Pathology of hard tissues of teeth. Abstract: "Hereditary diseases of hard tissues of teeth

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

Pathologically distinguish early and late phases of morphological changes in carious disease of hard tissues of the tooth crown. 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 a cavity of various depths in the hard tissues of the tooth (stages of superficial, medium and deep caries).

Pre-surface 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 focus, and then acquires a light brown tint - a pigmented spot. The latter differs from the white spot in a larger area and depth of the lesion.

In the late phase of caries, further destruction of enamel occurs, in which, with the gradual rejection of demineralized tissues, a cavity with uneven contours is formed. The subsequent destruction of the enamel-dentin border, the penetration of microorganisms into the dentinal tubules leads to the development of dentinal caries. The proteolytic enzymes and acid released at the same time cause the dissolution of the protein substance and the demineralization of the dentin up to the communication of the carious cavity with the pulp.

With caries and lesions of the hard tissues of the tooth of a non-carious nature, disorders of the nervous regulation are observed. In case of damage to the tissues of the tooth, access is opened to external non-specific stimuli of the nervous apparatus of the dentin, pulp and periodontium, which cause a pain reaction. The latter, in turn, reflexively contributes to neurodynamic shifts 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 rudiments of teeth in violation of mineral and protein metabolism in the body of the fetus or child (systemic hypoplasia) - or a cause locally acting on the rudiment of the tooth (local hypoplasia). It occurs in 2-14% of children. Enamel hypoplasia is not a local process that captures only the hard tissues of the tooth. It is the result of a severe metabolic disorder in a young body. It is manifested by a violation of the structure of the dentin, pulp and is often combined with malocclusion (pro-genius, open bite, etc.).

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

Fluorosis- a chronic disease caused by excessive intake of fluorine into the body, for example, when its content in drinking water is more than 1.5 mg / l. It is manifested mainly by osteosclerosis and enamel hypoplasia. Fluorine binds calcium salts in the body, which are actively excreted from the body: depletion of calcium salts disrupts the mineralization of teeth. A toxic effect on the rudiments of teeth is not excluded. Violation of mineral metabolism manifests itself in the form of a variety of fluoride hypoplasia (striation, pigmentation, mottling of enamel, its 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. Enamel prisms as a result of the resorptive process are less tightly adjacent to each other.

In the 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 occurs, the expansion of interprism spaces, which indicates a weakening of the bonds between the structural formations of enamel and a decrease in its strength.

Pathological abrasion of teeth is a loss of hard tissues of the crown of the tooth - enamel and dentin - in certain areas of the surface that increases with time. This is a fairly common disease of the teeth, occurs in about 12% of people over 30 years of age and is extremely rare at an earlier age. Complete erasure of masticatory tubercles of molars and premolars, as well as partial abrasion of the cutting edges of the anterior teeth in men are observed almost 3 times more often 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 are described in thyrotoxic goiter, after extirpation of the thyroid and parathyroid glands, in Itsenko-Cushing's disease, cholecystitis, urolithiasis, endemic fluorosis, wedge-shaped defect, etc.

The use of removable and non-removable prostheses of irregular design is also the cause of pathological abrasion of the surfaces of teeth of various groups, the teeth that are supporting for clasps are especially often erased.

Changes in the pathological abrasion of hard tissues of the crown of the tooth are observed not only in enamel and dentin, but also in the pulp. At the same time, the deposition of replacement dentin is most pronounced, which is first formed in the region of the pulp horns, and then throughout the entire arch of the coronal cavity.

wedge-shaped defect It 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 crown of the tooth is usually found in middle-aged and elderly people. An important role in the pathogenesis of the 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 the teeth,

The currently available data allow us to see in the pathogenesis of the wedge-shaped defect a significant role of both concomitant somatic diseases (primarily the nervous and endocrine systems, the gastrointestinal tract), and the effects of chemical (changes in the organic substance of the teeth) and mechanical (hard toothbrushes) factors. Many authors assign the 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 these depressions expand, they begin to take on the shape of a wedge, while the defect retains smooth edges, a hard bottom, and, as it were, 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 stimuli. Morphologically, at this stage of the disease, hardening 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 process.

Acute traumatic injury to the hard tissues of the tooth crown is tooth fracture. Such injuries are mainly the front teeth, moreover, mainly the upper jaw. Traumatic damage to the teeth often leads to the death of the pulp due to infection. Initially, the inflammation of the pulp is acute and is accompanied by profuse pain, then it becomes chronic with characteristic and pathological phenomena.

The most frequently observed fractures of the teeth in the transverse direction, rarely in the longitudinal. In contrast to dislocation with a fracture, only the broken off part of the tooth is movable (if it remains in the alveolus).

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

Among the hereditary lesions of hard tissues of the tooth are defective amelogenesis(formation of defective enamel) and defective dentinogenesis(violation of the development of dentin). In the first case, as a result of a hereditary disturbance in the development of enamel, a change in its color, a violation of the shape and size of the crown of the tooth, an increased sensitivity of the enamel to mechanical and thermal 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 the Stainton-Capdepon syndrome - a kind of family pathology of the teeth, characterized by a change in the color and transparency of the crown, as well as early onset and rapidly progressing tooth wear and enamel chipping.

Symptoms of diseases of the hard tissues of the teeth

Clinic of carious lesions of hard tissues of teeth 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.

Among the early clinical manifestations of caries include a carious spot that appears imperceptibly for the patient. Only with a thorough examination of the tooth with a probe and a mirror, you can notice a change in the color of the enamel. During the examination, one should be guided by the rule that incisors, canines and premolars are most often affected by contact surfaces, while in molars - chewing (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, and when 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 rapidly passing pain under the action of these stimuli in almost all patients. When probing, a shallow defect with a slightly rough surface is easily detected, and probing is a little painful.

Average caries proceeds 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 reaction of the pulp to irritation with an electric current remains within the normal range (2-6 μA).

At the last stage - the stage of deep caries - pain becomes quite pronounced under the action 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 region of the pulp horns. There are clinically detectable signs of pulp irritation, the electrical excitability of which may be reduced (10-20 μA).

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

Sometimes a defect in hard tissues with deep caries is partially hidden by the remaining surface layer of enamel and looks small when viewed. However, when removing the overhanging edges, a large carious cavity is easily detected.

Diagnosis of caries at the stage of the formed cavity is quite simple. Caries in the stain 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 cavity of the tooth in the absence of spontaneous pain makes it necessary to carry out a differential diagnosis.

With caries, pain from hot and probing occurs quickly and passes quickly, and with chronic pulpitis it is felt for a long time. Electrical excitability in chronic pulpitis is reduced to 1 5 - 2 0 mA.

Depending on the affected area (caries of one or another surface of the chewing and front teeth), Black proposed a topographic classification: Class I - a 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 - the area of ​​\u200b\u200bthe corners and cutting edges of the front teeth; Class V - cervical area. The letter designation of the affected areas is also proposed - according to the initial letter of the name of the tooth surface; O - occlusive; 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: MOVYA.

Knowledge of the topography and degree of hard tissue damage 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 various sizes and shapes, linear grooves of different widths and depths, encircling the tooth parallel to the chewing surface or cutting edge. If elements of a similar form of hypoplasia are localized along the cutting edge of the crown of the tooth, a semilunar notch is formed on the latter. Sometimes there is a lack of enamel at the bottom of the depressions 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 an underdevelopment of tubercles in premolars and molars: they are smaller than usual in size.

The hardness of the surface layer of enamel in 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 in nature damage to different groups of teeth. In mild forms of fluorosis, there is a mild loss of enamel luster and transparency due to a change in the light refractive index as a result of fluoride intoxication, which is usually chronic. Whitish, "lifeless" single chalk-like spots appear on the teeth, which, as the process progresses, acquire a dark brown color, merge, creating a picture of burnt crowns with a "pox-like" surface. Teeth in which the calcification process has already been completed (eg permanent premolars and second permanent molars) are less susceptible to fluorosis even at high concentrations of fluoride in water and food.

According to the classification of V.K. Patrikeev, the dashed form of fluorosis, which is characterized by the appearance of faint chalky stripes in the enamel, often affects the central and lateral incisors of the upper jaw, less often the lower, and the process captures mainly the vestibular surface of the tooth. In the spotted form, the appearance of chalky spots of different color intensity is observed on incisors and canines, less often on premolars and molars. Chalk OVIDNO-mottled form of fluorosis affects the teeth of all groups: dull, light or dark brown areas of pigmentation are located on the vestibular surface of the front teeth. All teeth can also be affected by an erosive form, in which the stain takes the form 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 content of fluorine in water (up to 20 mg/l), is accompanied by a change in shape and breakage of crowns, more often incisors, less often molars.

The clinical picture of the defeat of hard tissues of the crown of the tooth wedge-shaped defect depends on the stage of development of this pathology. The process develops very slowly, sometimes for decades, and in the initial stage, as a rule, there are no complaints from the patient, but over time there is a feeling of soreness, pain from mechanical and thermal stimuli. Gingival margin, even if retracted, with mild signs of inflammation.

The wedge-shaped defect occurs mainly 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 rarely affected.

In the initial stages, the defect occupies a very small area in the cervical region 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 certain outlines: the cervical edge follows the contours of the gingival margin and in the lateral areas at an acute angle, and then, rounding, these lines are connected in the center of the crown. There is a defect in the shape of a crescent. The transition of the defect to the root cementum is preceded by gingival retraction.

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

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

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

Hereditary lesions of hard tissues of the tooth usually capture all or most of the crown, which does not allow topographical identification of specific or most common lesions. In most cases, not only the shape of the teeth is disturbed, but also the bite. Efficiency of chewing 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 gingival pockets, retention points, which creates conditions for the traumatic effect of the food bolus on the gum, infection of the oral cavity with saprophytic and pathogenic microorganisms. These factors are the cause of the formation of chronic periodontal pockets, gingivitis.

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

The prognosis for the therapeutic treatment of caries, as well as for 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 the result of incorrect odontopreparation of the carious cavity of low strength of many filling materials.

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

Treatment of diseases of the hard tissues of the teeth

Treatment for partial destruction of tooth crowns

The main task of orthopedic treatment for partial defects in hard tissues of the tooth crown is to restore the crown by prosthetics in order to prevent further tooth decay or recurrence of the disease.

