Antimicrobial effect of photodynamic therapy using high‐power blue light‐emitting diode and red‐dye agent on Porphyromonas gingivalis

Abstract

Antimicrobial photodynamic therapy (a-PDT) using a combination of red-colored laser/light-emitting diode (LED) and blue dye has been employed for periodontal therapy and the antimicrobial effect seems promising. Blue light, which has favorable wavelength properties, would be more effective as a light source for a-PDT because blue light itself possesses an antimicrobial effect. This study aimed to investigate the effect of a-PDT using a novel combination of high-power blue LED and red-dye agent on Porphyromonas gingivalis in vitro. Porphyromonas gingivalis ATCC 33277 suspension was irradiated with blue LED (BL) (425-470nm) or red LED (RL) (625-635nm) at 30-90J/cm(2) , or was mixed with erythrosine (ER), phloxine B (PB) or rose bengal (RB) with or without BL irradiation (30J/cm(2) ). RL (30J/cm(2) ) in combination with toluidine blue was employed as positive control. All the suspensions of P. gingivalis were serially diluted, plated and incubated anaerobically, and the numbers of colony-forming units (CFUs) were counted on day 7. BL irradiation at 60 and 90J/cm(2) demonstrated a significant reduction in the numbers of CFUs. ER, PB and RB solutions at 160μg/mL showed almost no or only a minimal reduction in the numbers of CFUs. BL at 30J/cm(2) combined with ER, PB or RB at 160μg/mL resulted in a log reduction of 0.9, 1.0 and 7.1, respectively, in the numbers of CFUs; 30J/cm(2) BL with RB at 1.6, 16 and 160μg/mL demonstrated a log reduction of 6.3, 8.0 and 5.5, respectively; and a log reduction of 5.2 was obtained after 30J/cm(2) RL with 16μg/mL TB. Within the limits of this study, BL was found to have an antimicrobial/growth-inhibiting effect on P. gingivalis, and a-PDT using a combination of BL and RB shows promise as a new technical modality for bacterial elimination in periodontal therapy.