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ANSWERS FOR THE EXAM 1. Examination of the jaws by means of a gnatostat. Obtaining gnatostatic models. diagnostic value. The gnatostatic method was proposed by P. Simon. Gnatostat - a device with which the location of the models is determined in relation to three mutually perpendicular...

ANSWERS FOR THE EXAM 1. Examination of the jaws by means of a gnatostat. Obtaining gnatostatic models. diagnostic value. The gnatostatic method was proposed by P. Simon. Gnatostat - a device with which the location of the models is determined in relation to three mutually perpendicular planes: the mid-sagittal plane passes along the palatine suture and divides the face in half; ear-orbital or Frankfurt, the horizontal passes through the orbital point and the upper edge of the external auditory opening; the frontal or orbital plane perpendicular to the first two passes through both orbital points. Apparatus P. _ The Simon consists of a facebow connected to an impression tray and has four moving arrows placed on the auricular and inferoorbital points. With the help of a gnatostat, the base of the model is formed in accordance with the above planes, and thus the spatial orientation of the patient's dentition is simulated, which makes it possible to visualize the location of the jaws in the skull. The technique is as follows: an impression tray for the upper jaw is filled with an impression mass and inserted into the mouth. After the impression has hardened, the assistant holds the spoon in this position, the handle of which is fastened to the rod. The facial arch is put on the latter, orienting it with arrows at the level of the Frankfurt horizontal along the orbitale and tragion points. On the patient's face, these points are preliminarily marked with a bold pencil or black paper circles are pasted. Having arranged and fixed the arrows and the arc with screws, the movable sleeve is moved close to the arc and everything is fixed. Then the arc with the rod is disconnected from the impression tray, the impression is removed from the mouth and reconnected in the same position. The line connecting the ends of the two middle arrows is the line of intersection of the Frankfrut horizontal with the orbital plane. To transfer this line to the surface of the cast, use a ruler, which is applied to the sharp ends of the two arrows of the orbital arc. An arrow with a pointed end departs from the middle of the ruler at a right angle, which can move up and down and around the axis within the same plane. The ruler is laid so that the point of the arrow reaches the surface of the print. When moving the arrow up and down and sideways, the tip leaves a mark on the surface of the print in the form of an engraved line. Then the orbital arc is replaced by a platform and the upper model is cast. After the model is released from the cast, a drawn transverse line is found that passes through the tops of both canines, and the median plane is established along the palatal suture. Gnatostatic models made in this way have the following features: the upper plinth surface of the upper model corresponds to the Frankfrut horizontal, and the lower one is parallel to it; the distance between them is 8cm; the rear surfaces of the models are parallel to the orbital plane and are at a distance of 4cm from it. Models are drawn and studied using a symmetrograph. When comparing gnatostatic models with conventional ones, it can be seen that the occlusal curve does not pass the same way. On gnatostatic models, it decreases anteriorly, i.e. goes with an inclination in relation to the Frankfruit horizontal. If the upper canines coincide with the orbital plane - the norm, if ahead of it - prognathism and treatment should be directed to the upper jaw. If the upper canines are displaced beyond the frontal plane - medical manipulations on the lower jaw. 2. "Progenic" bite (mesial occlusion). Classification etiology, clinic, forms, differential diagnosis. Progenia ( pro - forward, genus - chin) is a fairly common dentoalveolar deformity that occurs in 1.4% to 30% of cases. Morphological disorders in this type of ratio of dental arches cause significant aesthetic and functional disorders in the maxillofacial region. The term progeny is a general one that refers to various types of anomalies. Classification: Depending on the degree of morphological changes, i.e. what formations have an abnormal structure, distinguish dentoalveolar and gnathic forms of progenic occlusion. A progenic bite is jaw or skeletal when it results from abnormal development of the bones of the facial skeleton; dental, or dentoalveolar - is the result of improper arrangement of teeth in the alveolar processes. By localization, a progenic bite happens General, when there is a discrepancy, both in the area of the frontal and lateral teeth (the lateral teeth are closed according to Angle's class III, there is a sagittal inter-incisor gap) and partial, if violations are noted only in the area of the frontal teeth (progenic ratio of the frontal teeth, lateral teeth are closed according to Angle's class I). Depending on the lateral displacement of the mandible, the progenic bite may be with or without displacement of the mandible. Depending on the etiological factor, L.V. Ilyin-Markosyan distinguishes true and false progeny. True penetration (lower macrognathia) is an increase in all or most parameters