A tooth consists of a dense substance. Tooth structure. Mineral metabolism of tooth tissues

Hard tooth tissues are composed of organic, inorganic substances and water.
By chemical composition enamel consists of 96% inorganic substances, 1% organic substances and 3% water.

Mineral enamel base make up crystals of apatite. In addition to the main thing - hydroxyapatite (75%), the enamel contains carbonatapatite (19%), chlorapatite (4.4%), fluorapatite (0.66%). Less than 2% of the mass of mature enamel are non-apatite forms.

The main components of enamel are hydroxyapatite Ca 10 (PO 4) in (OH) 2 and octalcium phosphate - Ca 8 H 2 (PO 4) 6 x 5H 2 0. There may be other types of molecules in which the content of calcium atoms varies from 6 to 14. Molar the Ca / P ratio in hydroxyapatite is 1.67. However, in nature there are hydroxyapatites with a Ca / P ratio from 1.33 to 2.0.
One of the reasons for this is the substitution of Ca in the hydroxyapatite molecule for Cr, Ba, Mg and other elements.

Of great practical importance is fluorine substitution reaction, as a result of which hydroxyfluoroapatite is formed, which has a greater resistance to dissolution. It is with this ability of hydroxyapatite that the prophylactic effect of fluorine is associated.

Enamel organic matter consist of proteins, lipids, carbohydrates. Water occupies free space in the crystal lattice, and is also located between crystals.

Dentine consists of about 70% inorganic substances in the form of apatites and about 30% organic substances and water. The organic basis of dentine is collagen, as well as a small amount of mucopolysaccharides and fat.

Hardness cement significantly inferior to enamel and partly to dentin. It consists of 66% inorganic substances and 32% organic substances and water. Of the inorganic substances, salts of phosphate and calcium carbonate predominate. Organic matter is represented mainly by collagen.

General information about the periodontium

A combination of several surrounding and supporting tissues of the tooth, related in their development, topography and function.
includes the gum, cement, periodical ligament and the alveolar bone proper. It can be conditionally divided into two large groups: the attachment apparatus and the gum.

The tooth is formed by hard (dentin, enamel, cement) and soft (pulp) tissues (Fig. 11). The basis of the tooth is dentin, dentinum, which limits the tooth cavity. In humans, dentin is covered in the area of \u200b\u200bthe crown with enamel, and in the area of \u200b\u200bthe root with cement, that is, in a healthy tooth, dentin is nowhere in contact with the external environment and tissues surrounding the tooth. Dentin is produced continuously throughout life. The formation of secondary and then tertiary dentin leads to a decrease in the tooth cavity with age. By its structure, dentin is similar to coarse-fibrous bone, differing from it in the absence of cells and greater strength. Distinguish between raincoat and parapulpal dentin. Dentin consists of dentin tubules (about 75,000 per cubic mm) and a base material. Dentin tubes in the mantle layer are oriented radially, and near-pulpal - tangentially. They contain the processes of odontoblasts located in the peripheral parts of the pulp. The main substance of dentin contains collagen fibers, between which mineral salts are deposited (phosphates and carbonates of calcium, magnesium, sodium salts, etc.). Non-mineralized portions of dentin are called interoglobular spaces.

Enamel, enamelium - covers the dentin in the crown area. It consists of enamel prisms and the main interprismatic substance that sticks them together. Its thickness in different parts of the crown is not the same and ranges from 0.01 mm in the neck area to 1.0-2.5 mm at the level of the tubercles and cusps of the chewing surface of molars, which should be borne in mind when opening the tooth cavity. Mature enamel is the hardest tissue in the human body, and the hardness increases from the cervical to the occlusal. The color of the enamel varies from yellow to various shades of gray-white, depending on the transparency of the enamel. The more transparent the enamel, the more the yellow dentin appears. The transparency of the enamel is determined by its homogeneity and high degree (up to 97%) mineralization. The enamel is covered with a thin, but strong, lime-free shell - cuticle, which protects it from the damaging effects of acids and alkalis. Cement, cementum - the substance that covers the root of the tooth, has a structure of coarse fibrous connective tissue. It consists of collagen fibers running in different directions and a basic substance saturated with calcium salts (up to 70%). At the apex and inter-root surfaces it contains cementocytes, nutrition is carried out diffusely from the periodontal side. Cement performs the following functions: connects tooth tissue with collagen fibers of the periodontal ligament; protects root dentin from damaging influences; carries out reparative processes after fractures or treatment. The configuration of the enamel-cement junction varies in different groups of teeth.