The important preventive value of orthopedic treatment of defects in hard tissues of the tooth, which is one of the main areas of orthopedic dentistry, is that crown restoration helps prevent further destruction and loss of many teeth over time, and this, in turn, avoids serious morphological and functional disorders of various sections of the dental system.

The therapeutic effect in prosthetics of crown defects is expressed in the elimination of violations of the act of chewing and speech, the normalization of the function of the temporomandibular joint, and the restoration of aesthetic norms. The odontopreparation used in this case, as an act of influencing the dental tissues, also creates certain conditions for the activation of reparative processes in the dentin, as a result of which a purposeful restructuring is observed, which is expressed in the regular compaction of the dentin and the formation of protective barriers at various levels.

Two types of prostheses are mainly used as therapeutic agents for defects in the crown part of the tooth: inlays and artificial crowns.

Tab- fixed prosthesis of a part of the tooth crown (micro prosthesis). It is used to restore the anatomical shape of the tooth. The tab 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 the tooth and is fixed on the stump of a natural tooth. Made from metal alloys, porcelain, plastic. Can serve as a supporting element of other types of prostheses.

As with any remedy, 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 crown of the tooth, and the degree (size and topography) of the destruction, are taken into account.

Tabs

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

Tabs are not shown in case of circular caries, MOD cavities in combination with cervical caries or wedge-shaped defect, in case of systemic caries. It is undesirable to use tabs in persons who take gastric juice or hydrochloric acid for medicinal purposes, working in acid shops. In these cases, artificial crowns are preferable.

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

The question of the method of treatment for partial defects of the crown part of the vital tooth can only be decided after the removal of all necrotic tissues.

Odontopreparation for inlays and treatment of inlays. Local treatment of defects in the crown part of the tooth consists in the prompt removal of necrotic tissues, the formation of a corresponding cavity in the tooth in an operative way (by odontopreparation) and the filling of 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.

Clinical and laboratory stages of restoration of the crown part of the tooth with inlays include: forming a cavity under the inlay by appropriate odontopreparation, obtaining its wax model, making the inlay by replacing the wax with the appropriate material, processing the metal inlay and fitting it on the model, fitting and fixing the inlay in the tooth cavity.

The formation of a cavity in the tooth for the purpose of its subsequent filling with an inlay is subject to the task of creating optimal conditions for fixing the inlay, which does not have a side effect on healthy tissues. The operational 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 food bolus of various consistency and density directly hits them, and pressure transmitted from the prosthesis when it is loaded during chewing. At the same time, 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. At the same time, the inlay material should be hard, but not brittle, not plastic in the cured state, not corrode and swell in the environment of the oral cavity, and have an expansion coefficient close to that of enamel and dentin.

The principle of the operational technique of cavity formation and its subsequent filling with a tab is subject to the laws of the redistribution of forces of masticatory pressure.

With caries, the cavity is formed in two stages. At the first stage, technical access to the carious cavity, its expansion and excision of pathologically altered tissues of enamel and dentin are carried out. At the second stage of odontopreparation, a cavity of an appropriate configuration is formed in order to create optimal conditions for fixing the inlay and optimal distribution of chewing pressure forces on the tissues.

To open the carious cavity, shaped carborundum and diamond heads, fissure or spherical burs of small diameter are used. A certain difficulty is the disclosure of the carious cavity on the contact surface. In these cases, the cavity is formed towards the chewing or lingual surface, removing unaltered tooth tissues 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 the expansion of the carious cavity, they proceed to necrotomy and the formation of a cavity for the insert. To facilitate further study of the topic, we describe the main elements of the formed cavity. In each cavity, the walls, the bottom and the junction of the walls between themselves and the bottom are distinguished - the corners. The walls of the cavity can converge with each other at an angle or have a smooth, rounded transition.

Depending on the topography of the lesion of the tooth crown, there may be two or three cavities combined with each other, or the main cavity (localization of the pathological process) and an additional one created in healthy tissues and having a special purpose.

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

• the relationship of the defect of hard tissues with the topography of the cavity of the tooth and the safety of the pulp;
• thickness and presence of dentin in the walls limiting the defect;
• the topography of the defect and its relation 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 vertical cavities;
• the ratio of the defect to the areas of greatest caries damage;
• the cause 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 tissues and microprostheses deserves special study. When eating, chewing pressure forces of different magnitude and direction act on the tooth tissue and the prosthesis. Their direction changes depending on the movement of the lower jaw and the food bolus. These forces, if present on the occlusal surface of the tab, cause compression or tension stress in it and in the walls of the cavity.

So, with cavities of type 0 (Class I according to Black) in a vertically standing tooth and a formed box-shaped cavity, the 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 stressed states arise. With thin walls over time, this can lead to their breaking off. If the tooth axis is tilted, then the forces R and Q cause an increased deformation of the wall on the side of the slope. To avoid this and reduce the deformation of the wall, the direction of the walls and the bottom of the cavity should be changed or an additional cavity should be created, which makes it possible 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 parallelogram rule of forces, can also be applied to cavities of the MO, OD type. Additionally, one should consider the action of the force P directed towards the missing wall. In this case, the horizontal component of the force tends to displace the tab, especially if the bottom is formed with an inclination towards the missing wall. In such situations, the rule of bottom formation also applies: it should be inclined away from the defect, if the thickness of the preserved contact wall allows, or a main cavity should be formed on the occlusal surface with retention points.

The patterns of redistribution of masticatory 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. With respect to this level, the walls of the cavity are formed at an angle of 90°. The pressure from the tab on the walls of the tooth with 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 with I-II classes of defects, V. Yu. Milikevich introduced the concept of IROPZ - the 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 Plexiglas 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 to the nearest 0.5 mm2.

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

If the value of IROPZ a is from 0.2 to 0.6, treatment of chewing teeth with cast metal tabs with the following features is indicated. With the localization of type O cavities and the index value of 0.2 on the premolars and 0.2 - 0.3 on the molars, the cast inlay includes the body and the fold. If the value of IROPZ is 0.3 on premolars and 0.4 - 0.5 on molars, occlusal coating of tubercle slopes is carried out. With IROPZ values ​​of 0.3 - 0.6 on premolars and 0.6 on molars, the entire occlusal surface and tubercles are covered.

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

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

During odonto-preparation for inlays, as well as during odonto-preparation for other types of prostheses, it is necessary to know well the boundaries within which it is possible to confidently excise the hard tissues of the tooth crown without fear of opening the tooth cavity. To a greater extent, hard tissues of the crowns of the upper and lower front teeth can be excised from the lingual side at the level of the equator and neck. The most dangerous place for trauma to the pulp of the incisors is the lingual concavity of the crown.

With age, in all teeth, the zone of safe preparation expands at the cutting edge and at the level of the neck, since the cavity of the coronal pulp undergoes obliteration 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 in other types of prosthetics, in which it is necessary to excise the hard tissues of the tooth crown in order to avoid pulp injury, data on the thickness of the walls of the tooth tissues should be used. These data are obtained using X-ray examination.

An essential condition for preventing the development of secondary caries after the treatment of the affected tooth with an inlay is the obligatory preventive expansion of the entrance cavity to the "immune" zones. An example of such a prophylactic expansion is the interconnection of carious cavities located on the chewing and buccal surfaces of the molars. It excludes the possibility of developing secondary caries in the groove present on the buccal surface of the molars and passing to their occlusal surface.

Another condition for preventing secondary caries is the creation of tightness between the edge of the cavity formed in the tooth and the edge of the inlay. This is achieved by grinding 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 especially strictly observed when forming MO, MOD and other cavities, in which the walls of both cavities and the bridge must be strictly parallel.

During odontopreparation under the inlays, a cavity is created 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 slightly divergent walls while maintaining the overall box-like shape, i.e., the entrance to the cavity is slightly expanded compared to its bottom.

Consider the sequence of medical actions and reasoning on the example of the formation of cavities under the tab in case of carious lesions of I and II classes according to Black.

So, if, after removal of necrotic tissues, an average caries is established in the center of the occlusal surface, in which the area of ​​the lesion does not exceed 50 - 60% of this surface, the use of metal inlays is indicated. The task of operational technology in this case is the formation of 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 ones exceeds 10-15 °, and the wall thickness is insignificant (less than half the size from the fissure to the vestibular or lingual surface), the bottom formation rule changes. This is due to the fact that occlusal forces directed at an angle and even vertically on the inlay have a displacing effect and can cause tooth wall spallation. Consequently, the bottom of the cavity, obliquely directed away from the thin walls, which are not very resistant to the mechanical action of the forces, prevents the spallation of the thinned wall of the cavity.

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 crown of the tooth. This requires the creation of an additional cavity to distribute the forces of masticatory pressure to thicker and, consequently, more mechanically strong sections of the tooth tissues. 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 masticatory pressure can be achieved with minimal surgical removal of enamel and dentin and minimal pulp reaction.

An additional cavity should be formed somewhat deeper than the enamel-dentin border, but in vital teeth, a shape in which the width is greater than the depth will be optimal. Additional cavities are characterized by the presence of connecting and holding parts. The connecting part departs from the main one 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 inlay. So, when using a cast insert, a cavity is made smaller both in depth and in 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 spalling. To do this, the thinned sections of the wall are ground down by 1-3 mm in order to further cover the insert with the material. With deep caries and class I cavities 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 with pressure from 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 the carious cavity. In this case, it is necessary to take into account the redistribution of forces of masticatory pressure on the tooth tissues after insertion of the tab. Chewing pressure acting on the tab 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 tooth pulp, which causes irritation of its neuro-receptor apparatus. Mechanical irritation of the pulp is accompanied by pain sensations of varying intensity only in the process of eating and can be regarded by the doctor as a symptom of periodontitis. In such cases, unreasonable 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 cause the development of pulpitis, it is necessary, after removing the softened dentin and creating the parallelism of the walls, additional excision of 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 insert overlapping the occlusal surface.

With 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 burr to obtain a hole with a diameter of 0.5–1.5 mm and a depth of 2–3 mm. As pins, it is recommended to use a clasp wire of the appropriate diameter.

In the manufacture of inlays, the pins are cast together with the body of the inlay, with which they form a single whole. This makes it necessary to obtain holes in the channel parallel to the walls of the main cavity.

