Common mouthwash could alter saliva pH, microbes

March 25, 2020

AMID the coronavirus (COVID-19) pandemic, a new study disclosed that many dentists are using chlorhexidine mouthwash as a pre-rinse before doing dental procedures.

A team led by Dr. Raul Bescos from the University of Plymouth's Faculty of Health found that many dentists are now using chlorhexidine as a pre-rinse but he said they need more information on how it works on viruses.

The first study looking at the effect of chlorhexidine mouthwash on the entire oral microbiome has found its use significantly increases the abundance of lactate-producing bacteria that lower saliva pH, and disrupted the ability of oral bacteria to turn nitrate into nitrite, a key molecule for reducing blood pressure.

Dr. Bescos team found that chlorhexidine was able to reduce microbial diversity in the mouth, although the authors cautioned more research was needed to determine if this reduction in diversity itself increased the risk of oral disease.

One of the primary roles of saliva is to maintain a neutral pH in the mouth, as acidity levels fluctuate as a result of eating and drinking. If saliva pH gets too low, damage can occur to the teeth and mucosa -- tissue surrounding the teeth and on the inside of the mouth.

The research also confirmed findings from previous studies indicating that chlorhexidine disrupted the ability of oral bacteria to turn nitrate into nitrite, a key molecule for reducing blood pressure. Lower saliva and blood plasma nitrite concentrations were found after using chlorhexidine mouthwash, followed by a trend of increased systolic blood pressure. The findings supported earlier research led by the University that showed the blood pressure-lowering effect of exercise is significantly reduced when people rinse their mouths with antibacterial mouthwash rather than water.

Dr. Bescos said: "There is a surprising lack of knowledge and literature behind the use of these products. Chlorhexidine mouthwash is widely used but research has been limited to its effect on a small number of bacteria linked to particular oral diseases, and most has been carried out in vitro.”

Dr. Louise Belfield, a lecturer in the Peninsula Dental School at the University of Plymouth, and one of the co-authors of the study said: "We have significantly underestimated the complexity of the oral microbiome and the importance of oral bacteria in the past. Traditionally the view has been that bacteria are bad and cause diseases. But we now know that the majority of bacteria -- whether in the mouth or the gut -- are essential for sustaining human health."

(ScienceDaily/University of Plymouth)