Three types of enamel and cement connection are possible:

1) they are joined end-to-end;

2) they overlap each other;

3) the enamel does not reach the edge of the cement and an open area of \u200b\u200bdentin remains between them.

Tooth cavity and pulp (fig. 10). The cavity of the tooth, cavitas dentis (pulparis) is a chamber inside the tooth, bounded by dentin. The cavity of the tooth is subdivided into the cavity of the crown, cavitas coronae and the root canal, canalis radicis dentis - the areas of the cavity located in the corresponding parts of the tooth. The wall of the cavity facing the occlusal surface (incisal edge) is called the arch. In the fornix of the cavity there are depressions in the direction of the tubercles on the chewing surface. The part of the cavity of the tooth crown opposite to the arch is called the bottom of the cavity. In single-rooted teeth, the bottom of the cavity, gradually narrowing, passes into the root canal; in multi-rooted teeth, it is flattened and has holes (orifices) leading to the root canals.

Figure: 10. The structure of the tooth.

1 - enamel, 2 - cement, 3 - enamel-cement border, 4 - dentin,

5 - cavity of the crown, 6 - root canal, 7 - tip of the tooth apex.

Enamel is the protective sheath that covers the anatomical crown of the teeth. In different areas, it has a different thickness: for example, in the area of \u200b\u200bthe bumps it is thicker (up to 2.5 mm), and in the cement-enamel joint it is thinner.

Despite the fact that it is the most mineralized and hardest tissue in the body, at the same time, it is very fragile.

Enamel is the hardest tissue in the human body, which is explained by the high content of inorganic substances - up to 97%. There is less water in the tooth enamel than in other organs, 2-3%. The hardness reaches 397.6 kg / mm² (250-800 Vickers). The thickness of the enamel layer differs in different parts of the coronal part of the tooth and can reach 2.0 mm, while at the neck of the tooth it disappears.

Proper care of your tooth enamel is one of the key points of a person's personal hygiene.

The enamel of permanent teeth is a translucent tissue, the color of which varies from yellowish to gray-white shades. Due to this very translucency, the color of the tooth depends on the color of the dentin more than on the color of the enamel. That is why almost all modern methods of teeth whitening are aimed at lightening the dentin.

As for milk teeth, here the enamel looks whiter due to the high content of opaque crystalline forms.

Chemical composition

The enamel has the following composition: inorganic substances - 95%, organic - 1.2%, water - 3.8%. A more detailed chemical composition of tooth enamel will be presented below.

Tooth enamel consists of many types of apatite, the main of which is hydroxyapatite Ca10 (PO4) 6 (OH) 2. The composition of the enamel inorganic substance is presented: hydroxyapatite - 75.04%, carbonapatite - 12.06%, chlorapatite - 4.39%, fluorapatite - 0.663%, calcium carbonate - 1.33%, magnesium carbonate - 1.62%. As part of chemical inorganic compounds calcium 37% and phosphorus 17%. The Ca / P ratio largely determines the condition of the tooth enamel. It is unstable and can change due to the action of various factors, moreover, it can change within the same tooth.
More than 40 microelements have been identified in the enamel of the teeth; their location in the enamel is uneven. In the outer layer revealed great content fluorine, lead, iron, zinc with a lower content of sodium, magnesium, carbonates. Strontium, copper, aluminum and potassium have a more uniform arrangement over the layers.

In enamel, organic matter is represented by proteins, lipids and carbohydrates. The total amount of proteins is 0.5%, lipids - 0.6%. Also, citrates (0.1%) and very few polysaccharides (0.00165%) were found in the enamel.

Tooth enamel structure

Enamel prisms are the main structural formation of enamel, their diameter is only 4-6 microns, but due to their sinuous shape, the length of the prism exceeds the thickness of the enamel. The enamel prisms, gathering in beams, form s-shaped bends. Due to this, dark and light stripes are found on the enamel sections: in one area the prisms are cut in the longitudinal direction, and in the other - in the transverse direction (Gunther-Schroeger stripes).

On the thin sections of the enamel, you can see lines going in an oblique direction and reaching the surface of the enamel - these are Retzius lines, they are especially clearly visible when the enamel is treated with acid. Their formation is associated with the cyclical nature of enamel mineralization in the process of its formation. And just in these areas, mineralization is less pronounced, therefore, during acid etching in the Retzius lines, the earliest and most pronounced changes occur.

