1. R&D of dental therapeutic devices based on radical disinfection technique
Photo-irradiation of 3% hydrogen peroxide used as a disinfectant results in the generation of hydroxyl radicals. We have developed a novel antimicrobial chemotherapy utilizing the hydroxyl radicals, one of reactive oxygen species, generated by hydrogen peroxide photolysis.
Our previous studies have demonstrated potent antimicrobial activity of hydrogen peroxide photolysis (Ikai et al. Antimicrob Agents Chemother 54, 5086-5091, 2010, Nakamura et al. Int J Antimicrob Agents 48, 373-380, 2016) as well as non-irritation potential against oral mucosa (Niwano et al. Regul Toxicol Pharmacol, 90, 206-213, 2017).
Furthermore, we found that the technique had little or no risk to induce bacterial resistance to the disinfection treaeatment （Ikai et al. PLoS ONE, 8, e81316, 2013）.
Based on these pre-clinical studies, we have developed a novel therapeutic device for periodontal treatment. In an investigator-initiated clinical trial, efficacy and safety of the treatment using the device have been demonstrated (Kanno et al. Sci Rep, 7, 12247, 2017).
Currently, we are trying to apply this disinfection technique to treatments for dental caries and peri-implantitis.
2. Novel antimicrobial treatment utilizing pro-oxidant activity of photo-irradiated polyphenol
Polyphenol, a generic term of substances containing multi-phenolic hydroxy group in their structre, occurs in fruits, nuts, vegetables, and flowers.
It is well-known that polyphenols have antioxidant activity, and as such, it is expected to contribute to health promotion when ingested into body. We have focused on the pro-oxidant activity exerted by photo-irradiation of polyphenol, which is on the reverse side of antioxidant activity.
The pro-oxidant activity is attributable to hydrogen peroxide generated by photo-oxidation of polyphenol as well as hydroxyl radical generated by photolysis of the hydrogen peroxide.
This reaction can be used for antimicrobial chemotherapy (Nakamura et al. J Agric Food Chem 63, 7707-7713, 2015).
The photo-irradiated polyphenol exerts bactericidal effect only during photo-irradiation.
After photo-irradiation, it can be expected that the remaing polyphenols would protect the healthy tissue from excessive oxidation.
We are conducting R&D so that the technique can be applied to dental caries treatment or oral hygiene control technique (Nakamura et al. Sci Rep 7, 6353, 2017).
3. Evaluation of mechnical and biological propeties of dental materials used for dental CAD/CAM system
CAD/CAM-produced dental prostheses have been increasingly used in clinical situation.
The materials such as zirconia and composite resin blocks are newly designed for CAD/CAM application.
Thus, it is necessary to throughly evaluate their properties in clinical and non-clinical tests.
In this context, we have evaluated the mechanical strength, fatigue resistance, biocompatibility of the materials as well as bacterial addhesion on the materials.
Our previous in vitro studies have demonstrated that CAD/CAM-produced monolithic zriconia and composite resin crowns possess sufficient strength to withstand the bite force in the molar region（Nakamura et al. Acta Odont Scand, 73, 602-608, 2015, Harada et al. Eur J Oral Sci, 123: 122-129, 2015).
We will further study their clinical performance.
Our previous studies have demonstrated potent antimicrobial activity of hydrogen peroxide photolysis (Ikai et al. Antimicrob Agents Chemother 54, 5086-5091, 2010, Nakamura et al. Int J Antimicrob Agents 48, 373-380, 2016) as well as non-irritation potential against oral mucosa (Niwano et al. Regul Toxicol Pharmacol, 90, 206-213, 2017).
Furthermore, we found that the technique had little or no risk to induce bacterial resistance to the disinfection treaeatment （Ikai et al. PLoS ONE, 8, e81316, 2013）.
Based on these pre-clinical studies, we have developed a novel therapeutic device for periodontal treatment. In an investigator-initiated clinical trial, efficacy and safety of the treatment using the device have been demonstrated (Kanno et al. Sci Rep, 7, 12247, 2017).
We have focused on the pro-oxidant activity exerted by photo-irradiation of polyphenol, which is on the reverse side of antioxidant activity.
The pro-oxidant activity is attributable to hydrogen peroxide generated by photo-oxidation of polyphenol as well as hydroxyl radical generated by photolysis of the hydrogen peroxide.
This reaction can be used for antimicrobial chemotherapy (Nakamura et al. J Agric Food Chem 63, 7707-7713, 2015).
The photo-irradiated polyphenol exerts bactericidal effect only during photo-irradiation.
After photo-irradiation, it can be expected that the remaing polyphenols would protect the healthy tissue from excessive oxidation.
CAD/CAM-produced dental prostheses have been increasingly used in clinical situation.
The materials such as zirconia and composite resin blocks are newly designed for CAD/CAM application.
Thus, it is necessary to throughly evaluate their properties in clinical and non-clinical tests.