Dentinogenesis is the term used to describe the formation of dentin. Dentin is also called dental bone. It is a product of odontoblasts.
What is dentinogenesis?
Dentinogenesis is the term used to describe the formation of dentin. Dentin is also called dental bone. During dentinogenesis, the dentin of teeth is formed. A large part of each tooth is made up of dentin. The substance is also called dentine or substantia eburnea. Unlike tooth enamel, dentin can be formed anew throughout life. Dentin is similar in composition to bone. It consists of about 70 percent calcium hydroxylapatite. This in turn is largely formed from phosphate and calcium. Twenty percent of the components of dentin are organic. Of these, 90 % are collagens. 10% of the organic portion consists of water. The dentin is yellowish in color. On the dentin lies on the one hand the tooth enamel and on the other hand in the area of the tooth root also the root cement. The tooth pulp with blood vessels, connective tissue, nerves and lymphatic vessels is tightly enclosed and protected by the dentin.
Function and task
Dentin is formed by odontoblasts. Odontoblasts are cells with a mesenchymal origin. They are located at the junction of the dental pulp and dentin. The cells are arranged cylindrically and are capable of forming dentin throughout life. As a result, the space for the pulp becomes smaller and smaller during life. This is the reason why teeth are less sensitive in old age. Dentin is divided into primary dentin, secondary dentin and tertiary dentin. Primary dentin is produced during tooth formation. Secondary dentin, which is similar in structure, is reproduced throughout life. Tertiary dentin is also known as irritant dentin. Unlike primary and secondary dentin, it is not formed uniformly in the tooth, but only in response to an external stimulus. Tertiary dentin serves to protect the pulp from external stimuli. The primary dentin is formed even before the enamel. The odontoblasts produce uncalcified predentin at their tip. Through the incorporation of hydroxyapatite crystals, this predentin mineralizes and thus becomes dentin. Within the dentin, the odontoblasts form fine tubules. These dentinal tubules run centrifugally outward from the pulp. There they reach the dentin-enamel junction. Projections of the odontoblasts protrude through the dentinal tubules. These Tomes’ fibers are in close contact with free nerve endings. Along with the fibers, marrowless nerve fibers also pass through the dentin. These nerve fibers mediate tooth pain in caries. While primary dentin and secondary dentin are very similar in structure, the histology of tertiary dentin shows a different picture. Tertiary dentin or protective dentin is an expression of a defense reaction. The reason for such a defensive reaction of the body can be, for example, thermal stimuli or bacterial infections. The most common cause is caries. In contrast to primary and secondary dentin, protective dentin has a fibrin-like structure. It also has significantly fewer tubules. Tertiary dentin is also formed when the enamel shrinks and exposes the underlying dentin. The accumulation of the less sensitive irritant dentin can prevent wear of the more sensitive underlying dentin, at least for a period of time.
Diseases and complaints
In the disease dentinogenesis imperfecta (DGI), dentin formation is impaired. It is a hereditary disease that is inherited in an autosomal dominant manner. The cause of this genetic disorder is a mutation in the DSPP gene. The DSPP gene coordinates the proteins involved in dentin formation. The result is impaired dentin formation, which leads to abnormal dentin structure and thus abnormal tooth development. Characteristic symptoms of dentinogenesis imperfecta are worn teeth, bulbous crowns, narrowing of the tooth necks, as well as destroyed dental pulp chambers and destroyed root canals. The dentin is amber or even opalescent. Dentinogenesis is also disturbed in dentinal dysplasia. The disease can be divided into a radicular form (type 1) and a coronal form (type 2). Like dentinogenesis imperfecta, both forms are inherited in an autosomal dominant manner. Patients suffering from dentinal dysplasia 1 show so-called apical whitening. The teeth are free of caries and usually have a normal color. Diseased teeth often show abnormal mobility.However, most of those affected do not notice the disease. In the X-ray image, however, enlarged cavities within the dentine can be seen. The therapy depends on the respective symptoms. To preserve the teeth, endodontic or endosurgical procedures can be used. If the teeth cannot be preserved, implantation can be performed after the teeth are removed. Dentinal dysplasia type 2 is a mild form of the disease. It is rather rare and shows an abnormal deciduous dentition with normal tooth roots. Amber discoloration is visible in the deciduous dentition. Also, there may be bulbous crowns and faster wear of the teeth. The neck of the teeth is narrowed. To prevent wear of the deciduous dentition, artificial dental crowns can be placed on the molars. These are usually made of stainless steel. The later permanent dentition is usually not affected by the disorder. At most, slight anomalies can be seen in the X-ray image. The pulp cavities may be bell-shaped. This is referred to as “thistle tubes”. Multiple calcifications of the dental pulp are also observed. However, affected individuals are usually symptom-free.