The enamel prism has a transverse striation, which reflects the daily rhythm of the deposition of mineral salts. In cross-section, the enamel prism has an arcade-like shape or resembles scales in shape, but it can be round, hexagonal or polygonal. The enamel interprismatic substance consists of the same crystals as the prism itself, but differs in their orientation. The organic matter of the enamel has the form of the finest fibrillar structures, which, according to the existing opinion, determine the orientation of the crystals of the enamel prism.
In the enamel of the tooth, there are such formations as plates, tufts and spindles. The plates (also called lamellae) penetrate into the enamel to a considerable depth, the bundles - to a smaller one, the spindles (processes of odontoblasts) enter the enamel through the dentine-enamel joint.

The smallest structural unit of enamel is an apatite-like substance that forms enamel prisms. In section, these crystals have a hexagonal shape, from the side they look like small rods.

Enamel crystals are the largest crystals of human hard tissues. Their length is 160nm, width is 40-70nm, and thickness is 26nm. Crystals in the enamel prism adjoin tightly to each other, the space between them does not exceed 2-3 nm, in the core of the prism the crystals are directed parallel to the axis of the prism. In the interprismatic substance, the crystals are less ordered and directed perpendicular to the axis of the enamel prism.

Each crystal has a 1nm thick hydration shell. and is surrounded by a layer of proteins and lipids.
In addition to bound water, which is part of the hydration shell, there is free water in the enamel microspaces. The total volume of water in the enamel is 3.8%.

A thin layer of prism-free enamel is often found on the surface of the crown of a human tooth. Its thickness is 20-30 microns and the crystals in it adhere tightly to each other, being parallel to the surface. Prism-free enamel is often found in milk teeth and fissures, as well as in the necks of adults.

Tooth enamel functions

- Protection of dentin and pulp from external mechanical, chemical and thermal irritants.
- Due to its high hardness and strength, enamel allows teeth to fulfill their purpose - biting and grinding food.

Anatomical and histological structure

The main structural formation of enamel is an enamel prism (4-6 microns in diameter), consisting of hydroxyapatite crystals. The enamel interprismatic substance consists of the same crystals as the prism, but they differ in orientation. The outer layer of enamel and the inner layer at the dentino-enamel border do not contain prisms (prism-free enamel). These layers contain small crystals and larger ones - lamellar.

Also in the enamel there are enamel plates (lamellae) and bundles, which represent insufficiently mineralized interprismal substance. They pass through the entire thickness of the enamel.

The next structural element of enamel is enamel spindles - bulbous thickenings of odontoblast processes penetrating through dentinoenamel joints.

Personal hygiene

Located in the oral cavity, where the natural environment is alkaline, tooth enamel also needs to maintain alkaline balance. After each meal, with the breakdown of carbohydrates, under the influence of a variety of bacteria that process food residues and secrete acids, the alkaline environment is disturbed. The acid eats away at the enamel and leads to caries, which requires the installation of fillings to eliminate the irreversible consequences.

To prevent tooth decay, after each meal, you should at least rinse your mouth with water, or better with a special mouthwash, brush your teeth, or at least chew sugar-free gum.

Caries susceptibility of tooth enamel

Caries susceptibility or the resistance of the tooth surface depends on the following factors.
1. Property of the anatomical surface of the tooth: in natural fissures and in the spaces between the teeth, there are favorable conditions for long-term fixation of dental plaque.
2. Saturation of the tooth enamel with fluorine: the resulting fluorapatites are more resistant to acids.
3. Oral hygiene: timely removal of dental plaque prevents further development of caries.
4. Diet Factor: Soft, carbohydrate-rich foods contribute to plaque formation. The amount of vitamins and trace elements also affects the general condition of the body and especially saliva.
5. The quality and quantity of saliva: A small amount of viscous saliva promotes the attachment of bacteria to the "pellicle" and the formation of plaque (see. Dental plaque). The buffering properties of saliva (which neutralize acids) and the amount of immunoglobulins and other protective factors in saliva have a very important effect on enamel caries resistance (see Saliva).
6. Genetic factor.
7. General condition of the body.

Enamel Is a protective shell covering the anatomical crown of the teeth. In different areas, it has a different thickness: for example, in the area of \u200b\u200bthe bumps it is thicker (up to 2.5 mm), and in the cement-enamel joint it is thinner.

Despite the fact that it is the most mineralized and hardest tissue in the body, at the same time, it is very fragile.

