The development of the baby's baby teeth is complete. Your baby's dental development

The appearance of baby teeth (teeth cutting)

The timing of teething, that is, their appearance - the breakthrough of the gum line, differs for each child. For example, one child may grow their first tooth when they are just a few months old, while another may not start teething until 12 months or more. Although the timing may vary, the order in which they appear is usually the same. It includes:

Two front teeth (central incisors) lower jaw usually appear first. This occurs somewhere between six and 10 months of age.
Two front teeth (central incisors) upper jaw They grow up between the ages of eight and 13 months.
The lateral incisors on each side of the central incisors in the upper and lower jaws - between the ages of eight and 16 months. The bottom set is usually formed ahead of the top one.
The first set of upper and lower molars (flat back teeth) are between 13 and 19 months of age.
Canines next to the lateral incisors in the upper and lower jaws - between 16 and 23 months of age.
The second set of upper and lower molars are between 25 and 33 months of age.

Typically, the average child receives his full set of 20 baby teeth before the age of three.

Loss of baby teeth

At the ages of six and seven (sometimes earlier), baby teeth begin to fall out. First, the central and lateral incisors of the upper and lower jaws are renewed. Some children may be worried about losing their first teeth, but tooth Fairy, with its monetary reward for every tooth lost, tends to help ease anxiety.

Molars in children

Permanent teeth are molars in children, also known as adult or secondary teeth. Permanent teeth begin to develop in the jaw after the baby is born. Around age 21 average person has 32 permanent teeth, including 16 in the upper jaw and 16 in the lower jaw. (In some cases, however, third molars - commonly called wisdom teeth - do not develop.) Therefore, a set of 28 permanent teeth is considered normal...

At the age of six the first permanent teeth replaced by dairy. These are four molars - two central incisors in the upper jaw and two in the lower jaw. Then the lateral permanent incisors and canines replace the baby teeth.

Just like baby teeth, the timing of when permanent teeth appear varies from child to child. As a rule, their order and rough timing of appearance for each type of permanent teeth are as follows:

First molars - six to seven years
Central incisors - six to eight years
Lateral incisors - seven to eight years
Fangs - nine to 13 years
Premolars - from nine to 13 years
Second molars - 11 to 13 years
Third molars (wisdom teeth) - between the ages of 17 and 21.

What to remember

The average child receives his full set of 20 baby teeth before the age of three.
Between the ages of six and seven, baby teeth begin to fall out and are replaced by permanent teeth.
By age 21, the average person has 32 molars - 16 in the upper jaw and 16 in the lower jaw.

Human teeth begin to form at the stage intrauterine development(7-8 weeks). Part of the epithelium thickens, then a curved fold with its edges grows deep into the surrounding tissue, forming a dental plate (1). The fold itself is uneven, usually clusters of cells (dental papillae) are formed, above them something like bells protruding upward is obtained. Subsequently, enamel is formed from this epithelium itself (2), and dentin and pulp are formed from the tissues inside the bell (3). This same tissue supplies stem cells for the growing tooth. Large folds (2,3), laid down very first, become the rudiments of milk teeth. In the 5th month of pregnancy, the rudiments of permanent teeth begin to develop from smaller bell-shaped folds (4).

This process itself determines the further structure of the tooth: since the protein matrix of the enamel is formed only from the area of ​​​​the ingrown epidermis, the shape of the crown and the thickness of the tooth enamel in an adult strongly depends on the characteristics of its intrauterine development at the end of the second month of pregnancy. An epidermal plate that is not deeply ingrown or receives insufficient nutrition will give rise to a small crown, or a crown with an enamel defect or with thin enamel. At this same stage, the number of teeth is formed, and the rudiments of both milk and permanent teeth are immediately formed. Normally, a person has 20 primary teeth and 28-32 permanent teeth, but there may be more or fewer teeth: this depends on the number of markers and signal sources.
The roots of the tooth are formed before eruption, and the final shape is taken 6-8 months after it (sometimes later).

Sometimes third molars do not grow at all, sometimes they grow inside the jaw, causing problems.

After the eruption of permanent molars, dental plasticity disappears, and new teeth can no longer appear. However, if “extra” rudiments remain in the jaw, they can sometimes be activated. The shape and arrangement of teeth are unique to each person. According to some studies, early human ancestors had 44 teeth, so sometimes atavisms occur regarding the increase in the dentition: either additional teeth in the main arches, or additional teeth on the palate.

Important! The formation of teeth depends on the characteristics of pregnancy. Maternal malnutrition, vitamin deficiencies (especially lack of vitamin D) or the use of antibiotics can lead to dental hypoplasia in the newborn, and both milk and permanent teeth can be damaged.

Dental formulas

In humans different teeth have different functions, and are of four types in shape. To describe the location of teeth, there are so-called dental formulas. Dental formula a person has 32 teeth.

IN simple version dental formulas simply indicate the tooth number (No. 1 central incisor), in the second case they add a number that indicates on which jaw and side the tooth is located.

The dental formula for primary occlusion is written in Roman numerals or designated as numbers 5-8.

