The following factors play a role in etiology or the development of caries:
- Dental elements
- Dental plaque
The relationship between these four factors is shown in the picture below. For caries to occur, all four factors must be present at the same time (see figure below).
Caries is an attack on the hard tooth tissues. It can therefore only occur if teeth are still present.
Glaze is made up of enamel prisms: rod-shaped structures that extend from the enamel dentine border to the enamel surface. There is an interprismatic space between the bars. Both the enamel prisms and the interprismatic spaces are filled with hydroxylapatite crystals, or crystallites. The arrangement of the crystallites and the content of water and organic substances in the glaze prisms and the interprismatic space differ. As a result, the porosity of the interprismatic space is greater than that of the prisms. Exchange with substances from the oral cavity therefore takes place in the interprismatic spaces. This also applies to acids from dental plaque (see image below).
Enamel, dentin and root cement consist for the most part of inorganic material and only a few percent of water and organic material. The inorganic material is hydroxylapatite, Ca5 (PO4) 3OH, a lime salt. The apatite salts form the crystallites. The solubility of the apatite depends on the acidity of the surrounding environment. Glaze apatite is not soluble in water. The acidity (pH) of water is approximately 7. However, if the acidity becomes lower, the enamel is soluble. The crystals are slowly descaled under the influence of acids. We call this process of descaling demineralization.
After eating or drinking sweets, the dental plaque bacteria turn sugars into acid. This temporarily lowers the pH in the dental plaque. Such a temporary acidification of dental plaque is what we call an acid surge. A single acid attack or burst of acid on the enamel partially demineralizes the hard substance. The apatite crystals are dissolved from the edge and therefore become smaller with every shot of acid. This first descaling of the enamel is called initial or white spot caries. The crystals are affected, but not yet disappeared. The glaze surface is still continuous (see image below).
When an acid burst is ended and the acid is neutralized, the remineralization, the reconstruction of the crystal, can take place. The ions that are still present in the immediate vicinity of the tooth can be incorporated into the crystals again and the crystallite can recover. Demineralisation is faster than remineralisation. When one shot of acid follows another, new acid is always formed which is retained by the plaque for a long time. There is little or no time left for remineralisation. It can even go so far that the remineralization process can no longer repair the damage and a hole is created.
Reinforcement of the crystal structure of enamel is achieved when the hydroxyl group (OH-) is replaced at several places in the crystal with a fluoride ion. This creates fluorapatite. Incorporation of fluoride reduces the solubility of the tooth tissue.
In addition to inorganic material, dentine consists of collagen fibers. Dentine dissolves in acid sooner than the harder tooth enamel. Caries will therefore progress faster in dentine than in enamel. When the caries process has passed through the enamel cap, we often see a large expansion below the enamel dentin boundary. When the gums have been withdrawn, the root dents are exposed. Dentine can be directly affected by caries at these locations. We call this root caries.
Every mouth is full of microorganisms. All microorganisms from the healthy oral cavity together are called the mouth flora. The mouth flora is in a biological balance. Of the many types of bacteria in the oral cavity, the Streptococcus mutans in particular can break down sugar into lactic acid. This biochemical process is called glycolysis. Glycolysis is the breakdown of carbohydrates into an organic acid or alcohol in the absence of oxygen. In the absence of oxygen, the situation is called anaerobic. The breakdown of sugars into acid via the fermentation process is a normal metabolism of the Streptococcus mutans.
This acid formation only damages the hard tooth tissues if it takes place directly against the tooth surface and continues for a sufficiently long time. These conditions are only present in dental plaque.
Dental plaque is a layer that occurs on all surfaces in the mouth. It is best described as anything that remains on the tooth and soft tissues after vigorous rinsing.
After complete dental cleaning, glycoproteins attach to the tooth surface after just a few seconds. The first bacteria attach to this pellicle after two hours. If the teeth are not cleaned properly, the plaque can grow further; after ten to fourteen days it is fully grown. However, after three days the acidity (pH) can drop so much that the enamel can dissolve.
