Home Coated tongue Transitional fold of the oral cavity. Valve zone

Coated tongue

Transitional fold of the oral cavity. Valve zone

THEORY OF BUFFER ZONES

The study of the morphology of the tissues of the prosthetic bed and their reactions allowed E.I. Gavrilov to create a theory of buffer zones, which includes the following provisions:

1. The pliability of the mucous membrane of the prosthetic bed is explained by the ability of the vessels to change the volume of the bloodstream.

2. Buffer zones on upper jaw located between the base of the alveolar process and the middle zone corresponding to the palatal suture. These buffer zones project onto the dense vascular fields of the hard palate.

3. Thanks to a dense network of anastomoses between the vessels of the mucous membrane of the hard palate and nose vascular bed The prosthetic bed can quickly change its volume under the influence of the prosthesis, acting as if it were a hydraulic shock absorber. 4. The base of a complete removable denture, regardless of the functional impression technique, makes microexcursions under the influence of a pulse wave.

5. The provision on buffer zones allows us to reveal the mechanism for distributing the chewing pressure of the prosthesis between the alveolar process and the hard palate.

6. Taking into account the shock-absorbing properties of the mucous membrane of the buffer zones, the advantage of a compression impression over an impression without pressure has been proven.

7. The pathogenesis of functional and structural changes in the tissues of the prosthetic bed is also based on the vascular factor, i.e. disruption of the blood supply to the mucous membrane of the prosthetic bed as a result of side effect prosthesis (Fig. 17).

Rice. 17, Scheme of buffer zones (according to Gavrilov)

The compliance of the mucous membrane lining the prosthetic bed is measured using point compliance, which occurs when pressing on the mucous membrane with a thin rod of the device.

Depending on the general condition man and his constitution by professor Kalinina 4 were allocated type of mucous membranes:

1. Dense mucous membrane, which distributes chewing pressure well. As a rule, such a mucous membrane is observed in almost healthy people normosthenic physique, regardless of age. Alveolar process atrophy is moderate.

2. Thin mucous membrane, which occurs, as a rule, in asthenics with varying degrees atrophy of the alveolar processes. Occurs in older people with significant or complete atrophy alveolar processes.

3. Loose, pliable mucous membrane. Occurs in hypersthenics, in patients with general somatic diseases ( diabetes, cardiovascular diseases, etc.).

4. Mobile mucous membrane. Occurs in patients with periodontal diseases, observed with atrophy of the alveolar process and underlying bone as a result high blood pressure removable denture, i.e. in patients who have previously been fitted with removable dentures with pressure on the mucous membrane.

There are mobile and immobile mucous membranes. Mobile mucous membrane covers the cheeks, lips, floor of the mouth. It has a loose submucosal layer of connective tissue and easily folds. When the surrounding muscles contract, this mucous membrane is displaced. Its degree of mobility varies widely (from large to insignificant).

motionless the mucous membrane is devoid of a submucosal layer and lies on the periosteum, separated from it by a thin layer of fibrous connective tissue. Its typical locations are the alveolar processes, the area of the sagittal suture and the palatine ridge. Only under the pressure of the prosthesis is the compliance of the immobile mucous membrane towards the bone revealed. This compliance is determined by the presence of vessels in the thickness of the connecting layer.

The transitional fold is the fornix, which is formed between the mobile and immobile mucous membrane. On the upper jaw, a transitional fold is formed during the transition of the mucous membrane from the vestibular surface of the alveolar process to the upper lip and cheek, and in distal section- into the mucous membrane of the pterygomaxillary fold. On the lower jaw, on the vestibular side, it is located at the place of transition of the mucous membrane of the alveolar part to the lower lip, cheek, and on the lingual side - at the place of transition of the mucous membrane of the alveolar part to the floor of the oral cavity.

The neutral zone is located on the border of the transitional fold and the fixed mucous membrane (Fig. 18)

Rice. 18. Scheme of the location of the fixed mucous membrane (a), neutral zone (b) and transitional fold (c)

QUESTION 14 The concept of “prosthetic bed”, “prosthetic field”

The prosthetic bed is all the tissues and organs of the oral cavity that have direct contact with the prosthesis.

