Jasmine Deans
Background:
Microbiomes are all around us, in your gut, on your hands, in your ear, and especially in your mouth. The oral microbiome is one of the most interesting subjects to study because of the complex environment in your mouth. It’s wet, warm, and depending on the person can have a high or low pH. Many factors come into play when it comes to the health of your oral microbiome. One of those factors is chlorhexidine (CHX), an antiseptic mouthwash that has been around since the 1970s. Dentists regularly use chlorhexidine, so how does this affect our microbiome?
Chlorhexidine is an antiseptic agent that is used because of its long-lasting antibacterial effects and the large spectrum of action. It’s used by dentists because there have been studies that have shown its effectiveness in the clinical management of plaque, gingival inflammation, and bleeding (Amoian et al., 2017). Other studies show that it helps reduce the proliferation of some bacterial species associated with periodontal disease as well as reducing levels of bacteria that colonize the top surface of the tongue (Bescos et al., 2020).
The study done by Bescos et al., 2020, investigates the effects of chlorhexidine (CHX) mouthwash on the salivary microbiome and various biomarkers in healthy individuals.
A previous study found that there had been over 10 different species that colonized the tongue (Tribble et al., 2019). They noticed a reduction in the microbial community on the tongue with CHX use, however, there weren’t any other measurements taken. Due to the lack of information provided by this study, they wanted to take a closer look and measure other factors to see what else it affects besides the microbiota on the tongue.
Central Question:
What are the effects of 7-day use of Chlorhexidine mouthwash on the oral microbiome and how does it impact saliva markers like pH, buffering capacity, and lactate and glucose levels?
Evidence:
This study was set up to where they had 36 healthy individuals that were asked to rinse their mouth with a placebo mouthwash twice a day for 7 days and then repeat the process with the CHX mouthwash for another 7 days. At the end of each treatment, the researchers took samples of their blood and saliva so that they could test the diversity and the abundance of the oral bacteria, as well as the pH, Lactate, glucose, nitrate, and nitrate concentrations.
Figure 1A & 1B from Bescos et al., 2020. A displays the Shannon diversity index and how many different species are in a community and how evenly they are distributed. B shows the Bray-Curtis index which compares how similar or different the species compositions are between communities.
Bescos et al., (2020) found that CHX mouthwash significantly altered the oral microbiome, increasing good bacteria and decreasing non-beneficial bacteria. They linked these changes to a lower saliva pH. Their research also showed that using CHX raised saliva lactate and glucose levels. The researchers connected their genetic analysis with other common signs of oral health. They noticed a decrease in the overall variety of bacteria in the mouth after using CHX compared to a placebo.
In the previous study done on tongues, some matchups concurred with the new data (Tribble et al., 2019). This information correlates with the findings that a lower diversity of oral bacteria has been related to a higher risk of oral diseases. CHX also disrupted oral bacteria’s ability to reduce nitrate into nitrite, this is confirmed by their findings of lower nitrite availability for use by the body. This would affect blood flow, and blood pressure as lower levels of nitrite can affect how these processes work. Researchers noted how nitrite synthesis plays a key part in cardiovascular control by enhancing nitrite availability.
There have been other studies that say that CHX can lead to higher blood pressure however in this study researchers did not see that correlation. When CHX was used, systolic blood pressure did increase however it was not statistically significant. Not only that but CHX reduces nitrite availability, however, nitrite has been shown to have properties that stop the growth of periodontal bacteria.
Some findings showed an increase in certain bacteria while decreasing others. It’s unclear if these changes indicate a healthier environment or if they raise the risk of oral diseases. This is hard to assess because the shifts in bacteria linked to cavities and gum disease have been reported. CHX increased saliva lactate levels and reduced its buffering agents, which is associated with a higher risk of oral disease.
All these findings show that CHX increases the acidity of saliva by adjusting the abundance of different families of bacteria that are important to maintain the acid/base balance in the mouths of healthy people.
