Objectives: Nano-scaled surface modifications of dental implants are of increasing interest for optimizing both tissue- and saliva-exposed implant areas. Synergistic effects of hydrophilic and nanostructured surfaces were reported to improve the bone response. Inflammations, induced by subgingival bacterial infiltration, reduce the overall survival rates of implants. Photocatalytic thin films offer the capability to decompose organic material and to improve wettability upon UV-A irradiation. Data on multifunctional properties of such coatings are presented and envisioned clinical applications are discussed.
Methods: Magnetron-sputtered 500 nm nano-crystalline anatase coatings on titanium were irradiated by UV-A and UV-A/VIS. Contact angle analysis was used to study wettability as a function of irradiation time. Quartz crystal microbalance with dissipation (QCM-D) was used as an acoustic sensor system to study online initial saliva adsorption, Streptococcus gordonii DL 1 adhesion and wavelength dependent antibacterial effects of photocatalysis. Differences between means were statistically analysed by one-way ANOVA and Tukey-Kramer post hoc tests (p<0.05).
Results: UV-A irradiation of 25 mWcm-2 for 120 s did not lower contact angles on Ti below 58°. In contrast, anatase films significantly induced smaller contact angles dependent on the UV irradiation time. Superhydrophilicity with contact angles < 5 deg was observed after a minimum UV treatment of 75 s. Salivary pellicle could be photocatalytically decomposed from 320 nm UV-A till 410 nm VIS. In contrast, effective photocatalytic attack of bacteria could be observed by UV-A as well as by UV-A/VIS at 380 nm < λ < 390 nm only.
Conclusions: Our study results have shown potential for dental and orthopaedic clinical applications of anatase using its multifunctional properties. Chair-side irradiation by pure UV-A allows superhydrophilization of root parts of implants in short time. In addition, anatase coatings might be irradiated at UV-A/VIS threshold wavelengths to support peri-implantitis treatments by a photocatalytic attack of surface-associated bacterial films.