Study Finds Chlorhexidine Mouthwash May Lower Salivary pH

Healthy human saliva has a pH of 7.4, just like blood. If salivary pH drops too low, it can create an imbalance that demineralizes tooth enamel. A new study has found that chlorhexidine mouthwash may reduce microbial diversity in the mouth and lower salivary pH.

Thirty-six healthy people with an average age of 26 participated in the study. They used a placebo mouthwash for 7 days and then used a chlorhexidine mouthwash for 7 days. At the end of each 7-day period, the researchers measured the abundance and diversity of bacteria in the mouth, pH, the ability of saliva to neutralize acids in the mouth, lactate, glucose, nitrate, and nitrite concentrations.

Use of chlorhexidine mouthwash was shown to increase the abundance of Firmicutes and Proteobacteria, and lower the abundance of Bacteroidetes and Fusobacteria. These changes were associated with lower salivary pH and reduced ability to neutralize acids in the mouth.

Chlorhexidine use was also associated with a disruption in the ability of oral bacteria to turn nitrate into nitrite. Nitrite is a key molecule for keeping blood pressure in a normal range. In addition, salivary lactate and glucose were significantly increased.

The study was conducted by researchers from the University of Plymouth. It was published on March 24, 2020 in the journal Scientific Reports.