The prosthetic field is all tissues, organs and systems of the body that have direct and indirect contact with the prosthesis. This is a broader concept that includes the concept of a prosthetic bed. For partial removable dentures, the prosthetic bed is:

The mucous membrane of the hard palate, alveolar part, as well as the cheeks, lips and tongue, which have direct contact with the prosthesis constantly or sometimes.

Abutment teeth

Chewing surface antagonist teeth. For fixed dentures (inlays, crowns), the bed is: The wound surface of the crown; Walls of the cavity for the inlay; The mucous membrane of the gingival pocket; Chewing surface of antagonist teeth. The prosthetic field, in addition to the above, are: 1. the mucous membrane of the gastrointestinal tract, since the work of the gastrointestinal tract depends on the quality of food processing in the oral cavity, that is, the better the food is processed, the less the load on the gastrointestinal tract and vice versa;

2. temporomandibular joint and masticatory muscles;

3. the patient’s psyche, since the prosthesis has an effect on the psyche.

QUESTION 15 Facial muscles, their functions

Facial muscles, starting on the surface of the bone or from the underlying fascia and ending in the skin, are capable, when contracted, of causing expressive movements of the facial skin (facial expressions) and reflecting the state of mind (joy, sadness, fear). They are also involved in articulate speech and the act of chewing!

Majority facial muscles concentrated around the mouth and palpebral fissure. Their muscle bundles have a circular or radial course. The circular muscles act as sphincters, and the radially located muscles act as dilators. Human facial muscles due to the high differentiation of the central nervous system, in particular With the existence of a second signaling system, the most perfect. The participation of facial muscles in the act of chewing is to capture food and hold it in the mouth while chewing. These muscles play a special role in the act of sucking when taking liquid food.

Highest value V orthopedic dentistry have muscles surrounding the opening of the mouth. In a child, they affect the growth of the jaws and the formation of the bite, and in an adult, they change the facial expression with partial or complete loss of teeth. Knowledge of the functions of these muscles helps to correctly plan treatment, for example, using myogymnastics, or design prostheses taking into account facial expressions. This muscle group includes:

1) orbicularis oris muscle (orbicularis oris);

2) the muscle that lowers the angle of the mouth (t.

3) muscle that lowers the lower lip (m.

4) mental muscle (t. teshanz);

5) buccal muscle (t. buccal muscle);

6) muscle that lifts the upper lip (t.

7) zygomatic minor muscle (t.

8) zygomaticus major muscle (t. g!§otap "siz ta]og);

9) muscle that lifts the angle of the mouth (t.

10) muscle of laughter (i.e. drowning).

Materials for filmed prints, their classification, indications for application and properties. Medical-technical

requirements for sending materials

At our department, we consider all materials from the perspective of three groups: 1. Basic or structural materials. 1, Auxiliary materials, 3. Impression or impression materials.

Classification

It is very difficult to classify impression materials. You can select

the following groups:

1) impression materials that harden in the oral cavity (zincoxy-

eugenol masses, gypsum);

2) impression materials that acquire elasticity after polymerization (alganate, silicone, thiokol materials),

3) thermoplastic masses, which, like the masses of the first group, harden in the oral cavity. Distinctive property them is that they become plastic when heated (wall, thermomass MST-2: 3, stomoplast, orthocor, dentofol, xantigen, etc.). As these materials cool, they become hard, exhibiting reversibility.

Classification by I.M. Oksman (according to physical condition material after hardening):

Crystallizing materials (gypsum, Repin, Dentol)

2. Thermoplastic (Stene, Acrodent, Orthocor, Stomoplast, Dentafol)

3. Elastic:

e Alginate (Stomalgic)

« Silicone (Sielast 03, 05, 21, 22, 69) (Elastic).

* Thiokol (Tiodent)

Indications to the use of gzttisk materials

1, for obtaining impressions in the manufacture of removable dentures with partial loss of teeth and complete absence teeth.

