Milk tooth
introduction
The first application of the teeth occurs in humans as milk teeth. For reasons of space, this only contains 20 milk teeth. As the jaw grows, it is gradually replaced. The teeth change.
The tooth system is a so-called diphydontia - double teeth. One differentiates between two generations. The first to develop are Dentes deciduiwho have favourited milk teeth. The 2nd generation form the Dentes permanenteswho have favourited permanent teeth.
Development of the milk tooth
The development of the milk tooth begins as early as the sixth week of development, i.e. still in the womb. This is a continuous process that takes place in various stages. In the sixth week of development, a U-shaped toothed ridge forms (dentogingival ridge), which grows into the connective tissue of the upper and lower jaw.
In the eighth week of development, ten tooth buds each form from the upper and lower ridge. Each one forms the attachment of a milk tooth.
The embryonic connective tissue grows into the tooth bud (Mesenchyme) a. This area is called the dental papilla. The tooth bud is now called the enamel organ because it also produces the enamel formers. The inner and outer cells each form the inner and outer enamel layer. The tissue in between is called enamel pulp. The mesenchyme that still surrounds everything forms the tooth sac.
Now the different cell types can differentiate from which the milk tooth ultimately emerges.
The adamantoblasts, the enamel formers, develop from the cells of the inner enamel layer. They release enamel proteins, from which apatite crystals are formed through the storage of calcium. The crystals arrange themselves into enamel prisms and thus form the tooth enamel. Above a certain thickness of the tooth enamel, the adamantoblasts transform, so that finally the upper cuticle (Cuticle dentis) arises. After the milk tooth has broken through, this membrane is gradually rubbed off by chewing and grinding the food. By losing the Adamantoblasts however, the enamel can no longer be reproduced. Damage caused by tooth decay, for example, cannot be repaired.
The mesenchyme of the dental papilla differentiates into odontoblasts. You are the dentist. They contain a lot of potassium, calcium and phosphates and give the uncalcified Predentess which is mineralized to dentine. In addition, it is also retained as a thin layer of predentin between the dentin and the odontoblasts and, thanks to the constant supply of minerals, can always provide a replenishment of dentin. As a result, the dentin of the milk tooth is regenerated for a lifetime - in contrast to the enamel. Many nerve fibers in small dentinal tubules cause pain when damaged.
In addition to the dentin and enamel, the following are also formed:
The tooth pulp, which develops from the mesenchymal cells of the dental papilla, contains nerves and vessels for supply. The Membrana preformativa, a thin basement membrane, lies between the inner enamel layer and the surface of the tooth pulp.
Finally, after the hard substances of the later milk tooth crown (dentin and enamel) have formed, the tooth root is created. It is also formed by the odontoblasts and also consists of dentine. In addition, the cells develop from the external tooth sac Cementoblaststhat attach to the dentin of the tooth root. They are the precursors of cement.
Then the alveolar bone is formed from the cells of the milk tooth sac as well as the periodontal membrane of the tooth, the Periodontium.
Perforation
As the root grows in length, the pressure against the jawbone finally results in the milk tooth breaking through. This is called the first toothing (first dentition).
As a rule, the eruption of all 20 milk teeth is complete by the age of 30 months. They are fully developed by the age of three, while the roots continue to grow for a year or two.
- Middle incisor: Ø eruption age 6th - 8th month
- Lateral incisor: 8th - 12th
- first deciduous molar: 12. - 16.
- Canine: 16th - 20th
- second deciduous molar: 20th - 30th
As a rule, the milk tooth erupts first in the lower jaw. The respective antagonist of the upper jaw follows at a short distance. When the deciduous tooth root dissolves by the permanent tooth that follows, the tooth change takes place. This was also created as a tooth bud in the replacement tooth ridge from the tenth week of development. The second dentition usually begins around the age of six with the first molar.
Read more on the topic: Teething in the toddler
