Ultraviolet photofunctionalization of titanium surfaces has been shown to dramatically increase its osteoconductivity. However, it is unknown whether UV-photofunctionalization improves the osteoconductive capacity of zirconia. This study evaluated whether UV treatment enhances the osteoconductive capacity of a zirconia-based material.
Method:
Miniature implants and disks of a zirconia-based material with machined and roughened surfaces were treated by UV-light for 48h. Surface characterization was performed by scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and contact angle measurements. Human alveolar bone-derived osteoblasts were cultured onto zirconia disks. Cell attachment and proliferation were evaluated by SEM, Immunofluorescence microscopy and by the reduction of resazurin assay. The differentiation capacity was assessed via real-time polymerase chain reaction, alkaline phosphatase activity and Alizarin-red staining assays. Zirconia implants were placed in femurs of 8-week-old male Sprague-Dawley rats. The strength of osseointegration was assessed via an implant push-in test and a histomorphometric analysis was carried out to evaluate peri-implant osteogenesis.
Result:
SEM and AFM revealed different micro-roughened and machined topographies that were not affected by UV treatment. XPS showed a decrease of surface carbons by 50-75% and an increase of oxygen by 10-20% on all UV-treated samples. The hydrophilic status changed by UV treatment from hydrophobic to super-hydrophilic (p<0.0001). A significant enhancement of cell attachment, proliferation as well as an increase of the expression levels of collagen I, osteopontin and osteocalcin and higher alizarin-red positive areas were found on all UV-treated samples (p<0.001). Compared to non-treated samples, UV-treated implants showed up to 182% greater push-in values (p<0.0001). Histomorphometric analyses revealed a significantly greater amount of new bone (p<0.0001) and a greater bone-implant contact around UV-treated implants (p<0.0001).
Conclusion:
UV treatment induced changes in the physico-chemical properties of the tested zirconia samples and led to a substantial enhancement in their osteoconductivity.