In 2018, the very year the first edition was published, "The Story of Microorganisms Starting in the Mouth," which was selected as an "Outstanding Science Book" by the National Foundation for the Advancement of Science and Creativity and recommended as a book by Seoul National University School of Dentistry, has returned in a revised and expanded edition with even more in-depth information, incorporating the latest research and actual clinical experience.
The author, through ten years of research, clinical practice, and daily practice, presents the insight that “the mouth is a mirror of the health of the entire body” with concrete data and examples.
Additionally, each chapter includes QR codes linking to blog posts and YouTube videos run by the author, allowing interested readers to delve deeper.
The mouth, which is only 100 cc in volume, is the most diverse and dynamic microbial ecosystem in our body.
It is also a sensitive area where our physical condition is clearly expressed, and has a powerful influence on our entire body.
The revised and expanded edition of "The Story of Microorganisms Starting in the Mouth" reflects the latest microbiome research, scientifically explaining how oral microorganisms connect with the gut, brain, and blood vessels, and influence systemic health and disease.

Recently, the salivary bacterium most often mentioned in relation to oral cancer is Fusobacterium nucleatum (F.
nucleatum) and P. gingivalis.
gingivalis).
These two are considered the most representative oral harmful bacteria, and at the same time, they are often mentioned as influencing diseases outside the oral cavity (Fusobacterium affects colon cancer, and gingivalis affects cognitive function).
Recently, the amount of oral harmful bacteria such as Fusobacterium and Gingivalis can be analyzed using the PCR (Polymerase Chain Reaction) technique, which has become famous due to COVID-19.
By looking at the distribution of microorganisms through a simple saliva collection, we can know to some extent the risk of oral cancer, colon cancer, and dementia without having to do complex tests.

--- From "1-1"

Some foods are made with microorganisms as the main players.
Things like kimchi, soybean paste, soy sauce, yogurt, wine, and cheese.
These foods contain the microorganisms that are eaten along with them.
We humans maintain our health by providing a sealed environment in which the microorganisms that enter our bodies with food can thrive and break down the ingredients we eat, and by absorbing the products of their breakdown.
Fermented foods like these, which are neither cooked nor raw, were an important part of human diet until the invention of the refrigerator in the 19th century.
Conversely, it is also the food that modern people most need supplementation for.
The probiotics market, which has grown rapidly over the past decade, may actually be a response to the modern lifestyle's need to consume more fermented foods, as they are lactic acid bacteria and beneficial bacteria extracted from such fermented foods.

--- From "1-2"

As you might expect, saliva provides far more reliable information than blood when it comes to early diagnosis of diseases occurring in the mouth.
A representative example is the oral harmful bacteria test.
In 2024, our hospital and Doxmedi Co., Ltd. used the PCR technique, which was generalized due to Corona, to identify P. gingivalis, a representative harmful bacteria in the oral cavity.
It was reported that seven types of harmful bacteria, including S. gingivalis, could be quantified with great accuracy.
By detecting these harmful oral bacteria, it is possible to predict and manage not only major oral diseases such as periodontal disease, peri-implantitis, and cavities, but also systemic problems such as dementia and metabolic diseases to a certain extent.
Oral cancer is a cancer that is very difficult to diagnose early, so the 5-year survival rate is still around 50%.
However, since the microorganisms and cytokines in the saliva of oral cancer patients are significantly different from those of normal people, the possibility of oral cancer can be identified early through a saliva test before a biopsy.

--- From "1-3"

Recently, there have been claims that the amylase gene existed as early as 800,000 years ago, before the divergence between modern humans, Homo sapiens, and Neanderthals.
In this case, the beginning of agriculture 10,000 years ago was not an event that triggered a new mutation, but rather an event that strongly selected for specific mutations among the vast genetic diversity that already existed.
This is a good example of what genetics calls soft sweep selection.
Unlike hard selection, where a new genetic advantage suddenly appears and dominates the entire population, soft selection means that the frequency of a few genotypes that are advantageous to the environment gradually increases among the various genotypes that already exist.
It remains to be seen.