of the lower jaw and dentition. The closure of the first permanent molars is always in grade 3. False progeny means that the size of the lower jaw is normal and the anomaly occurs due to the underdevelopment of the upper jaw or its retroposition relative to the base of the skull. This is the first form of false progeny. The closing of the sixth teeth can be 1 or 3 classes according to Engel. The second form is due to the anterior displacement of the lower jaw with normal sizes of both jaws in the sagittal direction. This form is often called forced or articular progeny, and the closing of the sixth teeth is always in the 3rd class. According to the classification of A. I. Betelman, the mesial occlusion is classified as a sagittal anomaly and is represented by the following clinical forms: 1) upper micrognathia with a normal lower jaw; 2) lower macrognathia with a normal upper jaw; 3) lower macrognathia with upper micrognathia. Etiology and pathogenesis of progenic occlusion The reasons for the development and formation of progenic occlusion are different. These include: illness of the mother during pregnancy; underdevelopment of the premaxillary bone, in which the incisors develop, its formation occurs from the fourth month of intrauterine life; congenital nonunion of the palate and alveolar process; atypical position of the rudiments of teeth; adentia of the upper anterior teeth; premature extraction of teeth; late change of teeth. The development of a progenic (mesial) occlusion is promoted by mouth breathing with hypertrophy of the palatine tonsil; macroglossia. These functional disorders lead to a violation of the physiological balance of the masticatory and facial muscles, as a result of which the tongue has a greater effect on the mandibular bone and stimulates its excessive development. In the development of progenic (mesial) occlusion, especially its forced form, the main role is played by unworn tubercles of milk fangs and incorrect position of the head during sleep. Clinic: True progenia is one of the most severe anomalies. Facial signs are very characteristic and sharply violate the shape of the face. Noteworthy is the protrusion of the chin and lower lip, the increase in the gonial angle of the lower jaw. The lower third of the face is enlarged, and the middle third sinks along with the upper lip. These changes disturb the aesthetics, make a person look older than his age and can cause mental disorders. Dental signs with true progeny are always pronounced. The lower jaw is located in front of the upper, the front teeth are characterized by a reverse overlap from a small with the presence of contacts to deep or open with a gap between the front teeth in the position of central occlusion. Diastemas and tremas are observed between the lower incisors, canines and premolars. This is due to the discrepancy between the increased size of the lower jaw and the teeth that have retained their size. The mesiodistal ratio of the first permanent molars corresponds to the 3rd class according to Engel. Cross-overlapping can be observed in the lateral areas. The mesial occlusion limits the movements of the lower jaw in the horizontal plane, which significantly reduces the chewing function of the dentition. Differential Diagnosis For differential diagnosis of dentoalveolar and gnathic forms of mesial occlusion, a functional test is performed: if, when the patient tries to move the lower jaw back to the marginal closure of the anterior teeth, the ratio of the first permanent molars approaches Engel class 1, then the dentoalveolar form of progeny or forced false is diagnosed. Diagnosis of true progeny is based on anamnesis data (including genetic), examination of the face, study of occlusive relationships in the oral cavity and on diagnostic models, anthropometric measurements on the face and on models. When examining, it is necessary to accurately distinguish between the position of central occlusion and posterior (synonyms: retrocuspid, posterior contact position) - when the essential heads of the lower jaw are in the upper, mid-sagittal position, which is called the central ratio. When choosing a method of treatment, especially surgical, this position should be the starting point. 3. "Progenic" bite (mesial occlusion). Methods of treatment depending on the form of the anomaly and age. Prevention. Orthodontic interventions in the milk occlusion are reduced to separation of the occlusion, which can be achieved with crowns with soldering on the occlusal surfaces or removable and non-removable trays fixed on the milk molars. To inhibit the growth of the lower jaw in the sagittal direction, a chin sling is used, fixed with a rubber rod to the cap. When using a chin sling, it is necessary in each case to individually set the direction of the rubber traction and adjust its strength. The rubber band must be oblique from front to back and from bottom to top. The rubber should not be too elastic so that it does not cut into the skin of the cheeks and does not cause pain to the child. In milk occlusion, a forced progenic position of the lower jaw is often observed. It is due to the lack of abrasion and the incorrect position of the lower canines, which, with their cutting tubercles, overlap the labial surface of the antagonists and fix the lower jaw in an extended position. By grinding the sharp tubercles of the canines, conditions are created for free movements of