Evaluation of the effect of photoactivated disinfection with Radachlorin® against Streptococcus mutans (an in vitro study)

Background: The use of photoactivated disinfection has had a significant medical and technological effect in bacterial inactivation, as an alternative to conventional antimicrobial methods. The main goal of this study was to investigate the effect of photoactivated disinfection on Streptococcus mutans, when Radachlorin (R) was used as a photosensitizer. Methods: Streptococcus mutans samples of two different initial concentrations were treated with Radachlorin (R) gel (0.1%), irradiated by the light of a He-Ne laser (633 nm), with energy density of 6 J/cm(2), and cell viability was evaluated after culturing. Results: It was observed that the combination of Radachlorin (R) and laser was more effective than Radachlorin (R) or laser alone (p < 0.05), in reduction of S. mutons and Radachlorin was cytotoxic, in the dark, only for the lower concentration of bacteria. Lower concentration of S. mutans resulted in higher amount of killing, in the case of using Radachlorin (R) with or without laser. Conclusions: The photoactivation of Radachlorin (R) using a He-Ne laser could inactivate S. mutans to a significant level. In addition Radachlorin (R) might be cytotoxic in the dark, for the lower concentration of bacteria. (C) 2011 Elsevier B.V. All rights reserved.