Which bones contain alveoli? Scientific review
The alveolar process is the part of the upper and lower jaws that extends from their bodies and contains teeth. There is no sharp boundary between the body of the jaw and its alveolar process. The alveolar process appears only after teeth erupt and almost completely disappears with their loss. The alveolar process is divided into two parts: the alveolar bone itself and the supporting alveolar bone.
The alveolar bone itself (alveolar wall) is a thin (0.1-0.4 mm) bone plate that surrounds the tooth root and serves as a site for attachment of periodontal fibers. It consists of lamellar bone tissue, which contains osteons, is penetrated by a large number of perforating (Sharpey's) periodontal fibers, and contains many holes through which blood and lymphatic vessels and nerves penetrate into the periodontal space.
The supporting alveolar bone includes: a) compact bone that forms the outer (buccal or labial) and inner (lingual or oral) walls of the alveolar process, also called the cortical plates of the alveolar process;
b) spongy bone, filling the spaces between the walls of the alveolar process and the alveolar bone itself.
The cortical plates of the alveolar process continue into the corresponding plates of the body of the upper and lower jaw. They are thickest in the area of the lower premolars and molars, especially on the buccal surface; in the alveolar process of the upper jaw they are much thinner than in the lower jaw (Fig. 1, 2). Their thickness is always less on the vestibular side in the area of the front teeth, in the area of molars - thinner on the lingual side. Cortical plates are formed by longitudinal plates and osteons; in the lower jaw, the surrounding plates from the body of the jaw penetrate into the cortical plates.
Rice. 1. Thickness of the walls of the alveoli of the upper jaw
Rice. 2. Thickness of the walls of the alveoli of the lower jaw
Spongy bone is formed by anastomosing trabeculae, the distribution of which usually corresponds to the direction of forces acting on the alveolus during chewing movements (Fig. 3). The lower jaw bone has a fine-mesh structure with a predominantly horizontal direction of trabeculae. In the bone of the upper jaw there is more spongy substance, the cells are large-loop, and the bone trabeculae are located vertically (Fig. 4). Spongy bone forms interradicular and interdental septa, which contain vertical feeding canals, bearing nerves, blood and lymphatic vessels. Between the bone trabeculae there are bone marrow spaces, filled with red bone marrow in children, and yellow bone marrow in adults. In general, the bone of the alveolar processes contains 30-40% organic substances (mainly collagen) and 60-70% mineral salts and water.
Rice. 3. Structure of the spongy substance of the alveoli of the anterior (A) and lateral (B) teeth
Rice. 4. The direction of the trabeculae of the cancellous bone of the alveolar part on the transverse (A) and longitudinal (B) sections
The roots of the teeth are fixed in special recesses of the jaws - alveoli. The alveoli have 5 walls: vestibular, lingual (palatal), medial, distal and floor. The outer and inner walls of the alveoli consist of two layers of compact substance, which merge at different levels in different groups of teeth. The linear size of the alveolus is somewhat shorter than the length of the corresponding tooth, and therefore the edge of the alveolus does not reach the level of the enamel-cement junction, and the apex of the root, due to the periodontium, does not adhere tightly to the bottom of the alveolus (Fig. 5).
Rice. 5. The relationship between the gums, the apex of the interalveolar septum and the crown of the tooth:
A - central incisor; B - canine (side view)
Bone skeleton periodontal tissues are the alveolar process of the upper jaw and the alveolar part of the body of the lower jaw. The external and internal structure of the jaws has been sufficiently studied both at the macroscopic and microscopic levels.
Of particular interest are data on the structure of the bone walls of the alveoli and the ratio of spongy and compact substance. The importance of knowing the structure of the bone tissue of the alveolar walls on the vestibular and oral sides is due to the fact that none of the clinical methods can establish the normal structure of these areas and the changes occurring in them. In works devoted to periodontal diseases, they mainly describe the condition of the bone tissue in the area of the interdental septa. At the same time, based on the biomechanics of the periodontium, as well as on the basis of clinical observations, it can be argued that the vestibular and oral walls of the alveoli undergo the greatest changes. In this regard, let us consider the alveolar part of the dentofacial segments.
Alveolus has five walls: vestibular, oral, medial, distal and fundus. The free edge of the alveolar walls does not reach the enamel border, just as the root does not fit tightly to the bottom of the alveolus. Hence the difference between the parameters of the alveolus depth and the length of the tooth root: the alveolus always has larger linear dimensions than the root.