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

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

With a unilateral carious lesion, within the healthy tissues of the tooth, the main cavity is formed rectangular, with parallel vertical walls. The cervical wall of the cavity can be at different levels of the crown and should be perpendicular to the vertical walls. In the case of using an inlay, the protection of the edges of the enamel is achieved not by the formation of a bevel (fold), but by an inlay that overlaps a part of the contact surface in the form of a shell or scaly coating. To create this type of bevel with a one-sided separation disc, the enamel layer is removed along the plane 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 into the occlusal one.

In order to neutralize horizontally acting forces that displace 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 form of a dovetail or T-shaped with a center along the medio-distal fissure. This form causes the redistribution of the angular component of the masticatory pressure directed towards the missing wall.

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

In class III and G/ class 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 form of an additional cavity is one that ensures sufficient stability of the insert with minimal removal of tooth tissues and preservation of the pulp. However, the cosmetic requirements for the restoration of the 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 place for the formation of an additional cavity on the occlusal surface of the anterior tooth, it is necessary, along with other factors, to take into account the peculiarity of the 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 at the cervical part of the contact sides. The specificity of the surgical technique of odontopreparation of the anterior teeth for restoration with inlays lies in the formation of the vertical walls and bottom of the cavity, not only taking into account the redistribution of all components of masticatory pressure (the leading component is the angular component), but also the way in which the inlay is inserted.

There are two ways of inserting the tab: vertical from the side of 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. The stifts are inserted into the tissues of the tooth in the cervical region and the cutting edge, focusing on the safety zones, which are well defined on the 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 if the cutting edge is of sufficient thickness. A nail only in the main contact side of the cavity cannot provide sufficient stability of the tab, since the force directed to the tab from the palatal side and to the cutting edge can turn 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 incisal angle is preserved, then in teeth of considerable and medium thickness, the formation of the main cavity in the direction of the tooth axis is in principle excluded, since this would require cutting off the incisal angle, which must be preserved. Therefore, the cavity is created at an angle to the axis of the tooth. In such cases, an additional cavity on the occlusal surface is also formed at an angle to the axis of the tooth. This direction of formation of the additional cavity is also necessary because it ensures the stability of the insert and prevents its displacement 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. The preservation of a thin layer of enamel in the future will necessarily lead to its breaking off due to the redistribution of chewing pressure throughout the 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 size 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 tab is cleaned of sawdust of the hard tissues of the tooth crown and modeling is started.

With the direct method of inlay modeling, carried out directly in the patient's oral cavity, heated wax is pressed into the formed cavity with a slight excess. If the chewing surface is being modeled, the patient is asked to close the dentition until the wax has hardened in order to obtain impressions of the opposing teeth. If there are none, the modeling of the cutting edge and tubercles is carried out taking into account the anatomical structure of this tooth. In the case of modeling inlays on the contact surfaces of the teeth, contact points are subject to restoration.

In the manufacture of 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, excluding its deformation. With a small tab, it is removed with one wire gate-forming pin; if the inlay is large, parallel U-shaped pins are used. In a well-formed cavity, removing the inlay model is not difficult.

With the indirect method, the modeling of the wax reproduction of the inlay is carried out on a pre-made 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 in such a way that their diameters match. The edge of the ring on the buccal and lingual (palatal) surfaces should reach the equator. When making an inlay on the contact side of the tooth, the edge of the ring should reach the gingival margin.

The ring is filled with thermoplastic mass and immersed in the formed cavity. After the mass has hardened, the ring is removed. The quality of the impression is evaluated visually. If a good cast is obtained, it is filled with copper amalgam or supergypsum. 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 the hands during the wax inlay modeling. After modeling the wax inlay, the metal model is cast.

In case of 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 obtaining a common impression, a combined model is cast. To do this, the ring is filled with amalgam and the base is modeled up to 2 mm long, then the model is cast according to the usual rules. To remove the thermoplastic mass ring, 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, on which all the teeth are cast from plaster, and the tooth prepared for the inlay is made of metal. On this tooth, a wax insert is modeled, taking into account occlusal relationships. Currently, two-layer impression materials are more often used for taking impressions. The model can be obtained entirely from supergypsum.

To cast a metal inlay, a wax reproduction is placed in a refractory mass placed in a casting ditch. Then the gates are removed, the wax is melted and the mold is poured with metal. The resulting tab is carefully cleaned of plaque and transferred to the clinic for fitting. All inaccuracies in the fit of the inlay are corrected by appropriate techniques using thin fissure burs. Fixation of the cement insert is carried out after thorough cleaning and drying of the cavity.

In the manufacture of inlays from composites, odontopreparation is carried out without the formation of a bevel (fold) along the edge of the cavity, since the thin and fragile layer covering the bevel will inevitably break. The modeled wax model of the insert is covered with a liquid layer of cement, after which the model with the sprue (and cement) is immersed in plaster poured into a cuvette so that the cement is located below and the wax is above. Replacing the wax with plastic of the corresponding color is carried out in the usual way. After fixing the tab on the tooth, its final machining and polishing is carried out.

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 in such a way that the edges of the foil overlap the edges of the cavity. The foil mold (impression) should accurately copy the shape of the cavity and have a smooth surface. The removed 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 thus obtained is fixed with phosphate cement.

Artificial crowns

In case of defects in hard tissues of the tooth crown, which cannot be replaced by filling or using inlays, various types of artificial crowns are used. There are restorative crowns, which restore the disturbed anatomical shape of the natural crown of the tooth, and abutment crowns, which ensure the fixation of bridges.

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

Depending on the material, metal crowns are distinguished (alloys of noble and base metals), non-metallic (plastic, porcelain), combined (metal, lined with plastic or porcelain). In turn, metal crowns, according to the manufacturing method, are divided into cast, made by casting from metal according to pre-prepared forms, and stamped, 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., not eliminated by filling or inlays;
• nomalia of the shape, color and structure of the tooth;
• restoration of the anatomical shape of the teeth and the height of the lower third of the face with pathological abrasion;
• fixation of bridges or removable dentures;
• splinting for periodontitis and periodontitis;
• temporary fixation of orthopedic and orthodontic appliances;
• convergence, divergence or protrusion of the teeth, if significant grinding is required.

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

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

The latter circumstance, as shown by the long-term practice of orthopedic dentistry, is essential in terms of creating a functional and aesthetic optimum. In this regard, on the front teeth, as a rule, porcelain, plastic or combined crowns are used.

Untreated foci of chronic inflammation of the marginal or apical periodontium, the presence of dental deposits are contraindications to the use of artificial crowns. Unconditional contraindications are intact teeth, unless they are used as a support for fixed prosthesis structures, as well as the presence of pathological tooth mobility of the 3rd degree and milk teeth. The manufacture of full metal crowns consists of the following clinical and laboratory stages:

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

Odontopreparation for a metal crown consists in 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 neck area, and its gingival edge plunges into the physiological gingival pocket (dental groove) to the required depth without 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.

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Experts agree that it is necessary to attract public attention to the problems of cardiovascular diseases. Some of them are rare, progressive and difficult to diagnose. These include, for example, transthyretin amyloid cardiomyopathy.

14.10.2019

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

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The incidence of meningococcal infection in the Russian Federation in 2018 (compared to 2017) increased by 10% (1). One of the most common ways to prevent infectious diseases is vaccination. Modern conjugate vaccines are aimed at preventing the occurrence of meningococcal disease and meningococcal meningitis in children (even very young children), adolescents and adults.

Viruses not only hover in the air, but can also get on handrails, seats and other surfaces, while maintaining their activity. Therefore, when traveling or in public places, it is advisable not only to exclude communication with other people, but also to avoid ...

Returning 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. New opportunities for laser vision correction are opened by a completely non-contact Femto-LASIK technique.

Non-carious lesions of the teeth are a common occurrence in dental practice. This concept includes a wide range of diseases with different etiologies and clinical manifestations.

General concept

Non-carious lesions of the teeth are an extensive group of diseases and pathologies. These include all damage to the enamel, diseases of a non-bacterial nature. In terms of prevalence, they rank second after caries. Such lesions can have a variety of symptoms and clinical picture, they have different causes and causes. But they are all congenital or acquired.

They can have a different distribution - affect one or all teeth in a row, individual sections in a certain order. Many of these diseases are difficult to diagnose, since the signs of different pathologies are similar and difficult to distinguish from each other. This may be due to insufficient knowledge of the disease, which complicates its detection and increases the risk of complications. In such a situation, only the best can help where they choose the right treatment option (for example, SM-Clinic, which has several branches in Moscow, Diamed or DentaLux-M).

Classification of non-carious lesions

Due to the variety of diseases that relate to the concept of "non-carious lesions of the teeth", their classification does not have one generally accepted standard. If you summarize all the data, you can get a generalized list of types of lesions.

1. Pathology of development during teething:

• Anomaly of shape, size.
• Fluorosis (mottled teeth).
• Enamel hypoplasia (developmental disorder).
• Pathologies of the structure of the teeth of a hereditary nature (odontogenesis, amelodentinogenesis).
• Syphilis (congenital).
• Other developmental pathologies associated with external factors (antibiotics, rhesus conflict).

2. Pathological changes in the hard tissues of the tooth:

• Complete loss of a tooth.
• Erosion.
• Color change after cutting.
• Increased tissue sensitivity.

3. Changes in the internal structure of the tooth:

• Root fracture.
• Root dislocation.
• Fracture of the crown of the tooth.
• Pulp opening.

In our country, another classification, proposed in 1968 by V.K. Patrikeev, is more often used. According to it, non-carious lesions of the teeth are divided into two groups.

1. Lesions occurring before eruption:

• Anomaly of eruption and development.
• Hypoplasia of the teeth.
• Hyperplasia.
• Fluorosis.
• hereditary pathologies.

