Dentin

The dentin, and dentin (Latin substantia eburnea ), provides a large proportion of the tooth dar. In contrast to enamel, it can become life- long re- formed through a process of biomineralization, but only at the interface with the dental pulp. It is one of the most durable organic materials and all classes of vertebrates, which emerged from the cartilaginous fish, bear dentine genes.

Tooth structure

The dentin is similar to bone and consists of about 70 % of calcium hydroxylapatite (mainly phosphate and calcium) and 20% of organic components (of which 90 % collagen). The remaining 10 % is water. The color is yellowish. In the area of the tooth crown is the enamel on him ( " coronal " ) and in the area of ​​the tooth root cementum. The dentin surrounding the pulp cavity of the dental pulp ( pulp ), which consists of blood vessels, nerves, connective tissue and lymphatic vessels.

Dentinproteine

Dentinproteine ​​are poorly characterized, because they are anchored in a very solid matrix and to investigate non-destructively hardly are. As in the bone make collagen type I, acidic proteins and proteoglycans from a large portion of the extracellular proteins. Some collagen- free protein fractions could be separated due to their molecular mass: Group I with predominantly phosphoproteins fraction II with more acidic proteins, albumin, proteoglycans and a protein with low phosphate content, fraction III with a characteristic glycoprotein having a molecular mass of 95 kDa and minor amounts of other proteins, resemble including albumin and phosphoproteins and fraction IV with low molecular weight fractions of γ - carboxyglutamate - containing proteins, the bone proteins.

Education

The dentinbildenden cells called odontoblasts. The Odontoblastenkörper lie in the pulp and associated with free nerve endings in contact. Your extensions which Tomes'schen fibers extend into the fine tubules ( dentinal tubules ) that extend from the pulp centrifugally outwards up to the enamel-dentin border.

Depending on the time of formation of three types of dentin can be distinguished. While the tooth dentin formation produced is referred to as "primary dentin ." Structurally, the same is the " secondary dentine ". This will live long formed and concentrated so over the years the pulp chamber a. Thus, the sensitivity is reduced to the teeth in old age. Histologically, to distinguish them is called " tertiary dentin ," even irritation dentine. It does not develop uniformly in the whole area of the odontoblasts, but is formed due to an external stimulus in order to protect the pulp. Reasons for this are next to caries also bruxism, exposed tooth necks and periodontal disease.

Occurrence

Dentin is phylogenetically already in the shed and teeth of cartilaginous fish before ( Ganoidschuppe, Kosmoidschuppe or Placoidschuppe ) and was described there in the 19th century scientific. It can be made of most vertebrates, which had cartilaginous fish as ancestors. Although extant birds and extinct bear no teeth since about 60 million years ago, the dentin matrix protein 1 ( DMP1 ) gene was also detected in them.

Significance for palaeontology

Because of the resistance of dentin include teeth to the most enduring relics of vertebrates and allow due to its good state of preservation often their paleontological identification. The stammesgeschichliche consideration of tooth development often provides insight into changes in dietary behavior. By analyzing traces of dental finds of human ancestors conclusions on some lifestyle habits such as preferred food and tool use are possible.