Antimicrobial Photodynamic Therapy for Biofilm Control on Orthodontic Brackets

This study aimed to develop an effective antimicrobial photodynamic therapy (aPDT) protocol for controlling oral biofilm on orthodontic brackets. Four different interventions were compared to control microorganisms adhering to orthodontic brackets. This study was approved by the Research Ethics Committee under protocol N ^o 6.254.180. Twenty-four participants, providing 96 premolars, were randomly assigned to four groups based on their interventions: Group 1 - aPDT with 0.005% methylene blue and low-power red laser with 9 J/cm² energy density in a single central application on the bracket; Group 2 - the same substance and laser parameters as Group 1, but with 3 J/cm² energy density irradiated at 3 points (disto-incisal, mesio-cervical, and central); Group 3 - application of 0.12% chlorhexidine (CHX) and Group 4 - application of 0.9% sterile saline solution, both for 1 minute around the bracket. Colony-forming units were collected at three time points: before the interventions, immediately after the interventions, and 12 hours after the interventions. Data were obtained by counting colony-forming units (CFU/mL). Non-parametric Friedman and Nemenyi tests were used to compare the different protocols and time points. The results showed that both aPDT (independent of the application protocol) and CHX were effective in reducing biofilm on orthodontic brackets (p < 0.05). No significant variation was observed in the number of microorganisms in teeth treated with saline solution (p > 0.05). Furthermore, aPDT demonstrated similar efficacy to 0.12% chlorhexidine in controlling biofilm, with no statistically significant difference between the two groups.