Diseases of the dental system and oral cavity organs. Diseases of hard tissues of teeth etiology and pathogenesis In total, two groups of diseases of hard tissues of teeth are distinguished

The most common dental diseases include caries- progressive destruction of hard tooth tissues with the formation of a defect in the form of a cavity. The destruction is based on demineralization and softening of hard dental tissues.

Pathologically, early and late phases of morphological changes in carious disease of the hard tissues of the tooth crown are distinguished. The early phase is characterized by the formation of a carious spot (white and pigmented), while the late phase is characterized by the appearance of cavities of varying depths in the hard tissues of the tooth (stages of superficial, medium and deep caries).

Subsurface demineralization of enamel in the early phase of caries, accompanied by a change in its optical properties, leads to the loss of the natural color of the enamel: first, the enamel turns white as a result of the formation of microspaces in the carious lesion, and then acquires a light brown tint - a pigmented spot. The latter differs from the white spot in the larger area and depth of the lesion.

In the late phase of caries, further destruction of the enamel occurs, in which, with the gradual rejection of demineralized tissue, a cavity with uneven contours is formed. Subsequent destruction of the enamel-dentin boundary and the penetration of microorganisms into the dentinal tubules leads to the development of dentin caries. The proteolytic enzymes and acid released during this process cause the dissolution of the protein substance and demineralization of dentin until the carious cavity communicates with the pulp.

With caries and lesions of hard tooth tissues of a non-carious nature, nervous regulation disorders are observed. In case of damage to tooth tissue, access to external nonspecific irritants of the nervous system of dentin, pulp and periodontium, which cause a pain reaction, is opened. The latter, in turn, reflexively contributes to neurodynamic changes in the functional activity of the masticatory muscles and the formation of pathological reflexes.

Enamel hypoplasia occurs during the period of follicular development of dental tissues. According to M.I. Groshikov, hypoplasia is the result of a perversion of metabolic processes in the tooth germs due to a violation of mineral and protein metabolism in the body of the fetus or child (systemic hypoplasia) - or a cause locally acting on the tooth germ (local hypoplasia). Occurs in 2-14% of children. Enamel hypoplasia is not a local process, affecting only the hard tissues of the tooth. It is the result of a severe metabolic disorder in a young body. It manifests itself as a violation of the structure of dentin and pulp and is often combined with malocclusions (pro-genius, open bite, etc.).

The classification of hypoplasia is based on etiological characteristics, since hypoplasia of dental tissues of various etiologies has its own specifics, which are usually revealed during clinical and radiological examination. Depending on the cause, hypoplasia of hard dental tissues that are formed simultaneously is distinguished (systemic hypoplasia); several adjacent teeth that form simultaneously, and more often during different periods of development (focal hypoplasia); local hypoplasia (single tooth).

Fluorosis- a chronic disease caused by excessive intake of fluoride into the body, for example, when its content in drinking water is more than 1.5 mg/l. It manifests itself mainly as osteosclerosis and enamel hypoplasia. Fluoride binds calcium salts in the body, which are actively excreted from the body: depletion of calcium salts impairs the mineralization of teeth. A toxic effect on tooth buds cannot be ruled out. Violation of mineral metabolism manifests itself in the form of various fluoride hypoplasia (striations, pigmentation, mottling of enamel, chipping, abnormal shapes of teeth, their fragility).

Symptoms of fluorosis are represented by morphological changes mainly in the enamel, most often in its surface layer. As a result of the resorptive process, enamel prisms fit less tightly to each other.

In later stages of fluorosis, areas of enamel with an amorphous structure appear. Subsequently, in these areas, the formation of enamel erosions in the form of specks and the expansion of interprismatic spaces occur, which indicates a weakening of the connections between the structural formations of the enamel and a decrease in its strength.

Pathological abrasion of teeth represents a loss of hard tissues of the tooth crown - enamel and dentin - increasing over time in certain areas of the surface. This is a fairly common dental disease, occurring in approximately 12% of people over 30 years of age and extremely rare at an earlier age. Complete abrasion of the chewing cusps of molars and premolars, as well as partial abrasion of the cutting edges of the front teeth, is observed almost 3 times more often in men than in women. In the etiology of pathological abrasion of teeth, a prominent place belongs to such factors as the nature of nutrition, the constitution of the patient, various diseases of the nervous and endocrine systems, hereditary factors, etc., as well as the profession and habits of the patient. Reliable cases of increased tooth abrasion in thyrotoxic goiter, after extirpation of the thyroid and parathyroid glands, in Itsenko-Cushing's disease, cholecystitis, urolithiasis, endemic fluorosis, wedge-shaped defect, etc. have been described.

The use of removable and fixed dentures of incorrect design also causes pathological abrasion of the surfaces of teeth of various groups; teeth that support clasps are especially often abraded.

Changes in pathological abrasion of the hard tissues of the tooth crown are observed not only in the enamel and dentin, but also in the pulp. In this case, the most pronounced deposition of replacement dentin is formed first in the area of ​​the pulp horns, and then throughout the entire arch of the coronal cavity.

Wedge-shaped defect is formed in the cervical region of the vestibular surface of premolars, canines and incisors, less often than other teeth. This type of non-carious lesion of the hard tissues of the tooth crown usually occurs in middle-aged and elderly people. An important role in the pathogenesis of a wedge-shaped defect belongs to disturbances in the trophism of the pulp and hard tissues of the teeth. In 8 - 10% of cases, a wedge-shaped defect is a symptom of periodontal disease, accompanied by exposure of the necks of teeth,

Currently available data allow us to see in the pathogenesis of a wedge-shaped defect a significant role of both concomitant somatic diseases (primarily the nervous and endocrine systems, gastrointestinal tract), and chemical exposure (changes in the organic substance of teeth) and mechanical (hard toothbrushes) factors. Many authors assign a leading role to abrasive factors.

With a wedge-shaped defect, as with caries, an early stage is distinguished, which is characterized by the absence of a formed wedge and the presence of only superficial abrasions, thin cracks or crevices, detectable only with a magnifying glass. As they expand, these depressions begin to take on a wedge shape, while the defect retains smooth edges, a hard bottom and seemingly polished walls. Over time, the retraction of the gingival margin increases and the exposed necks of the teeth react more and more sharply to various irritants. Morphologically, at this stage of the disease, compaction of the enamel structure, obliteration of most dentinal tubules and the appearance of large collagen fibers in the walls of non-obliterated tubules are revealed. There is also an increase in the microhardness of both enamel and dentin due to increased mineralization.

Acute traumatic damage to the hard tissues of the tooth crown is tooth fracture. Mainly the front teeth, especially the upper jaw, are subject to such damage. Traumatic damage to teeth often leads to pulp death due to infection. Initially, pulp inflammation is acute and accompanied by severe pain, then it becomes chronic with characteristic and pathological phenomena.

The most common fractures of teeth are in the transverse direction, less often in the longitudinal direction. Unlike a dislocation, during a fracture, only the broken part of the tooth is movable (if it remains in the alveolus).

With chronic trauma to the hard tissues of the tooth (for example, in shoemakers), chipping occurs gradually, which brings them closer to professional pathological abrasion.

Hereditary lesions of hard dental tissues include defective amelogenesis(formation of defective enamel) and defective dentinogenesis(disorder of dentin development). In the first case, as a result of a hereditary disorder in the development of enamel, a change in its color, a violation of the shape and size of the tooth crown, increased sensitivity of the enamel to mechanical and temperature influences, etc. are observed. The pathology is based on insufficient mineralization of the enamel and a violation of its structure. In the second case, as a result of dentin dysplasia, increased mobility and translucency of both milk and permanent teeth are observed.

The literature describes Stainton-Capdepont syndrome - a unique family pathology of teeth, characterized by changes in the color and transparency of the crown, as well as early onset and rapidly progressing tooth abrasion and chipping of enamel.

Symptoms of Diseases of Hard Dental Tissues

Clinic of carious lesions of hard dental tissues is closely related to the pathological anatomy of the carious process, since the latter in its development goes through certain stages that have characteristic clinical and morphological signs.

Early clinical manifestations of caries include a carious spot that appears unnoticed by the patient. Only with a thorough examination of the tooth using a probe and a mirror can you notice a change in the color of the enamel. During the examination, one should be guided by the rule that the contact surfaces of the incisors, canines and premolars are most often affected, while the chewing surfaces of the molars (fissure caries), especially in young people.

Caries damage in the form of single foci of destruction in one or two teeth is manifested by complaints of sensitivity when the carious surface comes into contact with sweet, salty or sour foods, cold drinks, or upon probing. It should be noted that in the spot stage, these symptoms are detected only in patients with increased excitability.

Superficial caries is characterized by quickly passing pain under the influence of these irritants in almost all patients. When probing, a shallow defect with a slightly rough surface is easily detected, and probing is slightly painful.

Average caries occurs without pain; irritants, often mechanical, cause only short-term pain. Probing reveals the presence of a carious cavity filled with food debris, as well as softened pigmented dentin. The pulp's response to electric current stimulation remains within normal limits (2-6 μA).

At the last stage - the stage of deep caries - pain becomes quite pronounced under the influence of temperature, mechanical and chemical stimuli. The carious cavity is of considerable size, and its bottom is filled with softened pigmented dentin. Probing the bottom of the cavity is painful, especially in the area of ​​the pulp horns. Clinically detectable signs of pulp irritation are observed, the electrical excitability of which may be reduced (10-20 μA).

Pain when pressing on the roof of the pulp chamber with a blunt object causes a change in the nature of cavity formation at the time of treatment.

Sometimes the hard tissue defect in deep caries is partially hidden by the remaining surface layer of enamel and appears small upon examination. However, when the overhanging edges are removed, a large carious cavity is easily revealed.

Diagnosis of caries at the stage of the formed cavity is quite simple. Caries in the spot stage is not always easy to distinguish from lesions of the hard tissues of the tooth crown of non-carious origin. The similarity of the clinical pictures of deep caries and chronic pulpitis, occurring in a closed tooth cavity in the absence of spontaneous pain, forces differential diagnosis.

With caries, pain from heat and probing occurs quickly and goes away quickly, but with chronic pulpitis it is felt for a long time. Electrical excitability in chronic pulpitis decreases to 1 5 - 2 0 μA.

Depending on the affected area (caries of one or another surface of the chewing and anterior teeth), Black proposed a topographic classification: Class I - cavity on the occlusal surface of the chewing teeth; II - on the contact surfaces of chewing teeth; III - on the contact surfaces of the front teeth; IV - area of ​​the corners and cutting edges of the front teeth; Class V - cervical region. A letter designation of affected areas has also been proposed - based on the initial letter of the name of the tooth surface; O - occlusal; M - medial contact; D - distal contact; B - vestibular; I am lingual; P - cervical.

Cavities can be located on one, two, or even all surfaces. In the latter case, the topography of the lesion can be designated as follows: MODVYA.

Knowledge of the topography and degree of damage to hard tissues underlies the choice of caries treatment method.

Clinical manifestations of enamel hypoplasia expressed in the form of spots, cup-shaped depressions, both multiple and single, of different sizes and shapes, linear grooves of different widths and depths, encircling the tooth parallel to the chewing surface or cutting edge. If elements of this form of hypoplasia are localized along the cutting edge of the tooth crown, a semilunar notch is formed on the latter. Sometimes there is a lack of enamel at the bottom of the grooves or on the tubercles of premolars and molars. There is also a combination of grooves with rounded depressions. The grooves are usually located at some distance from the cutting edge: sometimes there are several of them on one crown.

There is also underdevelopment of the tubercles in premolars and molars: they are smaller than usual in size.

The hardness of the surface layer of enamel with hypoplasia is often reduced and the hardness of the dentin under the lesion is increased compared to the norm.

In the presence of fluorosis is a clinical sign different types of damage to different groups of teeth. In mild forms of fluorosis, a mild loss of shine and transparency of the enamel is observed due to changes in the refractive index as a result of fluoride intoxication, which is usually chronic. Whitish, “lifeless” single chalky spots appear on the teeth, which, as the process progresses, acquire a dark brown color and merge, creating a picture of burnt crowns with a “small-like” surface. Teeth in which the calcification process has already been completed (for example, permanent premolars and second permanent molars) are less susceptible to fluorosis, even with high concentrations of fluoride in water and food.

According to the classification of V.K. Patrikeev, the streak form of fluorosis, which is characterized by the appearance of barely noticeable chalky stripes in the enamel, most often affects the central and lateral incisors of the upper jaw, less often - the lower one, and the process mainly affects the vestibular surface of the tooth. With the spotted form, chalky spots of varying color intensity appear on the incisors and canines, and less often on premolars and molars. Chalk An OVID-mottled form of fluorosis affects teeth of all groups: matte, light or dark brown areas of pigmentation are located on the vestibular surface of the front teeth. All teeth can also be affected by the erosive form, in which the stain takes on the appearance of a deeper and more extensive defect - erosion of the enamel layer. Finally, the destructive form, found in endemic foci of fluorosis with a high fluorine content in water (up to 20 mg/l), is accompanied by a change in shape and breaking off of crowns, usually incisors, less often molars.

Clinical picture of damage to the hard tissues of the tooth crown by a wedge-shaped defect depends on the stage of development of this pathology. The process develops very slowly, sometimes over decades, and in the initial stage, as a rule, there are no complaints from the patient, but over time, a feeling of sore throat and pain from mechanical and temperature stimuli appears. Gingival margin, even if retraction has occurred, with mild signs of inflammation.

