The Microbial Secrets of Your Mouth

The human mouth provides an ideal environment for bacteria to thrive. With glistening white plateaus, dark crevices, and slimy surfaces, the temperature in your mouth reaches a steamy 95 degrees Fahrenheit. The humidity induced by saliva is a perfect 100 percent, creating a tropical rainforest-like setting. Researchers at the Forsyth Institute, an independent research institution in Boston affiliated with the Harvard School of Dental Medicine, have been studying the microbial inhabitants of the mouth and have identified a staggering 615 different species of bacteria so far, with the count still ongoing.

To put it into perspective, Sigmund Socransky, an associate clinical professor of periodontology at Harvard, points out that in one mouth, the number of bacteria can easily exceed the number of people who live on Earth (Teles et al., 2012). This rich and varied microbial community forms what researcher Donna Mager refers to as a "mini-jungle." However, what researchers have discovered is that the composition of these microbial communities can vary significantly between healthy and diseased mouths.

Through years of detecting and identifying the microorganisms residing in the oral cavity, scientists have found that the microbiomes of healthy mouths differ remarkably from those in mouths affected by oral cancer or gum disease. Some bacteria increase in number, while others decrease, leading to imbalances that contribute to oral health issues. Donna Mager, a fellow in oral medicine at the Forsyth Institute, has focused on comparing the microbial communities in healthy individuals with those in the mouths of people with oral cancer. By identifying patterns in these microbial signatures, Mager hopes to develop a method for the early diagnosis of oral cancers.

The mouth is home to a vast array of microorganisms, predominantly bacteria, numbering over 400 different species in each adult’s mouth. These billions and billions of microorganisms form layered communities, crowding together and wrapping around surfaces throughout the oral cavity. The mouth’s warm temperature of 95°F, combined with 100% saliva-induced humidity, creates an ideal environment for this diverse range of species. It’s not just the mouth that hosts this microbial biodiversity; the rest of the digestive system is also a hotspot for microbial diversity.

Efforts to reduce tooth decay have been a national campaign for decades, focusing on brushing, flossing, and the addition of fluoride to water supplies, toothpaste, and mouthwashes. These dental hygiene methods have significantly improved oral health, with 50% of US children under 12 having no tooth decay. However, the remaining 50% still struggle with cavities, and severe forms of tooth decay can be challenging to control, even with good dental hygiene practices.

Periodontal disease, which primarily affects adults, is another widespread oral health issue caused by several bacterial species. Over the past two decades, advancements in biological technology, such as genetic engineering and the study of anaerobic bacteria (which live without oxygen and contribute to periodontal disease), have enabled oral ecologists like Socransky to identify some of these organisms. Research indicates that the microorganisms in the mouth have coevolved with humans throughout our history, providing beneficial effects by protecting against disease-causing bacteria from the external environment.

The US National Institute of Dental Research has been funding research to understand the dozen or so species of bacteria and yeast that reside in the mouth and can potentially cause infections in teeth and gums. Recent advancements have shed light on how these organisms are transmitted from person to person, leading to the development of innovative dental care methods to prevent the spread of infection.

One approach involves varnishing mothers' teeth to hinder the transmission of bacteria to their babies. Another technique includes introducing less harmful strains of bacteria into the mouth, which can outcompete and crowd out harmful organisms. Additionally, scientists are developing medications that prevent undesirable bacteria from adhering to teeth and gums, allowing them to be washed away by saliva and the digestive system.

When newborn babies enter the world, their mouths are sterile. However, within minutes to hours, their mouths become colonized by various microorganisms that remain with them throughout their lives. Harmless bacteria, yeast, viruses, and protozoa enter the baby’s mouth through contact with the air, breast or bottle nipples, or fingers. This colonization marks the beginning of a lifelong relationship between humans and the microorganisms that inhabit their mouths.

Although it’s true that some bacteria in your mouth can cause diseases like gingivitis and tooth decay, not all bacteria are bad. In fact, there is a scientific understanding that highlights the potential health symbiosis of these bacteria. Good bacteria, similar to probiotics, play a crucial role in maintaining good oral health, breaking down food, and keeping your breath fresh.

Probiotics, including bacteria, fungus, and yeasts, can prevent the invasive growth of harmful microbiomes. The diverse range of beneficial bacteria also assists with specific functions in the mouth and digestive system, aiding in the digestion of sugar and milk, as well as washing away food particles to prevent decay.

So, what benefits does good bacteria provide?

In conclusion, the study of oral ecology has shed light on the intricate microbial communities that reside in our mouths. Understanding the delicate balance between beneficial and harmful bacteria is crucial for maintaining oral health and preventing diseases such as oral cancer and gum disease. Ongoing research in this field continues to unveil the secrets of the mouth’s microbial world, leading to innovative dental care approaches and early detection of oral diseases. So, next time you think about your mouth, remember the bustling mini-jungle housing a diverse range of microorganisms that can both support and challenge your oral well-being.

Deo, P. N., & Deshmukh, R. (2019). Oral microbiome: Unveiling the fundamentals. Journal of Oral and Maxillofacial Pathology, 23(1). https://journals.lww.com/jpat/Fulltext/2019/23010/Oral_microbiome__Unveiling_the_fundamentals.25.aspx

Teles, R. P., Teles, F. R. F., Loesche, W. J., Listgarten, M., Fine, D., Lindhe, J., Malament, K., & Haffajee, A. D. (2012). Rediscovering Sig Socransky, the Genius and His Legacy. Journal of Dental Research, 91(5), 433–439. https://doi.org/10.1177/0022034512443689