Composition of dental plaque
Dental plaque consists of more than 70% bacteria. One milligram of plaque contains 108 bacterial cells. Furthermore, dental plaque consists of:
- Saliva proteins;
- Substances dissolved from food;
The speed with which dental plaque is formed is influenced by, among other things:
- The condition of the gingiva (inflamed gums is a source of substrate);
- Sugar consumption;
- Saliva flood;
- Presence of retention places;
- Antimicrobial factors in the saliva;
- Bacteria-aggregating substances in the saliva;
- Composition of the pellicle.
The plaque is mainly located in places where the saliva flow and the cleaning as a result of chewing exert the least influence. These places are also difficult to clean for the patient. We call these characteristic places the plaque retention places. This mainly concerns:
- Fissures and foreca caeca;
- Interdental spaces;
- Cervical edges.
Dental plaque can cause damage in the form of:
- Caries through demineralization;
- Periodontal disorders due to the formation of toxins;
- Tartar through mineralization.
Dental plaque also has a positive effect: it protects the teeth against external influences (see images below).
The organic acids, and in particular lactic acid, are responsible for demineralization. Lactic acid is a breakdown product of the carbohydrates. Belonging to the carbohydrates group is:
- The mono- and disaccharides (single and double sugars, such as grape sugar, fruit sugar, malt sugar, cane sugar and beet sugar);
- The polysaccharides (multiple sugars, such as starch found in, for example, grain, rice and potatoes).
The western diet contains almost 25% sucrose. Other words for sucrose are sucrose, beet sugar or cane sugar. It is an important seasoning that is used in almost all industrially produced food. With frequent use, sucrose is responsible for caries and part of the obesity problems. Because lactic acid is a breakdown product of carbohydrates, we refer to this group of sugars as cariogenic, that is to say cause caries.
Research has shown that starch (polysaccharides) is less cariogenic than mono- and disaccharides. This is due to the molecular size. The mono- and disaccharides have a lower molecular weight than the polysaccharides and are more rapidly degraded to acids, especially to lactic acid.
There are also protective foods.
- Fluoride is known to reinforce the glaze, but it also has a cariostatic effect. It inhibits the acid formation of, among others, Streptococcus mutans bacteria. Fluoride occurs naturally in marine food products such as sea fish, seaweed and shellfish.
- Dairy products contain calcium, which helps with remineralization.
- Fats keeps food particles together, so that they are swallowed away more easily. They may also form a protective layer over the glaze.
- Cheese contains casein, a milk protein that makes the glaze less soluble.
- Sugar-free chewing gum stimulates the salivary glands when chewing vigorously. Saliva ensures that the pH becomes neutral and supplies calcium for remineralization of the tooth tissue.
Not only the amount of sugar absorbed is important. More important than the quantity is the frequency of sugar intake per day. This has to do with the time required to absorb an acid burst. Only 40 minutes after eating time does the pH in dental plaque return to its original value. In addition to the three main meals, the nutritional advice cannot be used for more than four snacks. If this advice is followed, there is sufficient time between meals to neutralize the acid pulse. The enamel is given the time to remineralize. However, if more sugary snacks are used, there is hardly any chance of recovery (see image below).
The preventive measures for the prevention of caries are focused on the caries-causing factors discussed above.
- Solubility of the hard tooth tissue: the lime salts are dissolved by organic acids. The more fluorapatite is stored in the enamel crystal, the better the resistance to external influences becomes. Sufficient fluoride must be offered for remineralization. This can be done by brushing with fluoride-containing toothpaste.
- Dental plaque: microorganisms form the majority of the plaque. It is not possible to make the oral cavity bacteria-free. However, an attempt should be made to keep the amount of plaque as low as possible. Plaque retention sites must be removed as much as possible. For example, by sealing molars.
- Nutrition: a low sugar-rich diet reduces the production of lactic acid.
- The total demineralization time per day: the less often food is taken,the shorter the total demineralization time per day.