Effects of Mouthwashes on the Oral Microbiome and Systemic Health

Plain-language summary

OVERVIEW While antimicrobial mouthwashes are proven to be clinically effective for management of certain oral microbial diseases, recent studies suggest tha, in addition to targeting bacteria responsible for gum diseases such as gingivitis and periodontitis, they may harm healthy bacteria and disturb the balance and protective role of the oral microbiome (dysbiosis). Most findings on the oral microbiome and mouthwashes involve chlorhexidine use, demonstrating that it may induce dysbiosis and compromise the host oral microenvironment . A recent study completed in 2025 has shown that CPC mouthwash can also inhibit nitrate synthesis in the mouth. However there remains a need for further research on other agents used in mouthrinses, such as hydrogen peroxide, essential oils, to determine whether their clinical effectiveness in managing oral disease is accompanied by changes to the oral microbiome. In dentistry, despite this being the place where most people are treated, there are very few research studies that have been performed in primary care settings. Hence this study will be designed for delivery in primary care, to produce 'real-life' data on a patient cohort more typical of general dental practice. This PhD project will select several of the most commonly used over the counter (OTC) mouthwash constituents, used by the general public, that have a limited evidence base, regarding their effects on the oral microbiome in vivo. . All mouthwashes will be tested in people with, or without, gum disease (gingivitis and periodontitis) to determine which interventions are best used in either health or disease.

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