Clinical and microbiological effectiveness of photodynamic therapy on primary endodontic infections: a 6-month randomized clinical trial

Introduction This short-term randomized controlled trial evaluated the effectiveness of photodynamic therapy (PDT) on clinical success (periapical healing) and on the microbiota of primary endodontic infections. Methods Thirty-two patients presenting mandibular molars with apical periodontitis (one tooth/patient) were selected and randomly allocated into two therapeutic groups: control (chemo-mechanical debridement [CMD]; n = 16) and PDT (CMD + PDT; n = 16). All teeth in both groups had intracanal medication with calcium hydroxide for 7 days before final obturation. Follow-up radiographs were made at 3 and 6 months. Periapical healing was evaluated by the periapical index (PAI). Samples were obtained at baseline, after CMD with or without PDT, and just before root filling to determine the frequency and levels of 37 taxa by checkerboard. Results Significant decreases in PAI scores were observed in both groups over time, although at 6 months, the PDT group presented a significantly better healing score than the control (p < 0.05). At baseline, the most prevalent species in all samples were Candida albicans (46.9%), Dialister pneumosintes (31.2%), Prevotella nigrescens (28.2%), Prevotella tannerae (28.1%), and Peptostreptococcus anaerobius (25%). Most species reduced over time in both groups, and no significant differences in frequency and levels of the tested species were observed between groups in any time point evaluated. C. albicans and D. pneumosintes were still detected in high frequency in both groups at 3 months post-therapy. Conclusions Conventional endodontic therapy with or without PDT is effective in reducing microbial load, resulting in periapical healing. Nevertheless, adjunctive PDT provides better periapical healing at 6-month follow-up.