2. Lesions occurring after eruption:

• Erosion.
• wedge defect.
• Necrosis of hard tissues.
• Hyperesthesia of the teeth.
• Erase.
• Tooth trauma.
• Pigmentation.

hypoplasia

This is the name of the pathology of the development of dental tissue during its formation, that is, in children before teething. Such a violation is caused by insufficient mineralization of tissues. The main symptom is the complete absence of an organ or its abnormally small development. Hypoplasia of the teeth can be either congenital or develop after the birth of a child. There are several reasons for this:

• Rh factor conflict between mother and child
• an infectious disease transmitted by the mother during pregnancy, infections in a child after birth,
• severe toxicosis accompanying pregnancy,
• premature birth, trauma during childbirth,
• pathology of the development of the child after birth,
• dystrophy, diseases of the gastrointestinal tract,
• metabolic disease,
• impaired development of brain activity,
• mechanical damage to the jawbone.

There are two types of hypoplasia - systemic and local. The first is characterized by the defeat of all teeth, low thickness of enamel or its absence. Yellow spots appear. Local is characterized by damage to one or two organs. Here, there is a lack of enamel (partial or complete), structural defects of the teeth - they can be deformed. Such disturbances cause pain. Hypoplasia in severe form causes increased tooth wear, tissue destruction or complete loss of an organ, and the development of malocclusion. Treatment of hypoplasia includes teeth whitening (at an early stage) or filling and prosthetics (for severe disease). At the same time, the enamel is remineralized with medications (for example, calcium gluconate solution). In order to prevent the occurrence of hypoplasia in children, pregnant women are recommended a balanced diet containing vitamins for teeth (D, C, A, B), calcium and fluoride, as well as strict oral hygiene.

Hyperplasia

Hyperplasia - non-carious lesions of the teeth associated with excessive formation of tooth tissues. Their appearance is due to an anomaly in the development of epithelial cells, enamel and dentin. It appears in the form of "drops", which are also called "enamel pearls". They can be up to 5 mm in diameter. The main area of ​​localization is the neck of the tooth. Such a drop consists of tooth enamel, inside there may be dentin or soft connective tissue resembling pulp. There are five types of such formations according to their structure:

• true enamel - consist only of enamel,
• enamel-dentine - the enamel shell contains dentin inside,
• enamel-dentine drops with pulp - there is connective tissue inside,
• drops Rodriguez - Ponti - enamel formations in the periodontium between the root and the alveolus,
• intradentinal - located in the thickness of the dentin.

Hyperplasia of the tissues of the teeth does not manifest itself clinically, it does not cause pain, inflammation or any discomfort. You can only highlight the aesthetic factor if the anomaly affects the front teeth.

In this case, grinding and leveling of the surface is carried out. In other cases, if the patient is not bothered by anything, treatment is not carried out. Preventive measures are to protect milk teeth from caries, since their destruction can cause disturbances in the development of permanent ones.

Fluorosis

Fluorosis occurs during the formation of dental tissue due to the increased intake of fluoride in the body. It changes the correct structure of the enamel and causes its external defects - the appearance of spots, stripes, furrows, dark blotches. In the development of such a pathology, not only an excess of fluorine plays a role, but also a lack of calcium. In the children's body, fluorine accumulates more and faster than in adults, coming from food and water. There are such forms of fluorosis:

• dashed - manifested by the appearance of white stripes without a clear outline;
• spotted - characterized by the presence of yellowish spots with a smooth surface;
• chalky-mottled - dull or shiny spots that are white, brown or yellow (can affect all teeth);
• erosive - multiple erosions of the enamel surface;
• destructive (a tooth broke off or completely collapsed) - the detrimental processes that accompany fluorosis.

Treatments for fluorosis vary depending on the form of the disease. So, with a spotted form, whitening and remineralization are carried out, if necessary, grinding of the upper layer of enamel. But the erosive form cannot be cured by such methods; here it is necessary to restore the teeth with veneers or crowns. General methods of treatment include remineralization, restoration of the shape and color of the organ, local effects on the body, control of fluorine intake.

Erosion

Non-carious lesions of the teeth include enamel damage such as erosion. Its formation leads to discoloration, aesthetic damage to the tooth, as well as increased sensitivity. Detected by visual inspection. Tooth erosion is characterized by progressive destruction of enamel and dentin, the course of the disease is chronic, and can take a long time. The cause of the pathology may be mechanical in nature, for example, when using hard brushes or pastes with abrasive particles. Also, erosion can be caused by a chemical effect on the enamel when eating foods and drinks with high acidity (picks, marinades, citrus juices, and others). Workers in industries associated with the constant inhalation of harmful substances most often suffer from such damage to the teeth. The use of certain drugs can contribute to the onset of the disease (for example, a large amount of ascorbic acid has a detrimental effect on enamel).

The cause may also be disturbances in the work of the stomach (increased acidity of its environment) or the thyroid gland. It is difficult to identify the disease at an early stage, since it is manifested only by a loss of luster in a separate small area of ​​​​the tooth. The further course of the disease leads to a gradual decrease in enamel and dentin. It looks like worn teeth, most often at the base. Treatment is based on stopping the destruction of dental tissues. It includes the use of applications containing fluorine and calcium for about 20 days, then the affected area is covered with fluorine varnish. It is possible to use veneers or crowns to restore the aesthetic appearance. The complex therapy includes calcium and phosphorus preparations, as well as vitamins for teeth. If left untreated, erosion can cause tooth hyperesthesia.

Hyperesthesia

Hyperesthesia of the teeth is manifested by increased sensitivity of the enamel and in most cases is a concomitant symptom of other non-carious diseases. The prevalence of this pathology is high: about 70% of the population suffer from hyperesthesia, more often women are affected. Manifestation - a sharp, severe pain that lasts no more than thirty seconds and appears when exposed to external factors on the enamel. Hyperesthesia is divided into types according to several criteria:

1. Distribution:

• limited form - affects one or more teeth;
• generalized - characterized by sensitivity of all organs.

2. Origin:

• a form of hyperesthesia associated with the loss of dental tissues;
• not associated with loss, due to the general condition of the body.

3. Clinical picture:

• pain occurs as a reaction to the temperature of external stimuli (cold water);
• teeth react to chemical stimuli (sweet or sour foods);
• reaction to all stimuli, including tactile ones.

Treatment of hyperesthesia is prescribed by a specialist, depending on the cause of its occurrence, the complexity of the problem and the form of the disease. In some cases, surgical intervention is necessary (for example, with pathological and denudation of the cervical region of the tooth), and sometimes therapeutic procedures can be dispensed with, such as the application of fluorine-containing applications to damaged areas. Orthodontic therapy may be required for hyperesthesia due to increased tooth wear. Preventive measures - eating all the necessary minerals and vitamins that strengthen dental tissues, regular and proper use of oral hygiene products, as well as an annual examination at the dentist.

wedge-shaped defect

A wedge-shaped defect is a tooth lesion in which its base is destroyed. Outwardly, it is manifested by damage to the neck of the tooth in the form of a wedge. Most often, fangs are defective. At the initial stage, it is invisible, it is difficult to diagnose. With a long course of the disease, a dark shade appears in the affected area. The main symptom of a wedge-shaped defect is that the teeth react painfully to the influence of high or low temperatures, sweet food, physical impact (cleaning). The reason for the development of the disease may be non-observance of oral hygiene, improper use of the brush - if after cleaning a bacterial plaque remains at the base of the bone formation, it destroys the enamel, leading to a wedge-shaped defect. It can also be caused by gum disease such as gingivitis and periodontitis, a malfunction of the thyroid gland, and increased acidity of the stomach, which causes heartburn. Treatment of a wedge-shaped defect depends on the severity of the damage.

With a slight destruction, it is enough to carry out restorative procedures that will replenish calcium and fluoride in the tooth enamel and reduce its susceptibility to external factors. In case of severe damage, a seal cannot be dispensed with. Due to the inconvenient location of the defect, such fillings often fall out. The best dental clinics are able to solve this problem by drilling a hole of a certain shape that holds the filling and using a material of special elasticity.

hard tissue necrosis

Necrosis of hard tissues of the teeth at an early stage is manifested by a loss of enamel luster, chalky spots appear. As the disease progresses, they turn dark brown. Softening of tissues occurs in the affected area, the enamel loses its strength, the patient may complain that his tooth has broken off. Dentin pigmentation occurs. Usually not one organ is affected, but several at once. Sensitivity to external stimuli increases. It is localized mainly at the neck of the tooth, as well as a wedge-shaped defect and erosion. But, despite the similar symptoms and the affected area, an experienced dentist can easily distinguish these diseases from each other and make the correct diagnosis. This pathology occurs against the background of hormonal disorders in the body. Treatment is aimed at strengthening dental tissues, eliminating hypersensitivity (hyperesthesia), and in case of severe damage, orthopedic therapy is prescribed.

Tooth trauma

The concept of “dental injury” combines damage to the mechanical nature of the external or internal parts of the tooth. The reasons for their occurrence can be called falls, blows to the jawbone during sports, fights, accidents. With prolonged exposure to a tooth with foreign objects or solid food, its tissues become thinner and become brittle. In this case, trouble can happen even when chewing food.

Injuries to the teeth can be the result of improper dental procedures, such as poor-quality pin installation. Some diseases can also lead to damage, such as hypoplasia, fluorosis, cervical caries, root cyst. Injuries include fractures of the crown or root, dislocation. The treatment of a bruise is based on the exclusion of physical impact on the diseased organ, the rejection of solid food. During treatment, it returns to the hole for further engraftment. If such an operation does not have prospects, according to the dentist, prosthetics or implantation is performed. A crown fracture needs immediate treatment to restore not only chewing functions, but also an aesthetic appearance, especially if the front teeth have been damaged. In this case, fixed crowns are installed. When a root is fractured, a complete tooth extraction is usually performed to install a post or implant.

Erasure of tooth tissues occurs in every person, which is the result of the physiological function of chewing.

Erasure of teeth is physiological and pathological.

Physiological abrasion of teeth. Depending on age, the degree of physiological abrasion of teeth increases. Normally, by the age of 40, the enamel of the tubercles of chewing teeth is worn out, and by the age of 50-60, abrasion is manifested by a significant loss of enamel on the tubercles of the chewing teeth and shortening of the crowns of the incisors.

Pathological abrasion of teeth. This term refers to an early, at a young age, and a pronounced loss of hard tissues in one tooth, in a group or in all teeth.

Etiology and pathogenesis. The following factors can be the causes of pathological abrasion of teeth: bite condition (for example, with a direct bite, the chewing surface of the lateral and cutting edges of the front teeth are subject to abrasion), overload due to loss of teeth, improper design of prostheses, domestic and professional harmful effects, as well as the formation of defective tissue structures .