The outer and inner walls of the alveoli consist of two layers of compact bone substance, which merge at different levels in differently functionally oriented teeth. The study of layer-by-layer vertical sections of the jaws and radiographs obtained from them (Fig. 4, 1, 2, 3) makes it possible to determine the ratio of compact and spongy substance in these areas. The vestibular wall of the alveoli of the lower incisors and canines is thin and consists almost entirely of a compact substance. The spongy substance appears in the lower third of the root length. The teeth of the lower jaw have a thicker oral wall.
The thickness of the outer compact substance varies both at the level of one segment and in different segments. For example, the greatest thickness of the external compact plate is observed on the lower jaw on the vestibular side in the region of the molar-maxillary segments, the smallest in the canine-maxillary and incisor-maxillary segments.
The compact plates of the walls of the alveoli are the main abutments that perceive and transmit, together with the fibrous structure of the periodontium, the pressure acting on the tooth, especially at an angle. A. T. Busygin (1963) identified a pattern: the vestibular or lingual cortical plate of the alveolar process and, accordingly, the internal compact layer of the alveolar wall are thinner on the side of the inclination of the tooth. The greater the inclination of the tooth relative to the vertical plane, the greater the difference in thickness. This can be explained by the nature of the loads and resulting deformations. The thinner the walls of the alveoli, the higher the elastic-strength properties in these areas. As a rule, in all teeth the walls of the alveoli (vestibular and oral) become thinner towards the cervical region; After all, in this zone, the tooth root, as well as in the apical zone, makes the greatest amplitude of movements. The structure of the bone of the alveolar process depends on the functional purpose of groups of teeth, the nature of the loads on the teeth and the axis of inclination of the teeth. The inclination determines the nature of the loads and the appearance of pressure concentration zones for compression or tension in the walls of the alveoli.
Cortical plates of the alveolar process on the vestibular and lingual (palatal) sides, the internal compact plate of the alveolar wall, as well as the bottom of the alveolus, have numerous feeding holes directed towards the tooth root. It is characteristic that on the vestibular and oral walls these holes pass mainly closer to the edge of the alveoli and precisely in those areas where there is no spongy bone substance. Blood and lymphatic vessels, as well as nerve fibers, pass through them. The blood vessels of the pericementum anastomose with the vessels of the gums, bones and medullary spaces. Thanks to these holes, there is a close connection between all the tissues of the marginal periodontium, which can explain the involvement of periodontal tissues in the pathological process, regardless of the localization of the pathogenic origin - in the gums, bone tissue or periodontium. A. T. Busygin points out that the number of holes and their diameter are in accordance with the chewing load. According to his data, the holes occupy from 7 to 14% of the area of the compact plate, vestibular and oral walls of the teeth of the upper and lower jaws.
In various parts of the internal compact plate there are openings (Fig. 5) connecting the pericementum with the medullary spaces of the jaw. From our point of view, these holes, being a bed for larger vessels, help relieve pressure on them, and therefore reduce the phenomena of temporary ischemia when moving teeth under load.
The specific structure of the vestibular and oral walls of the tooth sockets, their functional significance in the perception of chewing loads, force us to focus on the clinical assessment of their condition.
The cortical plate, its thickness and preservation throughout, as well as the spongy substance of the jaws, can be clinically assessed only from the mesial and distal sides of the tooth using radiographs. In these areas, the x-ray characteristics coincide with the microstructure of the bone tissue of the jaws.
The alveolar parts of the jaws in the interdental spaces, like other walls of the alveoli, are covered with a thin compact plate (lamina dura) and have the shape of triangles or truncated pyramids. The identification of these two forms of interdental septa is very important, since in the area of chewing teeth or in the presence of primary teeth and diastemas, this is the norm for the construction of bone tissue, however, provided that the compact plate is preserved.
The cortical plate on the lower jaw is thicker than on the upper jaw. In addition, its thickness varies among individual teeth and it is always somewhat thinner towards the tops of the interdental septa. The width and clarity of the radiological image of the plate changes with age; in children it is looser. Considering the variability of thickness and the degree of shadow intensity of the cortical plate, its preservation throughout its entire length should be taken as the norm.
Structure of the bone tissue of the jaws due to the pattern of bone beams of the spongy substance intersecting in different directions. On the lower jaw the trabeculae run mostly horizontally, while on the upper jaw they run vertically. There are small-loop, medium-loop and large-loop patterns of spongy matter. In adults, the pattern of the spongy substance is mixed: in the group of frontal teeth it is small-loop, in the area of the molars it is large-loop. N.A. Rabukhina correctly believes that “the size of the cells is a purely individual feature of the structure of bone tissue and cannot serve as a guide in the diagnosis of periodontal diseases.”