the lower jaw in the anteroposterior direction and its normal growth. A forced position can also be caused by pathology from the nasal part of the pharynx. Treatment is to eliminate this pathology. In a removable dentition, two periods are conditionally distinguished. The first period is characterized by the presence of permanent first molars, central and lateral incisors. The rest of the teeth are milk teeth. For the treatment of mesial occlusion in this period, devices that separate the occlusion are used. Depending on the depth of overlapping with the lower teeth, the upper uncoupling caps cover or leave permanent molars free. With a deep overlap, the kappa is fixed only on the milk molars, with a slight overlap - on the milk and first permanent molars, so as not to cause an open bite by the end of the treatment. The equipment that separates the bite can also lead to complications: the destruction of teeth under the mouthguards, and the occurrence of pathological processes in the gums. When using a removable mouth guard, it is necessary to carefully care for the oral cavity. Permanent molars are recommended to be pre-covered with temporary crowns and only then covered with a kappa. A removable mouthguard must be ground in the area where it fits to the gum in order to exclude its irritating effect on the mucous membrane. In the first period of interchangeable occlusion, in the presence of three in the area of the frontal teeth, it is recommended to use a dissociative bite guard, in which hooks are welded on the vestibular surface, open distally, on which rubber traction is put on at night. In the absence of lateral milk teeth, a removable claspless prosthesis is used with an increase in bite on artificial teeth. In the second period of interchangeable dentition, the treatment of the mesial occlusion is mainly aimed at correcting the position of the anterior teeth. The treatment is carried out approximately according to the same plan as the treatment of the palatal position of the group of anterior teeth. The correct ratio between the dentition achieved in the Frontal area contributes to the fact that the premolars and replacing milk (permanent) molars are often set in the correct position. In this period, the use of the following devices is shown: mouthguards with an inclined plane with all its varieties, plates with pushers and occlusal linings, etc. For the treatment of mesial occlusion with deep overlap in the presence of gaps between the lower frontal teeth in the replacement period, the Brukl apparatus is used, as well as the occlusion shaper proposed by O. M. Basharova. The basis of the apparatus in this case is located on the upper jaw. For the treatment of mesial occlusion in this period, you can use the function regulator R. Frenkel (1967). The third type of function regulator consists of four vestibular plate elements connected by wire, which can be rearranged. The labial pads are located on the vestibule of the upper jaw and contribute to the development of the upper jaw with a simultaneous effect on the soft tissues in the base area. The device is designed in such a way that its vestibular elements are separated from the upper jaw, while simultaneously blocking the lower one. Lateral shields and labile arches should fit snugly on the outside to the alveolar ridge, to the lateral, and sometimes to the anterior teeth of the lower jaw. To move the upper teeth forward, it is necessary to remove the blockade from the side of the lower teeth. To do this, the apparatus has biting pads adjacent to the relief of the lower premolars. The bite is separated as much as is necessary for the free movement of the upper front teeth anteriorly, since a large disconnection prevents the lips from closing and the normalization of the position of the tongue. Occlusal onlays on premolars should form a right angle with the side shield and loosely adhere to the vestibular surfaces of the teeth. This rule must be observed in order not to impede the shift of the lateral teeth to the vestibular side. The lingual arch only serves to stabilize the apparatus and is not used in many cases. The transversal arch is located distally from the last molar. The advantage of the device is that in the treatment of mesial occlusion, the intraoral space remains free from plate elements. The oral cavity remains free for the tongue, its exercises, suction contact is made between the tongue and the palate. The method of treatment with the Frenkel apparatus is effective in early childhood, i.e., in the period of milk and mixed dentition with the growth of the jaws. After the bite is corrected, there is no need to use retention devices, since the conditions for a recurrence are eliminated during the treatment. Treatment of upper micrognathia (the first form of mesial occlusion - according to Betelman) is aimed at increasing the size of the jaw. This is achieved by expanding the Angle arc, plates with retractors and expanding devices (screw, wire expander). The orthodontic arch is bent in such a way that it is separated from all the upper teeth, which are tied to it with a wire and thread ligature. The rotation of the nut contributes to the movement of the arch anteriorly and greater tension of the ligatures, as well as the movement of the teeth tied to the arch. This form of mesial occlusion is treated with devices that promote the movement of the upper frontal teeth anteriorly, as well as the expansion of the lateral parts of the jaw.  