteointegration, underlining its potential as a relevant innovation for next-generation implants.