Dental Biofilm Structure Influenced by Chlorhexidine-fluoride Mouthrinse Formulations

Objectives: The antimicrobial activity of chlorhexidine (CHX) mouthrinses depends on their active ingredients. Formulations supplemented with fluoride (NaF) as anticaries agent may have inferior antimicrobial properties. Therefore, aim of this study was to investigate the effect of CHX/NaF formulations on biofilm morphology and viability (V) while keeping the natural biofilm architecture intact.

Methods: Ten volunteers wore intraoral splints supplied with standardized human enamel slivers for in vivo generation of biofilms (24h). The biofilms were exposed ex vivo either to a NaF containing CHX-solution CHX+NaF (CHX 0.2%; F^- 250ppm; no alcohol) or CHX0.06 (Chlorhexamed 0.06+F^®; CHX 0.06%; F^- 250ppm; 7% alcohol). CHX0.2 (Chlorhexamed FORTE^®; CHX 0.2%; 7% alcohol) and NaCl 0.9% served as positive and negative control. The biofilms were analyzed by CLSM after staining using the LIVE/DEAD BacLight Viability Kit. Biofilm thickness (BT), surface area coverage (C) and V were measured, the latter in every second 1µm-biofilm layer. In addition the total bacterial counts (BC/mm²) were determined and the cells were cultivated (CFU/mm²). Mean and mean based 95% confidence intervals were calculated.

Results:

Conclusion: This in vivo approach for biofilm formation generated reproducible dental biofilms with comparable C, BT and log BC/mm². CHX formulations showed a strong antivital effect at the biofilm surface. However, their efficacy varied significantly in deep layers. CHX+NaF reduced V as effective as CHX0.2, whereas CHX0.06 had significantly less effect than 0.2% CHX formulations. CHX0.2 and CHX+NaF notably reduced CFU/mm², while CHX0.06 and NaCl did not. Thus, the combination of CHX (0.2%) and NaF showed high antimicrobial activity even in deep biofilm layers. (supported by GABA International, Switzerland)