With a deep incisal overlap and a high alveolar process in the region of the lower frontal teeth, in the first form of the mesial occlusion, a kappa with an inclined plane is used on these teeth in combination with an Angle's arch fixed on the teeth of the upper jaw. Medially open hooks are soldered to the kappa in the area of the fangs. The force of the rubber rings stretched between these hooks and tubes soldered to the crowns on the lower 6|6 teeth transfers pressure to the posterior teeth and displaces them anteriorly. After 3-4 days, by turning the nuts, the arch is extended to the vestibular side, and, consequently, the front teeth attached to it. At the same time, the entire dentition of the upper jaw is displaced anteriorly, the separation of the lateral teeth contributes to the growth of the alveolar processes and an increase in bite. With a severely underdeveloped upper jaw, the Bimler apparatus (1964) is used. The treatment technique is based on the use of a frame system created from a wire and interconnected small plastic fixing devices. The action of the device is carried out with the movements of the lower jaw due to the elasticity of the wire parts (Fig. 143). Bimler apparatus Treatment of lower macrognathia (the second form of mesial occlusion - according to Betelman) with the presence of gaps between the teeth is carried out with the sliding arc of Angle, the Eisenberg-Herbst apparatus, the Brückl apparatus and other devices that displace the frontal teeth posteriorly. Treatment of lower macrognathia and upper micrognathia (the third form of mesial occlusion) is carried out with the help of obliquely directed intermaxillary traction, which promotes the movement of the upper teeth medially, and the lower teeth distally (Fig. 144). More often, the Andresen-Goypl apparatus is used for this. This apparatus has occlusal pads on the lateral teeth to separate the bite in the frontal area, a vestibular arch located in the region of the lower frontal teeth, and a screw to move the upper teeth anteriorly. Oblique intermaxillary traction for the treatment of mesial occlusion With prolonged use of the activator, the presence of occlusal overlays often leads to hammering in of the lateral teeth and an increase in the overlap of the anterior teeth. As the upper teeth move anteriorly, the occlusal linings are ground off. For the treatment of mesial occlusion, you can also use the Wunderer and Hoffman activators, the Schwartz double plate, the open Klammt activator, the Brady and Jungto activators, the Buney functional apparatus, the Balters Bionator (type III), the Beamler bite shaper. Due to the complexity of manufacturing and using these devices, they are rarely used. Treatment of lower macrognathia is often carried out with the extraction of teeth (usually premolars). When moving the canine distally, the sixth and seventh teeth are taken as a support, if possible, so that the place of the extracted tooth is not replaced by the lateral teeth that have shifted anteriorly. Prevention: Prevention of mesial occlusion consists in the fight against bad habits, myogymnastics, as well as in the massage of the frontal area of the upper jaw from the palatine side, in the sanitation of the oral cavity and the nasal part of the pharynx. Treatment of mesial occlusion is more effective when functionally guiding devices are used at an early age or a combined method of treatment is used at an older age. 4. Diastema. Etiology, clinic, prevention, methods of treatment. Diastema is an abnormal position of the central incisors, characterized by the presence of a free space between them. The interdental gap with diastema can reach a value of 1 to 10 mm (average 2-6 mm). Diastema is one of the most common dentoalveolar deformities, occurring in approximately 8-20% of the population. In most cases, the interdental gap is located between the upper incisors, but it can also occur in the lower dentition. Diastema disrupts the appearance of a person and sometimes speech. it is often accompanied by a strongly developed frenulum of the upper lip, which attaches to the crest of the alveolar process, where it joins the incisive papilla. The roots of the upper central incisors are covered with bone of sufficient thickness or are clearly delineated, and at the same time a groove is formed between them into which the frenulum of the upper lip is woven. On the radiograph of the region of the central incisors, a wide dense palatine suture is usually revealed, which sometimes splits, and fibers of the connective tissue of the frenulum of the upper lip penetrate into it. F.Ya. Khoroshilkina proposed a classification of diastemas: 1st type - lateral deviation of the crowns of the incisors with the correct location of the tops of their roots; 2nd type - body lateral displacement of both crowns and incisor roots; 3rd type - mesial inclination of the crowns of the central incisors and lateral deviation of their roots. First of all, they distinguish between false and true diastema. False diastema is characteristic of the period of change of temporary occlusion to permanent. This is a normal, natural condition for childhood. Usually, by the end of the change of teeth, the diastema closes on its own. A true diastema is observed in permanent occlusion and does not disappear without special dental care. Etiology: The causes of diastema are