The enamel of permanent teeth is a translucent tissue, the color of which varies from yellowish to gray-white shades. Due to this very translucency, the color of the tooth depends on the color of the dentin more than on the color of the enamel. That is why almost all modern methods of teeth whitening are aimed at lightening the dentin.

As for milk teeth, here the enamel looks whiter due to the high content of opaque crystalline forms.

Tooth enamel composition

Tooth enamel consists of: 96% inorganic minerals, 1% organic matrix and 3% water. Due to this composition, the enamel looks optically homogeneous on histological sections.

With age, the amount of organic matrix and water decreases, and the content of inorganic minerals, respectively, increases. It should be noted that, unlike dentin and cement, organic enamel does not contain collagen. Instead, enamel contains two unique classes of proteins called amelogenins and enamelins. The direct purpose of these proteins is currently not well understood, but there are suggestions that they play an irreplaceable role in the mechanism of enamel development.

As for the inorganic substance of the enamel, it consists of 90-95% hydroxyapatite.

Tooth enamel structure

Tooth enamel consists of enamel prisms and inter-prism substance.

It should be noted that there are no prisms in the outer enamel layer and at the dentinoenamel border. Enamelprisms are the fundamental morphological unit of enamel. Each of them is formed from one single enamel-forming cell - ameloblast. The prisms cross the enamel along its entire thickness without interruption, and their location is strictly perpendicular to the dentine-enamel junction. The only exceptions are the cervical areas of the permanent teeth, where the enamel prisms are oriented somewhat apically.

Interprismatic enamel has the same structure as the prism, but differs from it in the direction of the crystals. Here are enamel beams and plates (lamellae), which pass through the entire thickness of the enamel and are hypomineralized zones. The function of these sites is unknown to this day. Lamellae, being defects in the structure of the enamel and containing mainly organic components, can serve as an entrance of bacteria into its structure, thereby contributing to the development

Dentin of a tooth is the main substance that gives color to teeth and protects them from the negative influence of harmful factors. The strength of its structure is much stronger than bone tissue. This material forms the tooth and ensures its elasticity. It is important to know how this fabric is built as well as its chemical composition. In addition, you need to have an idea of \u200b\u200bwhat happens to the tissue of this part of the tooth during pathological processes of the teeth. This will help maintain a strong dentin structure and good dental health for a long time.

Dentin is a specialized connective tissue that makes up the bulk of a tooth along its entire length. It has a lot in common with bone tissue, but unlike bone, dentin is more mineralized.

Dentin is considered a calcified substance, which contains mineral components. Due to this constituent element of the tooth, micronutrients are carried through the tubules to the enamel, which protect the pulp from various negative influences.

Attention! Dentin refers to the inside of a tooth. By its structure, it is much stronger and harder than bone tissue, but it is softer than the enamel that covers it. In addition, it has increased elasticity, this property resists its destruction.

The size of the dentin thickness in the masticatory and cervical regions has some differences. Its parameters can be from 2 to 6 mm, it all depends on the health and state of the body of each patient. By its structure, this component has a yellow or gray tint, which is considered the natural color of teeth.
Please note that dentin coverage varies from area to area. In the coronal part, this is the enamel that can be seen on visual inspection. In the root area, this coating is replaced by a cement base, which is not very strong in structure. The connection of dentine to enamel usually occurs due to special irregularities with a perfect fit to each other.

Features of the histological structure

Dentin contains the following types of fabrics:

predentin. This type of tissue surrounds the area of \u200b\u200bthe tooth pulp and provides its nutrition with various useful components.
Important! The main component of this tissue is odontoblasts, pear-shaped cells. Due to these elements, the sensitivity of the tooth is ensured, as well as metabolism occurs within its cavity;
interglobular part. This element fills the area between the dentin tubes. There is also a separate classification of this component - peri-pulpal dentin and mantle.

The first type is usually located around the pulp area, and the second type is adjacent to the enamel:

Components

Features: chemical composition dentin has some differences when compared with the composition of other tissues. The largest part, almost 70%, contains inorganic substances:

The basis is calcium phosphate;
Phosphate magnesium;
Calcium fluoride;
Sodium carbonate and calcium.

The remaining part, namely 20%, contains substances with an organic structure - collagen, amino acids, lipids, polysaccharides. The rest 10% is water.

Important! Due to its varied composition, dentin is considered a very hard and durable tissue with an increased degree of elasticity. For this reason, it protects the enamel structure from cracking, and also allows it to withstand increased chewing loads.

