Not Yet Recruiting

NCT Number: NCT07356271

Effects of Mouthwashes on the Oral Microbiome and Systemic Health

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.

Not Yet Recruiting

Trial opening soon.

Get Notified

Key information

Conditions

Hypertension Cardiovascular Diseases Vascular Diseases

Age range

18 year and older

Sex eligibility

All sexes

Study type

Interventional

Phase

Early Phase 1

About this study

PROJECT AIMS

The aim of this project is to determine the role of different mouthwashes on the oral microbiome and its relationship with cardiovascular health. We will achieve this by conducting a double-blinded randomised clinical trial (pilot study) in a primary care dental setting, to investigate (i) the composition of the oral microbiome in different oral niches in periodontal health and disease, and (ii) determine how the oral microbiome is altered by the use of different mouthwashes during oral health and disease, with either , essential oil (EOs), CPCs, hydrogen peroxide (H2O2); all versus placebo (water or saline).

OVERVIEW

While antimicrobial mouthwashes are proven to be clinically effective for management of certain oral microbial diseases, recent studies suggest that, 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).

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

Inclusion & Exclusion

All individuals aged 18 years and older will be eligible to take part in this study. Exclusion will apply to individuals who:

Are current smokers, due to the well-documented impact of smoking on oral and systemic health.

Have a known diagnosis of hypertension, diabetes, or cancer, as these systemic conditions may influence oral microbiome and inflammatory responses.

Have taken a course of antibiotics within the last three months, since antibiotics are known to disrupt microbial balance and may confound the interpretation of oral microbiome data.

Report allergies to essential oils or to milk proteins, as these ingredients may be present in the study mouthwash and could trigger adverse reactions.

In addition, participants who have never previously used a mouthwash will be excluded. This is a precautionary measure designed to avoid even the minimal possibility of adverse responses.

Treatment and study plan

Use of mouthwashes

Drug

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

Primary outcomes

effect of mouthwashes on oral microbiome

Time frame: three years

EXPECTED OUTCOMES / DELIVERABLES

One of the main expected outcomes of this study is to provide clear evidence on the clinical effectiveness of commonly used mouthwashes and their effect on oral microbiome and cardiovascular health. It is anticipated that some mouthwashes will significantly reduce dental plaque and bleeding on probing when compared with placebo. Demonstrating these effects will help confirm which products can genuinely support daily oral hygiene and clinical treatment of gum conditions, alongside either beneficial or no effects on the oral microbiome, such that their beneficial effects do not outweigh the risks.

In participants with good oral health, we thus expect that effective mouthwashes will not only reduce plaque but also maintain a balanced oral microbiome. This means that mouthwashes should support microbiome health, without causing dysbiosis or loss of diversity.

In participants with gingivitis or periodontal disease, the expectation is that mouthwash

Secondary outcomes

effect of mouthwashes on cardiovascular health

Time frame: three years

EXPECTED OUTCOMES / DELIVERABLES

One of the main expected outcomes of this study is to provide clear evidence on the clinical effectiveness of commonly used mouthwashes and their effect on oral microbiome and cardiovascular health. It is anticipated that some mouthwashes will significantly reduce dental plaque and bleeding on probing when compared with placebo. Demonstrating these effects will help confirm which products can genuinely support daily oral hygiene and clinical treatment of gum conditions, alongside either beneficial or no effects on the oral microbiome, such that their beneficial effects do not outweigh the risks.

In participants with good oral health, we thus expect that effective mouthwashes will not only reduce plaque but also maintain a balanced oral microbiome. This means that mouthwashes should support microbiome health, without causing dysbiosis or loss of diversity.

In participants with gingivitis or periodontal disease, the expectation is that mouthwash

Study contacts

Contact information is provided by the study sponsor or research team.

Zoe Brookes, PhD

CONTACT

[email protected]

441752586828

mimoza cana-bishop, MSc

CONTACT

[email protected]

+447903995399

Sponsors and collaborators

Lead sponsor

University of Plymouth

Other

Registry information

Important dates

Study start: 2026
Primary completion: 2028
Study completion: 2029
First posted: Jan 21, 2026
Registry last updated: Feb 17, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

Published trials that share one or more normalized conditions with this study.

Not Yet Recruiting