Are Chlorhexidine Mouthrinses all Acting the Same Towards Oral Biofilms?
Objectives: Chlorhexidine mouthrinses are marketed in different formulations. Therefore, this study aimed at evaluating the in-vitro effects of different chlorhexidine mouthrinses on bacterial load, ecology, and community structure of synthetic multispecies oral biofilms after single or multiple rinses.
Methods: Nine chlorhexidine mouthrinses were selected for this study. Two of the tested products are formulated with an anti-discoloration system, two products contain alcohol, and three products contain cetylpyridinium chloride (CPC) combined with the chlorhexidine. Tested products were grouped according to CHX concentration into 3 groups: low (L), medium (M), and high (H) concentration. Phosphate buffered saline (PBS) was used as a negative control rinsing solution. Multispecies oral biofilms were grown on the surface of hydroxyapatite discs for 48 h, then rinsed with the corresponding product. Biofilms were collected every 24 h for DNA extraction and vitality quantitative PCR (v-qPCR).
Results: The tested mouthrinses provoked different effects in terms of change in total viable bacterial load (VBL), ecology and community structure of the rinsed multispecies oral biofilms. There was no relation between chlorhexidine concentrations, presence, or absence of cetylpyridinium chloride and/or alcohol, and the observed effects. Some chlorhexidine mouthrinses that strongly lowered the total VBL, disrupted biofilm symbiosis. On the other hand, other chlorhexidine mouthrinses with limited impact on total VBL improved the biofilm ecology and community structure. These different effects could not be related to the presence of CPC, alcohol or the concentration of chlorhexidine.
Conclusions: Not all chlorhexidine mouthrinses have the same effect on oral biofilms. Therefore, a chlorhexidine product should not be selected randomly based on its composition. Product selection should depend on the indication: short-term treatment, long-term maintenance, or pre-/post- operative care. Clinical assessment seems important for patient-specific recommendations of a product.