Determination of the Diffusion Coefficient of Methylene Blue Solutions in Dentin of a Human Tooth using Reflectance Spectroscopy and Their Antibacterial Activity during Laser Exposure

Abstract

This study is devoted to the determination of the diffusion coefficients of methylene blue in an aqueous solution and in a micellar solution of the cationic surfactant in dentin sections of a human tooth in vitro using a method of diffuse reflectance optical spectroscopy and a model of free diffusion. The average diffusion coefficient was (6.74 ± 1.32) × 10⁻⁶ cm²/s for an aqueous solution of methylene blue and (1.93 ± 0.24) × 10⁻⁶ cm²/s for a micellar solution of the dye. The toxicity of methylene blue solutions in water and in a solution of cetylpyridinium chloride in daylight in the absence of laser radiation on the cells of Candida albicans, Staphylococcus aureus FDA 209P, and Lactobacillus, as well as the photodynamic effect of laser radiation (662 nm) on them, were studied. The photodynamic action of laser radiation was shown to have a pronounced suppressive effect on all the studied microbial strains.