If you use chlorhexidine mouthwashes in your daily hygiene routine, this interests you. And a lot. The reason is that a team of researchers from the University of Plymouth (UK) has found that these products significantly increase the number of lactate-producing bacteria, which lowers the pH of saliva (acidifies it) , thereby increasing the potential damage to the teeth.
Experiment participants were given a placebo mouthwash for seven days. They were then offered a mouthwash for another week, this time with chlorhexidine. The researchers analyzed the abundance and diversity of bacteria in the mouth (the oral microbiome), measured pH , the ability of saliva to neutralize acids in the mouth, and the concentrations of lactate, glucose, nitrate, and nitrite for each of periods.
What they saw was that using chlorhexidine mouthwash for seven days resulted in more bacteria from the Firmicutes and Proteobacteria families in the mouth, and fewer Bacteroidetes , TM7 and Fusobacteria . This change was associated with an increase in acidity, which was observed in lower salivary pH and in the ability of saliva to neutralize acids in the mouth.
Saliva serves, among other things, to maintain a neutral pH in the mouth . Acidity levels fluctuate as a result of eating and drinking. If the pH of saliva is too low, it can damage the teeth and the mucosa, the tissue around the teeth and inside the mouth.
Overall, the researchers found that the widely used chlorhexidine does reduce the microbial diversity in the mouth. Of course, the authors caution that more research is needed to determine that this reduction in itself increases the risk of oral disease.
In this study, recently published in Scientific Reports , it was found that chlorhexidine alters the ability of oral bacteria to convert nitrate to nitrite (a key molecule for lowering blood pressure). Lower nitrite concentrations were found in saliva and blood plasma after using chlorhexidine mouthwash, followed by an upward trend in systolic blood pressure. These findings support previous research conducted by the same university, which showed that the blood pressure-lowering effect of exercise is significantly reduced when people rinse their mouths with such a mouthwash instead of water.
“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 certain oral diseases , and most it has been carried out in vitro ”, commented Raúl Bescos, director of the investigation.
“ We have significantly underestimated the complexity of the oral microbiome and the importance of oral bacteria in the past. Traditionally, the opinion has been that bacteria are bad and cause disease. But now we know that most bacteria – whether in the mouth or in the gut – are essential to maintaining human health, ”said study co-author Louise Belfield.
“As dental clinicians, we need more information on how mouthwashes alter the balance of oral bacteria , in order to prescribe them correctly. This document is an important first step towards achieving this, ”said Zoe Brookes, a co-author.
Experts say that in the recent novel coronavirus pandemic, many dentists are using chlorhexidine as a pre-wash before performing a dental procedure, but more information is needed on how this substance works in viruses.
Referencia: Bescos, R., Ashworth, A., Cutler, C. et al. Effects of Chlorhexidine mouthwash on the oral microbiome. Sci Rep 10, 5254 (2020). https://doi.org/10.1038/s41598-020-61912-4.
