Immediate and residual antimicrobial effects of adjunctive photodynamic therapy on Enterococcus faecalis-infected human root canals.

OBJECTIVE

To evaluate the immediate and residual antimicrobial effects of adjunctive photodynamic therapy (PDT) associated with chemo-mechanical preparation (CMP) in Enterococcus faecalis-infected human root canals, with particular emphasis on whether PDT provides a persistent antimicrobial effect after treatment.

MATERIALS AND

METHODS

Sixty-four extracted single-rooted human teeth were infected with E. faecalis and randomly assigned to four experimental groups according to treatment protocol and evaluation time: CMP-immediate (n = 10), CMP-15d (n = 10), CMP+PDT-immediate (n = 10), and CMP+PDT-15d (n = 10). Positive controls consisted of infected, untreated specimens evaluated immediately (n = 4) or after 15 days (n = 4), whereas negative controls consisted of non-infected specimens subjected to the corresponding experimental procedures (n = 16). Microbiological samples were collected before treatment and either immediately or 15 days after treatment. Antimicrobial efficacy was assessed by CFU/mL counts and expressed as percentage bacterial reduction. Root canal surface contamination was evaluated by scanning electron microscopy (SEM). Percentage bacterial reduction and SEM contamination scores were analyzed using the Kruskal-Wallis test followed by Dunn's multiple-comparisons test (α=0.05).

RESULTS

All treatment protocols produced marked bacterial reduction (>99%) compared with baseline. Although the CMP+PDT groups showed numerically greater bacterial reduction and a higher frequency of specimens with undetectable bacterial growth than the CMP groups, these differences were not statistically significant (p > 0.05). No residual antimicrobial benefit attributable to PDT was detected after the 15-day observation period. SEM analysis confirmed significantly lower contamination scores in treated specimens than in untreated controls but showed no consistent differences between CMP alone and CMP+PDT.

CONCLUSIONS

Adjunctive PDT did not provide a statistically significant additional antimicrobial benefit over conventional chemo-mechanical preparation, either immediately after treatment or after 15 days. No residual antimicrobial effect attributable to PDT was detected.