Terapia fotodinâmica antimicrobiana com butil azul de toluidina O (BuTBO) para inativação de biofilme de Aggregatibacter actinomycetemcomitans em dentes bovinos

Abstract

As an adjunct intervention to mechanical periodontal treatment, antimicrobial photodynamic therapy (aPDT) aims to induce the production of reactive oxygen species, thereby reducing microbial infection. Butyl toluidine blue O, a photosensitizer recently developed from the phenothiazine family, presents physical-chemical modifications to the structure of toluidine blue O, resulting in decreased aggregation and increased singlet oxygen production. The objective of this study was to investigate the efficacy of butyl toluidine blue O in eliminating Aggregatibacter actinomycetemcomitans, using a pre-irradiation time of 1 minute. To achieve this, a biofilm was cultured on bovine dental samples, followed by the application of aPDT. Microbiological evaluations and scanning electron microscopy analyses were performed. The experiment was structured into a group called BuTBO, which was subdivided into six subgroups: control group, laser group, photosensitizer group (corresponding to a pre-irradiation time of 1 minute), and PDT groups with different irradiation times (1, 3, and 5 minutes). A laser with a wavelength of 660 nm and an irradiance of 250 mW/cm² was used, generating energies of 6, 18, and 30 J for exposure times of 60, 180, and 300 seconds, respectively, and radiant exposures of 15, 45, and 75 J/cm². After the procedures, the samples were cultured under microaerophilic conditions, counted, and converted into colony-forming units per milliliter (CFU/mL) for comparative analysis. The results indicated that the application of BuTBO with pre-irradiation time and irradiation time of 1 minute did not show a statistically significant difference (p > 0.05). However, with irradiation times of 3 and 5 minutes, a statistically significant difference was observed (p < 0.01). Irradiation for 5 minutes resulted in a 99.99% microbial reduction in the biofilm. We conclude that BuTBO shows potential as a photosensitizer for reducing A. actinomycetemcomitans microbial loads.