We all know that the process of oral hygiene maintenance is incomplete without the essential ‘swish’ of a mouthwash. In Fact, now it is ingrained in our routine oral care system. But, What if using these mouthwashes on a regular basis is rather exposing us to increased risk of diabetes?
A study has found out that use of a mouthwash twice daily or more leads to fifty percent increased risk of developing prediabetes or diabetes(combined), when compared to individuals who use mouthwash less than twice daily or none at all. The study gained considerable attention and sparked debates over daily use of mouthwashes.
The study was conducted by a group of researchers in Puerto Rico, monitoring the health of obese and overweight adults over a three-year period. Blood samples of the participants were collected at both the visits and glycated haemoglobin was determined, categorizing the participants as normoglycaemic, pre-diabetic or diabetic. This research, published in Nitric Oxide journal, highlighted the role of oral biome in our general health. A mechanism involving our oral microbiota and salivary nitrate-nitrite-nitric oxide pathway was explained as the probable reason behind this association, as reduced levels of Nitric Oxide (NO) is related to development of insulin resistance.
The Mechanism and the Role of Oral Bacteria
The nitrate-nitrite-nitric oxide pathway brings forth the symbiotic relationship between the oral bacteria and the host, with the nitric oxide production as its basis.
In this pathway, there is active uptake of about one-fourth of absorbed dietary nitrate (NO3-) by the salivary glands, while the rest is excreted by the kidneys. This nitrate that enters the saliva is acted upon by Nitrate-reducing oral bacteria, present particularly in clefts on the dorsum of the tongue, reducing it to nitrite form (NO2-), which is subsequently swallowed. Finally, this nitrite is reduced to nitric oxide (NO) on entering the acidic environment of the stomach.
Nitric oxide is involved in various aspects of cellular function throughout the body in general, and for vascular function in particular, as it regulates the vascular tone and blood flow causing vasodilatation and smooth muscle relaxation.
Hence, defects in NO production are commonly associated with endothelial dysfunction and cardiovascular ailments such as atherosclerosis and hypertension.
This cycle benefits the oral microbiome by providing the dietary nitrate, which acts as a terminal electron acceptor, allowing bacterial respiration in an anaerobic environment. The host on the other hand benefits by receiving the cycle’s by-product which is a source of NO which that is essential in many aspects of cellular function.
Relevance and Future Implications
Mouthwashes have an antibacterial effect in our oral cavity, their regular use was found to interfere with the usual commensals that play a part in the salivary nitrate-nitrite-nitric oxide pathway, and these reduced levels of nitric oxide are in-turn, implicated in insulin resistance and adverse cardiovascular effects such as impaired vascular function and hypertension.
When associated with risk of diabetes or pre-diabetes, lower NO bioavailability and resultant insulin resistance has been noted in experimental animals. It has also been noted that reduced NO levels play a part in regulating energy metabolism, with reduced NO bioavailability in obese patients and those with insulin resistance.
Knowledge and understanding of the nitrate-nitrite-nitric oxide pathway has enabled us to further explore the relationship between our oral and general health. This has raised considerable interest in the research community, allowing various studies particularly in the stream of antibacterial mouthwashes.
A small-scale study on hypertensive patients found that three days' use of an antibacterial mouthwash (such as, chlorhexidine)
Produced a significant decrease in oral nitrate to nitrite reduction, and hence, increased salivary nitrate, decreased salivary nitrite and a subsequent slight elevation in systolic blood pressure (approximately 2.3 mmHg).
Another study found that chlorhexidine mouthwash used for seven days resulted in reduced levels of oral nitrite by 90% and that of plasma nitrite by 25%. These alterations were accompanied by increase in both systolic and diastolic blood pressure by 2.0–3.5 mmHg.
Although the Mouthwashes are very effective oral hygiene measures it is essential to understand the importance of mechanical plaque control rather than chemical plaque control. Mouthwashes should not be considered as a substitute for ineffective mechanical plaque control and their use should be restricted in situations other than periodontal surgery where it is important for patients to avoid brushing a particular area during healing.
Although the present data is insufficient to advice against the regular use of mouthwashes, the available evidence on the role of oral bacteria in the nitrate-nitrite-nitric oxide pathway and the potential impact of antibacterial mouthwashes on the oral microbiota has brought forth concerns that possibly, large proportion of the population use mouthwash on a routine basis. Therefore, further research is required to estimate a safe frequency of its usage, depending upon the type of mouthwash being used and the rationale for use.
Hence, as a clinician one must evaluate the potential risks as well as the benefits in each individual case before writing a prescription or recommendation of a mouthwash therapy.
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