Classification. For therapeutic dentistry, the most convenient clinical and anatomical classification based on the localization and degree of abrasion (M. Groshikov, 1985), according to which there are three degrees of pathological abrasion.

Grade I - slight abrasion of the enamel of the tubercles and cutting edges of the crowns of the teeth.

Grade II- abrasion of the enamel of the tubercles of the canines, small and large molars and the cutting edges of the incisors with the exposure of the surface layers of dentin.

Grade III- erasure of enamel and a significant part of dentin to the level of the crown cavity of the tooth

Clinical picture. Depending on the degree of pathological abrasion, patients may complain of increased tooth sensitivity from temperature, mechanical and chemical stimuli. It is also possible that there are no complaints, since as the enamel and dentin wear out, due to the plastic function of the pulp, replacement dentin is deposited. More often, patients complain of trauma to the soft tissues of the oral cavity with sharp edges of the enamel, which are formed due to more intense abrasion of the dentin compared to the enamel.

As the bumps of the masticatory surface wear out with age, the wear of the incisors progresses intensively. The length of the incisor crowns decreases and by the age of 35-40 it decreases by 1/3-½. At the same time, instead of the cutting edge, significant areas are formed on the incisors, in the center of which dentin is visible. If treatment is not carried out, then the erasure of tissues progresses rapidly and the crowns of the teeth become much shorter. In such cases, there are signs of a decrease in the lower third of the face, which is manifested in the formation of folds at the corners of the mouth. In persons with a significant decrease in bite, changes in the temporomandibular joint may occur and, as a result, burning or pain of the oral mucosa, hearing loss and other symptoms characteristic of the underbite syndrome may occur.

In most patients with pathological abrasion, the EDI ranges from 6 to 20 μA.

Pathological changes depend on the degree of erasure.

Grade I - according to the area of ​​abrasion, a more intense deposition of replacement dentin is noted.

Grade II- along with a significant deposition of replacement dentin, obstruction of the dentinal tubules is observed. There are pronounced changes in the pulp: a decrease in the number of odontoblasts, their vacuolization. Petrificates are observed in the central layers of the pulp, especially in the root.

Grade III - pronounced sclerosis of the dentin, the tooth cavity in the crown part is almost completely filled with replacement dentin, the pulp is atrophic. Channels are poorly passable.

Treatment. The degree of erasure of hard tissues of the teeth largely determines the treatment. So, with I and II degree of erasure, the main task of treatment is to stabilize the process, to prevent further progression of erasure. For this purpose, inlays (preferably from alloys) can be made on antagonist teeth, mainly large molars, which are not amenable to abrasion for a long time. You can also make metal crowns (preferably from alloys). If the erasure is due to the removal of a significant number of teeth, then it is necessary to restore the dentition with a prosthesis (removable or non-removable according to indications).

Often, the erasure of tooth tissues is accompanied by hyperesthesia, which requires appropriate treatment (see. Hyperesthesia of hard tissues of the tooth).

Significant difficulties in treatment arise at the III degree of erasure, accompanied by a pronounced decrease in the height of the occlusion. In such cases, the previous bite height is restored with fixed or removable dentures. Direct indications for this are complaints of pain in the temporomandibular joints, burning and pain in the tongue, which is a consequence of a change in the position of the articular head in the articular fossa. Treatment, as a rule, is orthopedic, sometimes long-term, with intermediate production of medical devices. The main goal is to create such a position of the dentition, which would ensure the physiological position of the articular head in the articular fossa. It is important that this position of the jaw be maintained in the future.

wedge-shaped defect

The name of this pathological change is due to the form of the defect in the hard tissues of the tooth (wedge type). The wedge-shaped defect is localized at the necks of the teeth of the upper and lower jaws, on the vestibular surfaces.

This type of non-carious lesion of the hard tissues of the tooth is more common in middle-aged and elderly people and is often combined with periodontal disease.

Wedge-shaped defects most often affect canines and premolars, while lesions can be single, but more often they are multiple, located on symmetrical teeth.

Etiology and pathogenesis. In the etiology of the wedge-shaped defect, an increasing place is occupied by mechanical and chemical theories. According to the first, a wedge-shaped defect occurs under the influence of mechanical factors. In particular, it is believed that the defect is formed as a result of the action of the toothbrush. This is confirmed by the fact that it is most pronounced on the canines and premolars - teeth protruding from the dentition. Clinical observations have established that persons with a more developed right hand (right-handers) have more pronounced defects on the left, since they brush their teeth on the left side more intensively. In left-handers, who brush their teeth more intensively on the right side, the defects are more pronounced on the right side.

An objection to the mechanical theory is evidence that the wedge-shaped defect also occurs in animals and in individuals who do not brush their teeth at all.

Statements that acids play an important role in the occurrence of a wedge-shaped defect are unconvincing, since defects do not occur in other areas, including the cervical region of the interdental spaces. However, acids entering the oral cavity can contribute to the rapid progression of abrasion of tooth tissues at the neck that has already begun.

clinical picture. Wedge-shaped defect in most cases is not accompanied by pain. Sometimes patients indicate only a tissue defect at the neck of the tooth. Usually it progresses slowly, and with deepening the contour does not change and there is no decay and softening. In rare cases, there is a quickly passing soreness from temperature, chemical and mechanical stimuli. A calm course or the appearance of pain depends on the speed of loss of hard tissues. With slow abrasion, when replacement dentin is intensively deposited, pain does not occur. In cases where replacement dentin is deposited more slowly than tissue abrasion occurs, pain occurs.

The defect is formed by the coronal plane, which is located horizontally, and the second plane - gingival, located at an acute angle. The walls of the defect are dense, shiny, smooth. In cases where the defect comes close to the cavity of the tooth, its contours are visible. However, the cavity of the tooth is never opened. The wedge-shaped defect can reach such a depth that, under the influence of mechanical load, the tooth crown can break off. In most cases, probing is painless.

A wedge-shaped defect is often accompanied by gingival recession.

Pathoanatomy. There is a decrease in interprism spaces, obturation of dentinal tubules, and in the pulp - atrophy phenomena.

A wedge-shaped defect is differentiated from diseases of non-carious origin: erosion of hard dental tissues, cervical enamel necrosis, superficial and medium dental caries (see table).

Treatment. At the initial manifestations of the defect, measures are taken to stabilize the process. To do this, drugs are used that increase the resistance of hard tissues of the tooth (applications of 10% calcium gluconate solution, 2% sodium fluoride solution, 75% fluoride paste). In addition, precautions are taken to reduce the mechanical impact on the teeth. Soft brushes are used for brushing teeth, pastes containing fluorine or having a remineralizing effect are used. The movements of the toothbrush should be vertical and circular.

In the presence of pronounced defects in hard tissues, filling is recommended. As a filling material, the most convenient are composite filling materials, which can be used to seal wedge-shaped defects without preparation. With deep defects, it is necessary to manufacture artificial crowns.

Erosion of the teeth

Erosion- this is a defect in the hard tissues of the tooth with localization on the vestibular surface, having the shape of a saucer.

Etiology and pathogenesis not definitively elucidated. Some authors believe that tooth erosion, like a wedge-shaped defect, arises solely from the mechanical action of a toothbrush. Others believe that the occurrence of erosion is due to the consumption of large amounts of citrus fruits and their juices.

Yu. M. Maksimovsky (1981) assigns an important role in the pathogenesis of erosion of hard dental tissues to endocrine disorders and, in particular, hyperfunction of the thyroid gland. According to him, one of the symptoms of this disease is an increase in saliva secretion and a decrease in the viscosity of the oral fluid, which cannot but affect the condition of the hard tissues of the tooth.

Localization. Erosions of the hard tissues of the teeth appear mainly on the symmetrical surfaces of the central and lateral incisors of the upper jaw, as well as on the canines and small molars of both jaws. Defects are located on the vestibular surfaces in the region of the equators of the teeth. The defeat is symmetrical. There are practically no erosions on large molars and on the incisors of the lower jaw.

Classification. There are two clinical stages of erosion - active and stabilized, although in general any erosion of enamel and dentin is characterized by a chronic course.

For active stage a rapidly progressive loss of hard tissues of the tooth is typical, which is accompanied by an increased sensitivity of the affected area to various external stimuli (the phenomenon of hyperesthesia).

Stabilized stage erosion is characterized by a slower and more calm course. Another sign is the absence of tissue hyperesthesia.

There are three degrees of erosion according to the depth of the lesion.:

degree I or initial, - damage to only the surface layers of enamel;

degree II, or average,- damage to the entire thickness of the enamel up to the enamel-dentin junction;

degree III, or deep, - when the superficial layers of dentin are also affected.

clinical picture. Erosion is an oval or rounded enamel defect located on the most convex part of the vestibular surface of the tooth crown. The bottom of the erosion is smooth, shiny and hard.

Enamel erosion, unlike other types of abrasion, in most cases is characterized by severe pain under the action of various factors, especially cold air and chemical irritants. There are more complaints in the active stage than in the stabilized one.

Pathological picture. Microscopic examination of the area with enamel erosion shows changes in the surface layer, an increase in interprism spaces, and obliteration of dentinal tubules.

Differential diagnosis. Enamel erosion should be differentiated from superficial caries and wedge-shaped defect. Erosions differ from caries in localization, the shape of the lesion, and most importantly, in their surface (with erosion it is smooth, and with caries it is rough). A wedge-shaped defect differs from erosion in the shape of the lesion, localization at the neck at the border of enamel with cement, often when the root is exposed (see table).

Treatment. Treatment for erosion of tooth tissues should be carried out taking into account the activity of the process and the nature of the concomitant somatic disease.

In complex dental treatment, one should not forget about the general treatment, which involves the administration of calcium and phosphorus preparations, vitamins separately or in combination with microelements. It is necessary to limit the intake of citrus fruits.

Dental filling in case of erosion is often ineffective due to the often occurring violation of the marginal fit of seals and the formation of a defect around the seal. In this regard, it is recommended to carry out remineralizing therapy before filling the erosion. Composite materials, compomers, CRC should be used as filling materials. With a significant area of ​​​​damage to the tooth by erosion, it is more advisable to manufacture an artificial crown.

