The effect of aPDT with natural and chemical photosensitizers on reduction of bacteria around orthodontic brackets.

Purpose: One of the methods to reduce microbial plaque is antimicrobial photodynamic therapy (aPDT). The present study evaluated the different output power of diode laser(DL) and two photosensitizers in aPDT against microbial plaque around orthodontic brackets.

Methods: In this experimental laboratory research, the buccal surface of fifty-four human premolar teeth was prepared for metal bracket bond. The samples were contaminated with Streptococcus mutans suspension to form a bacterial biofilm. After ensuring the presence of bacteria in the samples taken out from the incubator (37 °C for 72 h), they were randomly divided into following groups: 100 µg/mL toluidine blue (TBO) with DL radiation at 200, 300, 400, and 500 mW, 1000 µg/mL phycocyanin (PC) with DL at aforementioned output powers, TBO and PC without light activation, negative control and chlorhexidine After treatment, the colonies were counted using the Miles and Misra method. One-way ANOVA, Tamhane, and Two-way ANOVA were implemented for statistical analysis.

Results: The bacterial colonies when using TBO were significantly lower than PC at all laser powers (p < 0.05). Pairwise comparisons of different output powers in each photosensitizer, showed that as the output power was increased, the more bacteria were eliminated. A comparison of studied groups with chlorhexidine showed a significant difference in favor of chlorhexidine (p < 0.05).

Conclusion: Both photosensitizers activated by each of the powers resulted in significant S.mutans colonies reduction compared to the negative control. However, a greater reduction was observed with 500mW output power. TBO was more effective than the PC.

Clinical trial number: Not applicable.