A wedge-shaped defect occurs predominantly on the buccal surfaces of the premolars of both jaws, the labial surfaces of the central and lateral incisors, and the canines of the lower and upper jaws. The lingual surface of these teeth is extremely rarely affected.

In the initial stages, the defect occupies a very small area in the cervical part and has a rough surface. Then it increases both in area and in depth. When the defect spreads along the enamel of the crown, the shape of the cavity in the tooth has a certain outline: the cervical edge follows the contours of the gingival edge and in the lateral areas at an acute angle, and then, rounding off, these lines are connected in the center of the crown. There is a crescent-shaped defect. The transition of the defect to root cement is preceded by gum retraction.

The bottom and walls of the cavity of the wedge-shaped defect are smooth, polished, and more yellow in color than the surrounding layers of enamel.

Traumatic damage to the hard tissues of the tooth is determined by the location of impact or excessive load during chewing, as well as age-related characteristics of the tooth structure. Thus, in permanent teeth, the most common fracture of a part of the crown is observed, in milk teeth - tooth dislocation. Often the cause of a fracture or breaking off the crown of a tooth is improper treatment of caries: filling when the thin walls of the tooth are preserved, i.e., with significant carious damage.

When part of the crown is broken(or its fracture), the boundary of the damage passes in different ways: either within the enamel, or along the dentin, or captures the root cement. Pain sensations depend on the location of the fracture border. When a part of the crown is broken off within the enamel, the tongue or lips are mainly injured by sharp edges; less often, a reaction to temperature or chemical irritants is noted. If the fracture line passes within the dentin (without exposing the pulp), patients usually complain of pain from heat, cold (for example, when breathing with an open mouth), and exposure to mechanical stimuli. In this case, the dental pulp is not injured, and the changes that occur in it are reversible. Acute trauma to the tooth crown is accompanied by fractures: in the enamel zone, in the enamel and dentin zone without or with. opening the pulp cavity of the tooth. In case of tooth trauma, an X-ray examination is required, and in intact teeth, electroodontodiagnostics is also carried out.

Hereditary lesions of hard dental tissues usually involve all or most of the crown, which does not allow topographical identification of specific or most common areas of the lesion. In most cases, not only the shape of the teeth is affected, but also the bite. Chewing efficiency is reduced, and the chewing function itself contributes to further tooth decay.

The occurrence of partial defects in the hard tissues of the tooth crown is accompanied by a violation of its shape, interdental contacts, leads to the formation of gum pockets, retention points, which creates conditions for the traumatic effect of a food bolus on the gum, infection of the oral cavity by saprophytic and pathogenic microorganisms. These factors cause the formation of chronic periodontal pockets and gingivitis.

The formation of partial crown defects is also accompanied by changes in the oral cavity, not only of a morphological, but also of a functional nature. As a rule, in the presence of a pain factor, the patient chews food on the healthy side, and in a gentle manner. This ultimately leads to insufficient chewing of food lumps, as well as excessive deposition of tartar on the opposite side of the dentition with the subsequent development of gingivitis.

The prognosis for the therapeutic treatment of caries, as well as some other crown defects, is usually favorable. However, in some cases, a new carious cavity appears next to the filling as a result of the development of secondary or recurrent caries, which in most cases is a consequence of improper odontopreparation of the carious cavity with low strength of many filling materials.

The restoration of many partial defects in the hard tissues of the tooth crown can be achieved by filling. The most effective and lasting results of crown restoration with a good cosmetic effect are obtained using orthopedic methods, i.e., through prosthetics.

Treatment of diseases of dental hard tissues

Treatment for partial destruction of tooth crowns

The main task of orthopedic treatment for partial defects of the hard tissues of the tooth crown is restoration of the crown through prosthetics in order to prevent further tooth destruction or relapse of the disease.

The important preventive value of orthopedic treatment of defects of hard dental tissues, which is one of the main directions of orthopedic dentistry, is that restoration of the crown allows you to prevent further destruction and loss of many teeth over time, and this in turn allows you to avoid serious morphological and functional disorders of various departments of the dental system.

The therapeutic effect of prosthetic restoration of crown defects is expressed in the elimination of disturbances in the act of chewing and speech, normalization of the function of the temporomandibular joint, and restoration of aesthetic standards. The odontopreparation used in this case as an act of impact on dental tissue also creates certain conditions for the activation of reparative processes in dentin, as a result of which a targeted restructuring is observed, expressed in the natural compaction of dentin and the formation of protective barriers at various levels.

As a treatment for defects in the coronal part of the tooth, mainly two types of prostheses are used: inlays and artificial crowns.

Tab- fixed prosthesis of part of the tooth crown (microprosthesis). Used to restore the anatomical shape of a tooth. The insert is made from a special metal alloy. In some cases, the prosthesis can be lined with an aesthetic material (composite materials, porcelain).

Artificial crown- a fixed prosthesis, which is used to restore the anatomical shape of a tooth and is fixed to the stump of a natural tooth. Made from metal alloys, porcelain, plastic. Can serve as a supporting element for other types of prostheses.

As with any medicinal product, there are indications and contraindications for the use of inlays and artificial crowns. When choosing a prosthesis, the disease that caused the destruction of the natural tooth crown and the degree (size and topography) of the destruction are taken into account.

Tabs

Inlays are used for caries, wedge-shaped defects, some forms of hypoplasia and fluorosis, and pathological abrasion.

Inlays are not indicated for circular caries, MOD cavities in combination with cervical caries or wedge-shaped defect, or for systemic caries. It is undesirable to use tabs for people taking gastric juice or hydrochloric acid for medicinal purposes, or working in acid shops. In these cases, artificial crowns are preferable.

It should be remembered that varying degrees of dental caries damage and a number of other diseases of hard tissues (hypoplasia, fluorosis, dysplasia) require complex treatment.

The question of a treatment method for partial defects in the coronal part of a vital tooth can be decided only after removal of all necrotic tissue.

Odontopreparation and treatment of inlays. Local treatment of defects in the coronal part of the tooth consists of surgical removal of necrotic tissue, surgical formation (by odontopreparation) of a corresponding cavity in the tooth and filling this cavity with an inlay in order to stop the pathological process, restore the anatomical shape of the tooth and connect it to the chewing function.

The clinical and laboratory stages of restoring the coronal part of a tooth with inlays include: forming a cavity for the inlay by means of appropriate odontopreparation, obtaining a wax model of it, making an inlay by replacing the wax with an appropriate material, processing the metal inlay and fitting it to the model, fitting and fixing the inlay in the tooth cavity.

The formation of a cavity in a tooth for the purpose of its subsequent filling with an inlay is subordinated to the task of creating optimal conditions for fixing the inlay, which does not have side effects on healthy tissue. The surgical technique of odontopreparation of cavities in a tooth is based on the principle of creating a cavity with walls that can perceive both pressure when a bolus of food of varying consistency and density directly hits them, and pressure transmitted from the prosthesis when it is loaded during the chewing process. The design features of the prosthesis should not contribute to the concentration of additional pressure on the remaining hard tissues: the pressure should be fairly evenly distributed over their entire thickness. In this case, the inlay material must be hard, but not brittle, not plastic in the hardened state, not corrode or swell in the oral environment, and have an expansion coefficient close to that of enamel and dentin.

The principle of the operational technique of forming a cavity and then filling it with an inlay is subject to the laws of redistribution of chewing pressure forces.

In case of caries, the cavity is formed in two stages. At the first stage, technical access is made to the carious cavity, its expansion and excision of pathologically altered enamel and dentin tissues. At the second stage of odontopreparation, a cavity is formed according to the configuration in order to create optimal conditions for fixing the inlay and optimal distribution of chewing pressure forces on the tissue.

To open a carious cavity, shaped carborundum and diamond heads, fissure or spherical burs of small diameter are used. The opening of a carious cavity on the contact surface presents a certain difficulty. In these cases, the cavity is formed towards the chewing or lingual surface, removing unchanged tooth tissue to facilitate access to the cavity. A free approach to the cavity from the chewing surface is also necessary to prevent the occurrence of secondary caries.

After expanding the carious cavity, necrotomy and formation of a cavity for the inlay begin. To facilitate further study of the topic, we will describe the main elements of the formed cavity. In each cavity, there are walls, a bottom, and the place where the walls connect with each other and the bottom - the corners. The walls of the cavity may converge with each other at an angle or have a smooth, rounded transition.

Depending on the topography of the damage to the tooth crown, it is possible to have two or three cavities combined with each other, or a main cavity (localization of the pathological process) and an additional one, created in healthy tissues and having a special purpose.

The nature and scope of surgical interventions on hard dental tissues are determined by the following interrelated factors:

• the relationship between the hard tissue defect and the topography of the tooth cavity and the preservation of the pulp;
• thickness and presence of dentin in the walls delimiting the defect;
• topography of the defect and its relationship to occlusal loads, taking into account the nature of the action of chewing pressure forces on the tooth tissue and the future prosthesis;
• the position of the tooth in the dentition and its inclination in relation to the vertical cavities;
• the relationship between the defect and the areas of greatest caries damage;
• the reason that caused the damage to hard tissues;
• the possibility of restoring the full anatomical shape of the tooth crown with the proposed design of the prosthesis.

The question of the effect of occlusal loads on tooth tissue and microprosthesis deserves special study. When eating food, chewing pressure forces of varying magnitude and direction act on the tooth tissue and denture. Their direction changes depending on the movement of the lower jaw and the food bolus. These forces, if there is an inlay on the occlusal surface, cause compressive or tensile stress in it and in the walls of the cavity.

Thus, with cavities of type 0 (class I according to Black) in a vertically standing tooth and a formed box-shaped cavity, force Q causes deformation - compression of the tissues of the bottom of the cavity. The forces R and P are transformed by the walls of the cavity, in which complex stress states arise. With thin walls, over time this can lead to their breaking. If the tooth axis is inclined, then the forces R and Q cause increased deformation of the wall on the inclined side. To avoid this and reduce wall deformation, you should change the direction of the walls and bottom of the cavity or create an additional cavity that allows you to redistribute part of the pressure to other walls.

Similar reasoning, which is based on the laws of deformation of a solid body under pressure and the rule of the parallelogram of forces, can be applied to cavities of the MO and OD types. Additionally, the effect of force P directed towards the missing wall should be considered. In this case, the horizontal component of the force tends to displace the inlay, especially if the bottom is formed with an inclination towards the missing wall. In such situations, the rule for forming the bottom also applies: it must be inclined away from the defect, if the thickness of the preserved contact wall allows, or a main cavity must be formed on the occlusal surface with retention points.

The patterns of redistribution of chewing pressure forces between the cavity wall microprosthesis system allow us to formulate the following pattern of cavity formation: the bottom of the cavity should be perpendicular to the vertically acting pressure forces, but not to the vertical axis of the tooth. In relation to this level, the walls of the cavity are formed at an angle of 90°. The pressure from the inlay on the tooth walls under occlusal forces depends on the degree of destruction of the occlusal surface.

As an indicator (index) of the degree of destruction of hard tissues of the crowns of chewing teeth in classes I-II of defects, V. Yu. Milikevich introduced the concept of IROPD - index of destruction of the occlusal surface of the tooth. It represents the ratio of the size of the “cavity-filling” area to the chewing surface of the tooth.

The area of ​​the cavity or filling is determined by applying a coordination grid with a division value of 1 mm2, applied to a transparent plexiglass plate 1 mm thick. The sides of the mesh square are aligned with the direction of the proximal surfaces of the teeth. The results are expressed in square millimeters with an accuracy of 0.5 mm2.

To quickly determine IROPD, V. Yu. Milikevich proposed a probe that has three main sizes of defects in the hard tissues of teeth for cavities of classes I and II according to Black.

If the value of IROPD a is from 0.2 to 0.6, treatment of chewing teeth with cast metal inlays with the following features is indicated. When cavities of type O are localized and the index value is 0.2 on premolars and 0.2 - 0.3 on molars, the cast inlay includes the body and the rebate. If the value of IROPD is 0.3 on premolars and 0.4 - 0.5 on molars, occlusal covering of the slopes of the tubercles is carried out. With values ​​of IROPD a of 0.3 - 0.6 on premolars and 0.6 on molars, the entire occlusal surface and cusps are covered.

When the cavity is displaced towards the lingual or vestibular surface, it is necessary to cover the area of ​​the corresponding tubercle with a cast inlay. On molars with IROPZ = 0.2 - 0.4, the slopes of the cusps should be covered; with IROPZ = 0.5 - 0.6 - completely cover the tubercles. The design of the inlays must include retention micropins.

When cavities of the MOD type are localized on premolars and the value of IROPD = 0.3 - 0.6, on molars and the value of IROPD = 0.5 - 0.6, it is necessary to completely cover the occlusal surface with the tubercles.

When odontopreparation for inlays, as well as when odontopreparation for other types of prostheses, it is necessary to know well the boundaries within which you can confidently excise the hard tissues of the tooth crown without fear of opening the tooth cavity. To a greater extent, the hard tissues of the crowns of the upper and lower front teeth can be excised on the lingual side at the level of the equator and cervix. The most dangerous place for injury to the incisor pulp is the lingual concavity of the crown.

With age, in all teeth, the safe preparation zone expands at the cutting edge and at the level of the neck, since the coronal pulp cavity is obliterated due to the deposition of replacement dentin. This is most often observed in the lower central (2.2±4.3%) and upper lateral (18±3.8%) incisors in people aged 40 years and older.

When forming cavities for inlays, as with other types of prosthetics, in which it is necessary to excise the hard tissues of the tooth crown in order to avoid injury to the pulp, you should use data on the thickness of the walls of the tooth tissues. This data is obtained using radiographic examination.