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Etiology, pathogenesis and clinic of diseases of hard tissues of the tooth

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

Enamel. Human teeth are an organ that performs the primary mechanical processing of food. The main function of the teeth determined the morphological features of their tissues. The crown part of the teeth is covered with enamel - the most durable tissue. Withstanding great pressure during chewing, enamel is also fragile and weakly resists sudden loads, such as impact, which cracks and chips 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 region of the bottom of the fissures - 0.1-1.5 mm, on the cutting edge of unworn teeth - 1.7 mm, on the hillocks - 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). Outside, the enamel is covered with a very dense, non-calcified, resistant to acids and alkalis film (Nasmite shell) 3-10 microns thick, which is near the neck The tooth is connected to the epithelium of the mucous membrane of the gums, being, as it were, its continuation.Shortly after teething, the film is erased, primarily on the contact 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 - the cells of the inner epithelium of the enamel organ.

The data obtained in recent years using electron microscopy make 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 dentin-enamel 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 interprism substance that performs a nutritional function in enamel) with a smooth surface, facing the walls of the prism. The interprism substance appears to be amorphous, is located in the form of a thin, often barely noticeable strip, or forms clusters - enamel: beams 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 wedged between the underlying prisms. The ends of the enamel prisms, wide at the base, are separated by tapered 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 evenly mineralized, the degree of mineralization is high. With age, the crystals thicken the protein-rich interlayers between the prisms, and the "boundary lines" become thinner.

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

Dentine. Dentin makes up about 85% of the tissues of the tooth 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 location 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 the near-pulpal dentin, rich in tangential fibers.

Dentin belongs to highly mineralized tissues (about 73% of organic compounds) and is second only to enamel in terms of the degree 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 dentine.

Interglobular spaces are often found on the border of the mantle and peripulpal dentin, the origin of which is presumably associated with the uneven process of calcification. Similar but smaller formations, referred to as Tomes granular layers, are noted at the dentin-cement margin. Interglobular spaces and granular layers of Tomes, arranged in several rows, constitute Owen's contour lines, which are identical to the Retzius lines in enamel by the mechanism of formation.

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

On electron microscopic replicas, non-decalcified dentin of intact teeth consists of a basic substance (matrix) in which a network of dentinal tubules is determined. Dentinal tubules are tubules of different diameters. In areas located closer to the pulp chamber, their diameter is 0.5-0.8 µm on average. As it approaches the enamel-dentine 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 on the periphery, which corresponds to the peritubular hypermineralized zone. This serves as evidence that the centers of apatite crystal formation are formed along the protofibrils of dentin collagen.

The width of the hypermineralized peritubular zone depends on the area of ​​the dentin and the age of the person. At the age of 20-30 years, she is somewhat narrower than at 40-50 years old. As the dentinal tubule approaches the dentinal-enamel border, the hypermineralized peritubular zone becomes wider; 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 grains of crystals and collagen fibers is lower compared to the peritubular zone.

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

The question of the existence of a Neumann membrane (peritubular dentin), which supposedly lines the dentinal tubules, has not been finally resolved. Some authors recognize its existence [Falin L.I., 1963]. In their opinion, the Neumann sheath consists of amorphous plasma substances and is located between the processes of Toms (the dentinal process of the ondoblast) and the inner surface of the wall of the dentinal tubules. The authors came to this conclusion on the basis of data obtained using an optical microscope. This information is still given in textbooks, although there is enough new 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 go 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 the dentin. Some fibers penetrate the enamel in the form of flask-shaped swellings - enamel spindles or bushes.

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

Cement. There are cellular and acellular cement covering 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 on the tops of the roots of all teeth, is superimposed on acellular, or primary. With age, the amount of cellular cement increases. Quite often, cavities with cells are found in the newly formed cementum. There is a known case when the newly formed cement acquired the character of lamellar bone.

No blood vessels were found in both cellular and acellular cement, and there is also no information about its innervation. The main substance of the primary cementum consists of collagen fibrils, which diverge mainly in the radial direction, sometimes in the longitudinal direction. Radial fibrils directly continue in the sharpei (perforating) fibers of the periodontium and then penetrate into the alveoli.

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

Dentin hydroxyapatite crystals are similar in size and shape to bone tissue crystals. 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. The crystals increase in size as the degree of mineralization of the tooth substance increases. Dentinal fluid (dental lymph) penetrates into the dentin and enamel through the processes of Toms, with which nutrients from the blood enter the hard tissues of the tooth.

Many issues of the physicochemical and biological nature 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 the tissues of the tooth. At the same time, the presence of a close morphological and functional relationship between the organic and inorganic components of the tooth was established. It has also been proven that collagen protofibrils of hard dental tissues serve as a base, on the surface and inside of which crystallization centers are created. As a result of the deposition of inorganic salts of calcium and phosphorus, individual apatite crystals (hydroxyapatite, fluorapatite) gradually form in the centers of crystallization. As they grow, they approach neighboring ones, become cemented and form a group of crystals. The process of crystallization is characterized by certain intervals and periods.

Each crystal of hydroxyapatite is surrounded by the thinnest immovable liquid layer - the so-called hydrated layer. It is formed due to a pronounced electrical asymmetry, due to which a strong electric field is created on the surface of the crystals. As a result of this, layers of bound ions are formed, which constantly hold around the crystals a fixed solvent layer - the hydrate layer. The hydrated layer contains high concentrations of hydrated calcium ions and polarized phosphorus ions. The crystals themselves are composed 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 interconnected using the electric field formed around the ions.

Calcium and phosphorus in the bones and tissues of the teeth are presented in the form of two fractions - labile and stable. Labile calcium is 20-25%, phosphorus - 12-20%. The exchangeable and labile fractions are a kind of depot of ions, which provide an exchange reaction in the hydration layer of the liquid around the crystals and are in quantitative equilibrium with blood phosphorus and calcium. In the process of mineral metabolism, growth and formation of crystals, calcium and phosphorus pass from the labile 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 hydrate layer, which is carried out due to the charge asymmetry on the crystal surface. The second zone is the transition from the hydrate layer to the crystal surface, which occurs under the action of ionic force. The third zone is the transition from the crystal surface to crystal lattices due to thermal motion 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 valency and the force of interionic attraction. The first two phases of ion exchange—between the diffuse and hydrate layers, as well as between the hydrate layer and the crystal surface—occur quite rapidly. Inside the crystals, the exchange rate depends on the number of free places 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 traced. Various lesions of the hard tissues of individual or groups of teeth gradually lead to a change in their morphology, as a result of which there may be violations of the masticatory function of the dentition, the normalization of which is the main goal of dental prosthetics.

The ratio between the height of the clinical crown and the length of the root varies widely both in individual teeth or groups of teeth, and individually for each patient. In some cases, the clinical crown corresponds to the anatomical one, in others the length of the clinical crown is longer than the anatomical one. In childhood and adolescence, the clinical and anatomical contours of the tooth crown usually coincide: the transition of enamel into cement coincides with the line of the clinical neck. The root is usually not visible or palpable and can only be examined radiologically. Teeth with such a morphology are highly stable and can take additional load, which is important when choosing fixed and removable dentures.

With periodontitis, the dimensions of the clinical crown and root of the tooth undergo certain changes. Due to alveolar atrophy and gingival 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 resistance lever of the tooth complicates the choice of prosthesis design, excluding the 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 the second and third molars, the root surface increases as you move away from the midline to the distal side.

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 tissues of the teeth, the restoration of their anatomical shape should give 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 parts 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 between the so-called safety zones. He considered these zones to be areas of the crown part of the tooth, on which the thickness of hard tissues allows the necessary amount of grinding to be carried out without fear of opening the pulp chamber in the manufacture of fixed dental structures. Dangerous zones are called areas of the crown of the tooth, on which there is a small thickness of hard tissues and, therefore, the pulp cavity is close to the surface of the tooth. For example, incisor safety zones are located at the incisal edge, on the oral side, and on the proximal surfaces of the crown and neck of the tooth. Danger zones are the spaces between the safe zones of the incisal edge and the oral side, as well as the vestibular and oral sides of the neck of the tooth.

In fangs, the 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, the safety zones are located on the proximal surfaces. The zone of the apex of the tubercle, the vestibular and oral sides of the neck of the tooth are easily vulnerable, since here the pulp is located close to the surface.

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, and also at the neck of the tooth. Dangerous places are the tops of the tubercles, the oral and vestibular sides of the neck of the tooth.

Molar safety zones are the contact points of the crown, the central part of the chewing surface, the spaces between the tubercles, 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 tubercles, the vestibular and oral sides of the neck of the tooth.

The structural features of each tooth are taken into account when determining the amount of grinding of hard tissues during the preparation of teeth, as well as when deciding whether it is advisable to create 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 the grinding of hard dental tissues: opening of the pulp, pulpitis, thermal burns of the pulp. Approximately the dimensions of the safety zones can be determined by measuring 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 indications for the use of street crowns up to 16 years old and porcelain crowns - up to 18-19 years old.

The functional morphology of the anterior 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 anterior teeth are included in the function and the more often they cut hard food, the faster the crown height decreases due to wear, and the cutting surface increases. This functional wear is considered as physiological wear. However, under the influence of a number of factors, the wear of hard tissues of the teeth can progress and acquire the character of a pathological process, which leads to shortening of the crowns of the teeth up to the gum level, 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 passable root canal. This provides the possibility of their expansion and use for the manufacture of post teeth, post post inlays and post crowns. The roots of the lower incisors are flattened from the proximal sides, which excludes 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. The 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 structures for prostheses.

The first and second molars of the upper jaw have three roots each: two buccal, shorter and less massive, somewhat diverge in the sagittal plane, and the palatine, longer and more voluminous, goes towards the sky. The characteristic direction of the palatine root, which is the result of functional adaptation, makes it possible to redistribute the masticatory load along the main axis of the tooth. The structural features of the palatine roots, in comparison with the buccal ones, provide more favorable conditions for the introduction and fixation of prosthesis pin structures.