Anatomical structure of the tooth

In a tooth, there is a crown (protrudes above the gum, covered with enamel), a root (located in the jaw socket, covered with cement) and a neck - the place where the enamel ends and cement begins; such a neck is called “anatomical”. Normally, it should be slightly below the level of the gum. In addition, a “clinical neck” is distinguished, this is the level of the dental-gingival groove. The neck looks like a narrowed part of the tooth; above and below it it usually widens.

Normally, the clinical neck is higher than the anatomical one, and the gum border runs along the enamel. However, with age, the gums atrophy and the enamel is destroyed. At certain times, it may happen that the clinical and anatomical necks coincide. In old age, when the gums descend lower and the enamel becomes thinner, wears out and disappears (near the neck it is thinner and disappears earlier), a gap again appears between these conventional boundaries, but now the level of the clinical neck will pass along the exposed dentin of the tooth.

The crown of the incisors is chisel-shaped, slightly curved, with three cutting cusps; in fangs - flattened-conical; in premolars it is prismatic or cubic, with rounded sides, with 2 chewing cusps; molars (molars) are rectangular or cubic in shape with 3-5 chewing cusps.

The tubercles are separated by grooves - fissures. Incisors, canines and second premolars have one root, first premolars have a double root, and molars have a triple root. However, sometimes molars can have 4-5 roots, and the roots and canals in them can be curved in the most strange way. That is why tooth depulpation and canal filling are always done under X-ray control: the dentist must make sure that he has found and filled all the canals.

The tooth is secured in the alveolar socket using strong collagen strands. The cementum covering the root is made of collagen impregnated with mineral salts, and the periodontium is attached to it. The tooth is nourished and innervated by the arteries, veins and processes of the trigeminal nerve entering the opening of the root apex.

The length of the root is usually twice the length of the crown.

Histological structure of the tooth

The tooth consists of three types of calcified tissue: enamel, dentin, cement. Enamel is the strongest, dentin is 5-10 times weaker than it, but 5-10 times stronger than ordinary bone tissue. Both dentin and enamel are a protein mesh-fibrous matrix impregnated with calcium salts, although dentin in structure is between enamel and dense bone tissue. If crystals of mineral salts (apatites) are lost, the strength of the tooth can be restored, since salt crystals, under favorable conditions, will again be deposited on the protein framework; however, if part of the protein matrix of the enamel is lost (for example, by chipping, drilling or grinding), this loss is irreplaceable for the tooth.

The thickness of the enamel on the lateral surfaces of the crown is 1-1.3 mm, on the cutting edge and chewing cusps up to 3.5 mm. The tooth erupts with non-mineralized enamel, at which time it is covered with a cuticle. Over time, it wears out and is replaced by the pellicle, and further mineralization of the pellicle and enamel occurs in the oral cavity due to the salts contained in saliva and dental-gingival fluid.

There are no cells inside dentin; it can partially become compacted and loosened; a protein matrix can grow in it, but only in a chamber limited by the inner surface of the enamel. Nevertheless, age-related demineralization predominates in humans. Dentin consists of thin calcified tubes running radially from the enamel to the pulp. If foreign substances or liquid enter these tubes, increased internal pressure transmitted to the pulp, causing pain (the greater the pressure inside the dentinal tubule).

Pulp is loose connective tissue. It is penetrated by nerves, lymphatic and blood vessels and fills the pulp chamber of the crown and root, and the shape of the chamber can be any. The larger the pulp relative to the overall size of the tooth, the weaker and more sensitive it is to temperatures and chemicals.
Functions of the pulp:

• transmits sensory information to the brain;
• nourishes living tooth tissues;
• participates in the processes of mineralization and demineralization;
• its cells synthesize proteins that are integrated into the protein matrix of the tooth.

The structure of baby teeth

A child is born with practically formed primordia of baby teeth. They begin to erupt already at 3-4 months of life and already at this time require care. By the time teeth erupt, the roots have not yet been fully formed, since the root grows for quite a long time. The rudiments of permanent teeth also continue to develop in the jaw, their crowns grow, but the roots will begin to form only by the time the teeth change.

In baby teeth, the tops of the roots are bent to the buccal side, and between their roots there are the rudiments of permanent teeth.

Milk teeth have a weaker layer of dentin and less mineralized enamel, their roots are shorter and thicker than those of permanent teeth of the same name. The cutting edge of the incisors usually has slightly pronounced tubercles, and the chewing tubercles are also insignificant. A large volume of pulp and a thin layer of dentin make such teeth more sensitive to sour, sweet, and hot foods. Since they are less mineralized, they are more susceptible to caries and pulpitis, and local anesthetics during treatment, the production of stem cells and the growth of dentin in the buds of permanent teeth are inhibited.

Important: caries that begins in baby teeth is easily transmitted to the permanent ones that replace them, since the bacteria that cause it continue to develop in oral cavity. A baby usually gets these bacteria from the mother if she feeds him with the same spoon she eats with, or licks a fallen pacifier (instead of washing it).

Replacing teeth with permanent ones

By the time the teeth change and the active growth of the branches of the jaw begins, the child has 20 teeth. At this time, there are 2 molars on each side, but no premolars. It is the premolars that will take up the free space that appears in the branches growing in length. If the jaw does not grow quickly enough, a defect in the dentition may appear.