often supernumerary teeth, the eruption of which preceded the eruption of the central incisors, the bad habit of biting a nail, pencil or other objects is often the cause of not only the diastema, but also the rotation of the upper central incisors along the axis. The incorrect position of the lower central incisor in the dentition can cause a diastema between the upper incisors, partial edentulism (absence of the rudiments of one or two upper lateral incisors), significant compaction of bone tissue in the region of the median interalveolar septum, low attachment of the frenulum of the upper lip, loss of the lateral incisor, canine or anomalies of their position, with odontoma, multiple adentia. Sometimes diastema occurs under the influence of not one, but several reasons. The first and second types of diastema are more common than the third. With all three types of diastema, the location of the crowns of the incisors can be as follows: 1) without rotation along the axis; 2) with rotation along the axis of the medial surface in the vestibular direction; 3) with rotation along the axis of the medial surface in the oral direction. To eliminate the diastema, the following methods of treatment are used: orthodontic, surgical, instrumental- surgical, prosthetic, etc. The effectiveness of certain methods of treatment depends on the etiology of this anomaly, the degree of its severity, the period of bite formation, the location of the central incisors, lateral incisors, canines or their rudiments, as well as hereditary factors. The period of early interchangeable dentition. The possibility of self-regulation and the effectiveness of preventive and therapeutic measures are most pronounced in the initial period of mixed dentition. Timely convergence of the central incisors prevents rotation along the axis of the lateral incisors and canines and their eruption outside the dental arch. Treatment should begin after an x-ray examination of the area of the central incisors and the alveolar process adjacent to them, in order to determine the location of the roots and crowns of the incisors, the width and density of the median interalveolar septum, identify supernumerary teeth, the structure of the median palatine suture between the incisors, the place of attachment of the frenulum of the upper lip, and also clarifying the etiology of this anomaly, taking into account hereditary factors. Designs of orthodontic appliances are selected taking into account the type of diastema. It is advisable to eliminate the diastema with orthodontic appliances with mechanically acting devices for unilateral or bilateral medial inclination of the incisors. Removable devices: 1. devices with hand-shaped springs (according to Kalvelis); 2. apparatus with a vestibular arch and springy processes; 3. an apparatus with a vestibular arch, springs that protract and bring together the incisors (in cases of their rotation along the axis). Adigezalov apparatus In the period of late removable and permanent occlusion (after the completion of apexogenesis of the roots of the central permanent incisors), a fixed technique is used. Of the fixed devices, the Korkhauz apparatus is used, i.e., metal rings for central incisors with vertical rods soldered closer to their medial surface and rubber traction. The reduction of the rubber rings stretched between the ends of the rods contributes to the convergence of the incisors. In order not to injure the frenulum of the upper lip, it is advisable to pull the elastic rings not in parallel, but crosswise. A variation of the Korkhauz apparatus are rings for central incisors with vertical tubes and a spring that brings the incisors together. The use of tangent beams is necessary to redistribute the force of the orthodontic appliance to the center of rotation of the lever (tooth), to ensure body movement of the teeth. Diastema So, to eliminate the diastema of the second type, it is possible to use rings for central incisors with vertical grooves soldered to them in combination with a removable orthodontic appliance with a vestibular arch and springy loops included in the grooves (Korkhauz apparatus). The rod apparatus of Ya. M. Adigezalov is widely used (Fig. 98). It is a ring for central incisors with vertical rods. A horizontal crossbar is soldered to one rod, which is inserted into the bracket on the other rod. The incisors are brought together by rubber traction. With a wide diastema, Angle's vestibular arch supported by molars and rings with horizontal tubes for the central incisors are used.  The best results are achieved using the edgewise technique. To do this, after normalizing the position of the anterior teeth on the initial round nitinol arches, rectangular arches and ligature binding are used for the mesial movement of the central incisors. For example, metal ligatures in the form of a figure eight (Fig. 99). Tremas and diastemas of the dentition are eliminated with the help of a power module - an elastic chain. In those cases when, after elimination of the diastema of the first type, the lateral incisors are installed close to the central ones, no recurrence of the anomaly is observed. It is more difficult to ensure the retention of the results achieved in the treatment of diastema of the second type, especially in the case of congenital absence of upper lateral incisors, shortening of the dentition and medial occlusion. In this case, after correcting