--- From "1-4"

In my case, and also in my acquaintances' cases, they say that their occasional gastroesophageal reflux has improved a lot since they started chewing thoroughly.
In fact, many clinical studies have reported that increasing the number of times you chew improves gastroesophageal reflux.
Gastroesophageal reflux disease is on the rise among modern people who enjoy late-night snacks or chicken and beer, and as a result, the use of proton pump inhibitors, the medications prescribed for this, is increasing at a very fast rate. However, like many other lifestyle-related diseases, gastroesophageal reflux disease should be resolved through 'habits' such as chewing food thoroughly or eating lightly early in the evening.
Proton pump inhibitors, which block the production of stomach acid, a mechanism that protects our bodies by killing microorganisms that enter through food, cause many side effects, such as making us more susceptible to infections.

--- From "1-6"

The bacteria in our mouths are all living organisms that live in the mouth.
In fact, most of the over 800 species of bacteria currently collected in the oral microbiome are commensal bacteria.
Just as humans live on Earth, bacteria also reside in our bodies and mouths.
Just like humans, bacteria also form colonies in the mouth, cooperating and competing with each other to maintain a certain balance.
At the same time, the various cells (hosts) in our body surrounding the oral cavity and the immune function also recognize these bacteria and become tense while maintaining balance.
Also, some of the 800 species are beneficial bacteria that are essential for oral health and even for regulating blood pressure throughout the body.
(I hope you remember this part)
--- From "2-2"

Swollen lips or under-lips are the first sign that you are tired.
It is a herpes virus infection that lies dormant in the trigeminal ganglion on the inside of the face and appears when the body is tired or has a problem with the immune system.
So, are these blisters caused by herpes (the external virus) or by my body (the internal host)? Of course, both factors are involved, but if herpes is an inescapable virus already coexisting with my body, the issue is how to manage my body.
So when I get herpes, I always rest.
The problem is me!
--- Among 「2-3」

It's not just about competition.
Microorganisms also cooperate with each other within biofilms.
They provide leverage for one another to stick together, and some microbes even feed on the metabolites produced by other microbes.
For example, the oral bacterium Fusobacterium nucleatum, which can cause colon cancer, is more likely to cause colon cancer than S. auris, another bacterium commonly found in gastrointestinal cancer tissue.
The proliferation ability can be further increased by using a metabolite produced by a bacterium called oris.
It is similar to humans eating beer or bread made through fermentation by yeast.
They also cross-feed, and have been observed exchanging food by forming long tubes that connect E. coli to each other.
During the long evolutionary process of life, this type of cooperation would have become established as it was confirmed to be advantageous for survival.

--- From "3-2"

There is a small space between the teeth and gums.
It may seem like the teeth and gums are directly connected, but that is not the case.
This groove is called a periodontal sulcus or periodontal pocket.
Gum pockets are created when baby teeth fall out and permanent teeth come through the gums.
There are gum pockets around every tooth, and although each one is a small groove, they all add up to about 12cm2.
It is a huge space from the perspective of microorganisms.

--- From "3-3"

Problems can arise even after implant surgery if it is not properly managed.
Bacteria in the mouth can cause mild inflammation around the implant and even dissolve the surrounding jawbone, ultimately requiring the implant to be removed.
When we looked at the data on implant inflammation, 63.0% of implants showed mucositis around the implants, and 25.0% of implants showed alveolar bone loss beyond the surface mucosa.
Unsurprisingly, the rate drops significantly in non-smokers.
This is why we always emphasize oral hygiene to patients who have had implants in our clinic and especially recommend that they quit smoking.

--- Among 「3-5」

This process of nitric oxide being recycled through the oral cavity is also called enterosalivary circulation.
So, what kind of bacteria play such a valuable role in saliva? Currently, it's known that bacteria that reside in the mouth, including Neisseria and Veillonella, are involved.
These are the bacteria that live in abundance in our mouths, as we saw in Chapter 2.
Oral microorganisms are not only the main culprits of cavities and gum disease. In fact, most of these resident bacteria are simply living in this way or are essential companions to our bodies.
The fact that oral microbes produce nitric oxide makes us re-evaluate our oral care habits.
We need to look back and see if we are using too many chemicals.

--- From "4-1"

The mouth is a sensitive area.
Also, as I said before, the defenses are weak.
So, if you have mild inflammation, you will start to feel pain right away and your gums will bleed.
Then, bacteremia may occur.
Bacteremia (bacteria found in the blood) occurring in the mouth raises the possibility that oral microbes may be involved in cardiovascular problems.
In fact, even brushing your teeth can cause bacteremia, and if bleeding occurs after brushing, the incidence of bacteremia increases eightfold.
Moreover, the research results that attracted attention were that when the blood of people with gum disease was drawn and tested for bacteria, 98 types of bacteria were detected, 32 of which were known to cause endocarditis.