An essential condition for preventing the development of secondary caries after treating an affected tooth with an inlay is the mandatory preventive expansion of the entrance cavity to the “immune” zones. An example of such preventive expansion is the connection between carious cavities located on the chewing and buccal surfaces of molars. It eliminates the possibility of the development of secondary caries in the groove present on the buccal surface of the molars and extending to their occlusal surface.

Another condition for preventing secondary caries is the creation of a tightness between the edge of the cavity formed in the tooth and the edge of the inlay. This is achieved by grinding down enamel prisms along the edge of the tooth defect.

The next important rule of odontopreparation is the creation of mutually parallel walls of the cavity, forming right angles with its bottom. This rule must be observed especially strictly when forming MO, MOD and other cavities, in which the walls of both cavities and the bridges must be strictly parallel.

During odontopreparation, a cavity is created under the inlays from which the simulated wax model can be removed without interference and then the finished inlay can also be freely inserted. This is achieved by creating weakly diverging walls while maintaining the overall box-like shape, i.e., the entrance to the cavity is slightly expanded compared to its bottom.

Let us consider the sequence of medical actions and reasoning using the example of the formation of cavities under the inlay for carious lesions of class I and II according to Black.

So, if, after removing necrotic tissue, medium caries is established in the center of the occlusal surface, in which the affected area does not exceed 50 - 60% of this surface, the use of metal inlays is indicated. The task of the surgical technique in this case is to form a cavity, the bottom of which is perpendicular to the long axis of the tooth (the direction of inclination is determined), and the walls are parallel to this axis and perpendicular to the bottom. If the inclination of the tooth axis to the vestibular side for the upper chewing teeth and to the lingual side for the lower teeth exceeds 10-15°, and the thickness of the wall is insignificant (less than half the size from the fissure to the vestibular or lingual surface), the rule for the formation of the bottom changes. This is explained by the fact that occlusal forces directed at the inlay at an angle and even vertically have a displacement effect and can cause chipping of the tooth wall. Consequently, the bottom of the cavity, obliquely directed away from the thin walls that are not resistant to mechanical forces, prevents spalling of the thinned cavity wall.

With deep caries, the depth of the cavity increases the load on the tooth wall, and the increased size of the wall itself creates a moment of tearing force when a food bolus hits the occlusal surface of this wall. In other words, in these situations there is a danger of breaking off part of the tooth crown. This requires the creation of an additional cavity to distribute the forces of chewing pressure onto thicker, and therefore more mechanically strong, areas of tooth tissue. In this example, such a cavity can be created on the opposite (vestibular, lingual) wall along the transverse intertubercular groove. For an additional cavity, it is necessary to determine the optimal shape in which the greatest effect of redistribution of all components of chewing pressure can be achieved with minimal surgical removal of enamel and dentin and minimal pulp reaction.

The additional cavity should be formed somewhat deeper than the enamel-dentin border, but in vital teeth the optimal shape will be one in which the width is greater than the depth. Additional cavities are characterized by the presence of connecting and holding parts. The connecting part departs from the main part in the vestibular direction and connects with the retaining part, which is formed in the mediodistal direction parallel to the walls of the main cavity. The dimensions of the additional cavity depend on the strength of the material used for the insert. Thus, when using a cast inlay, a cavity is created that is smaller in both depth and width than when filling with amalgam.

The thinned wall, especially its occlusal part, also requires special treatment and protection from occlusal pressure in order to prevent partial spalls. To do this, the thinned sections of the wall are ground down by 1-3 mm in order to subsequently cover the inlays with material. In case of deep caries and cavities of class I according to Black, it is especially necessary to carefully determine the thickness of the remaining hard tissues above the pulp. Painful probing of the bottom of the cavity, discomfort when pressing with a blunt instrument on the bottom, a thin layer of tissue above the pulp (determined by x-ray) determine the specificity and purposefulness of odontopreparation of a carious cavity. In this case, it is necessary to take into account the redistribution of chewing pressure forces on the tooth tissue after insertion of the inlay. Chewing pressure acting on the inlay strictly along the axis of the cavity deforms the latter and is transmitted to the bottom of the cavity, which is also the roof of the dental pulp, which causes irritation of its neuroreceptor apparatus. Mechanical irritation of the pulp is accompanied by pain of varying intensity only during eating and can be regarded by a doctor as a symptom of periodontitis. In such cases, unjustified depulpation is often performed, although percussion of the tooth and x-ray examination do not confirm the diagnosis of periodontitis.

In order to prevent such a complication, which over time can lead to the development of pulpitis, after removing the softened dentin and creating parallelism of the walls, it is necessary to additionally excise healthy enamel and dentin at a level of 2.0 - 1.5 mm below the enamel-dentin border along the entire perimeter of the cavity. As a result, a ledge with a width of 1.0 - 1.5 mm is created, which makes it possible to relieve pressure from the bottom of the cavity and thereby the side effect of the inlay on the tooth tissue. This can be done with thick walls surrounding the main cavity (IROPZ = 0.2 - 0.3). With further destruction of the occlusal surface, the pressure on the bottom of the cavity decreases due to the sections of the inlay covering the occlusal surface.

For similar defects in the crowns of pulpless teeth, instead of an additional cavity, a pulp cavity and root canals with their thick walls are used. The canal (or canals) of the tooth root is expanded with a fissure bur to obtain a hole with a diameter of 0.5 - 1.5 mm and a depth of 2 - 3 mm. It is recommended to use clasp wire of the appropriate diameter as pins.

When making inlays, the pins are cast together with the body of the inlay, with which they form a single unit. This necessitates the need to obtain holes in the channel parallel to the walls of the main cavity.

In case of tooth crown defects of class II according to Black, it is necessary to surgically remove part of the healthy tissue and create an additional cavity on the occlusal surface. The main cavity is formed in the lesion. If two contact surfaces are simultaneously affected, it is necessary to combine the two main cavities into a single additional one, running along the center of the entire occlusal surface.

In the case of deep caries, when the occlusal and contact surfaces are simultaneously affected, the use of fillings is contraindicated. Odontopreparation for inlays in this case, in addition to creating the main (main) and additional cavities, involves removing tissue from the entire occlusal surface by 1-2 mm in order to cover this surface with a layer of metal.

In case of unilateral carious lesions within healthy tooth tissues, a rectangular main cavity is formed, with parallel vertical walls. The cervical wall of the cavity can be at different levels of the crown and must be perpendicular to the vertical walls. When using an inlay, protection of the enamel edges is achieved not by the formation of a bevel (rebate), but by an inlay that rests on part of the contact surface in the form of an armor-like or scaly coating. To create this type of bevel, a layer of enamel is removed along the plane using a one-sided separating disk after the formation of the main cavity. From the contact surface, the bevel has the shape of a circle. The lower part of its sphere is located 1.0-1.5 mm below the cervical edge of the cavity, and the upper part is at the level of the transition of the contact surface to the occlusal one.

In order to neutralize the horizontally acting forces that shift the tab towards the missing wall, it is necessary to create additional elements. An additional cavity is formed on the occlusal surface, most often in the shape of a dovetail or T-shaped with a center along the medio-distal fissure. This shape causes a redistribution of the angular component of chewing pressure directed towards the missing wall.

In case of extensive damage to the contact and occlusal surfaces by the carious process and thinning of the remaining tooth tissues (IROPZ = 0.8 or more), medical tactics consist of devitalization of the tooth, cutting off the coronal part to the level of the pulp chamber, and from the contact sides to the level of the carious lesion, making a stump inlay with pin. In the future, such a tooth should be covered with an artificial crown.

In class III and G cavities, the main cavities on the anterior and lateral teeth are formed in places of carious lesions, additional cavities are formed only on the occlusal surface, mainly in healthy enamel and dentin.

The optimal shape of the additional cavity is one that ensures sufficient stability of the inlay with minimal removal of tooth tissue and preservation of the pulp. However, cosmetic requirements for the restoration of anterior teeth, as well as their anatomical and functional differences, determine the characteristic features of the formation of cavities in these teeth.

When choosing a location for the formation of an additional cavity on the occlusal surface of the front tooth, it is necessary, along with other factors, to take into account the unique shape of this surface and the different location of its individual sections in relation to the vertical axis of the tooth and the main cavity.

A horizontally located bottom can be formed perpendicular to the long axis of the tooth in the cervical part of the contact sides. The specificity of the surgical technique for odontopreparation of anterior teeth for restoration with inlays is the formation of vertical walls and the bottom of the cavity, not only taking into account the redistribution of all components of chewing pressure (the leading component is the angular component), but also the route of insertion of the inlay.

There are two ways to insert the insert: vertical from the cutting edge and horizontal from the lingual side anteriorly. In the first case, vertical walls are formed along the contact surface; additional cavities are not created, but parapulpal retention pins are used. Pins are inserted into the tooth tissue of the cervical region and cutting edge, focusing on safety zones that are clearly visible on an x-ray. A recess for the retention pin is created along the cutting edge, grinding it down by 2-3 mm, but this is only feasible in cases where the cutting edge is of sufficient thickness. A pin only in the main cavity on the contact side cannot provide sufficient stability of the inlay, since the force directed towards the inlay from the palatal side and the cutting edge can rotate it. The use of an additional small pin on the cutting edge significantly increases the stability of the inlay.

If the carious cavity is localized in the middle part of the tooth and the angle of the cutting edge is preserved, then in teeth of significant and medium thickness the formation of a main cavity in the direction of the tooth axis is in principle excluded, since this would require cutting off the angle of the cutting edge, which must be preserved. Therefore, the cavity is created at an angle to the tooth axis. In such cases, an additional cavity on the occlusal surface is also formed at an angle to the tooth axis. This direction of formation of an additional cavity is also necessary because it ensures the stability of the inlay and prevents it from moving towards the missing vestibular wall.

An indispensable condition for the formation of a cavity in case of damage to the vestibular wall, as well as the cutting edge, is the complete removal of the enamel layer, which does not have a dentin sublayer. Preserving a thin layer of enamel in the future will certainly lead to its breaking off due to the redistribution of chewing pressure throughout the entire volume of the tooth.

With small transverse dimensions of the crown, i.e. in thin teeth, the use of retention pins is difficult. Therefore, an additional cavity is formed on the palatal side of such teeth, which should be shallow, but significant in area on the occlusal surface of the tooth. The location of the additional cavity is determined based on the fact that it should be in the middle of the vertical dimension of the main cavity. Retention pins must be placed along the edges of the vertical dimension of the main cavity.

The cavity formed under the inlay is cleaned of sawdust from the hard tissues of the tooth crown and modeling begins.

In the direct method of modeling an inlay, carried out directly in the patient’s mouth, heated wax is pressed into the formed cavity with a slight excess. If the chewing surface is being simulated, the patient is asked to close the dentition until the wax hardens in order to obtain impressions of the antagonist teeth. If there are none, modeling of the cutting edge and tubercles is carried out taking into account the anatomical structure of the tooth. In the case of modeling inlays on the contact surfaces of the teeth, contact points must be restored.

When making an inlay reinforced with pins, pins are first inserted into the corresponding recesses, after which the cavity is filled with heated wax.

An important element of prosthetics is the proper removal of the wax model, eliminating its deformation. If the insert is small, it is removed with one wire sprue-forming pin; if the inlay is large, parallel U-shaped pins are used. In a well-formed cavity, drawing out a model of the inlay is not difficult.

With the indirect method, modeling of a wax reproduction of an inlay is carried out on a pre-fabricated model. In order to obtain an impression, a metal ring is first selected or made from calcined and bleached copper. The ring is fitted to the tooth so that their diameters match. The edge of the ring along the buccal and lingual (palatal) surfaces should reach the equator. When making an inlay from the contact side of the tooth, the edge of the ring should reach the gingival edge.

The ring is filled with thermoplastic mass and immersed in the formed cavity. After the mass hardens, the ring is removed. The quality of the cast is assessed visually. If a good cast is obtained, it is filled with copper amalgam or superplaster. Copper amalgam is introduced in excess, which is used to form a base in the form of a pyramid, which is convenient when holding the model in your hands while modeling the wax insert. After modeling the wax inlays, the metal model is cast.

In the case of the presence of antagonists, as well as to create good contact points, an impression of the entire dentition is made, without removing the impression with the ring from the tooth. After receiving the general impression, the combined model is cast. To do this, the ring is filled with amalgam and a base up to 2 mm long is modeled, then the model is cast according to the usual rules. To remove the ring with thermoplastic mass, the model is immersed in hot water, the ring is removed and the thermoplastic mass is removed. This is how a combined model is obtained, in which all the teeth are cast from plaster, and the tooth prepared for the inlay is made from metal. A wax inlay is modeled on this tooth, taking into account occlusal relationships. Currently, two-layer impression materials are more often used to take impressions. The model can be made entirely from supergypsum.

To cast a metal inlay, the wax reproduction is placed in a refractory mass placed in a casting cuvette. The sprues are then removed, the wax is melted, and the mold is filled with metal. The resulting insert is carefully cleaned of plaque and transferred to the clinic for fitting. All inaccuracies in the fit of the inlay are corrected using appropriate techniques using thin fissure burs. The cement insert is fixed after thorough cleaning and drying of the cavity.

When making inlays from composites, odontopreparation is carried out without forming a bevel (rebate) along the edge of the cavity, since the thin and fragile layer covering the bevel will inevitably break. The simulated wax model of the inlay is covered with a liquid layer of cement, after which the model with the sprue (and cement) is immersed in plaster poured into a ditch, so that the cement is located below and the wax is on top. Replacing the wax with plastic of the appropriate color is carried out in the usual way. After fixing the inlay on the tooth, it undergoes final mechanical processing and polishing.

