Zirconium Dental Implants as Potential Optical Waveguides in Photodynamic Inactivation of Bacterial Biofilms—A Pilot Study

In patients with predisposing risk factors, bacterial colonization of dental implants can lead to periimplantitis (PI). Established individual treatment protocols can be effective, but antimicrobial resistance (AMR) and biofilm formation may impede successful treatment, therefore requiring surgical intervention. Photodynamic Inactivation (PDI) combined with optical waveguides could eradicate such pathogens without the risk of new AMR emergence and reduce the need for surgery. In this pilot study, we investigated the waveguiding function of light-transmitting zirconium dioxide (ZrO₂) dental implants of different diameters by quantifying their transmission spectrum, fraction of transmitted red-light intensity, and potential polarizing properties. In addition, PDI experiments involving in vitro grown <i>Staphylococcus epidermidis</i> biofilms on ZrO₂ and titanium alloy (TAV) discs were performed. Colonized discs were treated with Methylene Blue (MB) photosensitizer before red-light illumination (670 nm) at various intensities. A reduction in bacterial colony-forming units (CFUs) of up to 85% was observed on ZrO₂ discs. Meanwhile, the biofilms grown on TAV discs showed no significant reduction in CFUs. These findings make ZrO₂ a potential candidate in augmentative PDI treatment of PI. The successful use of PDI combined with waveguiding ZrO₂ dental implants can support the reduction in antibiotic prescriptions, thus advancing the WHO's One Health approach of antibiotic stewardship.