Gums - structure and pathologies. The structure and main functions of the human gums - anatomy and histology Transitional fold

In this article we want to tell you about periodontal disease.

So what will you learn:

Main concepts (nowhere without them). What is gum, periodontium, gingival epithelium, gingival sulcus, periodontal ligament, tooth root cementum, alveolar bone.
What are the types of periodontal diseases?
And why do they arise?

Ready? Then let's go!

Periodontal tissue

The definitions we give are absolutely scientific and generally accepted. At least tell me during the exam. But they are also absolutely incomprehensible (Unless, of course, you are a dentist, or a 2nd year dental student). Therefore, we will add our comments to the scientific definitions.

Periodontium

- a complex of tissues surrounding the tooth and holding it in the alveolus, having a common origin and function. I'll explain. Periodontal tissue is the tissue that holds the tooth in the jaw. If you remove at least one of them, the tooth will immediately fall out.

The periodontium unites four different, but closely related tissues: the gums, periodontal ligament, alveolar bone and dental cementum. They are connected by one chain by common origin and function. Gums – protects the periodontium. The other three hold the tooth.

Gum

- this is the mucous membrane that covers the alveolar process of the upper jaw and the alveolar part of the lower jaw and covers the teeth in the cervical area and extends to the transitional fold.

Well, here everything was immediately clear. The gum is a mucous membrane. Look in the mirror, everything around your teeth is gums. If you feel the gum, for example, on the lower jaw - it is dense tissue below the teeth, soft tissue begins even lower - this is no longer gums. The place where soft tissue transitions into hard tissue is called a transitional fold.

Gingival edge

- This is the edge of the gum that lies on the necks of the teeth. If you look in the mirror, you will see the gum line just above the tooth.

Dentists divide gums into two types:

Free gum(Or marginal) is gum that is not connected to bone or tooth. It is mobile and is located in the area of the necks of the teeth. It also fills gaps between teeth.

And again to the mirror - between the teeth there are triangular shaped gum protrusions. They are called gingival papillae.

Attached gum- motionless gum. It is firmly connected to the cementum of the root and to the alveolar bone. (In the mirror, this is almost the entire gum except for the papillae and gingival margin).

Gingival epithelium

Epithelium is the tissue that is the top layer of the mucous membrane. And the gingival epithelium covers the gum. It is divided into three types:

Oral epithelium - covers the largest surface of the gums. It starts from the transitional fold and ends at the gingival margin. Absolutely all of the gum that you see in the mirror is the oral epithelium.
Sulcular epithelium – lines the gingival sulcus (see below). This epithelium is permeable. Bacterial toxins and harmful substances easily enter the blood through it. It also secretes gingival fluid (also see below).
Attachmental epithelium is the epithelium that attaches to the tooth. If this epithelium is torn away from the tooth, a gum pocket is formed (This is no longer the norm).

Gingival sulcus

- This is a narrow gap between the tooth and the gum. It is located between the attachment epithelium (see above) and the gingival margin. Normally, the depth of the furrow is up to 3 mm. If more, this is a gum pocket.

Gingival fluid

The sulcus epithelium secretes a fluid called gingival fluid. (In fact, this is blood plasma). It interferes with placing a filling in the cervical area. It also contains immunoglobulins and leukocytes, and protects the gums from bacteria. And from this liquid subgingival tartar is formed. But it’s still a necessary thing.

Dental alveolus

- a hole in the alveolar bone in which the root of the tooth is located. If you had a tooth removed today, you can see it in the mirror. If not, here's a photo.

Periodontal ligament

It is located in the space between the root of the tooth and the wall of the dental alveolus. It binds them together and holds the tooth in the bone. The ligament contains collagen fibers - its main component. They perform the main function of the periodontium.

Also, cells (fibroblasts, osteoblasts, osteoclasts, cementoblasts, etc.) that synthesize collagen, build (and destroy - this is the norm!) tooth root and alveolar bone, regulate periodontal physiology. Vessels – nourish the periodontium and tooth root. And nerves are periodontal sensors. For example, they prevent you from clenching your teeth too hard. You can try it – it’s unpleasant.

Alveolar bone

It's just a bone. The same as the others. The only thing is that teeth grow in it. In special holes - dental alveoli. The rest is an ordinary bone.

This concludes the story about anatomy. You can remove the mirror. Next, we'll talk about what you shouldn't have in your mouth.

Classification of periodontal diseases.

As Carl Linnaeus said, knowledge begins with classification. And the most popular classification in the world is the International Classification of Diseases (ICD-10)

By 05.3 chronic periodontitis;
By 05.2 acute periodontitis:
other.
desquamative;
ulcerative;
hyperplastic;
simple marginal;
By 05.1 chronic gingivitis:
K.05.0 acute gingivitis.
simple;
difficult;
other.
By 05.4 periodontal disease.
By 05.5 others.
By 05.6 unspecified.
By 06.0 gum recession.

As you can see from the classification, the main periodontal diseases are gingivitis, periodontitis and gum recession. Now we will briefly tell you what kind of animals these are.

Periodontal diseases

Gingivitis- This is inflammation of the gums. It appears when the gums are affected by some unfavorable factors. Most often, this is plaque (but there are others). If the dentogingival attachment is not disturbed (I talked about it above), then this is still gingivitis. If it's broken, that's it. Periodontitis has arrived.

Periodontitis is an inflammation of periodontal tissue. Periodontitis can be caused by many factors, more on them below. This disease manifests itself as destruction of the periodontal ligament and jaw bone. As a result, teeth become loose and fall out.

Gum recession- This is the movement of the gums towards the root of the tooth. As a result, the root becomes exposed.

So what causes these diseases? What factors contribute to this?

Plaque. Everyone knows that bacteria live in dental plaque. They feed on leftover food and produce acid, which causes tooth decay. But this is not important, what is important is that the toxins of these bacteria cause gingivitis. It has been proven that proper brushing of teeth 2 times a day significantly reduces bleeding and inflammation of the gums.
Medical influence. These could be low-quality fillings or crowns that irritate the gums. There may be medications such as steroids, immunomodulators.
Overloading of the tooth, for any reason. If a neighboring tooth has been removed. Or the bridge was made incorrectly.
Lack of vitamin C. A rare cause today, but in the past thousands of people died from scurvy. And one of its symptoms is periodontitis.
Systemic diseases of the body, such as diabetes, diseases of the heart, liver, endocrine system.
Bad habits. In addition to the lack of habit of brushing your teeth, smoking significantly affects the periodontium. Let's not talk about the dangers of smoking now. Let's just say that nicotine constricts the blood vessels of the gums and reduces blood flow to the periodontium. Reduces its natural resistance to bacteria - accelerates the development of periodontitis.

