Effect of Indocyanine Green and Infrared Diode Laser to Streptococcus mutans Biofilms

The aim of this study was to quantitatively and qualitatively evaluate the effects of the indocyanine green (ICG)-near-infrared (NIR) photoreaction on Streptococcus mutans biofilms. ICG recently emerged as a photosensitive agent for photodynamic therapy. Although the effects of ICG-NIR on S. mutans inhibition are documented, little is known about its influence on biofilms, which are resistant to antimicrobial treatment and a major cause of plaque that leads to dental caries. ICG was used as a photosensitizer with a diode laser irradiated in a rectangular shape (810 nm, 300 mW) as a light source on S. mutans ATCC 25175 biofilms. Viability was determined by the colony forming unit (CFU) count and confocal laser-scanning microscopy. The biofilm surface temperature was measured with a one-channel thermocouple thermometer. ICG and NIR diode laser significantly decreased the CFU count of S. mutans compared with the control group in a time-dependent manner. When irradiated with light after ICG application, temperature changes of 8.4°C, 12.4°C, and 14.9°C were observed with 10, 30, and 60 sec of irradiation, respectively. The ICG-NIR diode laser photoreaction can inhibit S. mutans biofilms, especially at 60 sec. An optimized protocol is needed for clinical application of ICG-NIR diode laser treatment.