During life, the morphology of the occlusal surface of the teeth may remain unchanged or change depending on the nature of the occlusal contacts during chewing. In persons in whom vertical articulated movements of the lower jaw predominate (with a deep bite), there are no pronounced changes in the occlusal surface of the teeth for a long time. With a direct bite, in which the horizontal sliding movements of the lower jaw are carried out freely, the relief of the occlusal surface of the teeth changes due to the erasure of the tubercles. This must be taken into account when studying the state of the dentoalveolar system, establishing a diagnosis and choosing a method of orthopedic treatment of patients.

J. Williams (1911) proved the presence of a certain dentofacial harmony. In particular, the shape of the central incisors corresponds to the shape of the face: in patients with a square face, the anterior teeth are most often square, in those with an oval face, an oval shape, and with a triangular face, the anterior teeth are most often also triangular. In the process of orthopedic treatment of the anterior teeth, the nature of 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 the teeth in each patient has individual characteristics, which is the result of the layering of the color of the enamel on the color of the dentin. Dentin has a yellow color of various shades. The color of the enamel is white with a yellow, blue, pink, gray tint or a combination of them. In this regard, the vestibular surface of the anterior 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 the dentin to show through, is less transparent; in the cervical part, the enamel layer is thinner and the dentin shines through it more strongly, therefore this part 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, in particular in smokers, various pigmentations and atypical discolorations of the teeth appear. The color of the teeth largely depends on the observance of the rules of hygiene of the teeth and oral cavity.

Partial and complete destruction of the crown part of the tooth

To the pathology of hard tissues of the teeth include carious and non-carious lesions.

Tooth caries. The study of the problem of dental caries (etiology, pathogenesis, clinic, treatment and prevention) is devoted to a huge amount of scientific research. However, it remains very relevant throughout the world and the search for its resolution continues.

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

Tooth crown defects are divided into partial and complete. Partial defects can have different localization, size, shape and depth. In this case, the crown part of the tooth is not completely destroyed, and it is restored with the help of a filling material, and in some cases, orthopedic treatment is carried out according to indications. Complete defects of the crown part of the tooth (complete absence of a crown) are eliminated using pin teeth.

Non-carious lesions of the 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 tooth development; 2) lesions that occur after eruption: pigmentation of the teeth and plaque, erosion of the teeth, wedge-shaped defect, erasure of hard tissues, hyperesthesia of the teeth, necrosis of the hard tissues of the teeth, trauma to the teeth.

Enamel hypoplasia. Hypoplasia of tooth tissues occurs as a result of a violation of metabolic processes in the anamenoblasts of the rudiments of teeth. The occurrence of hypoplasia contributes to the violation of protein and mineral metabolism in the body of the fetus or child. According to etiological signs, focal odontodysplasia, 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, more often incisors, canines and permanent molars. The clinical picture of the disease is characterized by a rough surface, a yellowish color, a decrease in size and an uneven 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 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, which is formed in the same period of time.

Enamel hypoplasia is characterized by the formation of cup-shaped depressions of a round or oval shape. At the bottom of the recesses, enamel may be absent (aplasia) or it may be thinned and yellowish dentin shines through it. The dimensions, 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 striated 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 can be different, on their bottom there is a thinned layer of enamel, and in some cases there is no enamel.

Fournier, Getchinson and Pfluger teeth are considered a type of systemic hypoplasia. The crown of the tooth acquires a peculiar barrel-shaped shape with a semilunar notch on the cutting edge of the anterior incisors of the upper and lower jaws. Pfluger teeth are characterized by a cone-shaped permanent molars. Hypoplasia of the cutting edges and tubercles 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, less often two teeth are affected, and only permanent teeth. The disease develops under the influence of mechanical injury or inflammation.

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

Enamel hyperplasia (enamel drops, pearls). This pathology is an excessive formation of tooth tissue during its development, most often in the neck of the tooth on the line separating enamel and cementum, as well as on the contact surface of the teeth. Functional disturbances in 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 as a result of the use of drinking water with an excess content of fluoride compounds.

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

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

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

Capdepon's dysplasia(Stainton-Capdepon syndrome). With this disease, related to hereditary disorders of dental development, both temporary and permanent teeth are affected.

Erosion of hard tissues of the tooth. 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 anterior 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 as a round or oval enamel defect with a smooth, hard and shiny bottom, gradually increases in the transverse direction and takes the form of a grooved chisel. With a large area of ​​the lesion, when it is not possible to eliminate the defect with the help of a filling material, orthopedic treatment is performed.

wedge defect. This hard tissue lesion is more commonly seen on canines and premolars. less often - incisors and molars. The etiology of the disease has not been fully elucidated. Importance in the progression of wedge-shaped defects is attached to mechanical and chemical factors (toothbrushes and powder, demineralizing action. acids to as well as endocrine disorders, diseases of the central nervous system and gastrointestinal tract.

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

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

1) initial manifestations without visible loss of tissue, which are revealed with a magnifying glass. Sensitivity to external stimuli is increased;

2) superficial wedge-shaped defects in the form of scaly enamel damage, localized near the enamel-cement border. The depth of the defect is up to 0.2 mm, the length is 3--3.5 mm. The loss of tissue is determined visually. Increased hyperesthesia of the necks of the teeth is characteristic;

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, the length is 3.5-4 mm, the color of hard tissues is similar to the yellowish color of normal dentin;

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

With wedge-shaped defects, general treatment is carried out, aimed at strengthening the structure of the tooth and eliminating dentin hyperesthesia, as well as local filling. In case of poor fixation of the filling and the risk of fractures of the tooth crown, orthopedic treatment is indicated.

Hyperesthesia of hard tissues of the tooth. Hyperesthesia - increased sensitivity of hard tissues of the tooth to mechanical, thermal and chemical stimuli, observed in carious and non-carious lesions of 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 the preparation of teeth for artificial crowns or inlays.

2. 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 form of tooth erosion.

B. By origin.

1. Hyperesthesia of dentin associated with the loss of hard tissues of the tooth:

a) in the area of ​​carious cavities;

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

c) concomitant pathological abrasion of hard tissues of the tooth and wedge-shaped defects;

d) with erosion of hard tissues of teeth.

2) Hyperesthesia of dentin, not associated with the loss of hard tissues of the tooth:

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

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

B. According to the clinical course.

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

II degree - tooth tissues react both to temperature and chemical stimuli (cold, heat, salty, sweet, sour, bitter food). The threshold of electrical excitability is 3-5 μA;

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

Pathological abrasion of hard tissues of teeth. This form of hard tissue damage is quite common 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 due to the discrepancy between the transversal sizes and the shape of the dentition. The frequency of crossbite, according to the literature, is not the same at different ages: in children and adolescents - from 0.39 to 1.9%, in adults - about 3%. Various terms are used that characterize crossbite: oblique, lateral, buccal, vestibulo-occlusion, buccoocclusion, lintaocclusion, lateral - forced bite, articular crossbite, laterognathia, laterogeny, lateroversion, latero-deviation, laterodgnathia, laterodyskinesia, lateroposition.

The development of a crossbite may be due to the following reasons: heredity, the incorrect position of the child during sleep (on one side, placing a hand, a fist under the cheek), bad habits (supporting the cheek with a hand, sucking fingers, cheeks, tongue, collar), atypical arrangement of the rudiments of teeth and their retention, delay in the change of milk teeth by permanent ones, violation of the sequence of teething, unworn tubercles of milk teeth, uneven contacts of the dentition, early destruction and loss of milk molars, nasal breathing disorder, improper swallowing, bruxism, uncoordinated activity of chewing muscles, violation of calcium metabolism in the body , facial hemiatrophy, trauma, inflammatory processes and associated jaw growth disorders, ankylosis of the temporomandibular joint, unilateral shortening or lengthening of the mandibular branch, unilateral overgrowth of the jaw body or growth retardation, residual defects in the palate after uranoplasty, neoplasms ania and others.

Considering the great variety of the clinic of cross-occlusion, it is advisable to single out the following forms [Uzhumetskene II, 1967].

The first form is the 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, a combination of these signs;

b) bilateral, due to bilateral symmetrical or asymmetric narrowing of the upper dentition or jaw, expansion of the lower dentition or jaw, a combination of these signs.

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

a) parallel to the midsagittal plane;

b) diagonally.

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

The second form is lingual crossbite:

1. One-sided, due to a unilaterally expanded upper dentition, a unilaterally narrowed lower dentition, or a combination of these disorders.

2. Bilateral, due to a wide dentition or a wide upper jaw, a narrowed lower jaw, or a combination of these features.

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 expansion of the basis of the jaw (underdevelopment, excessive development);

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

Rice. 1. Varieties of crossbite.

destruction crown tooth bite

With a crossbite, the shape of the face is disturbed, transversal movements of the lower jaw are difficult, which can lead to uneven distribution of masticatory 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. Often, the function of the temporomandibular joints is disturbed, 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 median point of the chin, which is determined in relation to the median plane. The median line between the upper and lower central incisors usually coincides. However, with a close position of the anterior teeth, their displacement, asymmetry in the development of the dental arches, it can be displaced. In such cases, determine the location of the bases of the frenulums of the upper and lower lips, tongue.

The degree of violation of the ratio of dental arches in the bite is different. The buccal tubercles of the upper lateral teeth may be in tuberous contacts with the lower teeth, may be located in the longitudinal grooves on their chewing surface, or not in contact with the lower teeth.

With a buccal crossbite with a displacement of the lower jaw to the side, asymmetry of the face 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 hardly 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 the 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 move diagonally to the side. The articular heads of the lower jaw with its lateral displacement change their position in the joint, which is reflected in the meiodistal ratio of the lateral teeth in the occlusion. On the side of the displacement, a distal ratio of the dental arches occurs, on the opposite side, a neutral or mesial one. On palpation of the region of the temporomandibular joints during opening and closing of the mouth on the side of the displacement of the lower jaw, a normal or mild movement of the articular head is determined, on the opposite side - more pronounced. When opening the mouth, the lower jaw can move from the lateral position to the central position, and when closing, it can return to its original position. In some patients, there is an increase in the tone of the masticatory muscle proper on the side of the displacement of the lower jaw and an increase in its volume, which increases the asymmetry of the face.

