Potential deleterious effects to oral and medical health may outweigh the potential benefits of over-the-counter commercial mouthwashes; a series of scientific studies have raised questions important to dental professionals and how they advise patients regarding mouthwash use.
A 2017 study entitled, “Over-the-counter mouthwash use and risk of pre-diabetes/diabetes,” in the journal Nitric Oxide, by Rakesh Patel, Ph. D. and colleagues, indicates that mouthwash use twice or more a day may increase pre-diabetes and/or diabetes risk over three years.
The suspected causal agents are compounds in mouthwashes that produce collateral damage, destroying “good” bacteria important to the formation of nitric oxide along with the “bad” bacteria.
Patel and colleagues explained that nitric oxide is a chemical compound that helps to regulate insulin. Since insulin controls blood sugar levels, and nitric oxide regulates insulin, an obvious concern exists that merits an awareness by dental professionals of continued research.
But do dentists need to be concerned about how they advise their patients regarding mouthwash use?
Patel’s study concluded that, “Frequent regular use of over-the-counter mouthwash was associated with increased risk of developing pre-diabetes/diabetes in this population.” Yet further research is needed to determine the risk factor associated with mouthwashes.
The potential link between an oral health product and diabetes is one of many examples of the close nexus between dentistry and general medicine.
“This role of oral bacteria in reducing nitrate to nitrite as part of the salivary nitrate-nitrite-nitric oxide pathway has implications for our understanding of the links between oral health and general health,” said P.M. Preshaw, Professor of Periodontology, Center for Oral Health Research & Institute of Cellular Medicine, New Castle University, “and is currently a key area of research, particularly in the context of antibacterial mouthwash.”
Preshaw urged caution against a rush to judgment in a November 2018 article in British Dental Journal, “Mouthwash use and risk of diabetes,” noting that media outlets “erroneously” reported that mouthwash use increases the risk of developing diabetes by about 50%, when the increased risk was related to development of prediabetes/diabetes combined.
“Methodological limitations in the [Patel] study bring into question the generalisability of the findings,” wrote Preshaw. “It is important that dental professionals are aware of emerging research on this topic as patients frequently ask for advice on use of mouthwash as part of their oral hygiene regime.”
With respect to mouthwash use, my general opinion is that (in the context of periodontal diseases), for the vast majority of patients, mouthwash use won't achieve a clinically relevant benefit over and above that achieved by effective mechanical plaque control (that is, brushing and interproximal cleaning), and certainly should not be regarded as a substitute for ineffective mechanical plaque control. I also think that while at present there are insufficient firm data to advise patients to stop using mouthwash because of risk of adverse general health effects, the emerging evidence on the role of oral bacteria in the nitrate-nitrite-nitric oxide pathway and potential impacts of antibacterial mouthwash on the oral microbiome raises concerns given that a large proportion of the population use mouthwash on a regular basis.
On the question of how to advise patients, Preshaw advised, “As a specialist in periodontics…my oral hygiene advice is firm in emphasizing the importance of mechanical plaque control rather than chemical plaque control. I rarely advise mouthwash use other than in specific situations, such as periodontal surgery when it is important for patients to avoid brushing a particular area during healing.”
Further research may lead to specific recommendations regarding the frequency of mouthwash use, according to Preshaw—and risks and benefits must be evaluated for each individual case—but other potential health effects make moderation a reasonable recommendation even before the diabetes jury is out.
Another study in British Dental Journal by A. Dagher and N. Hannan, “Mouthwash: More harm than good?” cited concerns beyond the nitric-oxide/diabetes link.
“Using mouthwash straight after brushing reduces the fluoride concentration around the teeth, subsequently reducing the overall benefit of using toothpaste. Some patients, especially children, may be more likely to substitute toothpaste with mouthwash as this is less time consuming and requires less effort. Additionally, in vitro and in situ research has found that some mouthwashes have a low pH which can lead to erosion.”
Dagher and Hannan explained that these effects are “especially worse if patients use mouthwash straight before bed when their saliva flow is reduced.” They also pointed out that “chlorhexidine containing mouthwashes can also trigger a severe anaphylaxis in allergic patients.”
The same concerns about possible links to diabetes, as well as high blood pressure are factors in their advice as well, adding to their overall caution toward mouthwash use.
“Although mouthwash still has its role,” they concluded, “whether it is for post-surgery use or for xerostomia, its usefulness may be questionable and limited when it comes to daily use by the general population.”
“We believe the dental team has a vital role in encouraging correct use of mouthwash or discouraging its use if they are being used incorrectly. It will be interesting to see the turn of events as new research is brought to light.”
Dagher, A., Hannan, N. Mouthwash: more harm than good?. Br Dent J 226, 240 (2019).
Patel, Rakesh, et al., Over-the-counter mouthwash use and risk of pre-diabetes/diabetes. Nitric Oxide Volume 71 (2017)
Preshaw, P. Mouthwash use and risk of diabetes. Br Dent J 225, 923–926 (2018).
Author: Kelly John Walker is Senior Writer and Editor with Strategic Dentistry, the parent company of DOCS Education. He holds a Master of Science (MS) degree in Environmental Science from New Mexico State University and a Bachelor of Arts (BA) in English Composition.