--- From "4-2"

In the United States, the percentage of pregnant women exposed to polypharmacy, which involves taking five or more medications at once, including antibiotics such as amoxicillin and antidepressants, is exceeding 10%.
This is a very dangerous situation.
There may be reasons for taking each medication, but all medications inevitably have side effects.
And the side effects of those drugs cannot help but affect fetuses that have just begun to live.
Furthermore, antibiotics may also harm the microbiome that is just beginning to develop in the fetus's body.
The healthy resident microbes in our bodies have a significant impact on immunity and cognitive function from the time we are fetuses and infants. If these are destroyed by antibiotics, the result is an increase in atopy, asthma, attention deficit hyperactivity disorder (ADHD), and autism spectrum disorder in children.

--- Among 「4-5」

While diabetes and oral bacteria have a long-standing relationship, the relationship between high blood pressure and oral bacteria is one that has recently been rapidly gaining attention.
This is because nitric oxide, a key substance in blood pressure regulation, is recycled by normal resident bacteria in the oral cavity.
Nitric oxide, which is made from ingredients in foods such as spinach, functions as a vasodilator in the blood vessels, and then some of it (about 25%) is released into the saliva, chemically transformed (reduced) once by the resident bacteria in the oral cavity, and then recycled back into the intestines.
This is called ‘salivary circulation of nitric oxide’ (see Chapter 4, 01. ‘Entrance to the mouth’).
However, if harmful bacteria in the oral cavity overgrow, destroying the resident bacterial community and causing periodontitis, the salivary circulation is ultimately disrupted.
Blood pressure rises because nitric oxide is not recycled.
The American Heart Association reports that having periodontal disease can increase your blood pressure by about 3.39 points on a systolic scale.
Conversely, if you treat your gums, your blood pressure will go down.

--- From "4-7"

Dentistry is a battleground with oral microorganisms and oral bacteria, and dental treatment is the work of improving oral microorganisms and oral bacterial communities.
As treatment begins, the oral environment also changes.
However, oral bacteria and microorganisms still remain on the toothbrush you used.
According to one study, even a well-dried toothbrush can contain 10 to 100 billion colony forming units (CFU) of bacteria.
Additionally, if the period of use exceeds 3 months, the number of oral microorganisms in the toothbrush increases significantly.
So, there may even be a saying that toothbrushes are dirtier than toilets.


There is a saying in America:
'Floss or die?' This is a campaign that emphasizes the use of dental floss.
Among the entire gums, the area with the highest concentration of bacteria is the interdental space, or space between teeth.
So most gum diseases start between the teeth.
So, if the oral bacteria in this area are not managed, it is also a warning that we may be more exposed to various diseases, including cardiovascular disease, which takes the most life expectancy in Americans.
As previously described, much recent scientific literature on microbiota demonstrates that oral microbiota extends beyond the oral cavity and includes the cardiovascular system.

--- From "5-3"

The biggest issue in oral hygiene management right now seems to be toothpaste.
It's an issue on two fronts.
One is the fluorine problem, and the other is the synthetic surfactant problem.
It is well known that synthetic surfactant toothpaste not only damages the sense of taste, but also harms the oral bacteria and increases the risk of developing stomatitis.
Especially for cancer patients, we recommend toothpaste that does not contain synthetic surfactants.
This is because stomatitis, the most common side effect of cancer treatment, may occur more frequently and worsen.
I recently gave a lecture to researchers at the LG Household & Health Care Research Institute at their invitation, and I made a request of them.
Starting with large corporations, we are asking them to remove synthetic surfactants from their toothpaste.

--- From "5-4"

Deciding whether or not to take antibiotics is not an easy task.
Infection is a dynamic battle between microorganisms and our body's immune system, and we cannot know how quickly the microorganisms will multiply or how well our body's immune system will defend against them.
In these ambiguous situations, doctors usually choose to prescribe antibiotics.
Because they want to escape responsibility for the infection.
But no one takes responsibility for the resistant strains it brings.

--- From "5-5"