To determine the displacement of the lower jaw to the side, the third and fourth clinical functional tests are used according to L. V. Ilina-Markosyan and L. P. Kibkalo (1970), namely, the patient is offered to open his mouth wide and study the facial signs of deviations; the existing asymmetry of the face increases, decreases or disappears depending on the cause that causes it (third test); after that, 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 size of the interocclusal space in the region of the lateral teeth, the degree of narrowing (or expansion) of the dentition, the asymmetry of the bones of the facial skeleton, etc. (fourth trial).

When studying a direct radiograph of the head, asymmetric development of the facial bones of the right and left sides, their unequal location in the vertical and transverse directions, and diagonal lateral displacement of the lower jaw are often established. 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.

With a lingual crossbite, on the basis of an examination of the face in front and profile, a displacement of the lower jaw and a flattening of the chin are often detected. Sometimes hypotension of the masticatory muscles, a disorder in the function of chewing, blocking of the lower jaw and a violation of its lateral movements are determined. Change the shape of the dental arches and bite. 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 disorders, as well as dental, articular, muscular, etc., are characteristic of both literal and lingual crossbite.

The treatment of a crossbite depends on its type, causes of development, as well as the age of the patient. Basically, the width of the upper and lower dentition is normalized by unilateral or bilateral expansion, narrowing, and setting the lower jaw in the correct position (Fig. 2).

During periods of milk and early mixed dentition, the treatment consists in eliminating the etiological factors that caused the violation: the fight against bad habits and oral breathing, the removal of delayed milk teeth, the grinding off of unworn milk tubercles - molars and canines, which impede transversal movements of the lower jaw. Children are advised to chew solid food on both sides of their jaws. In cases of habitual displacement of the lower jaw to the side, therapeutic exercises are prescribed. After an early loss of milk molars, removable dentures are made to replace defects in the dental arches. Removable dentures for the upper jaw with a neutral and distal ratio of the dental arches are made with a bead platform - in the anterior area. The bite is also increased on artificial teeth, which makes it possible to separate the teeth on the abnormally developed side. This makes it easier to correct their position with springs, inclined plane screws, and other devices.

In addition to preventive measures, orthodontic appliances are used. According to the indications, the bite is increased by means of crowns or mouthguards, fixed on the milk molars, which makes it possible to create conditions for the normalization of the growth and development of the dental arches and jaws and the elimination of mixing of the lower jaw. With a lateral displacement of the lower jaw, crowns or mouth guards 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 with the help of 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.

In the manufacture of devices for the treatment of crossbite, a constructive bite is determined: the dentitions are separated on the side of deformation in order to facilitate their expansion or narrowing and the lower jaw is set in the correct position with its lateral displacement.

For the treatment of crossbite, combined with a lateral displacement of the lower jaw, an inclined plane is modeled on the plate for the upper jaw - palatine, 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. In case of bilateral crossbite, an expanding plate with occlusal pads on the lateral teeth without imprints of the chewing surface of the opposing teeth is used, which facilitates the expansion of the dental arch. With a significant narrowing of the upper dental arch or jaw, both unilateral and bilateral, expansion plates are shown with a screw or springs, as well as with bite pads in the lateral areas. With the help of such devices, the lower jaw is set 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 chewing muscles is rebuilt, and the position of the articular heads of the lower jaw in the temporomandibular joints is normalized.

With a pronounced malocclusion, including those combined with sagittal and vertical anomalies at the age of 5-6 years, functionally guiding or functionally operating orthodontic appliances are used. Of the functional guide vanes, the activator is more often used. With a one-sided discrepancy between the position of the lateral teeth (narrowing of the upper dentition and expansion of the lower one), 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 correcting the position of the teeth, the growth of the articular process and the branches of the lower jaw and the elimination of its displacement. You can use an activator with a one-sided sublingual pad (on the side of the correct closure of the dentition) or with a bilateral one. In the latter case, it should not fit (to the teeth subject to lingual inclination with the help of the vestibular arch.

Of the functionally operating devices, the Frenkel function controller is more often used. Treatment with this device is most effective in the final period of the milk and the initial period of mixed dentition. In buccal crossbite, the regulator is made so that the side shields are adjacent to the crowns and the alveolar process of the lower jaw and do not touch them in the region of the upper jaw on one side with a unilateral crossbite or on both sides with a bilateral one; with a lingual crossbite, the ratio of the lateral shields and dentoalveolar areas should be reversed. By compressing the median flexure of the palatine clasp of the regulator, it is possible to increase the pressure on the upper posterior teeth in the oral direction.

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

During the change of milk molars and the eruption of goremolars, active orthodontic appliances are usually replaced with retention ones. After (eruption of the premolars at half the height of their crowns, they are pressured by an orthodontic apparatus in order to establish in the correct position. Uncoupling of the bite during this period of treatment is not required.

In the final period of permanent occlusion 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, extraction of individual teeth, and compact osteotomy (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, compact osteotomy or other types of surgical interventions is detected after the jaw is established in the correct position. Compactosteotomy is done near the teeth subject to vestibular or oral movement both from the vestibular and oral sides of the alveolar process, and with indications for dentoalveolar shortening or lengthening, also at the level of the apical basis of the dentition.

Rice. Fig. 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 the removal of the lower first premolars, correcting the position of the teeth and lower jaw.

To move the upper and lower teeth in mutually opposite directions after bite disengagement with the help of a removable apparatus, rings are used on the upper and lower lateral teeth with intermaxillary traction. In the treatment of buccal crossbite, the rubber rings are hooked on the hooks soldered on the oral side of the rings on the movable upper lateral teeth, and on the hooks located on the vestibular side of the rings fixed on the lower lateral teeth. If occlusal contacts between the teeth remain on the side of tooth movement, the patient will bite through the rubber rings and the treatment will not be successful. Dental rows in these areas are subject to disassembly. It is necessary to ensure that the removable device that separates the teeth does not adhere to the teeth that are moved orally, to the alveolar process in this area.

Rice. Fig. 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.

Angle appliances are used to correct the size of dental arches. The distance between the vestibular surface of the moved teeth and the springy arch is adjusted. For the treatment of crossbite with displacement of the lower jaw, to the side or combined with sagittal and vertical bite anomalies, Entl devices with intermaxillary traction, including one-sided (Fig. 4), are used.

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Caries - a pathological process that occurs after teething, consisting in demineralization and softening of the hard tissues of the tooth, followed by the formation of a defect in the form of a cavity. It is one of the most common dental diseases.

Predisposing factors are: unbalanced diet with excessive consumption of carbohydrates, pathogenic microflora of the oral cavity, insufficient hygienic care of the teeth, the amount, composition and properties of saliva, hormonal changes (puberty, pregnancy), general somatic diseases.

By the defeat of the hard tissues of the tooth, caries of enamel, dentin, and cement are distinguished.

According to the clinical course - acute and chronic caries.

According to the localization of the carious process - fissure, approximal, cervical.

By the number of affected teeth - single and multiple.

Depending on the depth of the lesion, 4 stages of the process are distinguished:

1. Initial caries(spot stage) - there is a loss of natural luster of the enamel area, it becomes matte. Pain sensitivity is absent, the tooth does not react to temperature stimuli.

2. Superficial caries characterized by a violation of the integrity of the enamel, clinically manifested by softening, necrosis and the formation of a small defect. In this case, there may be short-term pain on chemical (sweet, salty, sour) irritants.

3. Medium caries accompanied by destruction of the hard tissues of the tooth with the formation of a defect reaching the surface layers of dentin. At the same time, short-term pains from mechanical, chemical and thermal stimuli are sometimes noted, after the elimination of which the pain quickly disappears. The cavity is filled with softened dentine.

4. deep caries characterized by a pronounced destruction of the hard tissues of the tooth with the formation of an extensive cavity separated from the pulp by a thin layer of dentin. Characterized by acute short-term pain from mechanical, chemical and thermal stimuli, after the elimination of which the pain quickly disappears. The cavity is filled with softened and pigmented dentin.

Classification of caries depending on the location of the lesion (according to Black):

Grade 1 - chewing surface of molars and premolars, blind pits on the buccal and lingual surfaces of molars and premolars, lingual and palatal surfaces of incisors.

Grade 2 - lateral (contact) surfaces of molars and premolars.

Grade 3 - contact surfaces of incisors and canines without violating the integrity of the angle and cutting edge of the tooth crown.

Class 4 - contact surfaces of incisors and canines with involvement in the carious process of the corners and the cutting edge of the tooth crown.

Grade 5 - cervical region of all teeth.

Treatment of dental caries is divided into general and local.

The general is used for progressive initial and multiple dental caries, carrying out a set of preventive measures:

1. Purpose of preparations of fluorine, calcium, vitamins.

2. Rational nutrition - limiting foods high in carbohydrates, eating foods rich in vitamins, hard foods (carrots, apples).

3. Identification and treatment of concomitant diseases.

Remineralizing therapy is carried out locally (applications of 10% calcium gluconate solution, 2-10% calcium phosphate solution)

In the case of superficial, medium and deep caries, local treatment consists of the following steps:

Anesthesia;

Opening and expansion of the carious cavity;

Excision of non-viable hard tissues (necrectomy);

cavity formation;

Processing the edges of the cavity;

Antiseptic treatment of the walls and bottom of the carious cavity;

Laying overlay;

Cavity filling.

Permanent filling materials should:

1. Be chemically resistant to the oral environment (do not dissolve in the oral fluid).

2. Be indifferent to the hard tissues of the tooth, the oral mucosa and the body as a whole.

3. Keep the volume constant and not deform during hardening.

4. To be plastic and convenient when forming a filling, it is easy to be introduced into the tooth cavity.

5. Have good adhesion to the hard tissues of the tooth.

6. Have thermal insulation properties.

7. Satisfy cosmetic requirements.

To conduct a comprehensive prevention of caries, it is necessary to draw up a program of measures, the main provisions of which are as follows:

§ Prevention of caries in children should be carried out simultaneously with the sanitation of the oral cavity.

§ The program should be based on indicators typical for the region, such as the composition of the child population, the incidence of caries in children, the existing level of organization of dental care.

§ The program must be targeted and cover 100% of children.

§ Specific timeframes for the implementation of the program should be determined.

Of great importance in the prevention of caries is a balanced nutrition in quantitative and qualitative terms. Of no small importance is oral hygiene: timely removal of soft plaque, regular oral care with the use of special therapeutic and prophylactic toothpastes.