There is more spongy substance in the alveolar process of the upper jaw than in the lower jaw, and it is characterized by a more finely cellular structure. The amount of spongy substance of the lower jaw increases significantly in the area of the body of the jaw. The spaces between the bars of the spongy substance are filled with bone marrow. V. Svrakov and E. Atanasova indicate that “the spongy cavities are lined with endosteum, from which bone regeneration predominantly occurs.”
Structure
The alveolar process consists of the following parts:
- outer wall - buccal or labial;
- the inner wall is lingual;
- spongy substance with dental alveoli in which the teeth are placed.
The dental alveoli are separated from each other by bony septa. In the sockets of multi-rooted teeth there are also inter-root partitions that separate the branches of the roots. They are shorter than the interdental ones and somewhat less than the length of the root.
The outer and inner surfaces of the alveolar processes consist of a compact substance and form the cortical plate of the alveolar process. The cortical plates are covered with a periosteum. On the lingual surface the cortical plate is thicker than on the buccal surface. In the region of the edges of the alveolar process, the cortical plate continues into the wall of the dental alveolus.
Development
The bone tissue of the dental alveolus and alveolar process undergoes restructuring throughout life. This is due to a change in the functional load falling on the teeth.
Function
The wall of the alveoli, located in the direction of the force, experiences pressure, and on the opposite side - tension. On the high-pressure side, bone resorption occurs, and on the traction side, new formation occurs.
Literature
Links
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See what “Alveolar process” is in other dictionaries: - (processus alveolaris, PNA, BNA, JNA) an arched bone ridge, which is a downward continuation of the body of the upper jaw; on the lower edge of the A. o. there are 8 alveoli of the teeth...
Large medical dictionary Facial bones - The upper jaw (maxilla) (Fig. 59A, 59B) is paired, participates in the formation of the orbit, oral and nasal cavities, infratemporal and pterygopalatine fossae. Uniting, both upper jaws, together with the nasal bones, limit the opening leading into the nasal cavity and... ...
Atlas of Human Anatomy- The upper jaw, maxilla, paired, is located in the upper anterior part of the facial skull. It is one of the air-bearing bones, since it contains a large cavity lined with mucous membrane, the maxillary sinus, sinus maxillaris. IN … - The upper jaw (maxilla) (Fig. 59A, 59B) is paired, participates in the formation of the orbit, oral and nasal cavities, infratemporal and pterygopalatine fossae. Uniting, both upper jaws, together with the nasal bones, limit the opening leading into the nasal cavity and... ...
JAWS- JAWS. The paired maxillary bone (maxilla) is the lightest, most fragile pneumatic bone and is firmly fused by sutures to most of the bones of the facial skeleton. Palate | its appendage is connected to the pair by means of | a special type of synarthrosis... ...
1) in animals, organs of various origins that serve to capture and crush food. Among representatives of various systematic. Ch. groups have different structures and are formed in the process of individual development from different rudiments,... ... Great Soviet Encyclopedia
Bones of the head (skull) - … - The upper jaw (maxilla) (Fig. 59A, 59B) is paired, participates in the formation of the orbit, oral and nasal cavities, infratemporal and pterygopalatine fossae. Uniting, both upper jaws, together with the nasal bones, limit the opening leading into the nasal cavity and... ...
AMMONIA- AMONGIA, Ammonium ca usticum solutum (more correctly Ammonia Cau stica soluta), Liquor Ammonii caustici, aqueous solutions of ammonia (see) of various concentrations. The official solution is 10%, spec. V. 0.959 0.960, representing... ... Great Medical Encyclopedia
1) organs for capturing and (often) grinding food in a number of invertebrates and most vertebrates. 2) Bone base cf. and lower parts of the face (upper and lower parts) in humans. Together with surrounding tissues, they provide chewing and speech. Rice. 1 … Natural science. encyclopedic Dictionary
The largest bones of the facial skull; together with the zygomatic bones, they form the bony basis of the face and determine its shape; they participate in the formation of the bone walls of the mouth, nose and eye sockets; are the most important anatomical components... ... Medical encyclopedia
BLOOD VESSELS- BLOOD VESSELS. Contents: I. Embryology................... 389 P. General anatomical sketch......... 397 Arterial system......... . 397 Venous system...... ....... 406 Table of arteries............. 411 Table of veins...... ..… … Great Medical Encyclopedia
Speaking about the anatomy of the human jaw, upper and lower, it is impossible not to touch on the subject of this article. The alveolar processes, and we will talk specifically about them, have structural features that are remarkable for study and familiarization and perform a number of important functions. Let's turn to their detailed definition, the characteristics of the components, and talk about their significance for the formation of the dentition and dental procedures.