When changing teeth, the growing germ of a permanent tooth compresses the roots of the milk teeth, pinching the blood vessels that feed them. Gradually, the roots of baby teeth, lacking nutrition, begin to collapse and completely dissolve, so that only the neck of the tooth and the crown remain. However, the rudiments of permanent ones may also suffer. Sometimes they are involved in the process and are completely destroyed, sometimes enamel defects occur, since its protein-collagen matrix, formed from the epithelium, can easily be damaged at this stage. Hypoplasia (underdevelopment) of the tooth and the eruption of teeth with damaged enamel are very common in recent years.

Anomalies of teeth and dentition

Anomalies of tooth structure

• too large (more than five) number of roots;
• root underdevelopment;
• uncharacteristic shape (subulate, hook-shaped, conical, flat crowns);
• underdeveloped, deformed crown;
• thin enamel;
• increased abrasion of enamel;
• absence of all or part of the enamel.

Anomalies of changing teeth

• the root may not resolve in time;
• the tip of the root can pierce the bone, causing an ulcer in the gum;
• the root is completely exposed, as all the tissue (both bone and gums) above it is destroyed;
• the permanent tooth began to grow before the baby tooth fell out;
• an additional row of permanent teeth or teeth in the roof of the mouth is formed;
• There is not enough space for normal tooth growth.

Anomalies of the dentition

• malocclusion;
• anomalies in the location of teeth in the dentition.

In all cases of anomalies with root resorption, baby teeth must be removed. If teeth grow in two or three rows or are crooked, extraction of baby teeth may also be indicated. At the same time, removing a tooth too early (for example, due to caries) can cause permanent teeth to start growing earlier, or cause the growth of additional teeth (usually small, conical ones). Additional teeth corresponding in shape to molars are formed less frequently.

Important! 5-7 years old second critical age for dental health. It is during this period that permanent bite problems and dental defects arise, so changing teeth should be taken very seriously and not neglecting visits to the pediatric dentist.

Video - The structure of the tooth. Types and functions of teeth

Video - Anatomy of teeth

As a rule, children's first teeth erupt at the age of 4.5-7.5 months. Of course, there are rare exceptions when children’s baby teeth first appear around one year or, conversely, at 3 months. This feature is due to genetic predisposition.

The development of teeth in children, or rather their eruption, occurs in a certain order - first the lower central incisors, then the upper central incisors, then the premolars, canines, and molars. Most babies during the teething period behave restlessly, refuse to eat or, conversely, “hang” on their mother’s chest for days, sleep poorly and are capricious for any reason.

As teeth develop, children may experience symptoms such as:

Such children constantly pull various objects into their mouths, trying to “gnaw” them with their gums in order to alleviate their condition. Give your baby special children's toys made from environmental material. Such toys are also called “gnawers” ​​and they are filled with liquid inside. You can put the chewer in the refrigerator for a while and give the baby a cool toy, which perfectly relieves pain in the gums. Of course, any mother should ensure that the toys that the baby tastes are perfectly clean, since during teething the immune system The baby weakens and some kind of infection can easily develop.

Before daytime and nighttime sleep, parents can use special baby gels that are designed to relieve pain and swelling of the gums during the eruption of the first teeth. Such gels are usually made on the basis medicinal herbs and natural ingredients, so there is nothing dangerous if part of the medicine gets inside with saliva.

When to expect the first teeth: standard development scheme

The development of baby teeth in a baby begins during the period of its intrauterine existence. The rudiments of teeth are hidden deep in the gums and after the baby is born, by a certain age, they erupt.

Pediatricians note that most often the first tooth erupts in a baby between the ages of 4 and 6 months, but everything is purely individual and depends on heredity. If your baby is already six months old and there is not even a hint of teeth, but the baby is developing well and does not suffer from rickets, do not worry!

Most often, baby teeth appear in the following order:

In most cases, by the age of 2.8-3 years, the baby has 20 milk teeth; in some children, they erupt much earlier. TO school age baby teeth begin to gradually fall out, often in the same order, and permanent molars erupt in their place.

Symptoms of the eruption of the first teeth

Already from childhood, most parents notice increased salivation in the baby, slight swelling of the gums, and a desire to taste everything. Many parents and pediatricians also associate these phenomena with rapid teething, but such thoughts are not always justified. When the teeth really appear soon, the baby will become restless and capricious, will constantly rub his mouth with his fists and try to “gnaw” his fingers, and will forcefully bite rubber rings and special toys with his gums.

A few days before the tooth erupts on the surface of the gum, an attentive mother may notice what appears to be a thin extruded line, reminiscent of a loose cut. Sometimes a thin white “thread” may appear through this “cut” - this is the tooth; after a few days it will make a loud clicking noise if you carefully touch it with a spoon.

Are diarrhea, fever and cough always signs of early teething?

Most young parents attribute any symptoms of a cold to “teeth,” but this is not always a true belief. Sometimes the temperature Cough and runny nose have nothing to do with teething, but rather are signs viral infection. In this case, just unsoldering the child breast milk and lubricating the gums will not be enough, the baby needs adequate treatment. Children infancy during a viral infection, literally within a few hours from the appearance of the first symptoms of the disease, they become very “severe”, and in the absence of timely medical care their condition may become critical!

