Comparison of the clinical and microbiological effects of chlorhexidine gluconate and hypochlorous acid-containing mouthwashes on microbial dental biofilm

Removing supragingival dental plaque biofilm is the primary factor in preventing periodontal diseases. In situations where mechanical oral hygiene practices are difficult and limited, the use of chemical mouthwashes can be beneficial in controlling supragingival dental plaque biofilm. Chlorhexidine gluconate (CHX) is considered the gold standard chemical agent for biofilm control due to its antigingivitis, antiplaque, and anti-inflammatory properties. However, there are various side effects associated with chlorhexidine, and concerns about bacterial resistance have been raised. Therefore, there is a need to develop alternative agents to chlorhexidine. Hypochlorous acid (HOCl) is a component of reactive oxygen species synthesized by immune system cells during the phagocytosis of antigens. HOCl possesses anti-inflammatory and broad-spectrum antimicrobial effects. It has been reported that HOCl may be effective in controlling dental plaque biofilm due to its antimicrobial effects. However, there are limited studies on this topic in the literature, and there is currently no clinical study evaluating the antimicrobial efficacy of HOCl in dental plaque. Hence, the primary aim of our study is to compare the antiplaque efficacy of HOCl mouthwash with CHX mouthwash. The secondary aim is to compare the antimicrobial effects of HOCl and CHX mouthwashes on dental plaque biofilm. This single-center, triple-blind, randomized controlled, crossover study was completed with 26 participants. In the study, the same participants used HOCl and CHX-containing mouthwashes for 4 days each, following a 4-day plaque regrowth model. After each mouthwash usage, supragingival dental plaque biofilm samples were collected, and clinical parameters including modified plaque index, bleeding on probing index, interproximal plaque index, bleeding on interproximal probing index, modified stain index, and tongue discoloration index were recorded. Additionally, participants were asked to evaluate the mouthwashes they used through a questionnaire. In the study results, all oral plaque index, bleeding on probing index, interproximal plaque index, and bleeding on interproximal probing index data were found to be statistically significantly lower with the use of HOCl compared to CHX. In all evaluated areas, the intensity, area, and stain index scores of the modified stain index were also found to be statistically significantly lower with HOCl usage compared to CHX. There was no statistically significant difference observed between the two mouthwashes regarding color changes on the tongue in nine regions and tongue coating thickness. In the questionnaires given to the participants, a statistically significant preference for CHX was observed only for the question "How do you evaluate the taste of the mouthwash you used?" According to the microbiological data of the plaque samples taken from the teeth, Staphylococcus spp. was found to be statistically significantly lower with HOCl usage, whereas Neisseria spp. was lower with CHX usage. No significant difference was found between the two mouthwashes regarding Streptococcus spp., Granulicatella spp., Rothia spp., and total bacterial count. In conclusion, HOCl has shown antiplaque efficacy comparable to CHX. When evaluating total bacterial count, both mouthwashes demonstrated similar antimicrobial efficacy. Within the limits of this study, HOCl can be considered a promising antimicrobial agent that could be used for dental plaque control. Keywords: Hypochlorous acid, chlorhexidine gluconate, dental plaque biofilm, antiplaque, anti-inflammatory.