Increased Efficiency of PDT Compared to Chlorhexidine on Exvivo Biofilm

Objective: The objective of the present study was to compare the efficiency of photodynamic therapy (PDT) using BLC 2003 with that of 0.2 percent chlorhexidine solution (CHX).

Methods: Plaque and saliva samples were taken from chronic periodontitis patients (sites, PPD > 8mm) treated at our clinic to culture ex vivo biofilms. The relevant 24-hour plaque cultures were pipetted onto microtiter plates conditioned with saliva. Following growth (1d) under anaerobic conditions, the biofilm was subjected to PDT with BLC 2003 (10µM, 15 min. of incubation, 20 J, 50 J, 532 nm Ceralas G2, CeramOptec Bonn, Germany) and chlorhexidine solution (0.2%, incubation: 1 and 3 min.), respectively. Thereafter, the biofilm was obtained from the bottom of the microtiter plate. The dilution series of the samples up to 10–6 were plated on Schaedler agar plates (8% sheep blood + vitamin K). Culturing under anaerobic conditions lasted seven to ten days. Then, the number of CFUs per ml was determined.

Results: Both PDT and CHX treatment had an antibacterial effect on the 1d ex vivo biofilm. A comparison with the control sample revealed that only a minor reduction of CFUs per ml (0.5 log) could be observed for 0.2% CHX at a 1-min exposure, with efficiency increasing somewhat (1.1 log) after 3 min. Photodynamic therapy produced much better results. At an energy density of 20 J, a reduction of 2.2-log steps could be identified. The PDT impact was at its most effective at an energy density of 50 J (2.6 log).

Conclusions: The present study shows that photodynamic therapy with BLC 2003 has a significantly greater effect on ex vivo biofilm than a 0.2 percent chlorhexidine solution.