Most often, the appearance of diarrhea, fever, cough and runny nose in pediatrics is not associated with teething at all, and all these symptoms develop against the background of a weakening of the child’s body’s defenses and the addition of a viral or bacterial infection. In any case, if the above symptoms appear, parents should call a local pediatrician to their home, who will examine the child and rule out a viral infection.

Diarrhea during the eruption of the first teeth is most often caused by the child swallowing copious amounts of saliva, as a result of which intestinal motility accelerates and stool liquefaction develops. Normally, diarrhea during teething occurs no more than 3 times a day and lasts no more than 2-3 days. With frequent and watery stools, the child’s body can quickly lose electrolytes, which threatens dehydration and requires immediate rehydration! The appearance of mucus, blood, green or purulent inclusions in the stool is in no way related to teething and requires immediate consultation with an infectious disease specialist!

A wet cough during teething in children appears as a result of the accumulation of a large amount of saliva, which flows down the back wall nasopharynx and irritates the respiratory canal. The use of antitussive or expectorant drugs in such cases is not required, but only if the doctor has really ruled out a viral infection.

How to relieve your baby's condition during teething?

Remember that the baby experiences severe discomfort and pain during the eruption of his first teeth, but he cannot tell his mother about it. There is no need to show your dissatisfaction and get annoyed when the baby is once again capricious and “asks” to be held. Take him in your arms, pat him on the back, calm him down, give him a breast or a bottle. To reduce gum pain, use one of the children's gels, such as Dentokind or Kamistad. These drugs have an excellent anesthetic effect and will help the baby cope with pain. Dentokind contains herbal ingredients that not only help relieve pain and swelling of the gums, but also have a calming effect on nervous system child. Be patient, as it usually takes a few days for the tooth to erupt. Then unpleasant symptoms They pass quickly, and the baby becomes cheerful and cheerful again.

What should you absolutely not give during teething?

In the time of our grandmothers, the only “life-saving” remedy during teething was to let the baby chew a crust of bread or a bagel. Remember that this is strictly forbidden! Despite the fact that the baby does not yet have teeth, he easily soaks bread or a bagel with saliva, a piece of which can get into the teeth. Airways. Unfortunately, there are many cases where such babies could not be saved...

Don’t repeat the mistakes of our mothers and grandmothers, don’t give your kids any crusts of bread!

Dental development is a very complex process that begins in the early stages of embryonic development and continues in humans until the age of 18-20. This process can be divided into several periods. The period is from the moment of birth to 6-7 months, when the child does not yet have teeth, but the rudiments of milk teeth are already embedded in the jaws, starting from the 40-45th day of intrauterine life. The first baby tooth appears in a newborn at 6-7 months of life. Period - from 6-7 months to 6-7 years. During this period, the milk bite develops. During this time, all 20 baby teeth erupt and grow. In the formation of the primary occlusion, in turn, two stages are distinguished: the first begins from the moment of eruption at 6-7 months of age and ends with the complete formation of the dentition at 2-3 years; the second stage lasts from 2.5-3 to 6 years. At this time, baby teeth are prepared to be replaced by permanent teeth. The period begins at the end of the 6th year of life and continues until 12-13 years. It is characterized by the gradual replacement of baby teeth with 32 permanent teeth.

The formation of primary teeth is completed between the 3rd and 5th years of life. Then there is an intensive increase in the height of the alveolar process and jaw growth. Therefore, most children in the primary dentition have pronounced spaces between the front teeth. The first permanent molar erupts at the age of 6-7 years. Around the same time, the incisors of the lower jaw erupt. This initially leads to slight crowding of the teeth, which should not be considered as a violation of the development of occlusion, since by the age of 12, thanks to intensive growth jaws, the bite is normalized.

Difference between baby teeth and permanent teeth.

Contrary to popular belief, baby teeth, just like permanent teeth, have roots and a nerve (pulp). The roots hold the tooth in the bone. Under the milk tooth is the germ of a permanent one. As the permanent tooth erupts, it stimulates root resorption baby tooth and by the time the baby tooth falls out, only the crown remains.

Since baby teeth (like permanent teeth) have a nerve (pulp), they can become painful if a carious cavity infection gets into the tooth cavity, causing the development of pulpitis.

Milk teeth differ significantly from permanent teeth in their size and structure.

Primary teeth are smaller than permanent teeth and have less massive roots;

Milk teeth have a more complex anatomical structure root canals, which leads to a more labor-intensive treatment process than in permanent teeth;

The hard tissues of primary teeth are less mineralized and less resistant to abrasion and the development of caries.

The hard tissues of baby teeth are much thinner than those of permanent teeth: inflammatory process quickly reaches the nerve of the tooth;

Why are baby teeth needed?

Milk teeth are involved in the development of functions in the child such as chewing and pronunciation of sounds. Without them, chewing hard food would be impossible. The aesthetic component plays an important role.

Also, baby teeth hold space in the dentition for permanent teeth. The eruption of primary teeth stimulates the primary growth of the jaws. The second wave of jaw growth begins during the period of replacement of baby teeth with permanent ones. Early removal of primary chewing teeth leads to the displacement of neighboring teeth into the area of ​​the missing one and the formation of crowding of teeth in the future!

Odontogenesis.

Odontogenesis - tooth development - begins at the 6th week of embryogenesis, when the follicles of baby teeth are formed, and is sometimes completely completed after 20 years, when the third permanent molars erupt and the formation of their roots ends.