the position of the central incisors, the missing lateral incisors are replaced by prosthetics. Auxiliary surgical interventions in the treatment of diastema include the removal of supernumerary teeth, the movement of the frenulum of the upper lip, and the violation of the bony septum between the sockets of the central incisors. These operations contribute to the self-regulation of the diastema and facilitate orthodontic treatment. Self-regulation of the position of the incisors after surgical removal of the cause of the anomaly - removal of supernumerary teeth or displacement of the place of attachment of the frenulum of the upper lip is possible during the period of early mixed dentition. It is observed in cases where the diastema does not exceed 4 mm and the operation is performed before the eruption of the upper lateral incisors (7-8 years) or canines (10-12 years). With a more pronounced diastema, the gap between the central incisors is reduced, but not completely, therefore, with a diastema width exceeding 4 mm, self-regulation should not be expected. In the presence of a wide diastema (more than 6 mm), including those caused by multiple adentia, prosthetics may be recommended. In the period of temporary and removable dentition, removable dentures are used for this purpose, at an older age - non-removable ones. By prosthetics, it is possible to give the supernumerary teeth (one or two) the shape of adjacent teeth, which makes it possible to achieve a coincidence of the midline between the teeth with the midline of the face. However, in such cases, a complete tooth that is outside the dental arch or rotated around an axis is usually subject to removal. A pronounced diastema can be eliminated after compact osteotomy in the area of the teeth to be moved, and the subsequent use of orthodontic appliances. Such a combined method of treatment is indicated in the presence of a wide diastema of the second and third type. 5. Clinical and laboratory stages of manufacturing functional-guiding plate devices (Katz) KATZ'S BITE PLATE The device is a removable plate for the upper jaw, which has a plastic inclined plane and tape-type flip-over clasps for the central and lateral incisors (Fig. 234). It is used to eliminate the distal deep bite. The apparatus is made on models fixed in the occluder in the position of a constructive bite, i.e., the desired ratio of the dentition. An insulating tin gasket is placed on the model of the upper jaw in the anterior third of the palatine vault, in the area from the necks of the anterior teeth, to the line connecting the distal surfaces of the canines. This is necessary so that the basis in the frontal area does not adhere to the mucous membrane in order to prevent the infringement of the mucous membrane of the hard palate as a result of moving the teeth with the alveolar process backwards. On the tin pad and the rest of the palate, a wax base of the plate is formed for the supporting teeth, then clasps are made on the first molars. From sheet steel with a width of 1.5-2.0 mm and a thickness of 0.5-0.7 mm, flip- over clasps are bent. Each clasp should tightly cover the lower third of the vestibular surface of the tooth and the cutting edge. On the palatal side, the clasp is bent so that it repeats the relief of the tooth up to the dental tubercle, and then it is bent away from the tooth. The value of the distance of the clasp from the tooth is determined by the line of closure of the lower teeth with the upper ones. The ends of the processes of the flip clasps are flattened for better retention in plastic. The made clasps are slightly heated, fixed on the teeth, and the processes are immersed in a wax plate. Having closed the occluder, check Fig. 234. Making a Katz bite block. a - arrangement of clasps; b - the position of the flip clasp on the tooth. Rns. 235. Apparatus Khurgina. a - a plate with an inclined plane, flip clasps and a palatal screw; b - apparatus on a plaster model. uniformity and density of contact of the flip clasps with the lower teeth and, if necessary, correct the bend of the clasp. The inclined plane is modeled, repeating the bend of the dental arch, from a softened wax roller 1.0-1.5 cm high in the area from canine to canine. A triangular-shaped roller is glued to the base wax plate and the occluder is closed before the wax hardens. Having opened the occluder, they proceed to the final modeling of the inclined plane so that it is no more than 45 ° in relation to the occlusal surface of the dentition. The rest of the steps are normal. After finishing the plate, the tin pad is removed from its palatal surface and polished. Ya. S. Khurgina introduced a sliding screw into Katz's bite block of functional action - a source of mechanical action force in order to simultaneously expand the narrowed upper jaw (Fig. 235). This apparatus is made in two stages: first, a wax reproduction of the Katz plate with all its elements is prepared, and then an orthodontic screw is inserted into the wax, usually in the middle of the plate. After polymerization, finishing and polishing, the plate is sawn in the anteroposterior direction into two halves. 6. Clinical and laboratory stages of manufacturing functional-guiding plate devices (Schwartz). Schwartz plate with a sectoral cut in the anterior or lateral sections and an expanding screw is a removable device for mesio-distal movement of the anterior and posterior teeth. