The effect of antibacterial photodynamic therapy with diode laser on chromogenic bacteria associated with dental black staining: An in-vitro study

Abstract

BackgroundAggregatibacter actinomycetemcomitan (A.a) and Actinomyces naeslundii (A.n) are two gram-negative chromogenic bacteria involved in the formation of dental black stainings. Our study aimed to investigate the antibacterial effect of photodynamic therapy (aPDT) using two photosensitizers, Methylene Blue (MB) and Indocyanine Green (ICG). Materials and methodsIn this in-vitro study, two isolates of each selected bacterium were cultured and treated as follows; Negative control with no treatment; CHX as a positive control; ICG; MB; ICG with 808 nm laser activation; and MB with 660 nm laser activation. The number of colonies (CFU/mL) was determined to compare the groups. The qualitative evaluation of biofilm formation was done by scanning electron microscopy of treated enamel pieces. The logarithmic values of the colony counts were compared using One-way ANOVA and the Welch test Tukey HSD and Games-Howell tests were used for multiple comparisons. P-values of less than 0.05 were considered statistically significant. ResultsThe use of ICG alone or along with laser irradiation at the wavelength of 808 nm significantly reduced the number of colonies of A.a and A.n bacteria. Comparing the colony counts in the MB group with the positive control showed no significant decrease in bacterial load. On the contrary, activation of MB with 660 nm radiation of diode laser showed a significant antibacterial effect. The density of bacterial biofilm was significantly lower in the groups treated with MB and ICG without laser activation than in the control group; however, the reduction in bacteria biofilm density was more robust using photodynamic therapy with ICG. ConclusionaPDT using MB with 660 nm laser and ICG with 808 nm laser significantly reduced the number of chromogenic A.a and A.n bacteria, and photodynamic therapy with ICG was proven to be significantly more effective than MB with or without laser radiation.