In rare cases, porcelain inlays are used. The formed cavity is crimped with 0.1 mm thick platinum or gold foil to obtain the shape of the cavity. The bottom and walls of the cavity are lined so that the edges of the foil overlap the edges of the cavity. The foil form (impression) must accurately copy the shape of the cavity and have a smooth surface. The resulting foil cast is placed on a ceramic or asbestos base and the cavity is filled with porcelain mass, which is fired 2-3 times in a special oven. The finished inlay obtained in this way is fixed with phosphate cement.

Artificial crowns

For defects in the hard tissues of the tooth crown that cannot be replaced by filling or with inlays, various types of artificial crowns are used. There are restorative crowns, which restore the damaged anatomical shape of the natural tooth crown, and support crowns, which provide fixation of bridges.

According to their design, crowns are divided into full, stump, half-crowns, equatorial, telescopic, crowns with a pin, jacket, fenestrated, etc.

Depending on the material, crowns are distinguished as metal (alloys of noble and base metals), non-metal (plastic, porcelain), combined (metal, lined with plastic or porcelain). In turn, metal crowns, according to the manufacturing method, are divided into poured ones, made by casting metal in pre-prepared forms, and stamped ones, obtained by stamping from disks or sleeves.

Since artificial crowns can have a negative impact on both the periodontium and the patient’s body as a whole, when choosing their type and material, it is necessary to carefully examine the patient. Indications for the use of artificial crowns:

• destruction of hard tissues of the natural crown as a result of caries, hypoplasia, pathological abrasion, wedge-shaped defects, fluorosis, etc., which cannot be eliminated by fillings or inlays;
• abnormalities in tooth shape, color and structure;
• restoration of the anatomical shape of the teeth and the height of the lower third of the face in case of pathological abrasion;
• fixation of bridges or removable dentures;
• splinting for periodontal disease and periodontitis;
• temporary fixation of orthopedic and orthodontic devices;
• convergence, divergence or protrusion of teeth when significant grinding is required.

In order to reduce the possible negative consequences of the use of artificial crowns on the periodontal tissue of supporting teeth and the patient’s body, crowns must meet the following basic requirements:

• do not overestimate central occlusion and do not block all types of occlusal movements of the jaw;
• fit tightly to the tooth tissues in the area of ​​its neck;
• the length of the crown should not exceed the depth of the dentoalveolar groove, and the thickness of the edge should not exceed its volume;
• restore the anatomical shape and contact points with neighboring teeth;
• do not violate aesthetic standards.

The last circumstance, as shown by many years of practice in orthopedic dentistry, is essential in terms of creating a functional and aesthetic optimum. In this regard, porcelain, plastic or combined crowns are usually used on the front teeth.

Untreated foci of chronic inflammation of the marginal or apical periodontium, the presence of dental plaque are contraindications to the use of artificial crowns. An absolute contraindication is intact teeth, unless they are used as a support for fixed prosthetic structures, as well as the presence of pathological tooth mobility of the 3rd degree and baby teeth. The production of full metal crowns consists of the following clinical and laboratory stages:

• odontopreparation;
• taking impressions;
• model casting;
• plastering the model into an occluder;
• teeth modeling;
• receiving stamps;
• stamping;
• fitting of crowns;
• grinding and polishing;
• final fitting and fixation of crowns.

Odontopreparation for a metal crown consists of grinding the hard tissues of the tooth from all five of its surfaces in such a way that the artificial crown fits snugly in the cervical area, and its gingival edge is immersed in the physiological gingival pocket (dental sulcus) to the required depth without putting pressure on the gum. Violation of this condition can cause inflammation of the gums and other trophic changes, scarring and even atrophy.

There are different points of view on the sequence of odontopreparation. You can start it from the occlusal surface or from the contact surface.

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On October 12, 13 and 14, Russia is hosting a large-scale social event for free blood clotting testing - “INR Day”. The campaign is timed to coincide with World Thrombosis Day.

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Regaining good vision and saying goodbye to glasses and contact lenses forever is the dream of many people. Now it can be made a reality quickly and safely. The completely non-contact Femto-LASIK technique opens up new possibilities for laser vision correction.

TO diseases of dental hard tissues include caries, hypoplasia, wedge-shaped defects, fluorosis, increased abrasion, traumatic injuries, radiation injuries and enamel necrosis. They cause defects of the crown part of the tooth of varying volume and nature. The level of damage to hard tissues is also related to the duration of the process, time and nature of medical intervention. Defects in the crowns of the front teeth spoil the aesthetic appearance of the patient, affect facial expressions, and in some cases also lead to speech impairment. Sometimes, with crown defects, sharp edges are formed, which contribute to chronic damage to the tongue and oral mucosa. In some cases, the chewing function is also disrupted. The most common dental diseases include caries - the increasing destruction of hard tooth tissues with the formation of a defect in the form of a cavity. The damage is based on softening and demineralization of hard dental tissues. There are early and late phases of morphological transformations in carious disease of the hard tissues of the tooth crown. The early phase is characterized by the creation of a carious stain (pigmented and white), while the late phase is characterized by the appearance of cavities of varying depths in the hard tissues of the tooth (stages of superficial, medium and deep caries).

treatment

The main goal of orthopedic treatment for partial defects of the hard tissues of the tooth crown is to reconstruct the crown using prosthetic methods in order to prevent further damage to the tooth or relapse of the disease. An important preventive role of orthopedic treatment of defects in hard dental tissues, which is manifested as one of the main areas of orthopedic dentistry, is the restoration of the crown, which helps prevent further damage and loss of many teeth over time, and this also avoids severe morphological and functional disorders of different parts of the dental system.

prevention

• Oral hygiene;
• proper brushing of teeth;
• healthy lifestyle;
• good nutrition;
• timely rehabilitation.

symptoms

Signs of carious lesions of hard dental tissues are closely related to the pathological anatomy of the carious process, because the latter in its formation goes through certain stages that have characteristic morphological and clinical signs. Early clinical manifestations of caries include a carious spot that appears unnoticed by the patient. Only with a thorough examination of the tooth using a probe and a mirror can a change in the color of the enamel be determined. Caries damage in the form of single foci of destruction in one or two teeth is expressed by complaints of sensitivity during contact of the carious surface with salty, sweet or sour foods, cold drinks, and during probing. It should be noted that during the period of the spot, this symptomatology is detected only in patients with increased excitability. Pain during caries from heat and during probing quickly arises and quickly passes, but with chronic pulpitis it is felt for a long time. With chronic pulpitis, electrical excitability decreases to 1 5 - 2 0 μA.

Dental diseases are very diverse. They are accompanied by the appearance of hard tissue defects characteristic of this disease. These include caries, wedge-shaped defects, hypoplasia, mottling (spotting) of enamel, etc.

Caries is a pathological process characterized by damage to hard tissues, expressed in the destruction of enamel, dentin and cement with the formation of a cavity. Caries is the most common dental disease, affecting the vast majority of people. According to various authors, the prevalence of the population ranges from 80 to 95% or more. Moreover, the frequency of caries in the rural population is usually lower than in the urban population (under the same climatic and geographical zone).

The reasons for the emergence and development of this process have not yet been sufficiently studied. At the same time, it is firmly established that a number of reasons play a certain role in the emergence of this process, in particular living and working conditions. The so-called caries of confectioners is well known, in which dental lesions are much more common, and the process is usually localized in the cervical part of the tooth. Workers in glass (E.D. Aizenshtein), iron ore production (V.P. Guzenko), trinitrotoluene production (E.P. Karmanov) and some others also had a high percentage of caries due to large amounts of dust with solid particles.

The nature of nutrition is also of great importance. When consuming large amounts of carbohydrate-containing foods, the carious process develops more often and more intensely.

The influence of climatic and geographical conditions cannot be excluded, especially taking into account the content of mineral salts and microelements, primarily fluorine, in water and food products. A big role is played by the hygienic maintenance of the oral cavity, as well as some other factors.

First of all, caries affects teeth that have pits, depressions and other places on their surface where food debris can be retained. Therefore, incisors and canines are affected by this process much less frequently than chewing teeth.

Caries occurs more often as a chronic process and less often as an acute one. The conditions for the development of a chronic caries process differ from the conditions for the development of acute caries. Chronic course is possible with good body resistance. In the acute course of the carious process, on the contrary, there are always factors that cause low body resistance (endocrine and autonomic disorders, nutritional disorders). Acute caries most often affects baby teeth and occurs in children suffering from general diseases.

There are four stages in the course of caries. The first of them - the spot stage - is also called initial caries. It is characterized by the appearance of a chalky stain in the absence of a defect in the tooth tissue. In this area, the normal shine of the enamel is absent. Typically, patients do not report any subjective sensations. In some cases, complaints of sore throat (pain) may appear when eating spicy or sour foods.

The second stage - superficial caries - differs from the first stage in that there is already a defect in hard tissues. This defect can be of various sizes, but is located only within the enamel. Subjective sensations include the appearance of pain when exposed to various chemical irritants (sour, sweet, salty). When the irritant is removed, the pain quickly goes away.

The third stage is called middle caries. In this case, a deeper defect of hard tissues is noted, crossing the enamel-dentin border. Dentin is usually pigmented and somewhat softened. At this stage there may be no pain. If they appear, they are only due to chemical or mechanical irritation and are of low intensity. The fourth stage - deep caries - is characterized by the presence of a deep cavity, the bottom of which is also the arch of the tooth cavity. They are separated by a thin layer of dentin, in some cases softened and almost always pigmented. Pain at this stage of the process occurs when food enters the carious cavity and when exposed to temperature stimuli. When the irritant is removed, the pain usually disappears quickly. In some cases, periodic short-term (1-2 minutes) appearance of so-called spontaneous pain is noted, which indicates the involvement of the dental pulp in the process. Probing the bottom of the tooth cavity reveals the presence of a particularly painful point (in contact with the pulp horn). In such cases, manipulations with the probe must be carried out carefully so as not to open the roof of the pulp chamber. If caries is not treated, then sooner or later the dental pulp is involved in the process.

Treatment caries is carried out by a dentist or dentist. It consists of processing the carious cavity using appropriate tools - burs (Fig. 28), excavators. All affected and softened tissues are removed. After medicinal disinfection (hydrogen peroxide, alcohol, ether) of the resulting cavity to restore the anatomical shape and physiological function of the tooth, the cavity is filled with special filling materials - amalgam, cement, plastic (Fig. 29, 30, 31). Only in childhood, during the initial stages of caries, is it possible to grind off the defect. First aid for caries consists of removing all food debris from the carious cavity of the tooth and covering it with a cotton swab to prevent the action of irritants, after which the patient should be referred for treatment to a dentist or dentist.

Wedge-shaped defects

These are defects found in the cervical region of a permanent tooth. The defect is so named because it has the shape of a wedge, on which two stripes can be distinguished, one of them lying horizontally, and the other meeting it at an angle. Wedge-shaped defect occurs mainly on incisors, canines and small molars. On large molars, wedge-shaped defects are less common. A typical place where a wedge-shaped defect is formed is the cervical region of the labial and buccal surface of the tooth.

Wedge-shaped defects usually occur on teeth that are not affected by caries. The surfaces of the defect are very smooth, hard and shiny, in contrast to the rough, soft and dark surfaces of caries. The development of a wedge-shaped defect proceeds slowly, while cervical caries progresses quite quickly.

Treatment in the initial stage of the defect, it comes down to smoothing the outer sharp edges of the planes forming the defect, since sharp edges can damage the mucous membrane of the mouth and tongue, as well as rubbing in an anesthetic paste. I. G. Lukomsky recommends rubbing in fluoride paste:

Rp. Natrii fluorati puri.......... 15.0

Glycerini ................ 5.0

D.S. For dental office

J. S. Pecker offers soda gruel containing 5 g of sodium bicarbonate, 2 g of sodium carbonate and glycerin in the amount necessary to obtain the consistency of a paste. E. E. Platonov suggests using an anesthetic solution of the following composition: 0.2 g of dicaine, 3 g of crystalline carbolic acid, 2 g of chloroform. This solution is mixed with another containing 0.2 g of dicaine, 2 ml of 96° alcohol, 6 ml of distilled water. Pastes made from methyl methacrylate monomer or polymer (AKR-7), thiamine paste, etc. are also used.

In each case, rubbing is done using a cotton swab. These pastes and solution can also be used to anesthetize sensitive dentin when treating a carious cavity. In cases of a pronounced wedge-shaped defect, treatment is reduced, as with caries, to filling.

Hypoplasia and fluorosis

Hypoplasia is a defect in the development of hard dental tissues. Violation of the structure is recognized by changes on the surface of the tooth enamel. A point or pit-shaped notches are formed on the enamel, mostly located several in one row. Sometimes hypoplasia is observed in the form of grooves, following several rows one after another (Fig. 32). Tooth enamel loses its smooth, even, shiny surface and becomes fragile and brittle.

Milk teeth are rarely affected by hypoplasia. On permanent teeth it occurs much more often, and several teeth of the same developmental period are affected simultaneously. If, for example, there is hypoplasia of the cutting edge of the upper molars, then this indicates a temporary disturbance in the deposition of lime that occurred in the first months of the child’s life. Most often, there is a symmetrical lesion (on the right and left side of the jaw) and simultaneous hypoplasia of all incisors, canines and first large molars on the upper and lower jaws.

