The oral microbiome (and how to keep yours healthy)

The human body harbours a vast ecosystem of microorganisms that play crucial roles in

maintaining health and disease. Among these is the oral microbiome, which is a community of about 700 kinds of microorganisms that exist in the human mouth, and these microbes constitute the human oral microbiota. Far from being merely a collection of bacteria, fungi, viruses, and other microorganisms responsible for dental decay and bad breath, the mouth microbiome is increasingly recognised as a dynamic ecosystem with far-reaching implications for overall health and well-being. In this article, we look into the importance of a balanced oral microbiome and low-cost ways of how to go about it.

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Understanding the oral microbiome

The oral cavity is colonised by a diverse array of microorganisms, that form complex communities that interact with each other and with the host in a delicate balance. These microorganisms consist of bacteria, fungi, and viruses, with bacteria being the main inhabitants of the mouth (1). The composition of the various microbiomes in the human body is diverse between different body sites (2).

Unlike other microbiomes in the body, these types of bacteria do not change significantly. (3). The oral microbiome begins to develop shortly after birth and undergoes dynamic changes throughout life. Factors such as diet, oral hygiene practices, genetics, and environmental exposures influence the composition and diversity of the oral microbiome. In a healthy state, these microorganisms coexist harmoniously. However, imbalances in the oral microbiota result in an overgrowth of certain bacteria and a lack of diversity found in the mouth. This makes the body susceptible to local and potentially systemic dysfunction and disease.mPerhaps the most commonly known local disease associated with an oral microbiome imbalance is dental caries (ie. tooth decay) which often develops into tooth cavities. However, other diseases such as periodontitis, oral potentially malignant disorders, and oral cancers are also associated with different imbalances (4).

The disproportionate predominance of certain microorganisms in the oral cavity has also been proposed to play a role in several other systemic diseases, including cardiovascular disease, rheumatoid arthritis, adverse pregnancy outcomes, stroke, pancreatic cancer, colorectal cancer, liver diseases inflammatory bowel disease, respiratory tract infection, meningitis or brain abscesses, lung, liver or splenic abscesses, appendicitis, pneumonia and diabetes (5, 3). In particular, due to the close connection between the mouth and the digestive tract, digestive diseases and gut microbiome imbalances have been strongly implicated as the result of microbiome imbalances (5, 3).

Dental caries

Dental caries is the most common chronic infectious disease in the oral cavity and is highly associated with microbiota changes in the oral cavity (6). A variety of factors, including microbial, genetic, immunological, behavioural, and environmental interact to contribute to dental caries onset and development (7). Streptococcus mutans (S. mutans) is the main component of the oral microbiota and is considered a major contributor to dental caries (8). 

When food is not present in the mouth (ie. when we are not eating and our mouth is clean), the bacteria obtain nutrients from our saliva that they break down into sugars and proteins. The bacteria then metabolise these sugars and proteins, producing acidic and basic molecules. When food is not present, these molecules neutralise each other and the mouth remains in a neutral state. However, in the presence of sugar or starch (carbohydrates), acid-producing bacteria will predominate. Their acid products will begin to corrode the teeth. In general, the speed at which teeth are corroded (demineralised) is comparable with the speed at which teeth are regenerated (remineralised).

In most people, this demineralisation and remineralisation processes occurs many times during the day, and the mouth is in either one state or the other. Remineralisation occurs as a result of pH adjustment in the oral cavity. However, if the food particles in the mouth are not cleaned up in time, then the corroding rate will be higher than the speed at which the teeth repair themselves and so caries will occur. (3). The time the mouth is more acidic or alkaline, therefore the time the teeth are in a demineralisation or remineralisation state dictates the degree to which cavities have a chance to form (9)

In the early stages, the caries progress can be stopped or reversed through increasing periods of remineralisation, but if left untreated, the disease may cause dysfunctions of the masticatory apparatus and systemic odontogenic infections. (10).

