Rose bengal-mediated photodynamic inactivation against periodontopathogens in vitro.

ABSTRACT

BACKGROUND: The main goal of periodontal therapy is to eliminate the spread of infection in the periodontium. Antimicrobial photodynamic therapy (aPDT) is a bactericidal method that has been recently introduced for controlling periodontal infection. The aim of this in vitro study was to evaluate the effect of aPDT using a combination of medium-power blue light-emitting diodes (LEDs) and rose bengal (RB) on selected key periodontopathogens. METHODS: Porphyromonas gingivalis ATCC33277, Aggregatibacter actinomycetemcomitans ATCC29523 and Fusobacterium nucleatum ATCC10953 were used in the experiments. Each bacterial suspension was irradiated with a blue LED (BL) (450-470 nm, output power density of 1.2 W/cm2) for 20-60 s (6-18 J/cm2), treated with RB (1 min), or subjected to a combination of RB treatment and BL irradiation (40 s, 12 J/cm2). All bacterial suspensions were serially diluted, plated and incubated anaerobically or microaerobically, and the numbers of colony-forming units (CFUs) were counted on day 7. One-way analysis of variance (ANOVA) and Tukey's HSD tests were used for statistical analysis. RESULTS: Treatment with BL irradiation from 6 to 18 J/cm2 did not significantly reduce the number of CFUs, whereas treatment with RB alone induced a low-to-high reduction in the bacterial CFUs in a dye concentration-dependent manner. Furthermore, the difference in the effects obtained with 16 µg/mL and 160 µg/mL RB was not statistically significant. Treatment with the BL at 12 J/cm2 combined with 160 µg/mL RB yielded maximal log reductions of 3.03, 4.2 and 2.23 in P. gingivalis, A. actinomycetemcomitans and F. nucleatum CFUs, respectively. CONCLUSION: Within the limits of this study, the three periodontal pathogens, especially A. actinomycetemcomitans, were susceptible to photodynamic inactivation by the combination of the BL and RB. RB-mediated aPDT may offer a viable alternative tool for periodontal pathogen treatment, especially for A. actinomycetemcomitans eradication. aPDT may be a valuable tool for the treatment of periodontal diseases, particularly those in which A. actinomycetemcomitans is a dominating pathogen.