Analysis of the concept
First, let's look at the definition. Alveolar (alveolus in this case is a cell, a hole for a tooth and its roots) processes are components of both the upper and lower jaws, whose purpose is to bear teeth. They are distinguished by their cone-shaped shape and spongy structure; height - several millimeters. It is customary to call the element of the upper jaw a process; on the bottom this formation is called the alveolar part.
The alveolar process of the jaw is:
- bone with osteons (walls of the tooth alveoli);
- supporting bone filled with spongy compact substance.
The shape of the process crest can be very diverse:
- semi-oval;
- rectangular;
- pineal;
- spinous;
- truncated;
- triangular;
- with a truncated cone, etc.
The bone tissue of both the process itself and the dental alveolar cell is rebuilt throughout human life. This development is associated with a change in the level of stress experienced by the teeth.
Structural features
The alveolar processes of the jaws consist of three elements, such as:
- buccal (labial for front teeth) outer wall;
- spongy substance with holes in which teeth are located;
- inner lingual wall.
The composition of the lingual and labial wall is a compact substance. Together they form the cortical (cortical) layer of the process with alveoli, covered with a periosteum (a film of connective tissue surrounding the bone). On the inner surface this layer is thinner than on the outer. Along the edges of the alveoli, the inner layer fuses with the outer layer, forming the so-called ridge. It is located 1-2 mm below the cemento-enamel junction of the teeth.
The alveoli themselves are separated from each other by bony partitions. Between the front teeth they are pyramidal, and between the lateral teeth they are trapezoidal. If a tooth is multi-rooted in nature, then between its branching roots there are also interradicular septa. They are somewhat shorter in length than the root and generally thinner than the interdental ones.
Alveolar bone is formed by both organic and inorganic elements; collagen has the advantage here. Its bone tissue is made up of osteocytes, osteoclasts and osteoblasts. Also, all parts of the process are penetrated by a system of tubules for the nervous and circulatory systems.
Important Features
The alveolar processes of the jaws perform few but important functions, such as:
- Fixation of the tooth, formation of the dentition.
- Changes in structure in case of tooth loss.
- In the part of the walls of the alveoli: new formation of bone tissue and its resorption (destruction, degradation, resorption).
Alveolar process of the maxilla
The alveolar is one of the four processes of the upper jaw; it continues its body downwards. It appears in the form of a curved arched bone ridge, convex forward. It contains 8 holes-alveoli for teeth and their roots. Each of them is a component of five walls: bottom, distal, medial, oral and vestibular. At the same time, their edges do not come into contact with the enamel of the tooth, and its root does not come into contact with the bottom of the alveoli. It logically turns out that the hole is much wider than the root of the tooth.
The shape and size of each alveoli depends on the tooth that is placed in it. The smallest is at the incisors, and the deepest, respectively, at the canine - 1.9 cm.
Alveolar process of the mandible
The lower jaw is an unpaired bone. She is the only cranial creature that can move. It consists of two symmetrical parts that grow together after one year of life. As in the upper jaw, the alveolar processes here are responsible for fixing the teeth. They are the first to experience pressure when chewing food, and they are the first to begin to rebuild during treatment and prosthetics. Thus, any violation of the functionality of the dentition leads to corresponding changes in the alveolar process.
In dentistry
From all of the above it follows that the placement of the dentition depends on the shape, anatomy, functions and development of the alveolar process. Although the interdental septum takes on its final appearance after teeth erupt, the process itself changes throughout a person’s life, reacting sharply to dental problems. For example, the alveolar ridge decreases when there is no load on it - after tooth loss and further overgrowth of the dental alveoli.
The height of the alveolar process itself depends on a number of individual factors - age, dental defects, and the presence of dental diseases. If it is small (in other words, the volume of bone tissue of the process with dental alveoli is insufficient), then dental implantation becomes impossible. To correct the situation, special bone grafting is performed.
Diagnosis of alveolar processes comes down to one, but quite effective method - x-ray.
The main task of the alveolar processes - containers for dental sockets - alveoli, as we found out, is to hold the tooth in a certain position. The behavior, functions, and structure of these processes directly affect the entire dentition, and vice versa - these elements are interdependent. Just as a lost tooth can change the appearance of the alveolar process (in particular, the alveolar ridge), so the latter, with its height and structure, largely determines the overall picture of the dentition.