2, for obtaining impressions in the manufacture of supported clasp

Prosthetics

3. .to obtain impressions in the presence of convergence and divergence of teeth.

4. to obtain impressions in the manufacture of fixed dentures:

a) crowns

b) pin teeth

c) tabs

d) bridges various designs.

6. in the manufacture of splints and prosthetic splints for orthopedic treatment

periodontal disease.

7. in the manufacture of complex maxillofacial prostheses, obturators.

8. for relining and correcting removable dentures in a laboratory manner.

9. for making two-layer bases (with soft lining)

10. when repairing removable dentures

Currently, the industry produces textile masses of various chemical compositions and properties. Each of them has its positive and negative qualities allowing its use in certain cases. It should be said that there is no universal mass suitable for all types of impressions. Therefore, the doctor must have a large assortment of impression materials at his disposal in order to choose the one that best suits the tasks.

THEORY OF BUFFER ZONES

The study of the morphology of the tissues of the prosthetic bed and their reactions allowed E.I. Gavrilov to create a theory of buffer zones, which includes the following provisions:

1. The pliability of the mucous membrane of the prosthetic bed is explained by the ability of the vessels to change the volume of the bloodstream.

2. Buffer zones on the upper jaw are located between the base of the alveolar process and the middle zone corresponding to the palatal suture. These buffer zones project onto the dense vascular fields of the hard palate.

3. Thanks to the dense network of anastomoses between the vessels of the mucous membrane of the hard palate and the nose, the vascular bed of the prosthetic bed can quickly change its volume under the influence of the prosthesis, being, as it were, a hydraulic shock absorber. 4. The base of a complete removable denture, regardless of the functional impression technique, makes microexcursions under the influence of a pulse wave.

5. The provision on buffer zones allows us to reveal the mechanism for distributing the chewing pressure of the prosthesis between the alveolar process and the hard palate.

6. Taking into account the shock-absorbing properties of the mucous membrane of the buffer zones, the advantage of a compression impression over an impression without pressure has been proven.

Rice. 17, Scheme of buffer zones (according to Gavrilov)

The compliance of the mucous membrane lining the prosthetic bed is measured using point compliance, which occurs when pressing on the mucous membrane with a thin rod of the device.

Depending on the general condition of a person and his constitution, the professor Kalinina 4 were allocated type of mucous membranes:

1. Dense mucous membrane, which distributes chewing pressure well. As a rule, such a mucous membrane is observed in practically healthy people of normosthenic physique, regardless of age. Alveolar process atrophy is moderate.

2. Thin mucous membrane, which occurs, as a rule, in asthenics with varying degrees of atrophy of the alveolar processes. Occurs in older people with significant or complete atrophy of the alveolar processes.

3. Loose, pliable mucous membrane. It occurs in hypersthenics and in patients with general somatic diseases (diabetes mellitus, cardiovascular diseases, etc.).

4. Mobile mucous membrane. Occurs in patients with periodontal diseases, observed with atrophy of the alveolar process and underlying bone as a result of increased pressure of the removable denture, i.e. in patients who have previously been fitted with removable dentures with pressure on the mucous membrane.

The transitional fold is the fornix, which is formed between the mobile and immobile mucous membrane. On the upper jaw, a transitional fold is formed when the mucous membrane passes from the vestibular surface of the alveolar process to the upper lip and cheek, and in the distal part - into the mucous membrane of the pterygomaxillary fold. On the lower jaw, on the vestibular side, it is located at the place of transition of the mucous membrane of the alveolar part to the lower lip, cheek, and on the lingual side - at the place of transition of the mucous membrane of the alveolar part to the floor of the oral cavity.

The neutral zone is located on the border of the transitional fold and the fixed mucous membrane (Fig. 18)

Rice. 18. Scheme of the location of the fixed mucous membrane (a), neutral zone (b) and transitional fold (c)

QUESTION 14 The concept of “prosthetic bed”, “prosthetic field”

The prosthetic bed is all the tissues and organs of the oral cavity that have direct contact with the prosthesis.

