The influence of photodynamic therapy on the supragingival plaque accumulation and bacterial composition in orthodontic patients: a randomized controlled trial

Background Photodynamic therapy is an alternative to chlorhexidine and fluoride products in controlling oral health during fixed orthodontic treatment. Objectives The primary aim was to evaluate the influence of toluidine blue–based dye and 660 nm diode laser on the accumulation of supragingival plaque and its bacterial composition in subjects undergoing fixed orthodontic treatment. The secondary outcomes were bacterial composition of the subgingival plaque, the gingival index, and evaluation of white spot lesions (WSL). Trial design Four-arm parallel randomized controlled trial. Methods In this single-blind study, 48 orthodontic patients were randomly allocated to four groups: photodynamic therapy (PDT), 1% chlorhexidine (CHX) varnish, tricalcium phosphate (TCP) varnish containing 5% NaF, and negative control. The interventions were performed immediately after bonding (T0), 6 weeks (T1), and 12 weeks (T2) later. Plaque index, total bacteria count in the supragingival plaque, and the gingival index were determined at T0 (before bonding), T1, T2, and T3 (18 weeks). Quantitative PCR of the bacteria in the subgingival plaque and evaluation of the WSL on intraoral photographs were performed at T0 (before bonding) and T3. Results Forty participants were included in the analysis. At T2 and T3, in the PDT and CHX groups, a significantly lower plaque index was noted compared with the control group (T2: P = 0.002, P < 0.001; T3: P = 0.005, P < 0.001). The total bacteria count significantly decreased in the PDT, CHX, and TCP-5% NaF groups during the study period (P = 0.023, P < 0.001). PDT, CHX, and TCP-5% NaF did not significantly decrease the number of bacteria in the subgingival plaque compared with that in the control group. A significant decrease in gingival scores between T1 and T2 was noted in the PDT group (P = 0.016). No new WSLs were noticed in the PDT or CHX groups. The least number of advanced lesions was diagnosed in the PDT group. No harms were encountered. Conclusion The effects of PDT on oral health were mostly comparable to those produced by CHX and TCP-5% NaF varnish and significantly different from those observed in the control group. Trial Registration ClinicalTrials.gov NCT06331442.