What is dentin, its types, composition, structure and function

Dentin is one of the hard tissues of the tooth, which is characterized by a peculiar histological structure and a lower amount of mineral substances, compared to enamel. It is a less durable dental tissue than enamel, but this strength in the absence of a pathological process is quite high.

For example, during an objective dental examination by probing, it is necessary to publish the sound of grinding of the working part of the instrument on the dentin - only this indicates the presence of healthy, unchanged fabrics. Dentin forms the bulk and shape of the tooth, in the area of ​​the crown it is covered with enamel, in the area root - cement.

Dentin functions

Solid fabric has several important functions:

• protective;
• trophic;
• sensory.

Protective

The dentinal layer is located directly above the neurovascular bundle of the tooth - pulp and prevents microorganisms from entering it in the absence of pathology of an individual tooth.

Also, in response to a pronounced infectious process - caries, the cells of the peripheral layer of the neurovascular bundle begin to produce replacement dentin, which performs a protective function.

Trophic

The layer is penetrated by a large number of tubules, which, according to numerous studies, contain dental liquor.

Thanks to this liquid, the trophism of the enamel and the dentin itself is provided. Dentinal tubules also provide neurotrophic function - innervation and nutrition of hard tissues.

Sensory

The dentinal layer is an extremely sensitive tissue to pain, which is due to the presence of such a histological border as enamel-dentin.

It contains peripheral sections of nerve cells (Toms' processes), which cause pain attacks with vital preparation (without anesthesia, provided that the pulp is viable) or when carious process.

Thus, the sensitivity of the tooth to external stimuli is ensured.

Structure and composition

Dentin is a calcified intercellular substance that is penetrated by numerous dentinal tubules. These tubules contain processes of odontoblasts - special nerve cells that produced this tissue during histogenesis, or the formation of dental tissues.

The layer is 70-75% composed of mineral, calcified substances, which are represented, for the most part, by hydroxyapatite. 20-25% of its composition is accounted for by organic substances - type 1 collagen. Water contains about 10-15%.

The intercellular substance is formed by collagen fibers, which are associated with hydroxyapatite crystals - crystals deposited in the form of specific lumps and grains, merging into spherical formations - globules and calcospherites.

Zones and views

Anatomically, peri-pulpal and mantle dentin is isolated. Cloak is located directly under the enamel, near-pulp - above the neurovascular bundle - the pulp.

From a histological point of view, dentin is divided into radial and tangential, which is due to the location of the collagen fibers that make up its composition.

The mantle layer is characterized by radial Korf fibers, which diverge in a ray-like manner towards enamels, and for the near-pulpal - Ebner's tangential fibers, which diverge more parallel to each other and to the cloak.

All collagen fibers go to the dentin-enamel border, which is an extremely sensitive area due to the fact that the peripheral divisions of odontoblast processes are located there.

There are the following types:

• primary, the formation of which begins before the eruption of teeth;
• secondary, the formation of which begins after eruption;
• tertiary (irregulatory, reparative, replacement) - produced in response to damage to the tooth tissues.

Secondary dentin has fewer tubules, and the fibers are less ordered than primary dentin.

The tertiary is characterized by a chaotic arrangement of tubes, fibers and a rather weak mineralization - a low percentage of inorganic substances.

Histologically, predentin is also isolated, which is an unusual part of the dentin, which is located from the inside - the layer closest to the pulp. Subsequently, it is from it that secondary or tertiary dentin is produced - this zone is growth.

Microscopically, the following types are distinguished:

• interglobular;
• Toms granular layer;
• peritubular.

Interglobular is represented by unusual fibrils, between which globules of low-mineralized dentin are located. The peritubular, in turn, is located around each of the dentinal tubules and is more saturated with inorganic substances dental tissue.

The Toms granular layer is a portion of the peripheral root dentin layer. It, like interglobular dentin, consists of sparsely calcified areas - grains that are located along the dentin-cement border.

Age changes

Over time, the amount of minerals in the body changes. Closer to old age, the percentage of inorganic substances in the layer decreases due to degenerative changes in the neurovascular bundle.

The dentinal tubules become narrow - they become sclerosed and their trophic function is practically not fulfilled. These changes are also due to age-related changes in odontoblasts: as in any cell of the body, their functions and metabolic processes are disrupted in them.

However, along with the narrowing of the dentinal tubules, tissue caries resistance, or resistance to caries in the elderly, increases. Unfortunately, this property is practically not manifested, since few people have perfectly healthy teeth until old age.

Dentin diseases

The main pathological process that actively affects the tooth tissue is caries. Due to the increased consumption of carbohydrates, the enzymatic activity of the microflora of dental plaque and a local decrease in the level of acidity occurs demineralization of hard tissues and the development of caries.

With caries, the so-called "dead paths" are formed - dentinal tubules, in which the processes of odontoblasts die due to the activity of microorganisms.

This layer serves as an excellent medium for the growth, reproduction and nutrition of microorganisms due to the large amount of organic matter, rather than in other tissues of the tooth - this contributes to the rapid transition of caries to the pulp and the development of complications - pulpitis, periodontitis.

Enamel has good caries resistance compared to dentin: it is due to the structure of the enamel prisms, the orientation of the crystals and the composition of saliva, which constantly washes it, saturating it with the necessary ions and cleansing it from leftover food. In the dentin layer, the conditions are much less favorable: in it, the pathological process spreads extremely quickly, which is favorable for the development of acute forms of caries.

How can dentin be restored?

Despite the fact that this layer has good regeneration in general, with the development of a carious process, this ability is present insignificantly.

The main method of caries treatment is the complete removal of softened, demineralized tissues, followed by antiseptic treatment and filling of the carious cavity. By fillings restoration of both enamel and dentin is achieved.

Modern filling materials, namely photopolymers, they are also composites have excellent aesthetic properties, allowing imitate the natural color of hard tissues, provide a good functional optimum and restore anatomical options.

Composites have special colors Vita scale, sequentially selecting which the doctor first restores the dentin layer using opaque material, and then proceeds to recreate the enamel.

This layer is one of the most complex structures of the tooth in terms of morphology and function. It provides a variety of physiological processes that occur both in response to a local stimulus and, in general, during the vital activity of the tooth.

Against the background of the frequent occurrence of the carious process, it, like enamel, undergoes demineralization. For complete sanitation and elimination of the infectious focus, it is necessary to completely remove all pathologically altered tissues - necrectomy, with further treatment with antiseptic solutions and restoration with filling material.

It is impossible not to remove the softened tissue, because this will cause the development of complications of caries, which can significantly worsen the general condition of the patient.

Information about the structure and function of dentin is necessary for both dentists and patients - this is allows you to have a clearer idea of ​​the nature of the pathological process and the patterns of its development.