What is dentin?
The dentin or also called dentin, belongs to the hard tooth substances and forms proportionally their main mass. It is the second hardest substance in our body after enamel and is located between the enamel, which is on the surface, and the root cement, which is the surface of the root. The dentin encloses the pulp, the tooth marrow, which is permeated with blood and nerve vessels. Just as with enamel, the crystals of hydroxyapatite form the main component of dentin, but this proportion is not as high as with enamel, which makes dentin slightly softer. Purely in terms of colour, dentine is much more yellowish than light-coloured enamel, which is why exposed tooth necks form a strong contrast to the colour of enamel.
Anatomy
The dentine-forming cells are called odontoblasts. They are located at the edge of the tooth’s pulp, the pulp, towards the dentine layer and have small cell extensions that run completely through the dentine and are regarded as a kind of antenna. They float together with nerve fibres in a liquid and can therefore receive pain stimuli and transmit them to the pulp.
The odontoblasts do not disappear after dentine formation, but are preserved for life, so that dentine can always be formed. The primary dentin is the first dentin to be formed during tooth development. Any dentine formation that occurs after this is called secondary dentine.
Due to the preservation of the odontoblasts, there is constant dentin formation. This ensures that the pulp gradually retracts. This is the reason why older people feel thermal stimuli less well and the pulp in this group of patients is significantly smaller than in young people.
The dentin that is reproduced throughout life is called secondary dentin, while there is another form of dentin. The so-called irritant dentine is formed when a pain stimulus reaches the pulp through the dentine channels. This tertiary or irritant dentine attempts to protect the pulp from pain stimuli and to protect the nerve inside the pulp from damage. Tertiary dentine is also formed when stimulated by caries or by wear and tear of the teeth when grinding.
Function of dentin
The dentin forms the middle layer between the enamel and the pulp and creates a connection between these two structures. Through the extensions of the odontoblasts, which are located at the edge of the pulp and reach through the dentin to the enamel, any stimuli that reach the tooth from the outside will also reach the pulp from the inside. Through these extensions, the tooth feels cold, heat or pain and transmits these signals to the brain, so that the dentin acts as a mediator.
Furthermore, the tertiary or irritant dentine forms a protective mechanism for the tooth, in that the dentine is formed in response to any pain stimuli. It tries to protect the pulp at the affected area where the stimulus arrived so that it is not irritated or even damaged. Tertiary dentine is formed in the case of stimuli caused by grinding, caries or a periodontal inflammation, a periodontitis. By contrast, the regular and constant formation of secondary dentine, which takes place throughout life, causes the pulp to gradually retract, so that the older the person gets, the less sensitive the teeth are.
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