The mucous membrane of the hard palate, alveolar part, as well as the cheeks, lips and tongue, which have direct contact with the prosthesis constantly or sometimes.

Abutment teeth

Chewing surface of antagonist teeth. For fixed dentures (inlays, crowns), the bed is: The wound surface of the crown; Walls of the cavity for the inlay; The mucous membrane of the gingival pocket; Chewing surface of antagonist teeth. The prosthetic field, in addition to the above, are: 1. the mucous membrane of the gastrointestinal tract, since the work of the gastrointestinal tract depends on the quality of food processing in the oral cavity, that is, the better the food is processed, the less the load on the gastrointestinal tract and vice versa;

2. temporomandibular joint and masticatory muscles;

3. the patient’s psyche, since the prosthesis has an effect on the psyche.

QUESTION 15 Facial muscles, their functions

Most of the facial muscles are concentrated around the mouth and palpebral fissure. Their muscle bundles have a circular or radial course. The circular muscles act as sphincters, and the radially located muscles act as dilators. Human facial muscles due to the high differentiation of the central nervous system, in particular With the existence of a second signaling system are the most advanced. The participation of facial muscles in the act of chewing is to capture food and hold it in the mouth while chewing. These muscles play a special role in the act of sucking when taking liquid food.

The muscles surrounding the opening of the mouth are of greatest importance in orthopedic dentistry. In a child, they affect the growth of the jaws and the formation of the bite, and in an adult, they change the facial expression with partial or complete loss of teeth. Knowledge of the functions of these muscles helps to correctly plan treatment, for example, using myogymnastics, or design prostheses taking into account facial expressions. This muscle group includes:

1) orbicularis oris muscle (orbicularis oris);

2) the muscle that lowers the angle of the mouth (t.

3) muscle that lowers the lower lip (m.

4) mental muscle (t. teshanz);

5) buccal muscle (t. buccal muscle);

6) muscle that lifts the upper lip (t.

7) zygomatic minor muscle (t.

8) zygomaticus major muscle (t. g!§otap "siz ta]og);

9) muscle that lifts the angle of the mouth (t.

10) muscle of laughter (i.e. drowning).

Materials for filmed prints, their classification, indications for application and properties. Medical-technical

requirements for sending materials

At our department, we consider all materials from the perspective of three groups: 1. Basic or structural materials. 1, Auxiliary materials, 3. Impression or impression materials.

Classification

It is very difficult to classify impression materials. You can select

the following groups:

1) impression materials that harden in the oral cavity (zincoxy-

eugenol masses, gypsum);

2) impression materials that acquire elasticity after polymerization (alganate, silicone, thiokol materials),

3) thermoplastic masses, which, like the masses of the first group, harden in the oral cavity. Their distinctive property is that they become plastic when heated (wall, thermomass MST-2: 3, Stomoplast, Orthocor, Dentofol, Xantigen, etc.). As these materials cool, they become hard, exhibiting reversibility.

Classification by I.M. Oksman (according to the physical state of the material after hardening):

Crystallizing materials (gypsum, Repin, Dentol)

2. Thermoplastic (Stene, Acrodent, Orthocor, Stomoplast, Dentafol)

3. Elastic:

e Alginate (Stomalgic)

« Silicone (Sielast 03, 05, 21, 22, 69) (Elastic).

* Thiokol (Tiodent)

Indications to the use of gzttisk materials

1, for obtaining impressions in the manufacture of removable dentures with partial loss of teeth and complete absence of teeth.

2, for obtaining impressions in the manufacture of supported clasp

Prosthetics

3. .to obtain impressions in the presence of convergence and divergence of teeth.

4. to obtain impressions in the manufacture of fixed dentures:

a) crowns

b) pin teeth

c) tabs

d) bridges of various designs.

6. in the manufacture of splints and prosthetic splints for orthopedic treatment

periodontal disease.

7. in the manufacture of complex maxillofacial prostheses, obturators.

8. for relining and correcting removable dentures in a laboratory manner.