Modifiable factors that affect oral microbiome health

Diet

As we have just learned carbohydrates are the main energy source for caries-causing bacteria. Therefore, the carbohydrate-laden, highly processed modern Western diet is detrimental to oral health. A return to a more primitive and unprocessed diet is speculated to have significant health benefits by supporting the oral microbiome (11). Tobacco consumption and stress, can alter our microbiome and its properties, and induce a state in which this finely tuned ecosystem is no longer in balance (5). The modern-day excessive consumption of acidic drinks and refined sugar or cigarette smoking has further impacted the oral ecosystem, leading to diseases such as caries and periodontal disease. (5)

Floride

Fluoride has been used to combat dental caries through methods such as fluoridated toothpaste and drinking water for more than half a decade. Fluoride prevents and treats dental caries by promoting tooth remineralisation and impairing bacterial metabolism (12). Although the efficacy of fluoride treatments is well-documented, clearly the current prevalence of the disease illustrates that fluoride alone is insufficient to prevent dental caries in many situations (11). Additionally, there are legitimate concerns regarding the safety of ingesting fluoride in high doses.

Saliva

The role of saliva in promoting oral health is well established. In addition to facilitating mastication, swallowing, and speech, and aiding digestion, saliva contains vital enzymes and proteins that help maintain a balanced microbiota and is required for the development of a balanced microbiome. (5). Typically, the saliva in the mouth has sufficient buffering capacity to neutralise the organic acids produced by bacterial metabolism and repair acid-damaged enamel (11). However, individuals with reduced salivary flow have a greatly increased likelihood of caries. Chewing gums containing sweeteners such as xylitol, help to increase the saliva flow without providing fermentable carbohydrates that feed caries-causing bacteria (11).

Xylitol

Numerous studies support xylitol as a powerful tool for dental health and the prevention of tooth plaque (13,14,15,16,17). Xylitol, a low glycaemic sugar, is known to be harmful to many microorganisms (18). When used, it reduces the number of S. mutans in plaque and saliva, the adhesion of these microorganisms to the teeth' surface, and their acid production (19). When used as a chewing gum or lozenge, it also increases salivary flow; promoting tooth remineralisation. It is also available in some countries in mouthwashes, and, of course, as a sweetener in crystal form. Research indicates that a total daily consumption of 5–6 g divided into a frequency of three or more times per day is considered optimum for oral health. (19).

Note: Excess xylitol can have unpleasant gastric side effects when taken in high doses or used by sensitive individuals. Amounts beyond the recommended intake above should be experimented with tentatively. 

Salt (sodium chloride)

Oral saltwater rinses alkalises the oral cavity which, as you will remember, is favoured by the bacterial that support a healthy microbiome (an acidic environment promotes the growth of caries-causing bacteria) (20,21,22,23). Therefore, it makes sense that saltwater could reduce the growth of unwanted oral bacteria without harming ‘good bacteria’. In studies, saltwater or saline mouth rinses have been found to reduce plaque scores and colony counts in the saliva of bacteria such as S. mutans (24). There is still disagreement in the very limited scientific literature as to how beneficial it is for oral health and the microbiome. However, several studies have noted a reduction in bacterial biofilm and plaque indices, and improvements in gingivitis (18). From a practical perspective, the potential beneficial effects of rinsing with salt water seem to make it a very useful tool to promote oral health. 

Mouthwashes

With the exception of xylitol, the evidence surrounding the effects (positive and negative) of various ingredients commonly found in over-the-counter mouthwashes on the oral microbiome as a whole is limited. Several common ingredients were investigated: chlorhexidine, alcohol, hydrogen peroxide, cetylpyridinium chloride, povidone iodine, sodium fluoride, various essential oils, and propolis (25). At best, mouthwashes target certain disease-causing bacteria, but not others. At worst, they indiscriminately target all bacteria in the mouth (including the ones we need to support a healthy oral microbiome), increase susceptibility to diseases such as oral cancer (alcohol) or cardiovascular disease (chlorhexidine), or simply do very little at all. In particular, alcohol-based and antiseptic mouthwashes deplete components of the mucosal lining of the mouth and disrupt a healthy oral microbiome (9).