Human teeth develop from components of the oral mucosa of the embryo. Its epithelium gives rise to the structural elements involved in the formation of enamel, and the mesenchyme is the source of dentin, pulp and cement.

In the development of each tooth, 3 periods are distinguished: the formation of dental germs, their differentiation and histogenesis - i.e. development of basic tooth tissues (enamel, dentin, pulp, cement).

Formation of tooth germs.

First, in the area of ​​the future anterior teeth, a dental plate originates from the vestibular plate at a right angle and grows into the underlying mesenchyme. During their growth, the epithelial dental plates take the form of two arches located in the mesenchyme of the upper and lower jaws.

Then, along the free edge of the plate on the anterior (buccal-labial) side, flask-shaped protrusions of the epithelium (10 in each jaw) are formed - tooth buds (gemmae dentis). At 9-10 weeks of embryonic development, mesenchyme begins to grow into them, giving rise to dental papillae (papillae dentis). As a result, the dental bud takes the shape of a bell or bowl, transforming into an epithelial dental organ (organum dentale epitheliale). Its inner surface, bordering the mesenchyme, bends in a peculiar way and the outlines of the dental papilla gradually take on the shape of the future tooth crown. By the end of the 3rd month of embryogenesis, the epithelial dental organ is connected to the dental plate only by a narrow epithelial cord - the neck of the dental organ.

Around the epithelial dental organ and under the base of the dental papilla, a thickening of mesenchyme is formed - the dental sac (sacculus dentis)

Thus, in the formed dental germ, three parts can be distinguished: the epithelial dental organ, the mesenchymal dental papilla and the dental sac. This ends stage 1 of tooth development - the stage of formation of tooth germs, and the period of their differentiation begins.

Differentiation of tooth germs.

First, the dental organ is divided into several cellular layers. In its central part, a protein fluid accumulates between the cells, pushing them apart. These cells acquire a stellate shape, and their combination forms the pulp of the dental organ (pulpa organi dentis). The cells of the dental organ adjacent to the surface of the dental papilla become cylindrical and are called the internal dental epithelium (epithelium dentale internum). These cells give rise to enameloblasts, which are involved in the formation of tooth enamel.

Between the anameloblasts and the pulp of the dental organ there are several rows of flat or cubic cells that form the intermediate layer of the dental organ (stratum intermedium). External surface dental organ is formed by flattened cells of the external dental epithelium (epithelium dentis externum)

Subsequently, the cells of the outer dental epithelium gradually atrophy, and the cells of the intermediate layer of the enamel organ and its pulp take part in the formation of the enamel cuticle.

So, as a result of the differentiation of the dental organ, it is already possible to distinguish its pulp, internal and external dental epithelium and the intermediate layer. The dental papilla is then differentiated. By this time, it increases in size and penetrates deeper into the dental organ.

Blood vessels and nerve fibers penetrate the base of the dental papilla, growing towards its apex. On the surface of the mesenchymal dental papilla, several rows of densely located cells are formed - preodontoblasts, which later give rise to cells with basophilic cytoplasm - odontoblasts (dentin-forming cells). First they form at the top of the dental papilla, later - on its lateral surfaces. The layer of odontoblasts is adjacent to the inner dental epithelium (enameloblasts), separated from it by a thin basement membrane.

By the end of the 3rd month of intrauterine development, due to the proliferation of mesenchyme, the tooth germs separate from the dental plate, it loses contact with the epithelium of the oral cavity and is partially resorbed. Only the deep sections of the dental plates, which give rise to the rudiments of permanent teeth, are preserved and grow.

Histogenesis of the tooth.

By the end of the 4th month of embryogenesis, the period of differentiation of tooth germs is replaced by an intensive period of histogenesis, during which dentin, enamel, pulp and cement of the tooth are formed, and during embryogenesis the formation and formation of the crowns of milk teeth occur, and their roots are formed after the birth of the child.

Dentinogenesis.

The first dental tissue to form is dentin. Odontoblasts play an active role in this process. The nuclei of odontoblasts are oval in shape and are located in those sections of cells that are directed towards the center of the dental papilla.

During the process of dentinogenesis, proteins and acidic mucopolysaccharides are synthesized in the cytoplasm of odontoblasts, which are later removed outside the odontoblasts into the intercellular space (using the lamellar complex or another way). In the intercellular space, as a result of enzymatic processes, thin long argyrophilic fibrillar structures - precollagen fibers - are formed. This is how uncalcified dentin-predentin is formed. They find themselves immured in predentine peripheral parts odontoblasts, which gradually lengthen, turning into dentinal processes (Toms fibers).

Precollagen fibers of predentin have a mainly radial direction. Later they turn into collagen fibers. When the predentin layer reaches a thickness of 40-80 microns, it is pushed to the periphery by new masses of dentin, in which collagen fibers lose their original orientation and are located less orderly. These are tangential fibers that do not go through the precollagen stage, but immediately appear as collagen.

The thin peripheral layer of dentin, containing radial fibers, is called mantle dentin, and the powerful internal section of dentin with a predominantly tangential arrangement of fibers is called juxtapulpar dentin. As new masses of dentin are deposited, the processes of odontoblasts elongate, so that the bodies of these cells are not included in the dentin, but are always located on the periphery of the dental papilla or dental pulp.