So. If you notice signs of illness in your mouth, I have two news for you. First, you are not unique. Second, it won’t go away on its own, you need to see a doctor. And watch out for harmful factors, they can sneak up unnoticed.

If a doctor suddenly reads this article, well, don’t judge strictly. But everything is written here correctly, don’t let me lie. Read our more medical articles about gingivitis, periodontitis and the treatment of these diseases.

And rate the article, write your wishes in the comments. Good luck to all!

Periodontal tooth updated: December 22, 2016 by: Alexey Vasilevsky

The edge of the prosthesis is immersed in the mucous membrane and forms a closing valve. When moving, the edge of the prosthesis may move, but if at the same time its contact with the mucous membrane of the vestibular slope continues, the closing valve is preserved.
The mucous membrane that takes part in the creation of the marginal valve is called the valve zone. This term is used to refer to the contact of the edge of the prosthesis with the underlying tissues.
The mucous membrane located (1.5 mm) higher on the lower jaw or below the transitional fold of the upper jaw can take part in the formation of the closing valve.

Transitional fold.

Passively mobile mucous membrane - moves when forcibly displaced by an instrument, but does not move during muscle function (transitional fold area).

To form a valve zone and ensure fixation of the prosthesis. In this regard, a highly pliable mucous membrane is most favorable. A stubborn mucosa, on the contrary, worsens the quality of fixation of prostheses. To absorb chewing pressure coming from a removable denture. The best susceptibility to chewing pressure has a mucous membrane that has good and more or less uniform, that is, equal compliance over the entire area of the prosthetic bed. The mucous membrane, which is not very pliable, but who knows if it is unevenly pliable, leads to the concentration of chewing pressure in the areas of least pliability; it easily ulcerates under the base of the prosthesis, which is accompanied by severe pain.

Many people believe that the gums are the part of the jaw to which the teeth are attached. In reality this is not the case. The gum is the mucous membrane located around the teeth, lining the alveolar processes of the jaws. In this article we will talk about the structure and main functions of the gum, what the groove is, the marginal part, and what it consists of as a whole.

Anatomy and functions of human gums

Before talking about a person’s gums, it is necessary to understand what the tissues that hold the tooth in the jaw are. In anatomy, they are designated as periodontium, being a connective material formed by thick bundles of collagen fibers. The threads lie in a tortuous direction, due to which the tooth is firmly fixed in a suspended state. These fibers, on the one hand, cling to the cement of the tooth root, and on the other, to the periosteum of the alveolar process (the area of the jaw on which the bone organs are located).

The mucous membrane, called the gum, covers the periodontium, protecting the connective tissue from external influences, damage and infection. It withstands strong chewing pressure, helping to form a bolus of food in the mouth that travels from the oral cavity to the stomach.

The edge of the gum runs along the alveolar process: it is characterized by a brighter color of the mucous membrane, since it is covered by non-keratinizing epithelium, through which blood vessels are visible. As for the gums, its tissue is light pink in color, since it is covered with keratinizing epithelium.

The surface of the gum is uneven and resembles an orange peel due to small retractions in the area of its attachment to the alveolar part. With inflammation, these irregularities disappear, causing the mucous membrane to become smooth and shiny.

Names of gum parts

The structure of the gums implies the presence of:

All these parts can be clearly seen in the mirror. The alveolar area, the largest of them, is especially clearly visible, but dental instruments will help to examine the groove.

Marginal part or free edge

The edge of the gum located at the base of the teeth is called the free or marginal part. Marginal tissue is not connected to the bone or crown, is mobile, is located around the necks of the teeth (the part of the tooth between the root and the crown), and fills the spaces between them in the form of triangular projections (gingival papillae). The marginal gingiva has a width of 0.5 to 1.5 mm.

Alveolar

Attached, or alveal, is the immobile part of the gum, which is firmly connected to the alveolar bone and root cement. It is clearly visible in the mirror - it is almost the entire gum, with the exception of the free edge and gingival papillae. The width of the alveolar area ranges from 1 to 9 mm, and it itself is covered with stratified keratinizing epithelium.

If the attached epithelium is torn away from the tooth, a gum pocket is formed (the norm is no more than 3 mm). Its appearance is not normal, since it is filled with food debris, which is a good breeding ground for the development of pathogenic bacteria. In addition, large gum pockets can lead to periodontal disease and the loss of a perfectly healthy tooth.

Sulcular or sulcus

The sulcus in the mouth is the depression between the edge of the gum and the tooth. Its anatomy implies a depth of 0.5-0.7 mm, less often up to 2 mm. If the gingival groove is more than 3 mm, they speak of a gingival pocket. The bottom of the furrow is formed by epithelial cells, which quickly desquamate.

During inflammation, serum exudate (gingival fluid) penetrates from the vessels into the gingival sulcus, which is a breeding ground for various microorganisms and contributes to the formation of tartar. From here, bacterial toxins easily penetrate into the blood. Moreover, due to the presence of immunoglobulins in the composition, the exudate is characterized by an antimicrobial effect.

Transitional fold

The place where soft tissue meets hard tissue is called the transitional fold. This is where the gum ends. This is the only area where a loose submucosal layer is present, resulting in a soft transition to the mobile mucous membrane of the lips and cheeks.

The transitional fold is located on the border between the keratinizing epithelium of the attached gum and the non-keratinizing epithelium of the alveolar process. The transitional fold epithelium renews itself six times faster than other parts.

Histological structure of gingival tissues

Speaking about the gum, one cannot fail to mention its histological structure, in other words, the structure of the mucous membrane. Schematically, it consists of two layers - squamous keratinizing epithelium and lamina mucosa.

The histology of the epithelium consists of the following layers:

Three layers of the epithelium, with the exception of the stratum corneum, have nuclei. They contain cytoplasm with substances on which the ability of the gums to withstand loads and its elasticity depend.

The keratinizing epithelium of the marginal area of the gum allows the lining tissue to be resistant to temperature changes and the pressure to which the mucous membrane is exposed when chewing food. In the area of the gingival sulcus, the epithelium loses the stratum corneum.

The lamina of the mucous membrane contains a reticular (deep) and papillary (superficial) layer. The first includes many fibers and is characterized by high density. The papillary layer is characterized by loose connective tissue, and its papillae, where nerves and blood vessels are located, abut the epithelium, providing its nutrition and the ability of the gums to cope with their functions.

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.

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 a side effect of the 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 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.

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 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 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 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

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!