You can read in detail about each of the ingredients above here: https://www.researchgate.net/publication/374795318_Mouthwash_Effects_on_the_Oral_Microbiome_Are_They_Good_Bad_or_Balanced

Here are a few xylitol-based mouthwashes that will not damage the oral microbiome:

• XyloBurst fresh breath oral rinse mouthwash with natural xylitol:

https://amzn.to/3TFVgAz

• Epic xylitol spearmint flavored mouthwash:

https://amzn.to/43F8bap

• Xyli Swish Silver:

https://amzn.to/3xhFaFO

Personal note:

As mouthwash users, we were quite frankly horrified that for years we have been washing our money down the drain, and potentially damaging our oral microbiome in the process. Unfortunately, here in Mexico, xylitol-based mouthwashes are not easily available. Therefore, based on the information found in researching this article, we made our own homemade mouthwash using salt and xylitol. From a purely subjective unscientific perspective, after using it for one week, 3x per day, one of our contributors found her tooth sensitivity noticeably improved, and in general, our breath feels fresher. It is definitely not as pleasant as that minty fresh feeling you get from using a commercial mouthwash, but we are confident that it is far more beneficial.

If you are interested in trying out our science-based homemade mouthwash recipe for yourself, let us know in the comments section or reach out to us through DM @healthfullymyself!

General oral hygiene tips

• Brush and floss 2-3x per day with a soft toothbrush. Nighttime is the most critical time to brush as saliva production is substantially reduced (9). As you will remember, saliva is a key defence against acid-producing bacteria.
  

• Xylitol-based chewing gum, rinses, or lozenges are worthwhile as they can help neutralise the mouth between brushings and increase saliva flow. An increased saliva flow rate helps to reduce the time of teeth enamel exposure to acids and neutralises the acid environment that occurs after eating (10)

Avoid:

• Alcohol. It puts the mouth in a demineralisation state and kills some healthy cells of the mouth) (9).
  

• Stimulants (illegal and legal such as caffeine, and Adderall). Stimulants switch the mouth into demineralisation mode, and encourage mouth breathing (a dry mouth also means it is in a demineralised state).  

• Smoking cigarettes, cannabis, and vaping (9)  

• Sugar and acidic foods (these all change the pH of the saliva). Rinse your mouth or brush when possible after consuming these foods. You can also consider using a straw when drinking acidic drinks (9).
  

• Try to have extended periods when your mouth is clean, and you are not eating (this is another benefit of intermittent fasting). This period of not eating or drinking anything but water can promote remineralisation (9)

Conclusion

The oral microbiome, comprising a diverse array of microorganisms, plays a crucial role in maintaining oral and systemic health. Far beyond merely causing dental decay and bad breath, the mouth microbiome influences a myriad of physiological processes and is increasingly recognised as a dynamic ecosystem with far-reaching implications for overall well-being. Dental caries, periodontal disease, oral potentially malignant disorders, and oral cancers are just a few conditions linked to imbalances in the oral microbiome. Additionally, emerging evidence suggests that dysbiosis in the mouth may contribute to systemic diseases such as cardiovascular disease, diabetes, respiratory infections, and even certain cancers.

Adopting a diet rich in whole foods, minimising sugar and acidic intake, practicing good oral hygiene, and incorporating xylitol-based products can promote microbial diversity and support oral health. Regular dental check-ups, along with proactive measures to promote saliva flow and neutralise acidic environments, are crucial for preventing oral diseases and preserving overall well-being. By understanding the critical role of the oral microbiome and implementing evidence-based strategies to support its health, individuals can cultivate a thriving oral microbiome and enhance our quality of life from the inside out.

*Disclaimer*

The information presented in this article is for educational purposes only and is based on our interpretation of the current research. Individuals are recommended to consult with a qualified healthcare professionals or registered dietitians for personalised guidance and recommendations tailored to their individual needs and circumstances.

References

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