Plan
COMPOSITION AND FUNCTIONS OF PERIODONTAL
PERIODONTAL (PERIODONTAL LIGAMENT)
Functions of periodontium:
The structure of the periodontium
Intercellular substance of periodontium. Periodontal fibers. Classification of collagen fiber bundles
Blood supply to the periodontium
Innervation of the periodontium
Periodontal renewal and restructuring: clinical significance
ALVEOLAR PROCESSES
Structure and functional significance of the alveolar process and dental alveoli
Restructuring of the alveolar process
COMPOSITION AND FUNCTIONS OF PERIODONTAL
Supporting apparatus of the tooth (periodontium) includes: cement; periodontium; wall of the dental alveolus; gum.
Functions of the periodontium:
supporting and shock-absorbing;
barrier;
trophic;
reflex.
Barrier– forms a barrier that prevents the penetration of microorganisms and harmful substances into the root area.
Trophic– provides nutrition to cement.
Reflex– due to the presence of a large number of sensitive nerve endings in the periodontium.
Cement– (see description in other lectures “ Cement"
)
PERIODONTAL (PERIODONTAL LIGAMENT)
Periodontium– a ligament that holds the tooth root in the bony alveolus. Its fibers in the form of thick collagen bundles are woven into the cement at one end (see lecture “Cement”), and at the other into the alveolar process. Between the bundles of fibers there are gaps filled with loose fibrous unformed (interstitial) connective tissue containing vessels and nerve fibers; epithelial (islands) of Malasse are also located here - the remnants of Hertwig's epithelial root sheath and the epithelium of the dental plate.
Functions of periodontium:
supporting (holding and shock-absorbing);
participation in teething;
proprioceptive;
trophic;
homeostatic;
reparative;
protective.
Participation in teething.
Proprioceptive- due to the presence of numerous sensory endings. Mechanoreceptors that perceive loads contribute to the regulation of chewing forces.
Trophic– provides nutrition and vitality of the cement, partially (through additional channels) – the dental pulp.
Homeostatic– regulation of proliferative and functional activity of cells, processes of collagen renewal, resorption and repair of cement, restructuring of alveolar bone – i.e. all mechanisms associated with continuous structural and functional changes in the tooth and its supporting apparatus under conditions of growth, chewing function and therapeutic effects.
Reparative– participates in restoration processes through the formation of cement both during tooth root fracture and during resorption of its surface layers. Has great potential for self-recovery after damage. Due to the peculiarities of reparative processes in the periodontium, as a rule, ankylosis of the tooth root does not occur.
Protective– provided by macrophages and leukocytes.
The structure of the periodontium
Periodontal space- a very narrow gap, limited by the root of the tooth and the alveolar process. The width of this space averages 0.2-0.3 mm (varying within 0.15-0.4 mm) and is not the same in its different parts (minimum in the middle third of the root). In this gap, fibers are stretched, which, when the tooth is inactive, contract and grow under excessive occlusal loads. Collagen fibers occupy 62% of this volume, 38% is loose fibrous connective (interstitial) tissue.
The structural components of the periodontium are its fibroblast cells, poorly differentiated cells, osteoblasts, cementoblasts, macrophages, osteoclasts, epithelial remains (islets) of Malasse and odontoclasts and the intercellular substance, which is formed by fibers and the main amorphous one.
Epithelial islands (remnants) of Malasse
In newly erupted teeth, the epithelial tissue consists of perforated cell sheets, which later form a network of epithelial cords. With age, epithelial strands finally disintegrate into isolated epithelial islands (Malassé remnants). The largest number of epithelial islets is characteristic of the second decade of life, subsequently it decreases. In sections, epithelial islands are small compact clusters of small cells surrounded by a basement membrane.
Based on morphological characteristics, they are distinguished three types epithelial islets:
resting;
degenerating;
proliferating.
Degenerating– are small in size, the cells are gradually destroyed. The detritus is subsequently calcified and calcifications are formed, which can subsequently serve as centers for the formation of cementicles.
Proliferating– with signs of high synthetic and proliferative activity of the cells that form them. With age, the content of quiescent and degenerating islets decreases, and that of proliferating islets increases. Epithelial residues of Malasse can be a source of development of cysts and malignant tumors. With chronic inflammation in the periodontium surrounding the apex of the tooth, epithelial growths are found in 90% of cases as part of cellular infiltrates (periapical granulomas).
Intercellular substance of periodontium. Periodontal fibers. Classification of collagen fiber bundles
The intercellular substance of the periodontium consists of fibers and the main amorphous substance.Periodontal fibers.
