Evaluation of the antimicrobial effect of cannabidiol (CBD) in a multispecies subgingival biofilm model

Background: This study evaluated the antimicrobial effect of cannabidiol (CBD) on a multi-species subgingival biofilm model. Materials and methods: Biofilms were formed using 33 bacterial species on a Calgary device. Two protocols were tested: (A) biofilm in contact with CBD (125, 250 and 500 µg/mL) and chlorhexidine 0.12% (CHX) for the entire period; (B) treatments with CBD (500 and 1000 µg/mL) and CHX started on day 3, twice a day, for 1 minute. The total biofilm counts, the proportion of complexes, and the counts of each species were evaluated by DNA-DNA hybridization (Checkerboard). Results: In Experiment A, CBD at concentrations of 250 and 500 µg/mL, as well as CHX, significantly reduced the total biofilm count. At 500 µg/mL, CBD also decreased the proportion of the red complex and reduced the counts of 10 bacterial species, whereas CHX affected 20 species. In Protocol B, both CBD at 1000 µg/mL and CHX reduced the total biofilm count and the proportion of the red complex, while increasing the proportion of the green complex. Both protocols led to a reduction in Porphyromonas gingivalis and Tannerella forsythia. Conclusion: CBD reduced the total bacterial count and the red complex, inhibiting known periodontal pathogens. Within the limitations, the results provide exploratory evidence that CBD may reduce the total bacterial count in the proposed polymicrobial biofilm model, including the red complex bacteria, and may thus be postulated as an inhibitor of known periodontal pathogens. However, future in vivo studies with robust sample sizes and standardized CFU-based quantification are required to confirm these findings.