Dentin is the term used to describe the human dentine. It forms an extensive component of the tooth.
What is dentin?
Dentin (substantia eburnea) is a bone-like tissue. An important part of the tooth is formed by it. It also bears the name dentine. The dentin is located below the enamel. The difference between dentin and enamel is, among other things, that dentin can regenerate throughout its life, which takes place in the course of biomineralization. However, the new formation only takes place in the border area towards the dental pulp. Dentin is among the most continuous organic substances.
Anatomy and structure
Dentin extends from the crown region toward the root of the tooth. In the root region, the dentin is surrounded by the dental cementum. In dentistry, the dentin in the pulp region is called “pulpal dentin.” In the enamel region, its mineral content is lower. The dentine is made up of a dense collagen fiber network. This contains calcium salts such as hydroxyapatite. The high degree of mineralization has values of about 70 percent. Unlike enamel, dentin is living tissue. Its supply and nutrition is ensured by the fine dentin channels. These radiate into the dentin from the pulp. The odontoblast processes are also located within the canals. The odontoblasts ensure that new dentin is formed throughout life. The odontoblasts are located at the dentin margin. Further material can be formed by them via Tomes fibers. This is called secondary dentin. It is produced after tooth formation has been completed. Topographically, a distinction must be made between the root dentin, which is surrounded by the tooth cementum, and the crown cementum, which is covered by the tooth enamel. From a structural point of view, there are other forms of dentin. These include the mantle dentin. It is located 10 to 30 µm below the enamel. In this, it is not the odontoblasts but the mesenchymal cells of the dental papilla that are responsible for the formation of the dentin. The collagen fibers here are considerably more extensive than the b-fibrils formed by the odontoblasts. The main part of the dentine is formed from the circumpulpal dentin. Temporally, its production takes place after the mantle dentin. The mineralization of the dentin proceeds in cycles, resulting in a typical pattern of lines, which is called boar lines. Therefore, circumpulpal dentin is also known as Ebner’s dentin. Other dentin forms include peritubular dentin, which is formed in the inner wall of the small dentinal tubules, intertubular dentin, which is located between the tubules, and globular dentin. The latter is the name for the mineralization zones inside the dentine, which have the shape of globules. The composition of dentin consists primarily of phosphate, collagen and calcium. Furthermore, it contains water as well as organic and inorganic substances.
Function and tasks
Among the functions of dentin is the protection of the pulp, which is located inside the tooth. The pulp, in turn, is equipped with connective tissue, nerves, and blood and lymph vessels. The dentinal canals of the dentine also have the property of transmitting stimuli such as temperature or pressure to the dental nerves. While primary dentin is formed during the period of tooth formation, secondary dentin is formed subsequently. However, the secondary dentin increasingly constricts the tooth pulp cavities. This process in turn leads to a reduction in the sensitivity of the tooth nerves. In the event of damage to the teeth, such as caries, periodontitis or bruxism (teeth grinding), tertiary dentin develops in the affected areas. Its function is to provide protection for the dental pulp.
Diseases
The human dentine can be affected by various ailments. First and foremost among them is caries (tooth decay). In this case, damage to the tooth enamel as well as to the dentin occurs with the involvement of microrganisms. While in the case of initial caries, the preliminary stage of the disease, only the enamel is affected, in the case of dental caries (caries media) there is already a risk of toothache. In this case, the caries progresses from the enamel to the dentin. The dentin is much softer than the enamel. For this reason, caries can spread more rapidly below the enamel-dentin boundary.It is not uncommon for the enamel to crack at the edges of the affected areas as a result of chewing. As it progresses, caries can continue to penetrate the dentin to the dental pulp and finally to the dental nerve, where it causes considerable discomfort. Another problem is the exposure of the dental bone. This can be caused by increasing age and the associated recession of the gums at the neck of the tooth. However, gingivitis also often causes recession of the gums. Exposed dentin is usually noticeable by sensitivity to hot and cold temperatures as well as pain sensitivity when eating hot, cold, sweet or sour foods. Also within the realm of possibility is selective discoloration of the dentin. Because dentin is softer than enamel, harmful bacteria spread quickly in the dentin when damage occurs. Therefore, if problems with the dentin are suspected, a dental examination should be performed immediately. This will allow the dentist to identify possible lesions on the dentin and treat them accordingly. Care and cleaning of the dentin is also extremely important. The sooner therapy of the dentin is carried out, the greater the chances of success.