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) zygomaticus 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.

private histology and embryology of oral cavity organs
for dental students

General morphofunctional characteristics of the digestive apparatus. The structure of the wall of the digestive canal.

The digestive system includes the digestive tube (GI, or gastrointestinal tract) and its associated major glands: the salivary glands, the liver, and the pancreas. A huge number of small digestive glands are part of the wall of the digestive tube.

During the digestion process, mechanical and chemical processing of food and subsequent absorption of the products of its breakdown occur.

The digestive tube in any of its sections consists of four membranes:

internal - mucous membrane (tunica mucosa),
submucosa (tela submucosa),
muscle membrane (tunica muscularis) and
the outer membrane, which is represented by either the serous membrane (tunica serosa) or the adventitial membrane (tunica adventitia).

Development of the digestive apparatus. Embryonic primary intestinal tube. Oral and anal bays. Development and tissue sources of the intestinal membranes in its various parts.

The epithelial lining of the digestive tube and glands develop from endoderm and ectoderm.

From the endoderm, a single-layer prismatic epithelium of the mucous membrane of the stomach, small and most of the large intestine, as well as the glandular parenchyma of the liver and pancreas are formed. From the ectoderm of the oral and anal bays of the embryo, multilayered squamous epithelium of the oral cavity, salivary glands and caudal rectum is formed. Mesenchyme is the source of the development of connective tissue and blood vessels, as well as the smooth muscles of the digestive organs. From the mesoderm - the visceral layer of the splanchnotome - a single-layer squamous epithelium (mesothelium) of the outer serous membrane (visceral layer of the peritoneum) develops.

Starting from the 20th day of intrauterine development, the intestinal endoderm in the body of the embryo coils into a tube, forming the primary gut. The primary gut is closed in its anterior and posterior sections and is located anterior to the notochord. The primary gut gives rise to the epithelium and glands of the digestive tube (except for the oral cavity and anal region). The remaining layers of the digestive tube are formed from the splanchopleura - the medial plate of the unsegmented part of the mesoderm adjacent to the primary gut.

At the 3rd week of embryogenesis, an ectodermal recess is formed at the cephalic end of the embryo - the oral bay, and at the caudal end - the anal (anal) bay. The oral bay deepens towards the head end of the primary intestine. The membrane between the oral bay and the primary gut (pharyngeal membrane) breaks through in the 4th week of embryogenesis. As a result, the oral bay receives communication with the primary gut. The anal bay is initially separated from the cavity of the primary intestine by the anal membrane, which breaks through later.

At the 4th week of intrauterine development, the ventral wall of the primary intestine forms an anterior protrusion (future trachea, bronchi, lungs). This protrusion serves as the boundary between the head (pharyngeal) intestine and the posterior trunk intestine. The trunk intestine is divided into the foregut, middle and hindgut. The epithelium of the oral cavity and salivary glands are formed from the ectodermal lining of the oral bay. The pharyngeal gut gives rise to the epithelium and glands of the pharynx; the foregut - to the epithelium and glands of the esophagus and stomach, the midgut - to the epithelial cover of the cecum, ascending and transverse colon, as well as the epithelium of the liver and pancreas. The hindgut is the source of development of the epithelium and glands of the descending, sigmoid colon and rectum. The remaining structures of the walls of the digestive tube, including the visceral peritoneum, are formed from the visceropleura. The somatopleura forms the parietal peritoneum and subperitoneal tissue.

Oral cavity. Histophysiological characteristics of the mucous membrane: structural and histochemical features of its epithelium. Lip, gums, hard and soft palate.

The oral cavity (cavitas oris) is limited above by the hard and soft palate, below by the tongue and muscles of the floor of the mouth, in front and on the sides by the lips and cheeks. In front it opens with the oral fissure (rima oris), which is limited by the lips (labia). Through the pharynx (fauces) the oral cavity communicates with the pharynx.

The oral mucosa is formed by stratified squamous epithelium, located on the basement membrane, and the lamina propria, which is formed by loose fibrous connective tissue. The lamina propria of the mucous membrane passes into the submucosa without a sharp boundary. (The muscular plate of the mucous membrane, characteristic of the mucous membrane of the digestive canal, is absent in the oral cavity.) Visually, the surface of the oral mucosa is flat and smooth over a large area. The hard palate has transverse folds. In the area of the lips and cheeks there may be small yellowish elevations - Fordys spots. These are the excretory ducts of the sebaceous glands, which open onto the surface of the mucous membrane. They are a product of the secretion of ectopically located sebaceous glands, which are usually located in the skin near the hair follicles. Fordyce spots are more often found in the oral cavity of older people. They are rare in children and adolescence. On the mucous membrane of the cheek along the line of closure of the teeth (white line) there is an area of increased keratinization. There are papillae on the dorsal surface of the tongue.

In the oral cavity, 3 types of stratified epithelium can be distinguished:

1 - multilayer flat non-keratinizing;

2 - multilayer flat, keratinizing by orthokeratosis (orthos - true);

3 - multilayer flat, keratinizing by parakeratosis (para - about).

In the lip area (labia oris) there is a gradual transition of the skin located on the outer surface of the lip into the mucous membrane of the oral cavity. The transition zone is the red border of the lips.

The soft palate (palatum molle) separates the oral cavity from the pharynx. The basis of the soft palate is made up of thick bundles of striated muscle fibers and dense connective tissue. During swallowing, the soft palate is pulled upward and backward, closing the entrance to the nasopharynx.

Lips. Characteristics of the skin, transitional and mucous parts. Labial glands.

Skin section lips have the structure of skin. It is covered with stratified squamous keratinizing epithelium, there are sebaceous, sweat glands and hair. The connective tissue papillae are small. Muscle fibers are woven into the dermis, which ensures the mobility of this part of the lip.

IN intermediate department(red border) sweat glands and hair disappear, but the sebaceous glands remain. The excretory ducts of the sebaceous glands open directly on the surface of the epithelium. When the ducts are blocked, the glands become noticeable in the form of yellow-white grains visible through the epithelium. The stratified squamous keratinizing epithelium in the red border of the lips has a thin stratum corneum. The lamina propria of the mucous membrane forms numerous papillae, which are deeply embedded in the epithelium. Capillary networks come close to the surface and easily “shine through” the epithelium, which explains the red color of the lips. The red border contains a large number of nerve endings. In newborns, in the inner zone of the red border of the lips (villous zone) there are epithelial outgrowths, or “villi,” which gradually smooth out and disappear as the body grows.

