Effect of a Combination of Photodynamic Therapy and Chitosan on Streptococcus mutans (An in Vitro Study)

Introduction: this study aimed to assess the effect of photodynamic therapy (pdt) and chitosan separately and in combination on streptococcus mutans. methods: this in vitro experimental study evaluated 216 microbial samples in 6 groups. first, 5 μl of 0.5 mcfarland standard suspension of s. mutans was added to each well of an elisa microplate; 100 μl of mueller hinton broth was also added to each well; 180 wells contained s. mutans suspension while 36 wells were devoid of bacteria. group 1 served as the negative control and had no bacteria. group 2 served as the positive control and s. mutans in the positive control wells did not undergo any intervention. in groups 3 and 4, pdt with a 50 mw low-level laser was performed for 30 and 40 seconds respectively. in group 5, 3 mg/ml of chitosan (100 μl) was used. in group 6, 3 mg/ml (100 μl) of chitosan was used in combination with pdt (50 mw laser for 30 seconds). the laser was irradiated under aseptic conditions at a 660 nm wavelength with 50 mw power. data were analyzed using one-way anova and tukey’s test. results: pdt combined with chitosan showed maximum bactericidal effect followed by pdt for 40 seconds and chitosan groups (p < 0.05). pdt for 30 seconds showed a minimum bactericidal effect (p < 0.05). all pairwise comparisons revealed significant differences (p < 0.001). conclusion: chitosan and pdt alone can be used to decrease the s. mutans count. however, their combined use has a greater bactericidal effect on s. mutans.