A carious process very often occurs on the affected teeth, aggravating the overall picture.

In cases where a cavity can be formed in an area of ​​hypoplasia, it is necessary to restore the shape and function of the tooth with a filling. In case of severe disfigurement of the affected teeth and the impossibility of restoration with filling, artificial crowns are put on them.

Fluorosis

Fluorosis, or mottling(spotting) enamels. This lesion is a change in tooth enamel that develops as a result of chronic fluoride intoxication of the body, which occurs as a result of an increased amount of fluoride in drinking water and food products. Normal hygienic fluoridated water, which does not cause changes in the body when consumed, is considered water with a fluorine content of up to 0.5 mg per 1 liter. In some areas, due to the content of significant fluoride compounds in the soil, this indicator is increased and can reach 12-16 mg per 1 liter of water.

Fluorosis is observed in persons who used drinking water and food products with a high fluoride content during the development and formation of teeth. After the development and formation of a tooth is completed, drinking water with a high fluoride content no longer causes mottling of the enamel. Fluorosis usually affects permanent teeth; On milk teeth, mottling was noted only in areas with a fluoride content of at least 12-16 mg per 1 liter of water. Fluorosis in the initial stage is characterized by the presence of chalky spots or stripes on the surface of the enamel, characterized by the absence of the usual shine for enamel. In the last stage, along with the described chalky spots of various sizes, spots from light yellow to brown shades appear. The incisors and canines are mainly affected.

Along with the spots, there are small dark brown specks scattered over the entire surface of the enamel. Sometimes the enamel of all teeth on all surfaces has a white matte tint. With severe mottling, the enamel easily wears off and crumbles, giving the tooth a corroded appearance.

Treatment fluorosis is reduced to removing mottling using a 10% solution of hydrochloric acid or a saturated solution of citric acid. After this, the tooth is treated with soda slurry and polished. For polishing, cement powder mixed with glycerin is most widely used. If the teeth are severely deformed, artificial crowns must be placed on them.

For prevention purposes, according to V.K. Patrikeev, it is advisable for children to use water sources with a normal fluoride content (change of residence, taking children for the summer to pioneer camps in areas where the fluorine content in water sources is low). Containing large amounts of vitamins B 1 and C in food reduces the incidence of disease. Calcium and phosphorus salts are additionally introduced into the children's diet and more milk is given.

Other dental damage

Traumatic damage to hard dental tissues. Occupational damage to the front teeth of the uzur type occurs among shoemakers who have the habit of holding nails with their teeth, and among tailors and seamstresses who bite off threads with their teeth while working. According to our data, up to 70% of people employed in the sewing industry have patterns on their front teeth.

The teeth of musicians playing wind instruments are subject to mechanical damage.

There are frequent cases of damage to the front teeth as a result of everyday habits: smoking a pipe, cracking nuts and seeds.

In cases where this is possible, the shape and function of damaged teeth are restored by filling with conventional filling materials or by using inlays.

Abrasion of chewing and cutting surfaces of teeth. This tooth wear is considered a physiological phenomenon and occurs with age in all people. On the chewing surface of large molars, as a result of abrasion, the bumps are smoothed out or completely disappear.

In workers involved in the production of nitric and hydrochloric acids, the abrasion process extends mainly to the front teeth. This erasure is called “acid necrosis” of the enamel. For workers in acid workshops, the erasure process becomes more intense the longer a person works in this production. Currently, due to the improvement of chemical production, “acid necrosis” is observed very rarely and only in people with at least 10-12 years of experience in this industry.

According to A.E. Churilov, this results in an increase in the concentration of acid in the oral fluid. As a result, there is an increased “leaching” of minerals, primarily calcium, from the tooth enamel.

The abrasion process in this case proceeds as follows: the enamel of the teeth becomes rough, becomes covered with brown spots, becomes dull, and the crown of the tooth gradually wears off and shortens. Sometimes the shortening even reaches the level of the neck of the tooth.

In order to prevent the wear of teeth of workers in workshops with acid vapors, various protective devices are used (respirators, gauze bandages, as well as periodic rinsing of the mouth with a solution of baking soda (one teaspoon per 1/2 cup of water) during and after work. D.I. Kuzmenko considers it advisable in such cases to use fixed prosthetics as a preventative measure.

It is extremely important to introduce additional doses of calcium into the body of these workers. Calcium tablets can be recommended.

Damage to hard dental tissues due to radiation injury. Changes in the hard tissues of the tooth are characterized primarily by clouding of the enamel. Subsequently, necrosis of hard tissue occurs. In other cases, so-called radiation caries appears. A.I. Rybakov believes that in cases where the rays directly affect tooth tissue, the process occurs as a type of necrosis. In cases of general exposure to penetrating radiation on the body, a carious process develops in the teeth. It is necessary to use methods that stop further tooth decay: rubbing fluoride paste, electrophoresis with vitamin B 1, filling, putting crowns on the teeth. It is also necessary to administer medications that improve metabolism in dental tissues and increase the immunobiological properties of the body: a complex of vitamins C, B 1, D, K, calcium and phosphorus preparations, fish oil for children, restriction of carbohydrates (A. I. Rybakov).

Prevention of diseases of hard dental tissues is a set of preventive measures aimed at preventing caries and non-carious lesions of enamel and dentin. Dental diseases cause pain, discomfort, and discomfort in the oral cavity. Aesthetic and functional organ disturbances occur.

Diseases that occur after teething are divided into:

• caries;
• non-carious lesions.

These pathologies are the main cause of tooth loss, so the prevention of diseases of the hard tissues of teeth is one of the main goals of dentistry. Non-carious defects include:

• fluorosis;
• erosion;
• wedge-shaped defect;
• hyperesthesia;
• necrosis;
• erasure;
• injuries.

Caries

The carious process occurs when carbohydrates, microorganisms and dental deposits are present in the oral cavity. Microbes ferment acids from carbohydrates and provoke demineralization of enamel, the formation of cavities. To prevent the disease, comprehensive prevention is carried out, which begins during a woman’s pregnancy:

• Examination and treatment of the expectant mother.
• Balanced nutrition and taking vitamin complexes.
• Providing high-quality hygienic dental care immediately after teething.
• At a conscious age, the child is taught the rules of cleaning and the selection of hygiene products.
• Sealing fissures of permanent teeth.
• If indicated, fluoridation and calcination of hard tissues are performed.
• Orthodontic treatment and bite correction in the presence of dental anomalies.
• Strengthening the immune system.
• Balanced diet.
• Preventative examinations with a doctor twice a year.
• Professional oral hygiene, removal of dental plaque with ultrasound or Air-flow device.
• Timely detection and treatment of pathologies.

Prevention of non-carious lesions of hard dental tissues

Fluorosis is a systemic disease that occurs when excess fluoride enters the body. Most often, the trace element comes with water. The disease affects enamel and dentin and manifests itself with various symptoms depending on the stage. The severity of the manifestations depends on the concentration of fluoride and can be streaked, spotted, chalky-mottled, erosive or destructive.

Prevention of non-carious lesions of dental hard tissues due to fluorosis is as follows:

• Use a water source with a low fluoride content.
• Defluoridation of drinking water.
• Using toothpastes without fluoride.
• Balanced diet.
• Dental procedures – coating of teeth with 10% calcium gluconate solution, 3% Remodent solution.
• Treatment is removal and filling of the affected areas. In case of a destructive form, crowns are made.

Erosion

Erosion manifests itself as cup-shaped depressions on the vestibular surface of the teeth within the enamel. To prevent the disease, it is necessary to rinse the mouth after eating and limit the consumption of acidic foods. You should brush your teeth with a brush with soft bristles and a slightly abrasive paste with a remineralizing effect (Pearl, Cheburashka). It is recommended to take a course of Calcium Gluconate to strengthen your teeth.

Wedge-shaped defect

A wedge-shaped defect is characterized by loss of tooth tissue in the cervical area and the formation of a wedge-shaped defect. The occurrence of pathology is associated with excessive mechanical stress on the enamel. Prevention of wedge-shaped defect pathology:

• At the first sign of damage, replace your toothbrush with a softer one.
• When cleaning, use vertical movements.
• Strengthen enamel with remineralizing agents in dentistry. If a significant defect appears, a filling is performed.

Hyperesthesia is characterized by increased sensitivity of teeth to temperature, chemical and mechanical stimuli.

Pathology occurs when tissue is abraded, the neck or root of a tooth is exposed, and periodontal diseases occur. For the prevention and treatment of hyperesthesia of hard dental tissues:

• Use remineralizing toothpastes with a high content of fluoride, calcium, potassium, and magnesium.
• Consult your doctor. The doctor carries out the necessary medical procedures - strengthening the enamel with the help of special solutions, filling, manufacturing orthopedic structures (veneers, crowns, dentures).

Necrosis

Prevention of diseases of dental hard tissues from necrosis consists of ensuring good working conditions and eliminating the effects of chemicals on the human body. Rinse your mouth with alkaline solutions (2-3% sodium bicarbonate), use respirators or masks while working.

Erasing

Increased tooth wear occurs:

• after tooth loss;
• bite displacement;
• diseases of the temporomandibular joint;
• during orthodontic treatment.

To prevent disease, it is necessary to promptly treat dental diseases and strengthen the enamel. It is necessary to eliminate the factors that provoke pathology, use softer foods, and use a brush with soft bristles.

Traumatic injuries to hard tissues (fractures, bruises, chips) cannot always be prevented, as they occur in accidents. To prevent dental injuries:

• eliminate bad habits (biting foreign objects, cracking seeds);
• When playing sports, use a special mouthguard. The design is made by a dentist after taking impressions of the jaws. The product is worn on the dentition, protects teeth and soft tissues from damage.

A large number of diseases of enamel and dentin occur during the period of follicular tissue development, that is, during pregnancy. Pathologies arise due to the lack of treatment for maternal illnesses, exacerbation of diseases, taking illegal medications, malnutrition, drinking alcohol or drugs, and the bad habit of smoking. Non-carious diseases include:

• hypoplasia and hyperplasia of enamel;
• endemic fluorosis;
• anomalies of development and eruption;
• hereditary diseases.

Systemic hypoplasia– this is underdevelopment of enamel, the formation of tissue of insufficient thickness or irregular structure. The disease occurs when taking medications while carrying a child, malnutrition, or hereditary anomalies. The disease manifests itself in the formation of various types of defects, spots, and pits on the enamel. Characterized by tissue damage, chipping, and destruction under low pressure. Prevention consists of taking multivitamin complexes, adequate nutrition and treatment of body diseases.

Hyperplasia– this is the formation of additional drops or tubercles on the enamel. Pathology occurs when tissue develops excessively. Prevention of diseases of hard dental tissues of non-carious origin, such as hyperplasia, is not carried out. A pregnant woman is recommended to adhere to general rules and normalize the intake of microelements (calcium, potassium, fluorine, iron). The disease does not threaten complications; in case of aesthetic defects, the enamel is polished and restored.

Endemic fluorosis occurs in a baby when excessive fluoride enters the body of a pregnant woman during the formation and mineralization of future teeth. In this case, the child’s teeth will erupt with signs of the disease. Prevention consists of controlling and normalizing the fluoride that the expectant mother consumes. If the affected teeth have already erupted, then treatment is necessary.

TO developmental anomalies and teething include abnormalities in shape, number, color, shape and position. Prevention of anomalies is to ensure normal intrauterine and postnatal development of the baby. Includes proper nutrition, treatment of chronic diseases, endocrine disorders, regular visits to the dentist and gynecologist.

Prevention of pathologies of hard dental tissues that form during the period of follicular development of the rudiments should be carried out during pregnancy. During this period, there is a lack of minerals, which provoke a predisposition to dental diseases. The expectant mother should follow the doctor’s recommendations, undergo timely examinations and undergo treatment. Prevention measures:

• Examination of the body and treatment of diseases.
• Sanitation of the oral cavity.
• Taking folic acid before and during pregnancy.
• Monitoring the progress of pregnancy by a specialist.
• Regularly visit your doctor and follow his recommendations.
• Taking complexes of vitamins and minerals.
• Balanced diet.

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Etiology, pathogenesis and clinic of diseases of hard dental tissues

Brief information about the process of mineralization and ultrastructure of hard dental tissues

Enamel. Human teeth are the organ that performs the primary mechanical processing of food. The main function of teeth determined the morphological characteristics of their tissues. The crown part of the teeth is covered with enamel - the most durable tissue. While withstanding high pressure during chewing, the enamel is at the same time fragile and weakly resists sudden loads, such as an impact, which causes cracks and chips of the enamel.

The thickness of the enamel layer is not the same: at the neck of the tooth it barely reaches 0.01 mm, at the equator it is 1.0-1.5 mm, in the area of ​​​​the bottom of the fissures - 0.1-1.5 mm, at the cutting edge of unworn teeth - 1.7 mm, on the tubercles - 3.5 mm [Fedorov Yu. A., 1970]. The specific heat capacity of enamel is 0.23 J/(kg * K); its thermal conductivity is low (Ktp is equal to 10.5 * 10 -4 W/(m * K). On the outside, the enamel is covered with a very dense, non-calcified, acid- and alkali-resistant film (Nasmitian shell) 3-10 microns thick, which is located at the neck The tooth connects to the epithelium of the mucous membrane of the gum, being, as it were, its continuation. Soon after teething, the film is erased, primarily on the contacting surfaces of the teeth. The structural element of the enamel is the enamel prism. It is formed during the development of the tooth from adamantoblasts - cells of the internal enamel epithelium organ.