Odontoblasts not only form predentin, but also actively participate in the process of its mineralization. Calcification of dentin begins in the 5th month of embryonic development.

A characteristic feature of dentin is the globular nature of its calcification. Mineral salts in the main substance of dentin are deposited in the form of hydroxyapatite crystals, which, merging with each other, are arranged so that the calcified areas of dentin take on a spherical shape. Between these dentinal balls there may remain areas of uncalcified dentin - the so-called interglobular spaces or interglobular dentin. During life, areas of non-calcified interglobular dentin are usually preserved in the area of ​​the tooth crown near the enamel and in the root near the cementum border. Dentin formation always precedes enamelogenesis and is a necessary condition for the formation of enamel.

Enamelogenesis.

After a narrow layer of predentin forms at the top of the papilla, enamel begins to develop. Enamel is formed during secretory activity internal cells epithelial dental organ - enameloblasts. This process is preceded by some restructuring of the epithelial dental organ. His outside surface forms numerous depressions into which the mesenchyme of the dental sac with blood vessels grows. Apparently, these vessels were separated from their previous source - the vessels of the dental papilla. This leads to a change in the physiological polarity of enameloblasts: the cell nucleus and the lamellar complex change places. Now the basal (nucleus-containing) part of the cell faces the pulp of the dental organ, and the apex with the lamellar complex is adjacent to the predentin. Such enameloblasts are ready to form enamel. A sign of the beginning of the functioning of enameloblasts is the disappearance of glycogen from the cytoplasm of these cells.

Pulp development.

The source of dental pulp development is the mesenchyme of the dental papilla. Blood vessels grow into the base of the dental papilla already in the early stages of development of the tooth germ. Almost simultaneously (starting from the 9-10th week of embryonic development), nerve fibers begin to grow into the base of the dental papilla. Later, a hemocapillary plexus and nerve terminal branches are formed there.

The process of histogenesis of the tissue elements of the dental papilla begins at its apex and gradually spreads to the base. Under the layer of odontoblasts, which acquire an elongated, pear-shaped shape, a layer of small stellate cells forms, forming the subodontoblastic layer of the pulp. Mesenchymal cells of the central parts of the dental papilla become larger and differentiate into fibroblasts, macrophages and adventitial cells. Precollagen and collagen fibers, as well as interfibrillar substance, accumulate between them. Thus, the mesenchyme of the central parts of the papilla is transformed into loose connective tissue tooth pulp.

Development of tooth roots and cementum.

The development of the tooth root occurs in the postembryonic period and begins shortly before its eruption. After the tooth crown is formed, the epithelial dental organ is largely reduced, turning into several layers of flat cells that tightly adhere to the enamel and separate it from the surrounding mesenchyme. Soon they form a kind of epithelial diaphragm. This diaphragm subsequently grows into the underlying mesenchyme in the form of sleeves, the number of sleeves being equal to the number of roots of the developing tooth. Single-rooted teeth have one such sleeve, multi-rooted teeth have two or three.

(These sleeves are also called Hertwig's epithelial root sheaths.)

Mesenchymal cells adjacent to the sleeve from the inside transform into odontoblasts, forming root dentin. From the central part of this area of ​​mesenchyme the root pulp is formed.

When the epithelial sleeve disintegrates, the mesenchymal cells of the dental sac come into contact with the root dentin and transform into cementoblasts, which deposit acellular cement consisting of collagen fibers and interfibrillar substance on the surface of the root dentin. Later, cellular cement is formed, while cementoblasts become immured in the substance they form, turning into cementocytes. From the outer part of the mesenchyme of the dental sac, the periodontium develops, connecting the root cement with bundles of collagen fibers to the bone wall of the dental alveolus. They become sources of nutrition for enameloblasts, since predentin separated them from their previous source - the vessels of the dental papilla. This leads to a change in the physiological polarity of enameloblasts: the cell nucleus and the lamellar complex change places. Now the basal (nucleus-containing) part of the cell faces the pulp of the dental organ, and the apex with the lamellar complex is adjacent to the predentin. Such enameloblasts are ready to form enamel. A sign of the beginning of the functioning of enameloblasts is the disappearance of glycogen from the cytoplasm of these cells.

The process of formation of enamel prisms occurs as follows. Initially apical, i.e. Facing the dentin, the area of ​​enameloblasts narrows somewhat, taking on the appearance of a process. The anameloblasts then secrete components of the organic enamel matrix - thin, intertwined fibrillar structures.

In this case, periods of enameloblast activity are replaced by periods of rest. As a result, Retzius lines appear in the enamel, intersecting the enamel prisms at an angle. These lines correspond to periods of decreased activity of enameloblasts; subsequently, a smaller amount of mineral substances is deposited here. At the end of enamelogenesis, enameloblasts are reduced. Their remains form the enamel cuticle on the surface of the crown.

After the formation of the organic base of the enamel, its calcification occurs. It starts from the dentin-enamel junction and spreads to the surface of the enamel, is rhythmic in nature, as a result of which transverse irregularity appears in the enamel prisms, and first this occurs in the area of ​​​​the apex of the future cutting edge of the crown, and then the process spreads to its lateral sections. Enamel calcification occurs especially intensely after the enamel reaches its final thickness. It ends after teething.

