Antibacterial potential of riboflavin mediated blue diode laser photodynamic inactivation against Enterococcus faecalis: A laboratory investigation

This study aimed to evaluate the inactivation potency of riboflavin-mediated blue diode laser photodynamic inactivation (PDI) against Enterococcus faecalis at planktonic and biofilm stages and also investigated its effect on the tooth color change.The antibacterial and antibiofilm activities of riboflavin mediated PDI against E. faecalis were investigated. The numbers of colony-forming units (CFUs)/mL were calculated. Teeth discoloration were evaluated using the CIE L*a*b* based color difference (ΔE).Antibacterial analysis indicated that the blue diode laser irradiation at 12, 18, 24, and 30 J/cm2 alone and different concentrations of riboflavin solution (6.25 to 100 μM) reduced the number of CFU/mL of E. faecalis, but the reduction was not statistically significant (P > 0.05). Depending on the riboflavin concentration and the light dose, there can be as much as a 1-log effect on CFU/mL. In addition, E. faecalis biofilm was more affected with 30 J/cm2 irradiation dosage and 100 μM riboflavin than other groups. Meanwhile, bacterial suspensions treated with 5.25% sodium hypochlorite (NaOCl) showed maximum biofilm inhibition and colony number reduction, compared with the control. The teeth exhibited clinically acceptable color change after riboflavin treatment at concentration ranging from 6.25 to 50 μM (ΔE < 3.7).The riboflavin mediated PDI process is somewhat less effective than NaOCl but perhaps less toxic to tissues. It might be feasible to repeat the riboflavin + light treatment to further promote efficacy.