Data obtained in recent years using electron microscopy have made some adjustments to the understanding of the ultrastructure of enamel and its components. Enamel prisms are composed of collagen protofibrils and isolated crystals oriented perpendicular to the enamel-dentin junction. The cross-section of enamel prisms is 5-6 microns, their shape can be round, hexagonal, etc. The spaces between the prisms, 1-3 microns wide, are less mineralized and filled with fibrous tissue (an interprismatic substance that performs a nutritional function in the enamel) with a smooth surface, facing the walls of the prism. The interprismatic substance appears amorphous, is located in the form of a thin, often barely noticeable strip, or forms clusters - enamel: bundles or plates. In cross section and at the base, prisms most often have an arcade, oval or polyhedral shape. With their opposite sharp ends they wedge between the underlying prisms. The ends of the enamel prisms, wide at the base, are separated by narrowed ones. The ends of the enamel prisms, wide at the base, are separated by the narrowed ends of the prisms of the overlying layer.

Enamel prisms are mineralized evenly, the degree of mineralization is high. As crystals age, the protein-rich layers between the prisms become denser, and the “border lines” become thinner.

At the border of enamel and dentin, a continuous layer is formed from the adhesive substance - the so-called delimiting membrane. On its side facing the dentin, a border in the form of a brush is formed, the fibers of which pass into the Korf fibrils of dentin, which ensures a strong mechanical and physiological connection between the enamel and dentin. The results of studying the ultrastructure of hard dental tissues suggest that the enamel-dental junction as a morphological formation does not exist [Bushan M. G., 1979].

Dentine. Dentin makes up about 85% of tooth tissue and contains collagen fibers, between which there is an amorphous adhesive substance. These formations make up the main substance of dentin. The number and nature of the arrangement of these fibers are not the same in different layers of dentin, which determines the peculiar structure of the mantle, or peripheral layer of dentin, in which radial fibers predominate, and peripulpal dentin, rich in tangential fibers.

Dentin is a highly mineralized tissue (about 73% organic compounds) and is second only to enamel in terms of mineralization. The least mineralized is the zone of dentin, facing the pulp and separated by a fibrous line. In the literature, this zone is described as the poedentine or dentinogenic zone, although it has nothing to do with dentinogenesis.

Except for the quality of very low mineralization, it is identical to peripulpal dentin.

At the border of mantle and peripulpal dentin, interglobular spaces are often identified, the origin of which is presumably associated with the unevenness of the calcification process. Similar but smaller formations, referred to as granular layers of Tomes, are noted at the dentinocemental boundary. Interglobular spaces and granular layers of Tomes, located in several rows, make up Owen's contour lines, which, according to the mechanism of formation, are identical to Retzius lines in enamel.

The ground substance of dentin is penetrated by a huge number of dentinal tubules, mainly in a radial direction. According to G.V. Yasvoin (1946), in the peripulpar dentin their number reaches 75 thousand per 1 mm 2. Starting on the inner surface of the dentin and moving towards the periphery, the tubules narrow and, due to the radial direction, diverge. Near the enamel-dentin junction their number reaches 15 thousand per 1 mm 2.

On electron microscopic replicas, non-decalacinated dentin of intact teeth consists of a basic substance (matrix) in which a network of dentinal tubules is defined. Dentinal tubules are tubes of different diameters. In areas located closer to the pulp chamber, their diameter is on average 0.5-0.8 microns. As they approach the enamel-dentin junction, the tubules gradually become narrower - 0.2-0.4 microns.

The wall of the dentinal tubules is more mineralized and dense compared to the intertubular zone. 3 in the immediate vicinity of the dentinal tubules, collagen protofibrils are located more densely than at the periphery, which corresponds to the peritubular hypermineralized zone. This provides evidence that apatite crystal formation centers are formed along the dentin collagen protofibrils.

The width of the hypermineralized peritubular zone depends on the area of ​​dentin and the age of the person. At the age of 20-30, it is somewhat narrower than at 40-50. As the dentinal tubule approaches the enamel-dentin border, the hypermineralized peritubular zone becomes wider, and it is also well preserved around the lateral branches.

The intertubular zone is a less mineralized area of ​​dentin. In addition to crystals, the intertubular zone contains collagen fibers running in different directions. The density of crystal grains and collagen fibers is lower compared to the peritubular zone.

In most cases, dentin crystals are needle-shaped with pointed ends. The bulk of apatite crystals are of the same size: their length is on average 30-60 nm, width is 2-13 nm.

The question of the existence of the Neumann membrane (peritubular dentin), which supposedly lines the dentinal tubules, has not been completely resolved. Some authors acknowledge its existence [Falin L.I., 1963]. In their opinion, the Neumann membrane consists of amorphous plasmatic substances and is located between the Toms processes (dentinal process of the ondotoblast) and the inner surface of the wall of the dentinal tubules. The authors came to this conclusion based on data obtained using an optical microscope. This information is still given in textbooks, although there is enough recent data that completely refutes the existence of the Neumann shell.

Dentinal tubules are limited only by the plasma membrane. Toms fibers are protoplasmic processes of odontoblast cells that extend into the dentinal tubules.

These fibers act as a transfusion system that provides nutrition to hard tissues. Most of the fibers blindly end in the form of thickenings in the peripheral parts of dentin. Some fibers penetrate the enamel in the form of flask-shaped swellings - enamel spindles or bushes.

The question of the presence of neural cements in dentin also remains controversial, which is associated with significant difficulties that arise during neuro-otological processing of the object. Many authors deny the existence of these elements in dentin, and the processes of odontoblasts are assigned the role of transmitters of irritation to the marginal zone of the pulp, supplied with nerve fibers. Nerve fibers penetrating the dentinal tubules perform a dual function - sensitive and trophic.

Cement. There are cellular and acellular cement that covers the dentin of the tooth root. Cellular, or secondary, cement in certain areas of the root, mainly at the bifurcation of multi-rooted teeth and at the apices of the roots of all teeth, is layered with acellular, or primary. With age, the amount of cellular cement increases. Cavities with cells are often found in the newly formed cement. There is a known case when the newly formed cement acquired the character of lamellar bone.

No blood vessels were found in either cellular or acellular cement, and there is also no information about its innervation. The main substance of primary cement consists of collagen fibrils, which diverge predominantly in the radial direction, sometimes in the longitudinal direction. Radial fibrils directly continue in Sharpei's (perforating) fibers of the periodontium and further penetrate into the alveoli.

The tooth is not isolated from the surrounding tissues, but, on the contrary, forms an inextricable whole with them. It is believed that the tooth is genetically, anatomically and functionally related to periodontal tissues. Connective tissue, vessels, nerves of the tooth and periodontium unite these anatomical formations into a single, interdependent complex that performs a single function.

Dentin hydroxyapatite crystals resemble bone tissue crystals in size and shape. Due to the extremely small size of the crystals (length 20-50 nm, thickness about 10 nm, width 3-25 nm), favorable conditions are created for ion exchange. Crystals increase in size as the degree of mineralization of the tooth substance increases. Dentin fluid (dental lymph) penetrates into dentin and enamel through Toms' processes, with which nutrients flow from the blood into the hard tissues of the tooth.

Many issues of the physicochemical and biological essence of the process of formation of hydroxyalatite crystals and intracrystalline exchange have not yet been sufficiently studied. Their study was carried out mainly in vitro, so the data obtained cannot fully reveal the nature of these processes in dental tissues. At the same time, the presence of a close morphological and functional connection between the organic and inorganic components of the tooth has been established. It has also been proven that collagen protofibrils of hard dental tissues serve as the basis on the surface and inside of which crystallization centers are created. As a result of the deposition of inorganic calcium and phosphorus salts in the crystallization centers, individual apatite crystals (hydroxyapatite, fluorapatite) are gradually formed. As they grow, they get closer to their neighbors, become cemented and form a group of crystals. The crystallization process is characterized by certain intervals and periods.

Each crystal of hydroxyapatite is surrounded by a thin, stationary layer of liquid - the so-called hydration layer. It is formed due to pronounced electrical asymmetry, due to which a strong electric field is created on the surface of the crystals. As a result, layers of bound ions are formed, which constantly hold a stationary layer of solvent around the crystals - the hydration layer. The hydration layer contains high concentrations of hydrated calcium ions and polarized phosphorus ions. The crystals themselves consist of anions and cations, which form atomic crystal lattices repeating one after another. Anions and cations, being opposite in charge, are located in the crystal lattice at a strictly defined distance and are connected to each other using the electric field formed around the ions.

Calcium and phosphorus in bones and dental tissues are presented in the form of two fractions - labile and stable. Labile calcium is 20-25%, phosphorus is 12-20%. The exchangeable and labile fractions represent a kind of depot of ions that provide an exchange reaction in the hydration layer of liquid around the crystals and are in quantitative equilibrium with phosphorus and calcium in the blood. In the process of mineral metabolism, growth and formation of crystals, calcium and phosphorus pass from the labile fraction to the stable fraction of crystals by precipitation (recrystallization).

In the process of isoionic exchange, calcium and phosphorus ions pass into hydroxyapatite crystals through three zones. The first of them is the transition from the diffusion layer to the hydration layer, which occurs due to the asymmetry of the charge on the surface of the crystal. The second zone is the transition from the hydration layer to the surface of the crystal, which occurs under the influence of ionic force. The third zone is the transition from the crystal surface to the crystal lattices due to thermal movement and diffusion.

Calcium ions are polarizable, so a strong electric field is formed around them and the surface of the crystals has a mostly positive charge. Negative charges are located on their surface in the form of a mosaic. The rate of ion exchange also largely depends on the valence and the strength of interionic attraction. The first two phases of ion exchange - between the diffuse and hydration layers, as well as between the hydration layer and the surface of the crystals - proceed quite quickly. Inside the crystals, the rate of exchange depends on the number of free sites and defects in the lattice, so the process proceeds rather slowly.

Functional morphology of teeth

In the dental system, the unity and interdependence of form and function is especially clearly visible. Various lesions of the hard tissues of individual or groups of teeth gradually lead to changes in their morphology, as a result of which disturbances in the chewing function of the dentoalveolar system may occur, the normalization of which is the main goal of dental prosthetics.

The relationship between the height of the clinical crown and the length of the root varies widely both in individual teeth or their groups, and individually in each patient. In some cases, the clinical crown corresponds to the anatomical one, in others, the length of the clinical crown is greater than the anatomical one. In childhood and adolescence, the clinical and anatomical contours of the tooth crown are usually combined: the transition of enamel into cement coincides with the line of the clinical neck. The root is usually not visible or palpable; it can only be studied radiographically. Teeth with this morphology are highly resistant and can absorb additional load, which is important when choosing fixed and removable denture designs.

With periodontitis, the dimensions of the clinical crown and root of the tooth undergo certain changes. Due to alveolar atrophy and gum retraction, the root is exposed, and the clinical crown becomes longer than the anatomical one. As the clinical crown lengthens and the root shortens, the stability of the tooth and the reserve forces of the periodontium decrease. Changing the size of the arm of the tooth resistance lever complicates the choice of prosthesis design that eliminates functional overload of the periodontium.

It is known that the root surface is individually different, while the size of the surface of individual teeth is directly dependent on the size of the tooth crown and the function performed. With the exception of second and third molars, the root surface increases distally from the midline.

The anatomical equator divides the tooth surface into gingival and occlusal. The level at which the anatomical equator is located is different both on the oral and vestibular surfaces of one tooth, and on individual teeth.

In case of pathology of hard dental tissues, restoration of their anatomical shape should provide not only an aesthetic, but also a preventive effect aimed at preserving periodontal tissues.

The pulp cavity in general follows the shape of the coronal part of the corresponding tooth and has different wall thicknesses. Knowing the thickness of hard tissues in different areas of the tooth crown eliminates the possibility of damage to the pulp during the preparation process. The thickness of various sections of the crown part of the teeth was first presented in the form of diagrams by Boisson, who proposed to distinguish the so-called safety zones. He considered these zones to be areas of the coronal part of the tooth in which the thickness of the hard tissues allows the required amount of grinding to be carried out without fear of opening the pulp chamber during the manufacture of fixed dental structures. Danger zones are areas of the tooth crown where there is a small thickness of hard tissue and, therefore, the pulp cavity is close to the tooth surface. For example, the safety zones of the incisors are located at the cutting edge, on the oral side and the proximal surfaces of the crown and neck of the tooth. Dangerous zones are considered to be the spaces between the safe zones of the cutting edge and the oral side, as well as the vestibular and oral sides of the tooth neck.

In canines, safety zones are located on the approximal surfaces, pass to the oral surface, and extend to the equatorial region. At the neck of the tooth, safety zones are located on the proximal surfaces. The area of ​​the top of the cusp, the vestibular and oral sides of the neck of the tooth are easily vulnerable, since here the pulp is located close to the surface.

The safety zones of premolars are localized on the approximal surfaces, in the middle of the chewing surface, where the fissures end near the contact points, as well as at the neck of the tooth. Dangerous places are the tops of the cusps, the oral and vestibular sides of the neck of the tooth.

The safety zones of molars are the contact points of the crown, the central part of the chewing surface, the spaces between the cusps, the ends of the fissures on the vestibular, oral and contact points of the tooth and the contact sides of the neck of the tooth. Dangerous places are the tops of the cusps, the vestibular and oral sides of the neck of the tooth.

The structural features of each tooth are taken into account when determining the volume of grinding of hard tissues during tooth preparation, as well as when deciding on the advisability of creating a ledge, its location, length and depth. In cases where the presence and topography of dangerous zones are not taken into account, complications arise during grinding of hard dental tissues: opening of the pulp, pulpitis, thermal burn of the pulp. The approximate dimensions of the safety zones can be determined by measuring them on radiographs.

