Honghao Zhang,1,2 Satoshi Komasa,1 Chiho Mashimo,3 Tohru Sekino,4 Joji Okazaki1

1Department of Removable Prosthodontics and Occlusion, Osaka Dental University, Hirakata, Osaka, Japan; 2Department of Stomatology, Nanfang Hospital and College of Stomatology, Southern Medical University, Guangzhou, Guangdong, China; 3Department of Bacteriology, Osaka Dental University, Hirakata, 4The Institute of Scientific and Industrial Research, Osaka University, Suita, Osaka, Japan

Purpose: Alkali-treated titanium with nanonetwork structures (TNS) possesses good osteogenic activity; however, the resistance of this material to bacterial contamination remains inadequate. As such, TNS implants are prone to postoperative infection. In this work, we attempted to alter the biological properties of TNS by treatment with short-duration high-intensity ultraviolet (UV) irradiation. Methods: TNS discs were treated with UV light (wavelength =254 nm, strength =100 mW/cm2) for 15 minutes using a UV-irradiation machine. We carried out a surface characterization and evaluated the discs for bacterial film formation, protein adsorption, and osteogenic features. Results: The superhydrophilicity and surface hydrocarbon elimination exhibited by the treated material (UV-treated titanium with a nanonetwork structure [UV-TNS]) revealed that this treatment effectively changed the surface characteristics of TNS. Notably, UV-TNS also showed reduced colonization by Actinomyces oris during an initial attachment period and inhibition of biofilm formation for up to 6 hours. Moreover, compared to conventional TNS, UV-TNS showed superior osteogenic activity as indicated by increased levels of adhesion, proliferation, alkaline phosphatase activity, osteogenic factor production, and osteogenesis-related gene expression by rat bone marrow mesenchymal stem cells (rBMMSCs). This inverse relationship between bacterial attachment and cell adhesion could be due to the presence of electronhole pairs induced by high-intensity UV treatment. Conclusion: We suggest that simple UV treatment has great clinical potential for TNS implants, as it promotes the osseointegration of the TNS while reducing bacterial contamination, and can be conducted chair-side immediately prior to implantation.

Keywords: implant, nanonetwork, postoperative infection, UV treatment, superhydrophilicity, osteointegration

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