The oral biofilm.

Clearly explained.

The human body contains thousands of different types of microorganisms. In particular, these are bacteria. The human body has 10 times more bacterial cells than body cells. The microorganisms help break down food, produce nutrients and stimulate the immune system.

Many of these bacteria are found in the mouth. A thick layer of bacteria, called dental plaque or oral biofilm, grows on the teeth. They also occur between the teeth, on the gums, and on the tongue. In an oral biofilm, they form a complex ecosystem with saliva as the main source of nutrition. In addition, some bacteria feed on the metabolic products of other bacteria. Each individual creates a unique and extremely stable biofilm, which normally causes few problems.

Structure of a biofilm.

A biofilm consists of different layers of bacteria. The layers are divided by Sokransky¹ into different groups (see figure 1), with each group having its own color. An initial layer of proteins and cellular debris is formed around the tooth surface; this layer is called the pellicle. The first layer of bacteria, including Streptococci and Actinomycetes, attaches to this. These bacteria belong to the yellow and purple group and are hardly harmful because they have no virulence factors. They are among the good bacteria and contribute to a healthy structure of the biofilm.

Normally, bacteria disappear from the mouth through swallowing, chewing and the flow of saliva. Despite these mechanisms, these bacteria can survive oxygen-rich conditions in the oral cavity. The first layer of bacteria is always present on the tooth surface and, after cleaning the teeth, another layer forms immediately. The next group that attaches are bacteria from the green group, followed by bacteria from the orange group. Fusobacterium, in particular, play an important role, because this type of bacteria bridges the gap between early and late inhabitants of the biofilm. This could explain why Fusobacterium is present in large amounts in both healthy and unhealthy mouths.

The human body has 10 times more bacterial cells than body cells.

Late residents include bacteria from the red group, these are Porphyromonas gingivalis, Treponema denticola, and Tannerella forsythia. The bacteria in the red group are all paropathogens. In addition, Prevotella intermedia is also among the paropathogens, but it is classified in the orange group based on its properties. Another important paropathogen is Aggregatibacter actinomycetemcomitans (Aa), which can cause aggressive forms of periodontal disease. Because of the many enzymes that the Aa bacteria can produce, it is capable of causing a lot of tissue damage. Bacteria from the red group only occur if bacteria from the orange group are also present. Bacteria from the yellow, purple and green groups, on the other hand, are found in the absence of bacteria from the orange group. The human body contains thousands of different types of microorganisms. In particular, these are bacteria. The human body has 10 times more bacterial cells than body cells. The microorganisms help break down food, produce nutrients and stimulate the immune system.

Many of these bacteria are found in the mouth. A thick layer of bacteria, called dental plaque or oral biofilm, grows on the teeth. They also occur between the teeth, on the gums, and on the tongue. In an oral biofilm, they form a complex ecosystem with saliva as the main source of nutrition. In addition, some bacteria feed on the metabolic products of other bacteria. Each individual creates a unique and extremely stable biofilm, which normally causes few problems.

A microbial shift

A healthy oral flora contains many bacteria from the purple and yellow groups and, to a lesser extent, bacteria from the green and orange groups. These bacteria form a stable balance and are unique to each person. It is difficult for other bacteria to nest in a stable biofilm. However, changes can occur, for example when a person's resistance is reduced. This can be caused by smoking, stress, changes in hormonal levels or the use of an antibiotic, among other things. The use of certain drugs can also lower the immune system and there are diseases that can prevent your immune system from working optimally. At that time, a shift in the groups of bacteria in a biofilm can also occur. The good bacteria in the yellow and purple groups will decrease and the bacteria in the orange and red groups (paropathogens) will increase. This new situation can be very stable, so that bacteria from the red complex will not disappear by themselves either. An inflammation at the edge of the gums may result (gingivitis). If this inflammation spreads further to the jawbone, periodontitis occurs.

Treatment

Gingivitis and periodontitis are among the most important oral diseases and are the result of changes in the microbiological composition of a biofilm caused by changes in a person's immune system. Initially, the treatment of these infections focuses on removing the paropathogenic bacteria by scaling and root planing. In addition, treatment will focus on restoring a patient's immune system.

More and more bacteria are becoming resistant to common antibiotics, making it more difficult to combat these bacteria.

By removing a large part of the biofilm with scaling and root planing, bacteria can resettle and the composition of the biofilm changes again. The aim of the treatment is to reduce the number of paropathogens and to multiply the good bacteria. Not in all cases, the treatment will produce the desired results. The bacteria in the red complex do not or hardly decrease and the periodontal problems will therefore not decrease. In this case, the treatment can be supported by an antibiotic treatment to control gum inflammation (figure 2). Metronidazole and Amoxicillin are the most used antibiotics in dentistry. It is very important to start an antibiotic treatment shortly after mechanical cleaning. An intact biofilm is very compact and it is difficult for an antibiotic to work in an intact biofilm. The dose needed to kill bacteria in a biofilm is many times greater than the dose needed to kill 'loose' bacteria. For this reason, it is recommended to start an antibiotic treatment two hours before the start of the last cleaning.

Antibiotic resistance

Recently, an article was published by the World Health Organization (WHO) expressing concern about the development of resistance in bacteria. More and more bacteria are becoming resistant to common antibiotics, making it more difficult to combat these bacteria. This poses problems for public health. The article describes that, as a result of excessive use of antibiotics, resistance in bacteria occurs, which reduces the strength of antibiotics. Ultimately, this way, we lose the fight against bacteria and it is no longer possible to treat common infectious diseases. When a patient is prescribed an antibiotic treatment for dental problems, the practitioner must be aware that this can also cause resistances elsewhere in the body. It is therefore important that the right, informed choice is made. Bacteria have specific properties and it is useful to know which antibiotic is effective against which bacteria. The choice of an antibiotic therefore depends on the causative agent of the infection and on the amount of bacteria. Reticence in the use of antibiotics is appropriate. By performing a test prior to a course of antibiotics, the inflammation can be treated in a targeted manner.

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