Immediately after teething, the pulp cavity is very voluminous, and as age increases, its volume decreases; this feature is taken into account when determining the indications for the use of street crowns up to 16 years of age and porcelain crowns up to 18-19 years of age.

The functional morphology of the front teeth corresponds to the necessary conditions for the initial act of chewing - cutting and tearing food, and the lateral teeth - for crushing and grinding food. The more often the front teeth are included in the function and the more often they cut food of a hard consistency, the faster the height of the crown decreases due to wear, and the cutting surface increases. This functional wear is considered physiological wear. However, under the influence of a number of factors, the wear of hard dental tissues can progress and acquire the character of a pathological process, which leads to shortening of the crowns of the teeth down to the level of the gums, which is accompanied by a complex of other complications.

The front teeth, with the exception of the lower incisors, in most cases have a wide and easily accessible root canal. This makes it possible to expand them and use them for the manufacture of post teeth, core post inlays and core crowns. The roots of the lower incisors are flattened on the approximal sides, which eliminates the possibility of expansion of their canals due to the risk of perforation.

Premolars, with the exception of the first upper ones, have one root canal. Second upper premolars sometimes have two canals in one root. Single-rooted premolars with a passable canal can be used for the manufacture of pin-based denture structures.

The first and second molars of the upper jaw each have three roots: two buccal, shorter and less massive, diverge somewhat in the sagittal plane, and the palatal, longer and more voluminous, is directed towards the palate. The characteristic direction of the palatal root, which is the result of functional adaptation, allows the chewing load to be redistributed along the main axis of the tooth. The structural features of the palatal roots, compared to the buccal ones, provide more favorable conditions for the introduction and fixation of pin structures of prostheses.

Throughout life, the morphology of the occlusal surface of the teeth can remain unchanged without significant changes or change depending on the nature of the occlusal contacts during chewing. In persons in whom vertical hinge movements of the lower jaw predominate (with a deep bite), no pronounced changes in the occlusal surface of the teeth occur for a long time. With a straight bite, in which the horizontal sliding movements of the lower jaw are carried out unhindered, the relief of the occlusal surface of the teeth changes due to the abrasion of the cusps. This must be taken into account when studying the state of the dental system, establishing a diagnosis and choosing a method of orthopedic treatment of patients.

J. Williams (1911) proved the existence of a certain dentofacial harmony. In particular, the shape of the central incisors corresponds to the shape of the face: patients with a square face tend to have square-shaped front teeth, those with an oval face tend to have oval-shaped front teeth, and those with a triangular face shape tend to have triangular-shaped front teeth. In the process of orthopedic treatment of anterior teeth, the nature of the modeling, the creation of the shape, direction and size of the teeth are directly related to the restoration of the aesthetic appearance of the patient.

The color of teeth in each patient has individual characteristics, which is the result of layering of enamel color on dentin color. Dentin has a yellow color of various shades. The enamel color is white with yellow, blue, pink, gray tints or a combination thereof. In this regard, the vestibular surface of the front teeth has three color nuances. The cutting edge of the front teeth, which does not have a dentin sublayer, is often transparent; the middle part, covered with a thicker layer of enamel, which does not allow dentin to show through, is less transparent; in the cervical part, the enamel layer is thinner and the dentin shines through it more strongly, so this area of ​​the tooth crown has a pronounced yellowish tint.

In young people, the color of the teeth is generally lighter, while in adults, especially the elderly, it has a more pronounced yellowish or grayish tint. In some cases, particularly in smokers, various pigmentations and atypical changes in the color of teeth appear. The color of teeth largely depends on compliance with the rules of dental and oral hygiene.

Partial and complete destruction of the crown part of the tooth

Pathologies of hard dental tissues include carious and non-carious lesions.

Tooth caries. A huge amount of scientific research has been devoted to the study of the problem of dental caries (etiology, pathogenesis, clinical picture, treatment and prevention). At the same time, it remains very relevant throughout the world and the search for its solution continues.

Teeth affected by caries are covered with dentures according to indications only after thorough treatment. Along with other harmful effects on the dental system, the carious process disrupts the anatomical shape and structure of the tooth crown due to the formation of defects in hard tissues.

Defects of the tooth crown are divided into partial and complete. Partial defects can have different locations, sizes, shapes and depths. The crown part of the tooth is not completely destroyed, and it is restored with the help of filling material, and in some cases, orthopedic treatment is carried out according to the local authorities. Complete defects in the crown of a tooth (complete absence of a crown) are eliminated using pin teeth.

Non-carious lesions of teeth are divided into two main groups [Patrikeev V.K., 1968]: 1) lesions that occur during the period of follicular development of dental tissues, i.e. before eruption: enamel hypoplasia, enamel hyperplasia, dental fluorosis, anomalies of development and eruption teeth, changes in their color, hereditary disorders of dental development; 2) lesions that occur after eruption: tooth pigmentation and plaque, tooth erosion, wedge-shaped defect, abrasion of hard tissues, dental hyperesthesia, necrosis of hard dental tissues, dental trauma.

Enamel hypoplasia. Hypoplasia of dental tissue occurs as a consequence of disruption of metabolic processes in the anamenoblasts of the tooth buds. The occurrence of hypoplasia is facilitated by disturbances in protein and mineral metabolism in the body of the fetus or child. Based on etiological characteristics, focal odontodisplasia, systemic and local hypoplasia are distinguished.

Focal odontodysplasia (odontodysplasia, incomplete odontogenesis) occurs in several adjacent teeth of the same or different periods of development. The rudiments of both temporary and permanent teeth are affected, most often incisors, canines and permanent molars. The clinical picture of the disease is characterized by a rough surface, yellowish color, reduction in size and unequal density of the tissues of the tooth crown.

Systemic hypoplasia occurs under the influence of various factors, primarily diseases that can disrupt metabolic processes in the child’s body during the period of formation and mineralization of these teeth. Systemic hypoplasia is accompanied by a violation of the structure of the enamel of only that group of teeth that is formed in the same period of time.

Enamel hypoplasia is characterized by the formation of cup-shaped depressions of round or oval shape. At the bottom of the depressions, the enamel may be absent (aplasia) or it may be thinned and yellowish dentin can be seen through it. The sizes, depth and number of defects are different, the walls, edges of the recesses and the bottom are smooth. The cutting edges of teeth affected by hypoplasia form a semilunar notch.

With the grooved form of hypoplasia, the defects are localized parallel and at some distance from the cutting edge or chewing surface and are more pronounced on the vestibular surface of the teeth. The number of grooves may vary; at their bottom there is a thin layer of enamel, and in some cases there is no enamel.

Fournier, Hutchinson and Pfluger teeth are considered a type of systemic hypoplasia. The crown of the tooth takes on a peculiar barrel-shaped shape with a semilunar notch on the cutting edge of the front incisors of the upper and lower jaws. Pflueger teeth are characterized by the cone-shaped shape of the permanent molars. Hypoplasia of the cutting edges and cusps contributes to the development of increased abrasion of hard dental tissues and often leads to aesthetic dissatisfaction with the patient's appearance.

With local hypoplasia (Turier's teeth), one or less often two teeth are affected, and only permanent teeth. The disease develops under the influence of mechanical trauma or inflammation.

Therapeutic methods for treating hypoplasia are ineffective. Preference should be given to orthopedic methods: covering the affected teeth with prostheses, the design of which depends on clinical indications.

Enamel hyperplasia (enamel drops, pearls). This pathology is an excessive formation of tooth tissue during its development, most often in the area of ​​the tooth neck on the line separating the enamel and cement, as well as on the contact surface of the teeth. Functional disorders with enamel hyperplasia are usually absent. This damage to hard tissues must be taken into account when determining the indications for creating a ledge at the neck of the affected teeth in the manufacture of porcelain and metal-ceramic structures.

Dental fluorosis (spotted enamel, pockmarked enamel). This damage to hard tissues develops due to the consumption of drinking water with an excessive content of fluoride compounds.

V.K. Patrikeev (1956) distinguishes five forms of dental fluorosis: streaked, spotted, chalky-speckled, erosive and destructive. The streak form most often appears on the vestibular surface of the upper incisors in the form of faint chalky stripes. With spotted teeth, the front teeth are most often affected, less often the lateral ones. The disease is manifested by the appearance of chalky spots located in different parts of the tooth crown. The chalky-mottled form of fluorosis is considered a more severe disease, affecting all teeth, the crowns of which acquire a matte tint, along with this, areas of light or dark brown pigmentation are observed. Small defects in the form of specks with a light yellow or dark bottom form in the enamel. The erosive form is characterized by degeneration and pigmentation of the enamel with the formation of deep, extensive defects, accompanied by dentin exposure. The destructive form is the most advanced stage of fluorosis. This form is characterized by extensive destruction of the enamel, pathological abrasion, breakage of individual sections of the tooth and a change in the shape of its coronal part.

Thus, with fluorosis, depending on the form and degree of development of the process, various disturbances occur in both the shape and structure of hard tissues and the aesthetics of the face.

Local and general therapeutic treatment for severe forms of fluorosis (chalky-mottled, erosive, destructive) often does not give the desired effect. In such cases, orthopedic methods are indicated to restore aesthetic standards and the anatomical shape of the tooth crown.

Capdepon's dysplasia(Stainton-Capdepon syndrome). This disease, which is a hereditary disorder of dental development, affects both temporary and permanent teeth.

Erosion of hard dental tissues. Erosion occurs mainly in middle and old age from the mechanical impact of a toothbrush and powder. The etiology of the disease is not well understood. Erosion mainly occurs on the front teeth of the upper jaw, the premolars of both jaws and the canines of the lower jaw. It appears on the vestibular surface of the tooth crown in the form of a round or oval enamel defect with a smooth, hard and shiny bottom, gradually increases in the transverse direction and takes the shape of a grooved chisel. In case of a large area of ​​damage, when it is not possible to eliminate the defect using filling material, orthopedic treatment is carried out.

Wedge-shaped defect. This damage to hard tissues is most often observed on canines and premolars. less often - incisors and molars. The etiology of the disease is not fully understood. Mechanical and chemical factors (toothbrushes and powder, demineralizing effects of acids, as well as endocrine disorders, diseases of the central nervous system and gastrointestinal tract) are important in the progression of wedge-shaped defects.

Wedge-shaped defects are most often located symmetrically (right and left) on the vestibular surface of the tooth in its cervical region. They develop slowly and are accompanied by the deposition of replacement dentin. As the pathological process progresses, pain occurs under the influence of mechanical (when brushing teeth), chemical (sour, sweet) and temperature (hot, cold) stimuli.

S. M. Makhmudkhanov (1968) distinguishes four groups of wedge-shaped defects:

1) initial manifestations without tissue loss visible to the eye, revealed with a magnifying glass. Increased sensitivity to external stimuli;

2) superficial wedge-shaped defects in the form of squeal-like damage to the enamel, localized near the enamel-cementum border. The depth of the defect is up to 0.2 mm, the length is 3-3.5 mm. Tissue loss is determined visually. Characterized by increased hyperesthesia of the necks of the teeth;

3) medium wedge-shaped defects formed by two planes located at an angle of 40-45 °. The average depth of the defect is 0.2--0.3 mm, length 3.5--4 mm, the color of the hard tissues is similar to the yellowish color of normal dentin;

4) deep wedge-shaped defects more than 5 mm in length, accompanied by damage to the deep layers of dentin up to the pulp cavity, which can result in crown fracture. The bottom and walls of the defects are smooth, shiny, and the edges are even.

For wedge-shaped defects, general treatment is carried out aimed at strengthening the tooth structure and eliminating dentin hyperesthesia, as well as local filling. If the filling is poorly fixed and there is a risk of tooth crown fractures, orthopedic treatment is indicated.

Hyperesthesia of hard dental tissues. Hyperesthesia is an increased sensitivity of the hard tissues of the teeth to mechanical, temperature and chemical stimuli, observed in carious and non-carious lesions of the hard tissues of the teeth and periodontal diseases.

A. By prevalence.

1. Limited form, usually manifested in the area of ​​individual or several teeth, more often in the presence of single carious cavities and wedge-shaped defects, as well as after preparation of teeth for artificial crowns or inlays.

2. A generalized form, manifested in the area of ​​most or all teeth, more often in the case of exposure of the necks and roots of teeth in periodontal diseases, pathological abrasion of teeth, multiple dental caries, multiple progressive forms of dental erosion.

B. By origin.

1. Dentin hyperesthesia associated with loss of hard tooth tissues:

a) in the area of ​​carious cavities;

b) arising after the preparation of tooth tissue for artificial crowns, inlays, etc.;

c) accompanying pathological abrasion of hard dental tissues and wedge-shaped defects;

d) with erosion of hard dental tissues.

2) Dentin hyperesthesia, not associated with loss of hard tooth tissues:

a) in the area of ​​exposed necks and roots of teeth in periodontal diseases;

b) intact teeth (functional), accompanying general disorders in the body.

B. According to the clinical course.

I degree - tooth tissue reacts to a temperature stimulus (cold, heat). The threshold of electrical excitability is 5-8 µA;

II degree - tooth tissue reacts to both temperature and chemical stimuli (cold, heat, salty, sweet, sour, bitter food). Electrical excitability threshold 3-5 µA;

III degree - tooth tissue reacts to all types of stimuli (including tactile). The threshold of electrical excitability is 1.5-3.5 µA).