In addition, the composition contains a few particles and microelements. By its structure, dentin tissue is much stronger than bone and cementum tissue. But at the same time dentin is almost 5 times softer than enamel, but it is worth highlighting two important conditions:

despite the fact that the enamel coating is considered hard, but at the same time it is very fragile. For this reason, the enamel can quickly crack;
dentin is the base of the crown. It provides increased protection to the enamel coating against premature cracking.

Dentin contains less calcareous components than tooth enamel. It mainly consists of calcium phosphate, magnesium phosphate, calcium fluoride, sodium carbonate and calcium, and it also contains amino acids.

Kinds

In total, there are three types - primary, secondary, tertiary.
The primary form of dentin is noted at the earliest stage of the formation and development of this tooth material. This means that this species exists in humans only before the appearance of the first units of the dentition.
After the first teeth have appeared, they begin to perform their natural functions. At this time, they have a transformation of primary dentin into secondary. Unlike the primary form, this species has a slower growth rate, and the structure also becomes not so correct. It should be noted that the structure of this species differs little from the primary form of dentin. At the same time, milk teeth have wide dentinal tubules with a small length. It is this factor that provides easy access for pathogens to the pulp cavity. Permanent teeth have long and narrow dentinal tubules.
The process of synthesizing secondary dentin in humans occurs throughout life, while in men it happens much faster than in women. Due to the fact that secondary dentin is deposited inside the tubules, the size of the lumen of the pulp cavity becomes narrow with age. Sometimes the lumen can completely close.
The tertiary form has a certain peculiarity - its irregularity. This type is usually manifested as a result of exposure to the dentin tissue of various irritating factors:

erosive damage;
caries formation;
the presence of erasure of units of the dentition;
grinding teeth.

Dentin caries is accompanied by a violation of the integrity of the tooth with the formation of a cavity. But often a carious cavity is not visualized and is found only at a dentist's appointment when probing a tooth with a special tool for diagnosing caries.

The irregularity of this type of dentin is explained by the fact that in it the sinuous tubules are located in a chaotic state. In addition, this property provides increased enamel protection. When a strong pathological process appears, the tubules may completely disappear.

What are dentin diseases?

Attention! When a tooth is damaged, the doctor usually makes a diagnosis - the average form of carious lesions. During the ingress of food residues into the formed cavity after a carious lesion, patients may complain of the presence of hyperesthesia, which is characterized by increased sensitivity and severe irritability when exposed to hot or cold teeth.

In neglected forms, painful sensations appear.
If you do not start timely treatment, then as a result, severe complications can appear, and pathogenic bacteria can penetrate the pulp area. If appears inflammatory processthen the doctor can carry out a complete removal of dead tissue. After this operation, all metabolic processes are completely stopped in dentin.
It is also worth highlighting especially dangerous diseases that arise in the internal structure of the tooth:

Carious lesion of any form;
Increased enamel abrasion;
Wedge-shaped defect;
Hypersthesia. This disease can manifest itself independently or as a complication as a result of the appearance of the above pathologies.

A wedge-shaped defect is a non-carious lesion that occurs on the hard tissues of the teeth, characterized by the formation of a wedge-shaped defect in the neck of the tooth.

Dentin restoration process

Dentinal tissue regeneration occurs due to the functioning of odontoblasts. This process usually occurs when the innervation of the dental epithelium is healthy and intact. If the nerve is completely removed from a healthy tooth, the restoration of dentin stops.
Many world scientists in the field of dentistry, especially American ones, have been the best in the field of dentin restoration. They were the ones who were able to make a wide range of discoveries that can further ensure the natural restoration of dentin in the presence of its strong destruction. In laboratories, thanks to the activation of the necessary genes, it was possible to make a healthy natural tooth.
Subsequent research work consist in an attempt to restore the structure at the micromechanical level. Through the use of colloidal compounds of calcium phosphate, saline, collagen, electrical discharges, scientists were able to obtain a biocomposite material that fully corresponds to the natural structure of a natural tooth.

Important! But at present, in order to perform the usual restoration of dentin, vitamin-mineral complexes are used. For the nutrition of dentin, the following components are of particular importance - magnesium, calcium, phosphorus, vitamins - A, B, C, E and D.

In addition, regular oral hygiene using a special toothpaste is recommended to ensure high strength and health of dentin. It is recommended to brush your teeth in a circular motion; cleaning procedures should last at least 3 minutes. You also need to eat right.