Effectiveness of Photoactivated Disinfection (PAD) to Kill Enterococcus faecalis in Planktonic Solution and in an Infected Tooth Model

OBJECTIVE: The aim of this study was to investigate the effectiveness of photoactivated disinfection (PAD) in killing Enterococcus faecalis (EF) in planktonic solution and in an infected tooth model. METHODS: One hundred and thirty-two glass tubes of EF samples with concentration of 10(14) colony forming units (CFU)/mL and photosensitizer were prepared. Sixteen groups were set up and subjected to diode laser, and then received a radiation energy dose ranging from 0.5 to 5.5 J. The bactericidal effect was measured by the mean CFU of viable EF after irradiation. Sixty single-rooted teeth were selected and contaminated with EF, and then given PAD therapy; 5.25% NaOCl irrigation and saline solution were used to disinfect the root canals. Microbial samples were taken before and after disinfection, and after 72 h recovery, and then the CFU were counted. RESULTS: The bactericidal effect increased linearly with the irradiation energy dose in planktonic solution. For the same irradiation energy dose, the bactericidal effect was greater in group receiving 100 mW than in that receiving 50 mW and exposed to doubled irradiation time (p<0.05). No bacterium was detected after irrigation in the NaOCl group in the root canal model, but the recovery of bacteria after 72 h was detected in 11 samples. Bacteria were detected in all the other groups, and PAD was significantly more effective than saline solution in reducing the number of bacterial cells within the root canals (p<0.05). CONCLUSIONS: PAD was shown to have bactericidal effect on EF, and the bactericidal effect increased linearly with the irradiation energy dose and was superior using higher output power. PAD could decrease EF in root canals effectively, but was no more effective than 5.25% NaOCl, and PAD is more effective in planktonic solution than in root canals.