Antibacterial effect of yellow He-Ne laser irradiation with crystal violet solution on Porphyromonas gingivalis:: An evaluation using experimental rat model involving subcutaneous abscess

A study was conducted to evaluate the antibacterial effect of yellow He-Ne laser irradiation with crystal violet solution (CV) on Porphyromonas gingivalis (P.g.). Paper points were soaked with a P.g. suspension (10(9) mi) with 0.8 mg/l CV added, laser-irradiated for 60 s (laser group), and implanted subcutaneously on the back of rats. Three additional groups were studied: CV group: the paper point was soaked with the P.g. suspension plus 0.8 mg/l CV, but laser irradiation was not performed; P.g. group: the paper point was soaked with the P.g. suspension only and laser irradiation was not performed; control group: the paper point was soaked with sterilised isotonic sodium chloride solution and laser irradiation was not performed. Seven days after implantation, block sections of all implanted sites were examined histologically. The abscess area in the laser group was smaller than in the P.g. group or CV group, but larger than in the control group. The number of inflammatory cells was greatest in the P.g. and CV groups, with fewer in the laser group and still fewer in the control group. The results indicate that a yellow He-Ne laser with 0.8 mg/l CV solution exerts an antibacterial effect in vivo.