Background: Periodontal disease (PD) is a chronic inflammatory disease caused by the presence of microbial biofilm. The aim of this study was to evaluate antimicrobial effect of antimicrobial photodynamic therapy (APDT) mediated by methylene blue (MB) in monomer form on A. actinomycetemcomitans and P. gingivalis.Methods: A. actinomycetemcomitans ATCC 29523 and P. gingivalis ATCC 33577 were cultured on anaerobic jars at 37°C for 48 h, and we tested APDT in the presence of 0.25% sodium dodecyl sulfate (SDS) in phosphate-buffered saline (PBS) or in PBS alone. APDT was carried out with 100 µM MB under laser radiation (PhotolaseIII, DMC, Brazil) at ʎ = 660 nm and parameters as following (P = 100 mW; I = 250 mW/cm 2 , and doses of 15, 45 and 75 J/cm 2 ).Results: Following APDT, PBS groups of A. actinomycetemcomitans presented 4 Logs of microbial death after 5 min irradiation. However, there was no bacterial reduction in SDS groups. On the other hand, P. gingivalis was sensitive to APDT in the presence of 0.25% SDS with 2 logs reduction from dark toxicity. Conclusion:The presence of 0.25% SDS can lead to different responses depending on the different microbial species.

Background: The elimination of the pathogenic microorganisms of the periodontal pocket is one of the main points for success in periodontal treatment. The objective of this study is to investigate the clinical and antimicrobial effect of papain-mediated photodynamic therapy in the clinical treatment of periodontal disease. Methods: Twenty patients with chronic periodontitis will be selected. Patients will be randomly divided into 2 groups (n = 10). Group 1 will receive conventional periodontal treatment and group 2 will receive conventional treatment and antimicrobial photodynamic therapy (PACT). Conventional treatment will consist of oral hygiene guidance, with brushing technique instructions and recommendation of daily flossing. The calculus deposits on the teeth will be removed with ultrasound equipment and curettes for scraping and root planning. The PACT will be performed at the end of each periodontal treatment session, at sites with bags ≥4 mm. PapaMblue photosensitizer will be deposited in the periodontal pockets with a syringe and a pre-irradiation time of 1 minute will be adopted. Then, the laser emitting wavelength of 660 nm, with power of 100 mW, for 2 minutes, radiant exposure of 30 J/cm2 and power density of 250 mW/cm2 will be applied. Patients will undergo clinical evaluations before treatment (day 1) at 30, 60, and 90 days after the end of treatment; and microbiological evaluations before and immediately after treatment. The distribution of the data within each group and the homogeneity of the variances will be verified. With this information, the most appropriate statistical test in each evaluation will be used. The sample calculation is based on the literature and the significance level of 5% will be adopted. Discussion: The combination of PACT with methylene blue in a papain gel and the conventional treatment may increase the reduction of bacteria in periodontal pockets.

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