9. for making two-layer bases (with soft lining)

10. when repairing removable dentures

Currently, the industry produces textile masses of various chemical compositions and properties. Each of them has its own positive and negative qualities, allowing it to be used in certain cases. It should be said that there is no universal mass suitable for all types of impressions. Therefore, the doctor must have a large assortment of impression materials at his disposal in order to choose the one that best suits the tasks.

Source: infopedia.su

EMBRYOLOGY AND HISTOLOGY OF THE ORAL CAVITY AND TEETH

Structure of the oral cavity

Oral cavity. The oral fissure is limited by the upper and lower lips, which pass from the sides to the corners of the mouth. In the red border of the lips, external and internal surfaces are distinguished. Epithelium outer surface The lips have a stratum corneum, which, due to the content of eleidin in the cells, is relatively transparent. The outer surface of the red border, without a sharp border, turns into the inner one. In the anterior section of the lower lip along the closure line they open excretory ducts mucous glands (10-12), located deep in the submucosal layer (rice.1) .

Rice. 1 Lip structure

(rice.2) In the peripheral part of the outer surface of the lips, mainly in the area of the corners of the mouth, numerous glands are sometimes visible in the form of small yellowish nodules, the excretory ducts of which open on the surface of the epithelium. On the inner surface of the lips, along the midline, frenulums are attached, passing onto the alveolar process of the upper and alveolar part of the lower jaw. The thickness of the lips is made up of subcutaneous fat and the orbicularis oris muscle.

Rice. 2 Vestibule of the oral cavity

The part of the mucous membrane that covers the alveolar process of the upper jaw and the alveolar part of the lower jaw and covers the teeth and the areas of the necks of the teeth is called the gum, which, due to the absence of the submucosal layer, is immovably fused with the periosteum. At the base of the alveolar process of the upper jaw and the alveolar part of the lower jaw, the mucous membrane is mobile. The area of the gum mucosa between the movable and fixed parts is called the transitional fold. The marginal part of the gum, filling the spaces between the teeth, forms interdental papillae. The gums are covered with multilayered squamous epithelium, which in the most injured areas has a stratum corneum. No glands were found in the gums (rice.3).

1-upper lip; 2-lower lip;

3-bridle upper lip;

4-frenulum of the lower lip;

5-vestibule of the oral cavity;

6-transition fold;

7-dentition row of the upper jaw;

8-dentition of the lower jaw;

9-gum;

10-interdental gingival papilla;

11-hard palate; 12-palatal ridge;

13-soft palate; 14-palatal uvula;

15-pharynx;

16-palatine fossa;

17-palatoglossal arch;

18-velopharyngeal arch;

19-palatine tonsil;

20-pterygomaxillary fold;

21-pterygomaxillary groove;

22 retromolar space;

23-dorsum of tongue; 24-apex of tongue;

25-lead ducts of the mucous glands of the lower lip;

26-rudimentary (sebaceous) glands of the lower lip. Rice. 3 Oral cavity

Cheeks.

In the thickness of the cheek there is adipose tissue and bundles of buccal muscle. In the submucosal layer of the cheeks there is a large number of mucous and mixed glands, which are located mainly along the line of closure of the teeth. In the posterior part of the cheeks, under the layer of epithelium, numerous small glands are sometimes visible (Fordyce's area). Rice. 4 Area of the inner surface of the cheek

(Fig. 4)

On the inner surface of the cheeks, with the mouth open, in the area of the crown of the second molar of the upper jaw, an elevation of the mucous membrane is projected in the form of a papilla, at the top of which or under it the excretory duct of the parotid salivary gland opens.

The space bounded on one side by the cheeks and on the other by the alveolar processes and teeth is called the vestibule of the oral cavity. In the posterior region, the pterygomaxillary fold separates the oral cavity from the pharynx.

Solid sky

The mucous membrane of the gums and hard palate is motionless, since it does not have a submucosal layer.

In the posterolateral areas of the hard palate, in the submucosal layer there is a large accumulation of adipose and lymphoid tissue. The mucous membrane of the hard palate is covered with epithelium, which tends to become keratinized.