Periodontal contains collagen fibers forming thick oriented bundles and forming several main groups, the spaces between which (interstitium) are filled with thinner branching collagen bundles forming a three-dimensional network. In addition to collagen fibers, the periodontium contains a network oxytalan(immature elastic) fibers. There are no mature elastic fibers in human periodontium.
Collagen the fibers consist of bundles of collagen fibrils of a typical structure. Their only peculiarity is that they have a relatively small diameter and are characterized by a slightly wave-like stroke, which is why they are capable of somewhat elongating when tensioned. Thanks to this, they can allow limited tooth movements.
Bundles of periodontal collagen fibers are embedded in the cement with one end and in the bone of the alveolar process with the other, and their terminal areas in both tissues are called perforating (Sharpey) fibers . According to some observations, bundles of periodontal collagen fibers are represented by two components:
one comes off the bone (alveolar fibers);
the other is from cement (dental fibers).
Depending on the location of the attachment sites and the direction of travel, all bundles of collagen fibers are divided:
alveolar ridge fibers;
horizontal fibers;
oblique fibers;
apical fibers;
interroot fibers.
Horizontal– are located deeper than the first ones at the entrance to the periodontal space. They run horizontally, forming a circular ligament and also include transseptal fibers that connect adjacent teeth and pass over the apex of the alveolar process.
Oblique– numerically the predominant group, occupies the middle 2/3 of the periodontal space. The fibers are located obliquely in the coronal plane, connecting the root with the alveolar bone. In the direction of the crown they merge with the horizontal fibers, in the direction of the apex - with the apical fibers.
Apical fibers– diverge perpendicularly from the apical part of the root to the bottom of the alveoli; some of them go horizontally, others vertically.
Interroot fibers– in multi-rooted teeth, the root in the bifurcation area is connected to the crest of the interradicular septum, to which they are directed partly in the horizontal, partly in the vertical directions.
This arrangement of periodontal fibers ensures that the forces acting on the tooth are evenly distributed through the fibers in the form of traction on the alveolar bone.
Basic (amorphous) periodontal substance
Along with fibers, periodontium contains an unusually large amount of ground substance, which occupies 65% of the volume of the intercellular substance. The ground substance is similar in structure to that in most other connective tissues. It is a very viscous gel and is composed of 70% water, which makes it able to play a significant role in absorbing the stresses placed on the tooth.
Blood supply to the periodontium
The main sources of blood supply are the superior and inferior alveolar arteries. Most of the arterial blood enters the periodontium through arterioles (less than 100 microns in diameter), which penetrate into it from the bone marrow spaces of the interdental and interradicular parts of the alveolar process through bone openings (Volkmann canals) located at different levels of the alveoli. In the back teeth the number of such arteries is higher than in the front teeth, and in the lower teeth - more than in the upper.Blood supply is also provided by the branches of the dental artery, which run from the periapical part of the ligament towards the gums, and by the branches of the supraperiosteal arteries, passing through the mucous membrane covering the alveolar processes. The vessels are oriented parallel to the long axis of the root. Capillaries extend from them, forming a plexus around the root. Some periodontal capillaries are fenestrated, i.e. having increased permeability. It is believed that this is due to the need to ensure rapid transport of water into and out of the hydrophilic ground substance of the periodontium to adapt the pressure in the periodontal space to the changing chewing loads affecting the tooth.
Veins that collect blood from the periodontal area are directed to the bone septa, but do not follow the course of the arteries. There are numerous anastomoses between arterial and venous vessels in the periodontium.
Clinically, the connection of periodontal vessels with the pulp vessels passing through the root openings plays an extremely important role in terms of the spread of infection.
Innervation of the periodontium
The periodontium is innervated by both afferent and efferent fibers. Afferent nerves approach the periodontium from two sources. The first are the peripheral branches that arise from the dental nerve before it enters the apical foramen. These fibers pass through the periodontium to the gums. The second source of afferent fibers is the branches of nerves that penetrate the openings of the interdental and interradicular bone septa (Volkmann canals) and are directed towards the apex of the root or crown. Fibers from both sources mix to form a nerve plexus in the periodontal space. It includes thick bundles of fibers running parallel to the long axis of the root, as well as thin bundles from which terminal branches and individual fibers extend. About half of the afferent fibers are unmyelinated with a diameter of about 0.5 µm; the diameter of myelinated fibers varies from 5 µm or less to 16 µm.Nerve fibers are predominantly mechanoreceptors and pain receptors (nociceptors). They have the appearance of convoluted oval encapsulated bodies, lamellar, spindle-shaped and leaf-shaped structures or (most often) thin tree-like branching free endings. The highest concentration of nerve endings is characteristic of the root apex area. The exception is the upper incisors, in which the endings are distributed with equally high density in the apical and in the parts of the root adjacent to the crown. Sympathetic fibers are usually unmyelinated with a diameter of 0.2-1 microns. They form basket-shaped endings around the vessels and appear to be involved in the regulation of coronary blood flow. Parasympathetic fibers have not been described in the periodontium.