Eruption of baby teeth in children.

Teething usually begins around six months; On average, by the age of one year, a baby has 8 incisors, and the eruption of all 20 baby teeth should be completed by 2.5 - 3 years. However, the timing of teething can vary greatly - they depend on heredity and the child’s nutrition. Therefore, the possible dates and order of teething given below are very approximate:

First lower incisors - 6-9 months.

First lower incisors - 7-10 months.

Second (lateral) upper incisors - 9-12 months.

Second (lateral) lower incisors - 9-12 months.

First upper molars - 12-18 months.

First lower molars - 13-19 months.

Upper canines - 16-20 months.

Lower canines - 17-22 months.

Second lower molars - 20-23 months.

Second upper molars - 24-26 months.

There was a time when it was believed that late teething was due to rickets, but this is not true! Numerous studies in this area show that delayed teething is characteristic of many normally developing babies. Often baby teeth are located asymmetrically. Incorrect placement of baby teeth is not considered a disease! This kind of dental disorder has every right to exist until the complete closure of the dentition, that is, until the appearance of the first 16 teeth. Then, as a result of chewing food, the baby teeth rub in and fall into place.

Changing baby teeth.

The replacement of baby teeth with permanent teeth begins in children at approximately five and a half years of age. Sometimes it happens a little earlier or later. The child’s maxillofacial apparatus is preparing for the replacement of baby teeth. You may notice that the spaces between baby teeth have become larger - this means that the child’s jaw is growing, because more space is needed for permanent teeth. If the gaps do not increase, permanent teeth may begin to grow crooked, so be sure to take your baby to the doctor.

The process of replacing baby teeth with permanent ones is interesting and not quite complicated. Some time before a baby tooth falls out, its root gradually dissolves and the tooth begins to become loose. As the root of a baby tooth is reabsorbed, it becomes more and more unstable until it falls out. Simultaneously with resorption, the permanent tooth slowly grows. Sometimes baby teeth fall out on their own; often children loosen them and pull them out on their own. The root of the new tooth is not yet fully formed. This will take at least two to three years.

In order for the roots of permanent teeth to form strong, and for the health of the teeth themselves, a sufficient amount of calcium should be introduced into the child’s diet.

The timing of teeth change is very individual, but the sequence of this process is always the same. The first permanent teeth you will find in your baby's mouth are molars - the sixth teeth in a row, if you count from the middle of the jaw. The place for these teeth will appear when the jaw grows, and the appearance of sixth molars is not associated with the loss of baby teeth.

Next, the replacement of baby teeth with permanent ones occurs according to the same scenario in which baby teeth appeared. The incisors begin to wobble and change - first two on the upper and lower jaws, and then two more. After this, the premolars are replaced - the teeth that are located behind the fangs. The replacement of the first premolars occurs between the ages of nine and eleven years, then the second premolars must change until the age of twelve. Until the age of thirteen, the canines are replaced, followed by the second molars at the age of fourteen (they also grow by empty places formed as a result of jaw growth). The last to appear are the third molars, the so-called wisdom teeth. This happens after fifteen years. By the way, an increasing number of young people never get these teeth. In fact, they are no longer needed modern people, and nature solves this issue.

Usually, replacing baby teeth with permanent ones does not require any intervention from dentists. It happens quite painlessly. But there are cases when the permanent tooth is already visible, but the milk tooth is not even loose. This situation threatens the child with the fact that the permanent tooth will grow crooked and will subsequently have to be fitted with braces to straighten it. Therefore, if you notice anything like this in your baby, go to the dentist immediately. The milk tooth will be removed, and then the process will proceed as expected.

The formation of the most important systems of the child’s body occurs in the early stages of pregnancy, when the woman does not even suspect she is pregnant. The unfavorable factors of this period, one way or another, leave their mark on the development of the baby, including teeth. Due to the increasing number of cases of dental diseases that develop even before teeth erupt, the intrauterine formation and development of a baby’s teeth is of great interest.

Laying and formation of tooth germs

In the development of a child’s teeth, three stages or periods can be distinguished, which may be different from each other.

First The period is directly the laying and formation of tooth germs.

Second stage – differentiation of tooth germs, at this stage there is a “distribution of roles” between the tissues of the child’s teeth.

Third, most a long period– formation of dental tissues and their complete “maturation”, i.e. mineralization. This period is the most crucial, since if the mother’s condition is unfavorable, or pregnancy complications occur, the child develops various dental diseases of the teeth, and not only.

It's no secret that before erupting, teeth develop in the thickness of the jaw from the corresponding rudiments. Already at 6–7 weeks of pregnancy, when the woman has just learned about her pregnancy and begins to get used to her new status, the embryo already begins to thicken epithelial cells in the oral fissure, which gradually grows, it is in this thickening that flask-shaped growths appear - the enamel organ. As the name suggests, these are the future milk teeth; there are 5 of them on each child’s jaw, for a total of 20.

Do not be surprised, in fact, when a child is born, there are 4 jaws in the oral cavity - 2 upper and 2 lower. Only after a period of time do the two processes of the jaw fuse with each other, and a single jaw bone is formed. At approximately 10 weeks of intrauterine development of the fetus, the enamel organ begins to change; cells of other tissue begin to grow into the cells of the enamel organ, due to which the outlines of the future crown of the baby tooth appear.

