Parameters for antimicrobial photodynamic therapy on periodontal pocket-Randomized clinical trial

Background: Antimicrobial photodynamic therapy (aPDT) has been investigated as an adjunctive to periodontal treatment but the dosimetry parameters adopted have discrepancies and represent a challenge to measure efficacy. There is a need to understand the clinical parameters required to obtain antimicrobial effects by using aPDT in periodontal pockets. The aim of this study was to investigate parameters relating to the antimicrobial effects of photodynamic therapy in periodontal pockets.

Material and methods: This randomized controlled clinical trial included 30 patients with chronic periodontitis. Three incisors from each patient were selected and randomized for the experimental procedures. Microbiological evaluations were performed to quantify microorganisms before and after treatments and spectroscopy was used to identify methylene blue in the pocket. A laser source with emission of radiation at wavelength of ʎ = 660 nm and output radiant power of 100 mW was used for 1, 3 and 5 min. One hundred μM methylene blue was used in aqueous solution and on surfactant vehicle.

Results: The results demonstrated the absence of any antimicrobial effect with aqueous methylene blue-mediated PDT. On the other hand, methylene blue in the surfactant vehicle produced microbial reduction in the group irradiated for 5 min (p < 0.05). Spectroscopy showed that surfactant vehicle decreased the dimer peak signal at 610 nm.

Conclusion: Within the parameters used in this study, PDT mediated by methylene blue in a surfactant vehicle reached significant microbial reduction levels with 5 min of irradiation. The clinical use of PDT may be limited by factors that reduce the antimicrobial effect. Forms of irradiation and stability of the photosensitizers play an important role in clinical aPDT.