Periodontal renewal and restructuring: clinical significance
Renewal processes constantly occur in the periodontium, including the replacement of fibroblasts and other cells, as well as intercellular substance. The rate of collagen renewal in the periodontium is two times higher than in the gums, and four times higher than in the skin. Due to the high rate of collagen renewal, any disruption of its synthesis quickly affects the condition of the periodontium. Thus, a lack of vitamin C, necessary for collagen synthesis, leads to periodontal damage and loose teeth. The rate of collagen renewal in the periodontium decreases with age. When an antagonist tooth is lost, the chewing load on the remaining tooth decreases, the rate of collagen renewal and its orderly arrangement decrease. The periodontium atrophies.Periodontal damage may be accompanied by cement resorption, rupture of collagen bundles, hemorrhage and necrosis. The adjacent bone tissue undergoes resorption, the periodontal space expands, and the tooth becomes more mobile. Subsequently, the damaged areas are replaced due to active reparative processes in the periodontium. When the latter is injured, a reaction may develop with activation of osteoblasts, which leads to the formation of bone tissue that will connect the tooth root with the bottom of the dental alveoli. This condition is called ankylosis, which means immobility of the joint.
The penetration of infection into the periodontium can cause a chronic inflammatory process in it - periodontitis, which will result in progressive destruction of the periodontium, which will not be compensated by reparative processes. With periodontitis, however, the inflammatory process affects not only the periodontium itself, but to one degree or another also the cement, alveolar process and gum, i.e. the entire supporting apparatus of the tooth (periodontium). Inflammatory-dystrophic periodontal diseases (periodontitis) affect half of the child population and almost the entire adult population of the world. As a result of the disease, destruction of periodontal fibers, resorption of the alveolar process, damage to the cement occurs, which results in loosening and loss of teeth.
The periodontium plays an important role in the orthodontic movement of teeth. During orthodontic treatment, tooth displacement occurs due to resorption and new formation of bone tissue, which are stimulated by adequately regulated pressure and tension forces. These forces are transmitted through the periodontium, and its initial compression of the ligament on the pressure side is compensated by bone resorption, and on the tension side, new layers of bone tissue are deposited. At the same time, during orthodontic treatment, the periodontium not only mediates the forces acting on the tooth, but itself undergoes enhanced restructuring, which is regulated by the nature of the local influence of forces. Accordingly, in certain areas of the periodontium, the synthesis and (or) resorption of collagen fibers and its other components is accelerated.
Pathological processes often occur in the periodontal area surrounding the apical foramen. The most typical of them are various types periapical granulomas:
simple periapical granuloma;
complex, or epithelial granuloma;
apical cyst (cystogranuloma).
Complex or epithelial granuloma. Granuloma may also contain epithelial cells in the form of strands. The source of the epithelium in the periapical part of the root is usually considered to be the remains of Hertwig's root sheath (epithelial remains of Malasse), or, according to some data (in some cases), it can be the growing epithelium of the gingival groove (pocket).
Apical cyst (cystogranuloma). When the central section of a complex granuloma disintegrates, a cavity is formed in it, which is lined by multilayered epithelium, which grows under the action of cytokines and growth factors secreted by the cells of the inflammatory infiltrate. Extensive bone destruction may occur around the apical cyst. The latter is due to the fact that the cells of the apical cyst secrete prostaglandins and other substances in significant quantities, which activate osteoclasts in the surrounding bone tissue.
ALVEOLAR PROCESSES
Structure and functional significance of the alveolar process and dental alveoli
Alveolar ridge- part of the upper and lower jaws, extending from their bodies and containing teeth. There is no sharp boundary between the body of the jaw and its alveolar process.The alveolar process appears only after teeth erupt and almost completely disappears with their loss.
dental alveoli, or holes- individual cells of the alveolar process in which the teeth are located. The dental alveoli are separated from each other by bony interdental septa. Inside the alveoli of multi-rooted teeth there are also internal interradicular septa that extend from the bottom of the alveoli.
The alveolar process has two parts:
the alveolar bone itself (alveolar wall);
supporting alveolar bone.
