in vitro effect of photodynamic therapy with curcumin and methylene blue photosensitizers on staphylococcus aureus

Statement of the problem: staphylococcus aureus (s.a) can colonize in the skin, nasal cavity, and oral cavity. in the oral cavity, it can cause dental caries and periodontal dis-ease. mouthwashes can be used as an adjunct to mechanical plaque control methods to decrease the load of oral microorganisms. chlorhexidine (chx) is a commonly used antimicrobial mouthwash with side effects such as changing the sense of taste, tooth discoloration, oral mucosal burning, allergy, and xerostomia. it also has adverse system-ic effects, if swallowed. purpose: this study aimed to assess the effect of photodynamic therapy (pdt) with curcumin and methylene blue (mb) photosensitizers and different laser parameters on s.a colony count.materials and method: in this in vitro experimental study, 99 samples of standard-strain s.a were subjected to pdt with curcumin and mb photosensitizers with/without irradiation of 660 and 445 nm laser with different exposure parameters, and chx in 9 groups (n=11). the samples were cultured in microplates containing mueller-hinton agar, and the number of colony forming units (cfus) was counted after 24 h of incuba-tion at 37°c. data were analyzed by the kruskal-wallis and dunn tests. results: the minimum colony count was noted in chx group (cfus=0) followed by mb and 660nm diode laser group irradiated for 100 s (cfus=147.2727±169.35707). the difference in this respect was significant between mb+660nm diode laser for 100 s and other groups (p< 0.05) except for the mb + 660 nm diode laser for 60 s group. conclusion: chx is superior to laser for elimination of s.a. however, pdt with 660 nm diode laser + mb has considerable antimicrobial efficacy against s.a; increasing the duration of laser irradiation enhances the antimicrobial effect.