In vitro antimicrobial effect of curcumin-based photodynamic therapy on Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans.

Background: Photodynamic therapy (PDT) is a bactericidal method, which has recently been introduced in the field of dental medicine and therapy. Curcumin, a compound isolated from Curcuma longa L., exerts potent phototoxic effects at micromolar concentrations. The aim of our study was to explore the in vitro antimicrobial effect of curcumin-based PDT on two major etiological agents of periodontitis, Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans.

Methods: P. gingivalis ATCC33277 and A. actinomycetemcomitans ATCC24523 suspension was irradiated with blue LED (BL) (450-470 nm, output power density 1.2 W/cm) for 20-60 s (6-18 J/cm), treated with curcumin (2 min), or subjected to a combination of curcumin treatment and BL irradiation (60 s, 18 J/cm). A suspension of chlorhexidine gluconate (CHG) was used as the positive control. All bacterial suspensions used were serially diluted, plated, and incubated anaerobically or microaerobically. 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: BL irradiation at 6, 12, and 18 J/cm alone reduced the number of CFUs of both P. gingivalis and A. actinomycetemcomitans, but the reduction was not statistically significant. Compared with BL irradiation alone, curcumin solution at 20 μmol/L used alone achieved a lower reduction in the number of CFUs. Combined use of BL at 18 J/cm 20 μmol/L curcumin treatment yielded a log reduction of 0.43 and 1.51 for P. gingivalis and A. actinomycetemcomitans CFUs, respectively. Suspensions treated with 0.12 % CHG showed a log reduction of 0.29 and 0.28 for P. gingivalis and A. actinomycetemcomitans CFUs, respectively.

Conclusions: Although the bactericidal and growth-inhibitory effects of BL alone on P. gingivalis and A. actinomycetemcomitans were not significant, A. actinomycetemcomitans was susceptible to photodynamic inactivation by the combination of BL and curcumin.