The supporting alveolar bone consists of:
cortical plates of the alveolar process (compact bone);
spongy bone.
Cancellous bone formed by anastomosing trabeculae, the distribution of which usually corresponds to the direction of the forces acting on the alveolus during chewing movements. Trabeculae distribute forces acting on the alveolar bone proper to the cortical plates. In the area of the lateral walls of the alveoli they are located predominantly horizontally, and at the bottom of the alveoli they have a more vertical course. Their number varies in different parts of the alveolar process and decreases with age and in the absence of tooth function. Spongy bone forms both interradicular and interdental septa, which contain vertical feeding canals, bearing nerves, blood and lymphatic vessels. Between the bone trabeculae there are bone marrow spaces, filled in childhood with red bone marrow, and in adults with yellow bone marrow. Sometimes certain areas of red bone marrow can persist throughout life.
Restructuring of the alveolar process
The bone tissue of the alveolar process has high plasticity and is in a state of constant restructuring, which includes balanced processes of bone resorption by osteoclasts and its new formation by osteoblasts. Processes of continuous restructuring ensure adaptation of bone tissue to changing functional loads and occur both in the walls of the dental alveolus and in the supporting bone of the alveolar process.IN physiological conditions After teeth erupt, two types of movement occur:
associated with the erasure of approximal (facing each other) surfaces;
compensatory occlusal abrasion.
Compensatory occlusal abrasion– The abrasion of the tooth is compensated by its gradual advancement from the bone alveolus. An important mechanism of this process is the deposition of cement in the region of the root apex. At the same time, however, the alveolar wall is also reconstructed, at the bottom of which and in the area of the interradicular septa, bone tissue is deposited. This process reaches particular intensity with the loss of tooth function due to the loss of the antagonist.
The cancellous bone surrounding the alveolar bone itself also undergoes constant restructuring in accordance with the load acting on it. Thus, around the alveoli of a non-functioning tooth (after the loss of its antagonist), it undergoes atrophy - the bone trabeculae become thin, and their number decreases.
After damage bone tissue also has a high potential for regeneration. So after tooth extraction in the first, reparative phase, The alveolar defect is filled with a blood clot. The free gum, mobile and not connected to the alveolar bone, bends towards the cavity, thereby not only reducing the size of the defect, but also helping to protect the blood clot. As a result of active proliferation and migration of the epithelium, which begins after 24 hours, the integrity of its cover is restored within 10-14 days. Precursor cells also migrate into the alveolus, differentiate into osteoblasts and, starting from the 10th day, actively form bone tissue that gradually fills the alveolus. At the same time, partial resorption of its walls occurs. As a result of the described changes, after 10-12 weeks the first, reparative phase tissue changes after tooth extraction.
The second phase of changes (reorganization phase) lasts for many months and includes the restructuring of all tissues involved in reparative processes (epithelium, fibrous connective tissue, bone tissue) in accordance with the changed conditions of their functioning.
LITERATURE
Bykov V.P. Histology and embryology of human oral cavity organs: Textbook, 2nd ed. –SPb. – 1999
Histology textbook / Ed. Yu.I. Afanasyeva, N.A. Yurina - 5th ed., revised. and additional – M.: Medicine, 2006.
Histology textbook / Edited by E.G. Ulumbekova, Yu.A. Chelysheva. – “th ed., revised. and additional – M.: GOETAR MED, 2009.
Dzhulay M.A., Yasman S.A., Baranchugova L.M., Pateyuk A.V., Rusaeva N.S., V.I. Obydenko Histology and embryogenesis of the oral cavity: Textbook.-Chita: IRC ChSMA. - 2008.- 152 p.
V.I.Kozlov, T.A.Tsekhmistrenko Anatomy of the oral cavity and teeth: Textbook Publisher: RUDN IPK - 2009 -156 p.
Myadelets O.D. "Histophysiology and embryogenesis of the oral cavity organs." Vitebsk, VSMU, Educational and methodological manual VSMU - Vitebsk State Medical University - Publishing house 2004.-158 p.
Histology of the oral cavity: Educational manual / Compiled by Yu.A. Chelyshev. - Kazan, 2007. - 194 p.: ill. Educational and methodological, designed for intensive training of students of the Faculty of Dentistry in the histology of the oral cavity.
Danilevsky N.F., Lenontiev V.K., Nesin A.F., Rakhniy Zh.I. Diseases of the oral mucosa Publisher: OJSC "Dentistry" -: 2007- 271 p.: Ch. 1. Oral cavity - concept, features of structure, function and processes; Ch. 2 Histological structure of the oral mucosa