Pathological abrasion of hard dental tissues. This form of damage to hard tissues occurs quite often and causes a complex set of disorders in the dental system, and orthopedic treatment methods have their own specifics.

Crossbite

Crossbite refers to transversal anomalies. It is caused by a discrepancy between the transversal dimensions and shape of the dentition. The frequency of crossbite, according to the literature, varies at different ages: in children and adolescents - from 0.39 to 1.9%, in adults - about 3%. Various terms are used to characterize crossbite: oblique, lateral, buccal, vestibulo-occlusion, bucco-occlusion, linta-occlusion, lateral - forced bite, articular crossbite, laterognathia, laterogeny, lateroversion, laterodeviation, laterodgnathia, laterodyskinesia, lateroposition.

The development of crossbite can be caused by the following reasons: heredity, incorrect position of the child during sleep (on one side, placing a hand or fist under the cheek), bad habits (propping the cheek with the hand, sucking fingers, cheeks, tongue, collar), atypical location of the rudiments of teeth and their retention, delay in the replacement of milk teeth with permanent ones, violation of the sequence of teething, unworn cusps of milk teeth, uneven contacts of the dentition, early destruction and loss of milk molars, impaired nasal breathing, improper swallowing, bruxism, uncoordinated activity of the masticatory muscles, impaired calcium metabolism in the body , hemiatrophy of the face, trauma, inflammatory processes and resulting disturbances in jaw growth, ankylosis of the temporomandibular joint, unilateral shortening or lengthening of the lower jaw branch, unilateral excessive growth of the jaw body or growth retardation, residual defects in the palate after uranoplasty, neoplasms, etc.

Considering the wide variety of crossbite clinics, it is advisable to highlight the following forms [Uzhumetskene I. I., 1967].

The first form is a buccal crossbite.

1. Without displacement of the lower jaw to the side;

a) unilateral due to unilateral narrowing of the upper dentition or jaw, expansion of the lower dentition or jaw, or a combination of these signs;

b) bilateral, caused by bilateral symmetrical or asymmetrical narrowing of the upper dentition or jaw, expansion of the lower dentition or jaw, or a combination of these signs.

2. With a displacement of the lower jaw to the side:

a) parallel to the midsagntal plane;

b) diagonally.

3. Combined buccal crossbite - a combination of characteristics of the first and second varieties.

The second form is lingual crossbite:

1. Unilateral, caused by a unilaterally expanded upper dentition, a unilaterally narrowed lower one, or a combination of these disorders.

2. Bilateral, caused by a wide dentition or a wide upper jaw, a narrowed lower jaw, or a combination of these characteristics.

The third form is a combined (buccal-lingual) crossbite.

There are the following types of crossbite:

1) dentoalveolar - narrowing or expansion of the dentoalveolar arch of one jaw; a combination of disorders on both jaws;

2) gnathic - narrowing or widening of the base of the jaw (underdevelopment, excessive development);

3) articular - displacement of the lower jaw to the side (parallel to the midsagntal plane or diagonally). The listed types of crossbite can be unilateral, bilateral, symmetrical, asymmetrical, or combined (Fig. 1).

Rice. 1. Types of crossbite.

destruction of coronal tooth bite

With crossbite, the shape of the face is disrupted and transverse movements of the lower jaw are difficult, which can lead to uneven distribution of chewing pressure, traumatic occlusion and periodontal tissue disease. Some patients complain of biting the mucous membrane of the cheeks, incorrect pronunciation of speech sounds due to a mismatch in the size of the dental arches. The function of the temporomandibular joints is often impaired, especially with malocclusion with a displacement of the lower jaw to the side.

The clinical picture of each type of crossbite has its own characteristics.

With a buccal crossbite without displacement of the lower jaw to the side, asymmetry of the face is possible without displacement of the midpoint of the chin, which is determined in relation to the median plane. The midline between the upper and lower central incisors usually coincides. However, with the close position of the front teeth, their displacement, and asymmetry in the development of the dental arches, it can be displaced. In such cases, the location of the bases of the frenulums of the upper and lower lips and tongue is determined.

The degree of violation of the relationships of the dental arches in the bite varies. The buccal cusps of the upper lateral teeth may be in cuspal contact with the lower teeth, may be located in longitudinal grooves on their chewing surface, or may not be in contact with the lower teeth.

With a buccal crossbite with a displacement of the mandible to the side, facial asymmetry is observed due to the lateral displacement of the chin in relation to the midsagittal plane. The right and left profiles in such patients usually differ in shape, and only in preschool children is the asymmetry of the face less noticeable due to chubby cheeks. It progresses with age. The midline between the upper and lower central incisors usually does not coincide as a result of displacement of the lower jaw, changes in the shape and size of the dental arches and often the jaws. In addition to shifting the lower jaw parallel to the midsagittal plane, it can shift to the side diagonally. The articular heads of the lower jaw, when displaced laterally, change their position in the joint, which is reflected in the meiodistal relationship of the lateral teeth in the bite. On the side of displacement, a distal relationship of the dental arches occurs, on the opposite side - a neutral or mesial one. When palpating the area of ​​the temporomandibular joints during opening and closing of the mouth, normal or mild movement of the articular head is determined on the side of the displacement of the lower jaw, and more pronounced on the opposite side. When opening the mouth, the lower jaw can move from the lateral position to the central one, and when closing, it can return to its original position. In some patients, there is an increase in the tone of the masticatory muscle itself on the side of the displacement of the lower jaw and an increase in its volume, increasing the asymmetry of the face.

To determine the displacement of the lower jaw to the side, the third and fourth clinical functional tests according to L. V. Ilyina-Markosyan and L. P. Kibkalo (1970) are used, namely, the patient is asked to open his mouth wide and facial signs of deviations are studied; existing facial asymmetry increases, decreases or disappears depending on the cause that determines it (third test); after this, the lower jaw is set in the usual occlusion, and then, without the usual displacement of the lower jaw, the harmony of the face is assessed from an aesthetic point of view, the degree of displacement of the lower jaw, the amount of interocclusal space in the area of ​​the lateral teeth, the degree of narrowing (or widening) of the dentition, the asymmetry of the bones of the facial skeleton, etc. (fourth sample).

When studying a direct radiograph of the head, they often establish asymmetrical development of the facial bones of the right and left sides, their unequal location in the vertical and transversal directions, and diagonal lateral displacement of the lower jaw. Note the shortening of the body of the lower jaw or its branches on the side of displacement, the thickening of the body of this jaw and the chin on the opposite side.

In case of lingual crossbite, based on examination of the face from the front and profile, displacement of the lower jaw and flattening of the chin are often revealed. Sometimes hypotonia of the masticatory muscles, a disorder of chewing function, blocking of the lower jaw and a violation of its lateral movements are determined. The shape of the dental arches and bite change. With an excessively wide upper dental arch or a sharply narrowed lower apex, the lateral teeth partially or completely slip past the lower ones on one or both sides.

Rice. 2. Orthodontic appliances for the treatment of crossbite.

With a combined buccal-lingual crossbite, facial signs of disturbances, as well as dental, joint, muscle, etc., are characteristic of both literal and lingual crossbite.

Treatment of crossbite depends on its type, causes of development, and the age of the patient. Basically, the width of the upper and lower dentition is normalized by unilaterally or bilaterally expanding, narrowing, and placing the lower jaw in the correct position (Fig. 2).

During periods of primary and early mixed dentition, treatment consists of eliminating the etiological factors that caused the disorder: combating bad habits and mouth breathing, removing retained primary teeth, grinding off unworn cusps of primary teeth - molars and canines, which impede transversal movements of the lower jaw. Children are encouraged to chew solid foods on both sides of their jaws. In cases of habitual displacement of the lower jaw to the side, therapeutic exercises are prescribed. After early loss of primary molars, removable dentures are made to replace defects in the dental arches. Removable dentures for the upper jaw with a neutral and distal relationship of the dental arches are made with a jaw platform - in the anterior section. The bite is also increased on artificial teeth, which allows the teeth on the abnormally developed side to be separated. This makes it easier to correct their position using springs, inclined plane screws and other devices.

In addition to preventive measures, orthodontic devices are used. According to indications, the bite is increased by means of crowns or mouthguards fixed on primary molars, which allows creating conditions for normalizing the growth and development of dental arches and jaws and eliminating confusion of the lower jaw. In case of lateral displacement of the lower jaw, crowns or aligners are modeled taking into account its correct position. It is recommended to use a chin sling to normalize the position of the lower jaw, which is achieved using a stronger rubber traction on the side opposite to its displacement. To establish the lower jaw in the correct position, plates or mouth guards are used for the upper or lower jaw with an inclined plane in the lateral area.

When making devices for the treatment of crossbite, a constructive bite is determined: the dentition on the side of the deformation is separated to facilitate their expansion or narrowing and the lower jaw is set in the correct position when it is displaced laterally.

To treat crossbite combined with lateral displacement of the lower jaw, an inclined plane is modeled on the plate for the upper jaw - palatal, for the lower jaw - vestibular on the side opposite to the displacement. You can also make an inclined plane on the side of the displacement of the lower jaw: on the upper plate - from the vestibular side, on the lower - from the oral side. In case of bilateral crossbite, an expansion plate with occlusal overlays is used on the lateral teeth without imprints of the chewing surface of the opposing teeth, which facilitates the expansion of the dental arch. If there is a significant narrowing of the upper dental arch or jaw, both unilateral and bilateral, expansion plates with a screw or springs, as well as bite pads in the lateral areas, are indicated. With the help of such devices, the lower jaw is placed in the correct position, the lateral teeth are separated, which facilitates the expansion of the upper dentition, the bite is corrected, the tone of the masticatory muscles is reconstructed, and the position of the articular heads of the lower jaw in the temporomandibular joints is normalized.

In case of pronounced malocclusion, including those combined with sagittal and vertical anomalies at the age of 5-6 years, functional guides or functional orthodontic devices are used. Of the functional guiding devices, the activator is most often used. In case of unilateral discrepancy in the position of the lateral teeth (narrowing of the upper dentition and expansion of the lower), devices for moving the lateral teeth (springs, screws, levers, etc.) are added to the Andresen-Heupl activator. Occlusal adjustments are kept on the side of a correctly formed bite. The bite is normalized as a result of correction of the position of the teeth, growth of the articular process and branches of the lower jaw and elimination of its displacement. You can use an activator with a one-sided sublingual pelot (on the side of the correct closure of the dentition) or with a bilateral one. In the latter case, it should not be adjacent (to the teeth subject to lingual tilting using the vestibular arch.

Of the functional devices, the Frenkel function regulator is most often used. Treatment with this device is most effective in the final period of milk and the initial period of mixed dentition. In case of buccal crossbite, the adjuster is made so that the side shields are adjacent to the crowns and alveolar process of the lower jaw and do not touch them in the area of ​​the upper jaw on one side in case of unilateral crossbite or on both sides in case of bilateral crossbite; with a lingual crossbite, the ratio of the lateral shields and the dentoalveolar areas should be reversed. By compressing the median curve of the palatal clasp of the adjuster, the pressure on the upper lateral teeth in the oral direction can be increased.

In the final period of the mixed dentition and the initial period of the permanent dentition, the same preventive and therapeutic measures are used as in the previous period.

During the replacement of primary molars and the eruption of non-molars, actinoactive orthodontic appliances are usually replaced with retention ones. After the premolars have erupted to half the height of their crowns, pressure is applied to them with an orthodontic apparatus in order to establish them in the correct position. Bite separation is not required during this period of treatment.

In the final period of permanent dentition and in adults, it is possible to correct the position of individual teeth, change the shape of the dental arches and eliminate the displacement of the lower jaw. For treatment, mechanically-acting devices are more often used, combining their relationship with intermaxillary traction, removal of individual teeth, and compactosteotomy (Fig. 3). In case of lateral displacement of the lower jaw, the need for expansion or narrowing of individual sections of the dental arches, removal of individual teeth for orthodontic indications, compactosteotomy or other types of surgical interventions is identified after the jaw has been established in the correct position. Compactosteotomy is performed near teeth that are subject to vestibular or oral movement, both from the vestibular and oral sides of the alveolar process, and, if indicated for dentoalveolar shortening or lengthening, at the level of the apical base of the dentition.

Rice. 3. Diagnostic models of the jaws of patient D. in front (a) and in profile (b). On the left - before treatment: mesial crossbite with displacement of the lower jaw to the right, on the right - after removal of the lower first premolars, correction of the position of the teeth and lower jaw.

To move the upper and lower teeth in mutually opposite directions after the bite is released using a removable appliance, rings are used on the upper and lower lateral teeth with intermaxillary traction. When treating buccal crossbite, rubber rings are hooked onto hooks soldered on the oral side of the rings on the movable upper lateral teeth, and on hooks located on the vestibular side of the rings fixed on the lower lateral teeth. If occlusal contacts between teeth are maintained on the side of tooth movement, the patient will bite through the rubber rings and treatment will not be successful. The dentition in these areas must be disassembled. It is necessary to ensure that the removable appliance that separates the teeth does not adhere to the teeth that are moved orally, or to the alveolar process in this area.

Rice. 4. Patient P. Mesial crossbite with displacement of the lower jaw: on the left (a, c) - before treatment, on the right (b, d) - after treatment.

Engle devices are used to correct the size of dental arches. The distance between the vestibular surface of the teeth being moved and the spring arch is adjusted. To treat crossbite with displacement of the lower jaw, to the side, or combined with sagittal and vertical malocclusions, Entl appliances with intermaxillary traction, including one-sided ones, are used (Fig. 4).

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