Areas for future study:
There are lots of directions that could come from this study on CHX mouthwash and its effects on the oral microbiome. One particularly intriguing avenue would be to compare CHX with another over-the-counter mouthwash, such as those containing fluoride or essential oils, available at retailers like Walmart. It would be fascinating to investigate how these different formulations affect the oral microbiome and saliva acidity. Understanding the specific impacts of fluoride and essential oils on bacterial populations and pH levels could help consumers make informed choices about their oral hygiene products.
Additionally, shifting the focus from healthy individuals to those with oral diseases could uncover important findings. Exploring how CHX mouthwash interacts with existing conditions like cavities or periodontal disease might reveal whether it is beneficial or harmful. A comparative study that examines the differences in the oral microbiome between healthy individuals and those with various oral diseases could provide a lot of information on how CHX influences oral health.
Another research topic could involve individuals with oral cancer. By looking at saliva pH and the oral microbiome of healthy individuals, those with oral diseases, and patients with oral cancer, we could identify key differences and potential correlations. This research could shed light on the relationship between oral health and other diseases, which can help people understand how the oral environment affects overall well-being.
Lastly, as researchers have suggested, studying the oral microbiome of individuals with gingivitis could be valuable. This could help illuminate the microbial changes associated with this common condition and how they relate to overall oral health. By looking at different types of oral conditions, we can enhance our understanding of the role the oral microbiome plays in health and disease, ultimately paving the way for better oral health strategies and interventions. Overall, the implications of this research are pretty broad and could lead to better practices in oral care.
Further Readings:
The Clinical Evaluation of Vi-one Chlorhexidine Mouthwash on Plaque-Induced Gingivitis: A Double-Blind Randomized Clinical Trial
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5633216
This study assesses the effectiveness of Vi-one chlorhexidine mouthwash in reducing plaque and gingivitis through a controlled trial. The double-blind design ensures unbiased results, demonstrating the mouthwash’s impact on oral health.
Chlorhexidine in Dentistry: Pharmacology, Uses, and Adverse
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9275362
This article provides an overview of chlorhexidine’s pharmacological properties, including its effectiveness as an antimicrobial agent in dental care. It also discusses its various applications and potential adverse effects, highlighting its importance in oral health management.
Effects of Chlorhexidine Mouthwash on the Oral Microbiome
https://www.sciencedirect.com/science/article/pii/S0300571221001895
This research examines how chlorhexidine mouthwash alters the composition of the oral microbiome. It investigates changes in bacterial diversity and abundance, linking these shifts to potential implications for oral health.
All About Chlorhexidine Mouthwash | PERIODONTOLOGY
This video provides a comprehensive overview of chlorhexidine mouthwash, detailing its uses in dentistry and its benefits for oral health. It also covers important information regarding its effectiveness and application in periodontal treatment.
Works Cited:
Amoian, Babak, et al. “The Clinical Evaluation of Vi-one Chlorhexidine Mouthwash on Plaque-Induced Gingivitis: A Double-Blind Randomized Clinical Trial.” *Electronic Physician*, vol. 9, no. 9, 2017, pp. 5223-5228. doi:10.19082/5223.
“All About Chlorhexidine Mouthwash | PERIODONTOLOGY.” *YouTube*, 2021, youtu.be/Nxl38nHluPg?si=5n26kR8_tIlOnnJz.
Bescos, Raul, et al. “Effects of Chlorhexidine Mouthwash on the Oral Microbiome.” Scientific Reports, vol. 10, no. 1, 2020, article 5254. doi:10.1038/s41598-020-61912-4
Poppolo Deus, Frank, and Aviv Ouanounou. “Chlorhexidine in Dentistry: Pharmacology, Uses, and Adverse Effects.” *International Dental Journal*, vol. 72, no. 3, 2022, pp. 269-277. doi:10.1016/j.identj.2022.01.005.
Tribble, G. D., et al. “Frequency of Tongue Cleaning Impacts the Human Tongue Microbiome Composition and Entero Salivary Circulation of Nitrate.” *Frontiers in Cellular and Infection Microbiology*, vol. 9, 2019, article 39. doi:10.3389/fcimb.2019.00039.