The oral biofilm.

Clearly explained.

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

Many of these bacteria are found in the mouth. A thick layer of bacteria grows on the teeth, which is called dental plaque or oral biofilm. 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 live off the metabolic products of other bacteria. Each individual creates a unique and extremely stable biofilm, which normally causes few problems.

Construction of a biofilm.

A biofilm is composed of several layers of bacteria. Sokransky¹ divided the layers into different groups (see figure 1), with each group having its own colour. Around the tooth surface an initial layer of proteins and cell remains is formed; this layer is called the pellicle. The first layer of bacteria, consisting of Streptococci and Actinomycetes, among others, adheres to this. These bacteria belong to the yellow and purple group and are hardly harmful because they have no virulence factors. They belong to the good bacteria and contribute to a healthy build-up of the biofilm.

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

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

Among the late inhabitants are bacteria from the red group, these are Porphyromonas gingivalis, Treponema denticola and Tannerella forsythia. The bacteria from the red group all belong to the periopathogensperiopathogensPrevotella intermedia, but this is also classified in the orange group based on its properties. Another important paropathogen is Aggregatibacter actinomycetemcomitans (Aa), this bacterium can cause aggressive forms of periodontitis. Because of the many enzymes the Aa bacterium can produce, it is able to cause 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. These are mainly bacteria. The human body has 10 times more bacterial cells than body cells. The microorganisms help to break down food, produce nutrients and stimulate the immune system.

Many of these bacteria are found in the mouth. A thick layer of bacteria grows on the teeth, which is called dental plaque or oral biofilm. 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 live off the metabolic products of other bacteria. Each individual creates a unique and extremely stable biofilm, which normally causes few problems.

A microbial shift

In a healthy mouth flora many bacteria are present from the purple and yellow group and to a lesser extent bacteria from the green and orange group. These bacteria form a stable balance and are unique to each person. It is difficult for other bacteria to settle in a stable biofilm. Nevertheless, changes can occur, for example if a person's resistance is lowered. This can be caused by smoking, stress, hormonal changes or the use of an antibiotic. The use of certain medications can also reduce resistance and there are diseases that can cause your immune system not to work optimally. At that moment, a shift of the groups of bacteria in a biofilm may also occur. The good bacteria from the yellow and purple group will decrease and the bacteria from the orange and red group (paropathogens) will increase. This new situation can be very stable, with bacteria from the red complex not disappearing on their own. An inflammation at the edge of the gums can be the result (gingivitis). If this inflammation spreads further into the jawbone, periodontitis develops.

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. In the first instance, the treatment of these infections focuses on the removal of the paropathogenic bacteria by means of scaling and rootplaning. 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 rootplaning, bacteria can re-establish themselves and the composition of the biofilm changes again. The aim of the treatment is to reduce the periopathogensnumbers and increase the good bacteria. Not in all cases the treatment will produce the desired result. The bacteria from the red complex do not or hardly decrease and therefore the periodontal problems will not decrease. In this case, the treatment can be supported with a course of antibiotics to control gum inflammation (Figure 2). Metronidazole and Amoxicillin are the most commonly used antibiotics in dentistry. It is very important to start an antibiotic treatment shortly after mechanical cleaning. An intact biofilm is very compact and an antibiotic can hardly do its job 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 advised to start an antibiotic treatment two hours before the last cleansing.

Antibiotic resistance

Recently an article was published by the World Health Organisation (WHO), expressing concern about the resistance development of 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 occurs in bacteria, which reduces the potency of antibiotics. In the end we lose the fight against bacteria and it is no longer possible to treat common infectious diseases. When a patient is prescribed antibiotic therapy for dental problems, the practitioner should be aware that this can also cause resistance elsewhere in the body. It is therefore important that a correct, well-considered choice is made. Bacteria have specific properties and it makes sense to know which antibiotic is effective against which bacterium. The choice of an antibiotic therefore depends on the cause of the infection and the amount of bacteria. Reticence in the use of antibiotics is in order. By performing a test prior to an antibiotic treatment, the inflammation can be treated in a targeted way.

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