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Effects of Mouthwashes on the Oral Microbiome and Systemic Health
Sponsor: University of Plymouth
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.
Key Details
Gender
All
Age Range
18 Years - Any
Study Type
INTERVENTIONAL
Enrollment
200
Start Date
2026-02-01
Completion Date
2029-03-01
Last Updated
2026-02-17
Healthy Volunteers
Yes
Conditions
Interventions
Use of mouthwashes
Population This study aims to recruit up to 200 participants over a period of 3 years on a part-time basis. Recruitment will be carried out through three sites: (i) the University of Plymouth campus population (as successfully used in earlier studies such as Bescos et al., 2020), (ii) the Peninsula Dental School / Peninsula Dental Social Enterprise (PDSE) triage patient clinics (non-NHS clinics), and (iii) the Southside Dental Practice, a private primary care practice located in Southsea, Portsmouth. Sample size was calculated using G\*Power software, which showed that usually 20-30 participants per group are enough, depending on whether the focus is clinical outcomes, blood markers, or microbiome changes. For this project, the main outcome is clinical effectiveness, measured through changes in plaque and bleeding scores. The PDSE clinics collectively see around 400 patients per day across their sites, providing a large and diverse pool of potential participants. In compariso