Mucous department The lips are lined with a thick layer of stratified squamous non-keratinizing epithelium. The papillae in the lamina propria are few and lower than in the red border of the lips. In the submucosa there are bundles of collagen fibers that penetrate into the intermuscular layers of connective tissue (m. orbicularis oris). This prevents the possibility of wrinkles. In the submucosa there are also accumulations of fat cells and secretory end sections of the mucous and mixed salivary glands (glandulae labiales), the excretory ducts of which open into the vestibule of the oral cavity.

Cheek. Characteristics of the mandibular, maxillary and intermediate zones. Buccal glands.

The cheek (bucca) is a muscular formation covered on the outside with skin and on the inside with mucous membrane (Fig. 6). Between the skin and the cheek muscle there can be a fairly thick layer of fatty tissue, forming the cheek fat pad, which is especially well developed in children.

In the mucous membrane of the cheek, 3 zones are distinguished: upper or maxillary (zona maxillaris), lower, or mandibular (zona mandibularis), and middle, or intermediate (zona intermedia), located between them along the line of closure of the teeth.

Maxillary and mandibular the cheek zones have a structure similar to the structure of the mucous part of the lip. On the surface there is a thick layer of stratified squamous non-keratinizing epithelium. The lamina propria of the mucous membrane forms small, sparsely located papillae. The submucosa contains the salivary glands of the cheek - gl. buccalis. The salivary glands are often embedded in the muscle. The largest glands lie in the area of the molars.

Intermediate zone The buccal mucosa has some structural features. The epithelium along the line of closure of the teeth, as noted earlier, becomes keratinized through parakeratosis (white line). The lamina propria of the mucous membrane is involved in the formation of rather high papillae. There are no salivary glands, but there are sebaceous glands.

In newborns, in the intermediate zone of the buccal mucosa, epithelial “villi” are often found, similar to those in the inner zone of the red border of the lips. This feature apparently indicates that in the embryonic period the cheeks are formed due to the fusion of the edges of the upper and lower lips.

Solid sky. Features of the glandular and fatty part of the hard palate and palatal suture.

The hard palate (palatum durum) is covered with a masticatory mucous membrane. The mucous membrane is tightly fused with the periosteum, motionless, very thin in the area of the palatine suture and somewhat thicker in the posterior parts of the palate.

The structure of the submucosa varies in different parts of the hard palate. In accordance with its morphological characteristics, it is customary to distinguish 4 zones: fatty, glandular, palatal suture zone, marginal.

In the fatty zone (zona adiposa), corresponding to the anterior third of the hard palate, the submucosa contains accumulations of fat cells. In the glandular zone (zona glandularis), which occupies the posterior 2/3 of the hard palate, the end sections of the mucous palatine glands are located in the submucosa. The palatal suture zone (medial zone) is located in the form of a narrow strip along the midline of the hard palate. The marginal (lateral) zone is adjacent directly to the teeth. The palatal suture zone and the marginal zone are fibrous (zona fibroza). Despite the presence of a submucosa, the mucous membrane of the fatty and glandular zones of the hard palate is motionless. It is tightly fixed to the periosteum of the palatine bones by thick bundles of dense connective tissue. In the lamina propria of the mucous membrane of the palatine suture, accumulations of epithelial cells (“epithelial pearls”) are sometimes detected. They are formed during embryogenesis during the fusion of the palatine processes and represent the remains of the epithelium “embedded” in the underlying connective tissue.

Floor of the oral cavity. Transitional fold of lip and cheek. The structure of the frenulum of the upper and lower lips, the sublingual fold.

The mucous membrane of the floor of the mouth is limited by the gum and extends to the lower (ventral) surface of the tongue. The mucous membrane is mobile and easily folds.

The epithelium is a multilayered squamous non-keratinizing (thin layer).

The lamina propria of the mucous membrane is formed by loose connective tissue, contains a large number of blood and lymphatic vessels, and forms sparse low papillae.

Small salivary glands are located in the submucosa.

Teeth. General morphofunctional characteristics of teeth. The concept of hard and soft tissues of the tooth.

Teeth (dens) are organs that ensure the chewing of food and are important from an aesthetic point of view. They also take part in the production of speech sounds. In humans, teeth are represented in two generations: first, falling out or milk teeth are formed (20), and then permanent ones (32).

Anatomically, each tooth has a crown (corona dentis), a neck (cervix dentis) and a root (radix dentis). Inside the crown there is a pulp cavity (cavitas pulparis), which in the root area turns into canals (canalis radicis dentis). At the tops of the roots, the canals open with apical openings.

A tooth has soft and hard parts. The hard parts of the tooth are enamel, dentin, cement, and the soft parts are the pulp, which fills the pulp chamber of the crown and root canals. The periodontium connects the root of the tooth with the bony alveolus. The bulk of the tooth is dentin, which is found in the crown and root. The dentin of the crown is covered with enamel, the dentin of the root is covered with cement.

The anatomical neck is a narrow area where the enamel meets the cement, in the area of which the crown meets the root. The clinical neck is the zone of dense attachment of the gum epithelium to the tooth.

Enamel. Microscopic and ultramicroscopic structure and physical properties.

Tooth enamel (enamelum, substantia adamantia) is its hardest part. In terms of hardness, it is compared to quartz, but it is quite fragile. The content of mineral salts in enamel reaches 95-97%, the share of organic substances is 1.2%, and about 3% is water. Enamel is called tissue, although in fact it is a derivative of the epithelium, calcified by the secretion of epithelial cells - enameloblasts.

Enamel does not contain cells, blood vessels, or nerves; it is not capable of regeneration. But this is not a static tissue, since the processes of remineralization (intake of ions) and demineralization (removal of ions) occur in it. These processes depend on the pH of the oral cavity, the content of micro- and macroelements in saliva and a number of other factors. The color of the enamel depends on the thickness of its layer. If the enamel layer is thin, the tooth appears yellowish due to dentin showing through the enamel. The color of the enamel may change under certain influences. Thus, with an excessive intake of fluoride (fluorosis), white, yellow, and brown spots appear in the enamel (mottled enamel).

Enamel can be lost due to disordered eating (bulemia), excessive consumption of acidic drinks, bacterial exposure, etc. Demineralization of enamel leads to the formation of a cavity in the tooth - caries (caries - rot).

Enamel. Enamel prisms and interprismatic substance. Enamel bundles and enamel spindles. Features of calcification, metabolism and nutrition of enamel.