At the border with the soft palate, on the sides of the palatine suture, there are often symmetrical slit-like depressions (palatine fossae), into which the excretory ducts of the mucous glands open (rice. 5).

Rice. 5 Sky area

Soft sky. It is a muscular plate covered with a mucous membrane. The surface of the soft palate facing the nasopharynx is lined with multirow ciliated epithelium. The protrusion of the soft palate in the midline is called the uvula (palatine). On the sides of the soft palate there are two folds - the palatine lingual and the velopharyngeal, between which there is an accumulation of lymphoid tissue - the pharyngeal tonsil.

The submucosal layer of the soft palate contains a large number of mucous and mixed glands (Fig. 6).

Rice. 6 Throat area

The floor of the oral cavity is occupied by the tongue. In the sublingual region, the mucous membrane forms a series of folds. In the anterior section along the midline there is a fold running from the alveolar process to the lower surface of the tongue (lingual frenulum). On the sides of the frenulum there are small elevations, at the top of which the excretory ducts of the submandibular and sublingual salivary glands open (Fig. 7).

Language. It is a muscular organ covered with a mucous membrane. There is a posterior, wider section (root of the tongue), middle part (body of the tongue) and tip (apex of the tongue). The mucous membrane of the tongue has a rough, villous surface in which papillae lie: filiform, mushroom-shaped, leaf-shaped and surrounded by a ridge.

Filiform papillae evenly distributed over the entire back of the tongue. The surface epithelial cells of these papillae become partially keratinized, which gives the tongue a whitish tint.

Fungiform papillae have the appearance of red dots, located mainly in the area of the apex of the tongue; they have a narrow base and a wider top. The epithelium covering them does not keratinize and contains a large number of taste buds.

Leaf-shaped papillae located in the posterolateral parts of the tongue in the form of 3 - 8 transverse folds, separated by narrow grooves. The epithelium of the foliate papillae contains taste buds.

Vital papillae (papillae surrounded by a shaft) are located on the border of the root and body of the tongue in the form of a Roman numeral V, contain a large number of taste buds, and the excretory ducts of the protein glands open into the epithelium covering them. Behind the papillae, surrounded by a shaft, and the blind opening of the tongue located here in the midline, the mucous membrane has tuberosity due to the lymphoid tissue of which it consists lingual tonsil, located in the submucosal layer (Fig. 8).

Rice. 8 Language

On the lower surface of the tongue on the sides of the frenulum there are symmetrical thin fringed folds, as well as a clearly contoured pattern of blood vessels. In the thickness of the muscle tissue of the tip of the tongue there are paired anterior glands, the excretory ducts of which open with pinholes. The lateral glands are located on the lower lateral surface of the tongue in front of the leaf-shaped papillae. (Fig. 9).

Rice. 9 Language(side view)

The structure of the oral mucosa. The oral mucosa consists of three layers: the epithelium, the mucous membrane itself, and the submucosal layer.

Epithelium. The oral mucosa is lined with stratified squamous epithelium, the thickness of which is 200-500 microns. It consists of several layers of cells of different shapes, closely connected to each other by intercellular bridges; these bridges contain tonofibrils, which, fastening the cells together, like a zipper, determine the mechanical strength and elasticity of the epithelial layer.

Based on the shape of the cells and their relationship to dyes in the epithelium, several layers are distinguished: basal, subulate, granular, horny.

Areas of the epithelium of the oral mucosa that are subject to the greatest mechanical stress (hard palate, gums, dorsum of the tongue, lips) show signs of keratinization.

A layer of its own mucous membrane. This layer consists of dense connective tissue, permeated with collagen and elastic fibers, and forms projections towards the epithelium (connective tissue papillae), in which capillaries pass and nerve receptors are embedded.

Without a clear boundary, it passes into the submucosal layer, consisting of looser connective tissue. In some areas of the oral cavity (tongue, gums, solid sky) the submucosal layer is absent, and the mucous membrane is directly fused with the intermuscular connective tissue or periosteum and is relatively motionless.

TOOTH DEVELOPMENT.

There are three periods in the development of teeth:

laying and formation of tooth germs;

differentiation of tooth germs;

histogenesis of dental tissues.

Eruption of the crown baby tooth.

Baby teeth erupt at 6–7 months of a child’s life. By the time a tooth erupts, its crown is fully developed. The development of the root and its final formation occur after the eruption of the crown. For temporary teeth this takes 1.5-2 years, for permanent teeth – 3-4 years.

In the light of modern ideas, teething is caused by many external and internal factors and is closely dependent on the general condition of the child.

Immediately before eruption, a small protrusion of the mucous membrane (mound) forms at the apex of the alveolar process in the corresponding place of this process.

Subsequently, the epithelium of the tooth germ comes into contact with the mucous membrane of the alveolar process, which becomes thinner and breaks through at the top of the tubercles or the cutting edge of the erupting tooth. It is believed that the epithelium of the future gum fuses with the epithelium of the dental organ and, after tooth eruption, remains on the surface of its crown in the form of a thin structureless shell - the enamel cuticle.

After the crown has erupted in the neck of the tooth, the gingival epithelium fuses with the enamel cuticle, forming an epithelial attachment. The slit-like depression between the crown of the tooth and the gum is called the physiological periodontal groove.

The eruption of primary teeth occurs at certain times and in strict sequence, mainly in corresponding pairs, namely:

	central incisors - at the age of 6 - 8 months (Fig. 11);

	lateral incisors - 8 -12 months (Fig. 12);

	canines erupt at 16-20 months of age (Fig. 13);

	first molars erupt between 14 and 16 months of age second molars erupt between 20 and 30 months of age (Fig. 14).

	From the age of 5 years, the roots of the central and 6th incisors begin to dissolve in children. (Fig. 15).

During the teething period permanent tooth The alveolar bone tissue separating the root of the temporary tooth gradually dissolves. The so-called resorbing organ, which consists of young connective tissue with a large number of multinucleated giant cells (osteoclasts), as well as lymphocytes, takes an active part in the resorption process. Then the gradual resorption of the baby tooth root begins. Root resorption occurs asymmetrically in the form of lacunae, niches, primarily in areas of contact between the crown of a permanent tooth and the root of a temporary tooth.

The roots of incisors and canines are mostly absorbed from the lingual surface, molars - from the interroot surface. At the same time, in the upper temporary molars the buccal roots are absorbed faster, in the lower ones - the posterior (distal) root. It is assumed that the pulp of the baby tooth also takes an active part in the resorption of the root, which by this time turns into granulation tissue.

By the time the permanent tooth erupts, the root of the temporary tooth almost completely disappears, and its crown loses support and is, as it were, pushed out by the permanent tooth.

After the crown of a baby tooth falls out, as a rule, it is already possible to detect the tubercles or cutting edge of the corresponding permanent tooth in the dental alveolus.

Eruption of the crown of a permanent tooth.

This process is considered complete only after the crown is advanced into the oral cavity, which is accompanied by the formation of a physiological periodontal groove.

The timing and sequence of eruption of permanent teeth are as follows:

	central incisors - at the age of 7 – 8 years (Fig. 16);

	lateral incisors - 8 - 9 years (Fig. 17);

	fangs erupt at the age of 10 – 13 years the first premolars erupt at the age of 9–10 years second premolars erupt at the age of 11–12 years (Fig. 18);

	The first molars erupt at the age of 5 - 6 years second molars erupt at the age of 12 - 13 years, third molars - at 18 - 25 years (Fig. 19).

Teeth eruption of the lower jaw, both temporary and permanent dentition somewhat advances the eruption of the corresponding teeth in the upper jaw.

Periodontium. Periodontal tissue is the tissue immediately surrounding the teeth on all sides. It includes bone tissue alveoli, periosteum, periodontal ligament, gingival sulcus and gum. The alveoli consist of cancellous bone, which is bounded by lamellae of compact bone and contains blood vessels And Bone marrow. The periosteum is represented by dense connective tissue attached to the outer surface of the alveoli. The teeth are fixed in the alveoli by the periodontal ligament, which is attached to the cementum of the tooth and to the periosteum. The periodontal ligament covers the root of the tooth and reaches the base of the gingival sulcus. The gingival sulcus is lined from the inside with a thin epithelium (dental gingival epithelium), which serves as a barrier that prevents the penetration of microorganisms into the periodontal gap. Normally, the depth of the gingival sulcus does not exceed 3 mm. Bacteria inhabiting this groove can cause an inflammatory process and disrupt the integrity of the epithelium. When the depth of the gingival sulcus increases (more than 3 mm), for example as a result of repeated episodes of inflammation or insufficient oral care, a periodontal pocket forms. Although the main factor causing periodontal damage is dental plaque, which contains numerous bacteria, anomalies in the location of the teeth, malocclusions, and bad habits, treatment with certain drugs, abnormalities of the attachment of the frenulum of the lips and tongue.

Alveolar mucosa and frenulum.

Alveolar mucosa, or the mobile part of the gum, borders the apical edge of the periodontium. Its mobility is explained by the fact that it is not connected to the periosteum of the alveolar process of the jaw. The alveolar mucosa contains many vessels, which gives it a pinkish-red, red or bright red color. Upon careful examination, you can notice small arteries and capillaries in it. Through these vessels they enter nutrients, oxygen and performing protective function leukocytes. The alveolar mucous membrane in the posterior part of the alveolar arch passes to the cheeks, and in the anterior part to the lips.

Bridles represent elastic connective tissue cords connecting muscles to the alveolar mucosa. The frenulum can be clearly seen if the lip is pulled back. 6 frenulums are described. The frenulum of the upper lip is located in the midline between the upper medial incisors 4-7 mm above the border of the interdental space. The frenulum of the lower lip is located in the midline between the lower medial incisors under the alveolar mucosa. The upper and lower buccal frenulums are located under the alveolar mucosa at the level of the first premolars. Despite the fact that the frenulum, being attached for 3 mm at the level of the enamel-cementum border, does not perform a supporting function in relation to the periodontium, they can pull back the periodontal tissue, contributing to gum recession.

Transitional fold of the gums.

Transitional gingival fold- the boundary between the alveolar mucosa (the mobile part of the gum) and the fixed part of the gum. It is located on the buccal and labial surface of the mucous membrane of the alveolar process and has a curved shape, copying its curvature. It can be easily seen due to the differences in the degree of vascularization of both parts of the gum: the alveolar mucosa is usually red, the fixed part of the gum is pink.

The fixed part of the gum and the gingival margin.

The fixed part of the gums and the gingival margin directly adjacent to the tooth. They form outer wall gingival sulcus. The fixed part of the gum is located between the alveolar mucosa (the moving part of the gum) and the gingival margin and has a width of 2 to 7 mm. The fixed part of the gum is covered with epithelium with pronounced signs of keratinization, has pink color, a slightly convex granular surface resembling orange peel. It is fused with the underlying periosteum and is therefore immobile. On the stationary part of the gum you can see vertical grooves or narrow depressions corresponding to the space between the roots of the teeth. They are called interdental grooves.

Gingival edge rounded and covers the neck of the tooth in the form of a gingival collar. It is also pink in color and covered with keratinizing epithelium. Unlike the fixed part of the gum, the gingival margin is not connected to the periosteum and has a smooth surface. This gives it mobility and makes it easy to insert a periodontal probe into the gingival sulcus to determine its depth. The border between the fixed part of the gum and the gingival margin is called the gingival groove.

Gingival edge forms triangular elevations that fill part of the interdental spaces and are called interdental, or gingival, papillae. The base of these papillae are located near the fixed part of the gum, and the apex is in the proximal part of the interdental spaces. The papillae have a buccal and lingual surface. Normally, the interdental papillae are pointed, pink in color and almost do not move when palpated with a probe. At inflammatory processes and other diseases (for example, gingivitis), a change occurs in the color, configuration and consistency of the gingival margin and interdental papillae, which become red, painful, swollen and softened. Between the buccal and lingual surfaces on the interdental papillae there is a saddle-shaped depression.

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