With aggressive influence, the process of laying and formation of the rudiments of milk teeth may be disrupted, which may result in the absence of one of the teeth, or even a group of teeth.

Differentiation of tooth germs

This is a very important period, since changes occur both in the rudiments themselves and in the surrounding tissues. The fetal body is not a constant substance in terms of growth; throughout intrauterine development, active growth and differentiation of new cells, tissues and organs occur. At the same time, the period is quite short.

Perhaps the most important stage in this period is the separation of the tooth germs from the connection with the epithelial plate. Thus, the tooth germs become isolated and begin to mineralize and develop. If this gap is disrupted, the connection or attachment of tissues to each other is maintained, tumor processes can subsequently form.

During this period, which ends by the 16th week of pregnancy, the fetus may develop malformations and developmental anomalies. maxillofacial area, as a rule, which can be diagnosed already in the first three months of pregnancy. Most often, intrauterine anomalies are represented by a cleft upper lip and the sky. Which are formed precisely as a result of non-fusion of the jaw bones.

By the end of the second month of pregnancy, the embryo is practically formed, and the resulting defects and anomalies are less significant and are mainly a consequence of insufficient growth and development.

Maturation of tooth tissues

This period begins by the 4th month of intrauterine development of the embryo; it is during this period that dental tissues appear - enamel, underlying dentin and dental pulp. Initially, dentin is formed - this is the tissue that lies under the enamel. Dentin is an acellular tissue that has the shape of microscopic tubes filled with liquid. As dentin forms, enamel begins to form at the top - the hardest, and at the same time the most fragile tissue. human body. Development begins with a small area at the site of the future cutting edge or tubercle of the tooth, since it is in this place that the enamel will be much thicker, and gradually the enamel covers the entire crown of the future baby tooth. The main feature of baby teeth is a thin layer of enamel compared to permanent teeth. This feature is due to intrauterine development.

Already at the 5th month of pregnancy, the crowns of the anterior group of teeth are fully formed, and at the 7th month of pregnancy the crowns of the chewing group of teeth are formed. Until the moment of birth and teething, enamel and dentin continue to develop, accumulating in their composition the necessary microelements that are obtained from the mother’s body.

The formation of permanent teeth occurs in the 5th month of pregnancy; it is this period of pregnancy that is considered indicative of the dental health of the unborn baby. Negative influences on the baby, can affect the condition of not only milk, but also permanent ones. This effect can be expressed in the absence of one of the tooth buds, underdevelopment of tooth enamel, or its intrauterine damage. It is for these reasons that every pregnant woman needs to take care of her condition and regularly visit the doctor and follow all recommendations, especially in critical cases.

Timing of tooth mineralization

Knowing the timing of tooth mineralization, and comparing them with the negative effects during pregnancy, you can predict in advance certain dental diseases of the child, and take timely measures to treat and eliminate them. IN Lately Almost every 4 children in the oral cavity have teeth with underdeveloped enamel (enamel hypoplasia). It is difficult for parents to diagnose the disease, since the disease is quickly complicated by caries, which leads to early tooth loss. But, if you take the necessary measures in time, your baby’s teeth can be saved.

The beginning of mineralization of baby teeth, namely the anterior group, occurs at 17–20 weeks of pregnancy, and in the presence of provoking factors, one can even assume a group of teeth that will be subject to changes. Fangs and chewing teeth begin to mineralize from approximately 7 to 7.5 months of intrauterine development and continues throughout the first year of the baby’s life.

Mineralization of permanent teeth begins later, the anterior group of teeth begins its mineralization in the first six months of a child’s life, and the development of permanent teeth will no longer be influenced by the state of the mother’s health, but by the state of health, including the nutrition, of the baby himself. Mineralization of permanent chewing teeth begins from the age of 1.5 years and continues almost until the very moment of teething.

Aggressive factors

The formation and mineralization of primary teeth can be affected by various factors, but most importantly, in different periods of development. Negative Impact in the prenatal period, on early stages pregnancy, provokes the formation birth defects and developmental anomalies. Negative factors in the prenatal period include maternal gynecological pathology in the form of early toxicosis, chronic inflammatory diseases appendages, anemia of pregnant women, due to which the baby does not receive enough nutrients, vitamins and minerals, etc. They also have an influence infectious diseases, especially in the early stages of pregnancy - up to 12 weeks. Recently, vegetarianism has become fashionable, which is very harmful for the body of a pregnant woman and for the development of the child. A pregnant woman's diet should be complete and balanced! Don't forget about bad habits mothers during pregnancy - alcohol and smoking.

The influence on permanent teeth is most often exerted by factors that acted after the birth of the baby. This group includes malnutrition of a child - a lack of certain minerals, vitamins, etc. Mineralization of teeth begins from the cutting edge or tubercle of the tooth, and by the location of the affected enamel it is possible to diagnose at what period the pathological effect on the tooth tissue occurred, and vice versa.

Diseases can affect the condition of permanent teeth endocrine system, disorders of phosphorus-calcium metabolism, for example rickets. A deficiency or, conversely, an excess of certain minerals also has an effect.