The main structural unit of enamel is enamel prisms (prisma enameli) - thin elongated formations passing radially through the entire thickness of the enamel (Fig. 29). The diameter of the prisms increases approximately 2 times from the dentin-enamel border to the tooth surface. Enamel prisms are collected in bundles, and along their course wavy bends (S-shaped course) are formed, reminiscent of bundles of curved rods. This structural organization of enamel is associated with a functional adaptation that prevents the formation of radial cracks under the influence of occlusal forces during chewing. Enamel prisms are formed from an organic base and associated hydroxyapatite crystals. The organic component of enamel prisms (non-collagen proteins, phosphoproteins) is a secretion product of enameloblasts. The organic matrix adsorbs minerals and this leads to the formation of crystals. Subsequently, as the enamel matures, the organic matrix is almost completely lost. Enamel tufts (fasciculus enameli) are shaped like tufts of grass. In the area of the dentino-enamel border, enamel spindles (fusus enameli) are also found - flask-shaped structures at the ends of the dentinal tubules penetrating here from the dentin. Apparently, enamel spindles play a certain role in enamel trophism. Enamel spindles, like enamel plates and enamel bundles, are classified as hypomineralized areas of enamel.

Enamel. Features of the structure of the enamel of milk and permanent teeth. Enamel-dentin and enamel-cement joints. Cuticle, pellicle and their role in metabolic processes.

Retzius lines. On longitudinal sections they are located tangentially, parallel to the tooth surface, or have the form of arches running obliquely from the enamel surface to the dentino-enamel border. On transverse sections they appear as concentric circles, similar to growth rings on tree trunks. Retzius lines are hypomineralized areas of enamel. Apparently, they are a reflection of a certain metabolic rhythm of enameloblasts during the formation of the organic enamel matrix: an active secretory period and a subsequent inactive period (resting period). The formation of Retzius lines is also associated with the periodicity of enamel calcification processes. Areas of enamel containing different amounts of minerals refract light differently. Retzius lines are most clearly expressed in the enamel of permanent teeth.

A dark stripe is noticeable in the enamel of baby teeth - the neonatal line. This strengthened line of Retzius separates prenatal enamel from postnatal enamel. Thus, the neonatal line, as it were, marks the barrier between the enamel matrix formed by enameloblasts before and after the birth of the child. The presence of a neonatal line can be considered as evidence of the high sensitivity of enameloblasts to influences on the body, in particular to birth stress.

The lines of Retzius at the points where they reach the surface of the tooth form circular grooves (grooves) with the smallest thickness. Between the grooves there are ridges about 2 microns high - perikymatia, which surround the entire circumference of the tooth. They are visually noticeable in the cervical region of permanent teeth, but are not expressed in temporary teeth.

When a tooth erupts, the enamel is covered with a cuticle (cuticula dentis), which is not a permanent, temporary formation. There are 2 layers in the cuticle:

The primary cuticle is Nasmyth's shell, which is the last secretory product of enameloblasts;

Secondary cuticle formed by the outer layer of the reduced epithelium of the enamel organ.

Subsequently, an organic film is formed on the surface of the tooth - a pellicle, covering the enamel. It appears as a result of precipitation of proteins and glycoproteins of saliva. When mechanically cleaning the enamel surface, the pellicle disappears, but after a few hours it reappears, i.e. is constantly being restored.

If the pellicle is colonized by microorganisms and desquamated epithelial cells, bacterial plaque (plaque) is formed. Microorganisms in dental plaque release organic acids that promote demineralization and destruction of enamel. When mineral substances are deposited in the dental plaque, tartar is formed, which is difficult to remove from the surface of the tooth.

Dentin, its microscopic structure and ultramicroscopic characteristics.

Dentin (dentinum) makes up the bulk of the tooth in the area of the crown, neck and root. Mature dentin is 4-5 times softer than enamel, but stronger than bone and cement. Mature dentin is a crystallized material containing 70% inorganic substances, 20% organic substances and 10% water. Calcium hydroxyapatite, which is the main inorganic component of dentin, is similar to that which is part of enamel, bone, and cement. Dentin also contains other minerals (carbonate, fluoride, etc.).

Dentin is built from calcified intercellular substance, permeated by tubules (dentinal tubules), which contain processes of odontoblasts and tissue fluid. The bodies of the cells that form dentin (odontoblasts or dentinoblasts) are located outside of it, in the peripheral layer of the pulp.

In terms of morphofunctional properties, dentin is similar to coarse-fibered bone, but differs from it in the absence of cells and greater hardness. The relatively high content of organic components and the presence of dentinal tubules make this tissue resemble a sponge. Dentin easily adsorbs some coloring substances, and can become more yellow and even brown.

Dentine. Dentinal tubules, the main substance of dentin. Dentinal fibers, radial and tangential. The importance of odontoblasts for vital dentin.

Dentinal tubules, or dentin tubules (tubulus dentini, canaliculus dentini), run radially from the pulp through the entire thickness of dentin and are located in the ground substance along with collagen fibers. The diameter of the tubes is 0.5-3 microns. At the border with enamel and cement they branch and anastomose (see Fig. 33). The tubes contain processes of odontoblasts. The wall of the tube is formed by peritubular dentin (dentinum peritubulare), which has a higher degree of mineralization. Between the dentinal tubules there is intertubular dentin (dentinum intertubulare). The inside of the tube is covered with a thin film of organic matter - the Neumann membrane, which in electron micrographs looks like a fine-grained layer.

The periodontoblastic space, located between the odontoblast process and the wall of the dentinal tubule, contains dentinal tissue fluid, similar in composition to blood plasma.

Sometimes unmyelinated nerve fibers are found in the dentinal tubules located in the peripulpal dentin. These areas are characterized by increased pain sensitivity. However, according to most researchers, the nerve fibers in the dentinal tubules are efferent.

Apparently, hydrodynamic conditions play an important role in the occurrence of pain sensitivity during the preparation of carious cavities: pressure is transmitted through the processes of odontoblasts to the nerve elements of the pulp.

The intercellular substance in dentin is represented by collagen fibers and ground substance.

Collagen fibers in the outer (cloak) dentin run radially (Korff fibers), and in the inner, peripulpal dentin - tangentially (Ebner fibers). Korff fibers are collected into cone-shaped, tapering bundles. This arrangement of bundles of collagen fibrils determines the significant strength of dentin.

Dentin, features of calcification, types of dentin: interglobular dentin, mantle and peripulpar dentin. Predentin. Secondary dentin. Dentin response to damage.

Dentin, which has undergone only the 1st phase of mineralization, is hypomineralized. Areas of such dentin located between the globules of mineralized dentin are called interglobular dentin (dentinum interglobulare). Dentinal tubules pass through interglobular dentin (the same as in globular dentin). Areas of hypomineralized interglobular dentin in the shape of irregular rhombuses are found in the crown of the tooth at the border of peripulpar and mantle dentin. In the root of the tooth, along the border with cement, interglobular dentin is located in the form of grains and forms Toms' granular layer. Predentin, located between dentin and odontoblasts, is also hypomineralized. Here the most rapid deposition of dentin occurs and the largest calcospherites are localized. In cases of dentinogenesis disorders, most often associated with a deficiency of the hormone calcitonin, an increase in the volume of interglobular dentin occurs.

The need to distinguish between dentin formed during the development of the tooth and after its eruption led to the emergence of the concepts: primary and secondary dentin. Secondary dentin (physiological, regular), formed after tooth eruption, is characterized by a slow growth rate and narrow dentinal tubules.

Cement. The structure of cement. Cellular and acellular cementum. Nutrition of cement.

Cementum is one of the mineralized tissues. The main function of cement is to participate in the formation of the supporting apparatus of the tooth. The thickness of the cement layer is minimal in the neck area and maximum at the apex of the tooth. The strength of calcified cement is slightly lower than that of dentin. Cement contains 50-60% inorganic substances (mainly calcium phosphate in the form of hydroxyapatite) and 30-40% organic substances (mainly collagen).

The structure of cement is similar to bone tissue, but unlike bone, cement is not subject to constant restructuring and does not contain blood vessels. Cement trophism is carried out due to periodontal vessels.

There are acellular (cementum noncellulare) and cellular (cementum cellulare) cement.

Acellular cementum (primary) does not contain cells and consists of calcified intercellular substance. The latter includes collagen fibers and ground substance. Cementoblasts, synthesizing the components of the intercellular substance during the formation of this type of cement, move outward, towards the periodontium, where the vessels are located. Primary cementum is slowly deposited as the tooth erupts and covers the 2/3 of the root surface closest to the neck.

Cellular cement (secondary) is formed after tooth eruption in the apical third of the root and in the area of bifurcation of the roots of multi-rooted teeth. Cellular cementum is located on top of acellular cementum or is directly adjacent to dentin. In secondary cementum, cementocytes are immured in calcified intercellular substance. The cells have a flattened shape and lie in cavities (lacunae). The structure of cementocytes is similar to osteocytes of bone tissue. In some cases, contacts can be observed between the processes of cementocytes and dentinal tubules.

Similarities and differences in the structure of dentin, cement and bone.

In their function, dentinoblasts are similar to bone osteoblasts. Alkaline phosphatase was found in dentinoblasts, which plays an active role in the processes of calcification of dental tissues, and in their processes, in addition, mucoproteins were identified.

Soft tissues of the tooth. Morphofunctional characteristics, structural features of the pulp.

Pulp. The structure of the peripheral and central layers of the pulp. Crown pulp and tooth root pulp. Reactive properties and pulp regeneration. Denticles.

Dental pulp (pulpa dentis) is a specialized loose connective tissue that fills the tooth cavity in the area of the crown and root canals.

Specific cells for pulp are odontoblasts (odontoblastus) or dentinoblasts (dentinoblastus). The bodies of odontoblasts are localized only at the periphery of the pulp, and the processes are directed into the dentin. Odontoblasts form dentin during tooth development and after tooth eruption. The most numerous cells in the pulp are fibroblasts. During inflammation (pulpitis), fibroblasts take part in the formation of a fibrous capsule surrounding the source of inflammation. Pulp macrophages are able to capture and digest dead cells, components of the intercellular substance, microorganisms, and also participate in immune reactions as antigen-presenting cells.

In the peripheral layers of the coronal pulp near the vessels there are dendritic cells with a large number of branching processes. They are close in structure to Langerhans cells of the skin and mucous membranes. It has been established that dendritic cells of the pulp absorb antigen, process it and present it to lymphocytes during the development of immune reactions. There are also various subpopulations of T lymphocytes, B lymphocytes and plasma cells.

Coronal pulp (pulpa coronalis) is a very loose connective tissue. During microscopic examination, 3 main layers are distinguished in the coronal pulp:

I - dentinoblastic, or odontoblastic (peripheral);

II - subdentinoblastic (intermediate);

III - pulp core (central). The peripheral layer is formed by the bodies of odontoblasts. A layer of odontoblasts 1-8 cells thick is adjacent to the predentin. The processes of odontoblasts are directed into the dentinal tubules. Odontoblasts remain in the adult pulp throughout life and constantly perform their dentin-forming function.

In the intermediate (subdentinoblastic) layer it is customary to distinguish two zones:

a) external, cell-poor, containing a network of nerve fibers (Rashkov’s plexus);

b) internal, rich in cells, containing connective tissue cells and blood capillaries.

The pulp nucleus is located in the center of the pulp chamber and contains fibroblasts, macrophages, lymphocytes, poorly differentiated mesenchymal cells, fairly large blood and lymphatic vessels, and bundles of nerve fibers.

The root pulp (pulpa radicularis) contains connective tissue with a large number of collagen fibers and has a much higher density than the coronal pulp. In the root pulp, the “layering” of structures is not visible, and zones are not distinguished. In the root area, trophism of the hard tissues of the tooth occurs not only through the pulp, but also through the diffusion of nutrients from the periodontium.

The structure of the dental pulp. Blood supply and innervation. The role of odontoblasts in tooth development and in the formed tooth.

Vessels and nerves penetrate the pulp through the apical and accessory foramina of the root, forming a neurovascular bundle.

Microvasculature vessels are well developed in the pulp: capillaries of various types, venules, arterioles, arteriolovenular anastomoses that perform direct shunting of blood flow.

At rest, most of the anastomoses do not function, but their activity increases sharply when the pulp is irritated. The activity of anastomoses is manifested by the periodic discharge of blood from the arterial bed into the venous bed with corresponding sharp changes in pressure in the pulp chamber. The frequency of anastomoses affects the nature of pain during pulp inflammation. An increase in the permeability of microvasculature vessels during pulpitis leads to edema. Since the volume of the pulp is limited by the walls of the pulp chamber, the edematous fluid compresses the veins and lymphatic vessels, disrupting the outflow of fluid. This leads to the development of necrosis and death of the pulp.

The pulp contains nerve plexuses and a large number of receptor nerve endings. Pulp receptors perceive irritations of any nature: pressure, temperature and chemical influences, etc. The pulp also contains effector nerve endings. Some of the nerve fibers from the pulp enter the predentin and the inner zone of the peripulpal dentin.

The bodies of odontoblasts are localized only at the periphery of the pulp, and the processes are directed into the dentin. Odontoblasts form dentin during tooth development and after tooth eruption.

Structure and morphofunctional characteristics of soft tissues of teeth.

Pulp (pulpa dentis), or dental pulp, is located in the coronal cavity of the tooth and in the root canals. It consists of loose fibrous connective tissue, in which three layers are distinguished: peripheral, intermediate and central.

The peripheral layer of the pulp consists of several rows of multi-processed pear-shaped cells - dentinoblasts, characterized by pronounced basophilia of the cytoplasm. Their length does not exceed 30 microns, width - 6 microns. The dentinoblast nucleus lies in the basal part of the cell. A long process extends from the apical surface of the dentinoblast and penetrates the dentinal tubule. It is believed that these processes of dentinoblasts are involved in the supply of mineral salts to dentin and enamel. The lateral processes of dentinoblasts are short. In their function, dentinoblasts are similar to bone osteoblasts. Alkaline phosphatase was found in dentinoblasts, which plays an active role in the processes of calcification of dental tissues, and in their processes, in addition, mucoproteins were identified. The peripheral layer of the pulp contains immature collagen fibers. They pass between the cells and continue further into the collagen fibers of dentin.

In the intermediate layer of the pulp there are immature collagen fibers and small cells, which, undergoing differentiation, replace outdated dentinoblasts.

The central layer of the pulp consists of loosely lying cells, fibers and blood vessels. Among the cellular forms of this layer, adventitial cells, macrophages and fibroblasts are distinguished. Both argyrophilic and collagen fibers are found between the cells. No elastic fibers were found in the dental pulp.

The dental pulp is of decisive importance in the nutrition and metabolism of the tooth. Removing the pulp sharply inhibits metabolic processes, disrupts the development, growth and regeneration of the tooth.

Gums. Structure and histochemical characteristics. Gum papillae. Gingival pocket, its role in the physiology of the tooth. Epithelial attachments.

The gum (gingiva) is part of the chewing mucous membrane of the oral cavity. The gums surround the teeth and border the alveolar mucosa. Visually, the gums differ from the alveolar mucous membrane in a paler, matte shade.

The mucous membrane of the gums is divided into 3 parts: attached, free and gingival interdental papillae.

The attached part of the gum is tightly fused with the periosteum of the alveolar processes of the jaws.

The free (marginal) part of the gum is adjacent to the surface of the tooth, but is separated from it by a narrow gap - the gingival groove - and does not have a strong attachment to the periosteum.

Gingival interdental papillae are triangular-shaped areas of gum that lie in the spaces between adjacent teeth.

The gingival epithelium is a multilayered squamous keratinizing epithelium. Keratization in the gums occurs through both parakeratosis (75%) and true keratosis (15%). The gingival epithelium passes into the non-keratinizing epithelium of the gingival sulcus and the attachment epithelium, which fuses with the cuticle of the tooth enamel.

In the lamina propria of the gum mucosa, loose connective tissue forms papillae that protrude deeply into the epithelium. There are a large number of blood vessels here. Dense connective tissue with thick bundles of collagen fibers forms the reticular layer of the mucous membrane. Bundles of collagen fibers attach the gingiva to the periosteum of the alveolar process (attached gingiva) and connect the gingiva to the cementum of the tooth (gingival fibers of the periodontal ligament).

The alveolar mucosa covers the alveolar processes of the jaws. It has a bright pink color, as it is lined with non-keratinizing epithelium, through which blood vessels are clearly visible. The alveolar mucosa is firmly attached to the periosteum. The lamina propria of the mucous membrane forms conical papillae of varying sizes.

The transition zone between the lining alveolar mucosa and the attached gingiva is well defined in histological preparations. (In the gum area, the epithelium is multilayered flat keratinizing, and in the alveolar mucous membrane area it is non-keratinizing.)

Supportive apparatus of teeth. Periodontium. Features of the location of fibers in different parts of the periodontium. Dental alveolus, morphofunctional characteristics. Restructuring of the dental alveoli and alveolar parts of the upper and lower jaws when the functional load changes.

The periodontium (periodontium), or pericement, is somewhat conventionally called the ligament that holds the tooth root in the bony alveolus. The periodontium consists of a large number of thick bundles of collagen fibers located in the slit-like periodontal space. The width of this space averages 0.2-0.3 mm, but can shrink (in the absence of functional load) or increase (with strong occlusal loads on the tooth).

In the spaces between the bundles of collagen fibers of dense connective tissue in the periodontium there are layers of loose connective tissue (Fig. 44). About 60% of the volume of periodontal space is occupied by bundles of collagen fibers and 40% by loose connective tissue. In the loose connective tissue, along with blood and lymphatic vessels, nerve elements, epithelial remains, or islands of Malasse (fragmentum epitheliale), can be located. The cellular composition of the periodontium includes fibroblasts (the most common cells), cementoblasts (localized at the border with cement), osteoblasts (found at the border with the alveolar bone), macrophages, mast cells, all types of leukocytes, osteoclasts. The periodontium also contains poorly differentiated cells of mesenchymal origin. They are located near blood vessels and serve as a source of renewal of some periodontal cells. The main substance of the periodontium, in which glycosaminoglycans, glycoproteins and a large amount of water are detected, is a viscous gel. Collagen fibers have a slightly wavy course, so they can elongate somewhat when stretched. Periodontal fibers are woven into the cement at one end and into the alveolar process of the bone at the other. Their terminal sections in both tissues are called perforating (Sharpey's) fibers. In the periodontal fissure, thick bundles of collagen fibers have different directions: horizontal (at the edges of the alveoli), oblique (in the lateral parts of the fissure), radial (in the area of the tooth root) and arbitrary (in the area of the root apex). Based on the location of the attachment sites and the direction of the collagen fiber bundles, the following groups are distinguished:

1) fibers of the alveolar ridge - connect the cervical surface of the tooth with the ridge of the alveolar bone;

2) horizontal fibers - located deeper than the fibers of the alveolar ridge, at the entrance to the periodontal space; pass horizontally (at right angles to the surface of the tooth root and alveolar bone), form a circular ligament together with transseptal fibers connecting adjacent teeth;

3) oblique fibers - the numerically predominant group, occupy the middle 2/3 of the periodontal space, connect the root with the alveolar bone;

4) apical fibers - diverge perpendicularly from the apical part of the root to the bottom of the alveoli;

5) interradicular fibers - in multi-rooted teeth they connect the root in the bifurcation area with the crest of the interradicular septum.

The alveolar process contains the dental alveoli (sockets).

Development of the face, oral cavity and dental system. Oral pit. Primary oral cavity. Gill apparatus, slits and arches and their derivatives.

The development of the oral cavity, associated with the formation of the face, occurs as a result of the interaction of a number of embryonic rudiments and structures. At the 3rd week of embryogenesis, at the cephalic and caudal ends of the body of the human embryo, as a result of invagination of the skin epithelium, 2 pits are formed - the oral and the cloacal. The oral fossa, or bay (stomadeum), is the rudiment of the primary oral cavity, as well as the nasal cavity. The bottom of this fossa, in contact with the endoderm of the foregut, forms an oropharyngeal membrane (pharyngeal or oral membrane), which soon breaks through, creating a communication between the cavity of the oral fossa and the cavity of the primary intestine. In the development of the oral cavity, the gill apparatus plays an important role, which consists of 4 pairs of gill pouches and the same number of gill arches and slits (V pair is a rudimentary formation).

Gill pouches are protrusions of the endoderm in the pharyngeal region of the foregut. Gill slits are invaginations of the skin ectoderm of the cervical region, growing towards the projections of the endoderm. The places where both meet are called gill membranes. In humans they do not break through. Areas of mesenchyme located between adjacent pockets and slits grow and form roller-like elevations - gill arches - on the anterior surface of the embryo's neck. The mesenchyme of the branchial arches is of dual origin: the central part of each arch consists of mesenchyme of mesodermal origin; it is surrounded by ectomesenchyme, resulting from the migration of neural crest cells. The gill arches are covered on the outside with cutaneous ectoderm, and on the inside are lined with the epithelium of the primary pharynx. Subsequently, an artery, nerve, cartilage and muscle tissue are formed in each arch. The first gill arch - the mandibular - is the largest, from which the rudiments of the upper and lower jaws are formed. From the second arch - the hyoid - the hyoid bone is formed. The third arch is involved in the formation of the thyroid cartilage. Subsequently, the first branchial cleft turns into the external auditory canal. From the first pair of gill pouches the cavities of the middle ear and eustachian tube arise. The second pair of gill pouches is involved in the formation of the palatine tonsils. From the III and IV pairs of gill pouches, the anlage of the parathyroid glands and thymus is formed. In the area of the ventral sections of the first 3 gill arches, the rudiments of the tongue and thyroid gland appear.

Gill apparatus, its development and derivatives. Oral cavity formation. Development of the jaw apparatus. Anomalies and variations.

In the development of the oral cavity, the gill apparatus plays an important role, which consists of 4 pairs of gill pouches and the same number of gill arches and slits (V pair is a rudimentary formation).

Gill pouches are protrusions of the endoderm in the pharyngeal region of the foregut. Gill slits are invaginations of the skin ectoderm of the cervical region, growing towards the projections of the endoderm. The places where both meet are called gill membranes. In humans they do not break through. Areas of mesenchyme located between adjacent pockets and slits grow and form roller-like elevations - gill arches - on the anterior surface of the embryo's neck. The mesenchyme of the branchial arches has a dual origin: the central part of each arch consists of mesenchyme of mesodermal origin; it is surrounded by ectomesenchyme, resulting from the migration of neural crest cells. The gill arches are covered on the outside with cutaneous ectoderm, and on the inside are lined with the epithelium of the primary pharynx. Subsequently, an artery, nerve, cartilage and muscle tissue are formed in each arch. The first gill arch - the mandibular - is the largest, from which the rudiments of the upper and lower jaws are formed. From the second arch - the hyoid - the hyoid bone is formed. The third arch is involved in the formation of the thyroid cartilage. Subsequently, the first branchial cleft turns into the external auditory canal. From the first pair of gill pouches the cavities of the middle ear and eustachian tube arise. The second pair of gill pouches is involved in the formation of the palatine tonsils. From the III and IV pairs of gill pouches, the anlage of the parathyroid glands and thymus is formed. In the area of the ventral sections of the first 3 gill arches, the rudiments of the tongue and thyroid gland appear.

Disruption of morphogenetic processes during embryogenesis can lead to various developmental defects. The most common of them is the formation of lateral clefts of the upper lip. (They are located along the line of fusion of the maxillary process with the medial nasal process.) Median clefts of the upper lip and upper jaw are much less common. (They are located in the place where the embryo’s medial nasal processes fuse with each other.) When the palatine processes are underdeveloped, their edges do not come close and do not fuse with each other. In these cases, the child develops a congenital malformation - a cleft of the hard and soft palate.

Development of the jaws and separation of the oral cavity.

With the development of the oral cavity, the first branchial arch is divided into 2 parts - the maxillary and mandibular. At first, these arcs in front are not combined into a single bookmark.

At the end of the 1st - beginning of the 2nd month of embryogenesis, the entrance to the oral fossa looks like a gap limited by 5 ridges, or processes. The unpaired frontal process (processus frontalis) is located above; on the sides the opening is limited by the paired maxillary processes (processus maxillaris). The lower edge of the oral opening is limited by paired mandibular processes (processus mandibulares), which, fused along the midline into a single arcuate mandibular process, form the anlage for the lower jaw.

Simultaneously with the formation of the primary choanae, the rapid growth of the maxillary processes begins, they move closer to each other and to the medial nasal processes. As a result of these processes, the anlage of the upper jaw and upper lip is formed.

The mandibular processes also fuse together along the midline and give rise to the formation of the lower jaw and lower lip.

The division of the primary oral cavity into the final oral cavity and nasal cavity is associated with the formation of lamellar projections - palatine processes - on the internal surfaces of the maxillary processes.

At the end of the 2nd month, the edges of the palatine processes grow together. In this case, most of the palate is formed. The anterior part of the palate arises when the palatine processes fuse with the anlage of the upper jaw. The septum that arises as a result of these processes represents the rudiment of the hard and soft palate. The septum separates the terminal oral cavity from the nasal cavity.

After the fusion of the palatine processes and the formation of the palate, the primary choanae no longer open into the oral cavity, but into the nasal chambers. The chambers communicate with the nasopharynx through the final definitive choanae.

Development of the dental system. Ontogenesis. Development and growth of primary teeth. Formation of the buccolabial and primary dental plate. Formation of a tooth germ. Differentiation of the tooth germ.

Tooth development (odontogenesis) is a rather long process. It is customary to distinguish several stages of odontogenesis, although there are no clear starting and ending points between these stages.

The main periods of odontogenesis are:

1) the period of formation of tooth germs (initiation period);

2) the period of formation and differentiation of tooth germs (the “cap” and “bell” stages);

3) the period of histogenesis, the formation of dental tissues (stages of apposition and maturation).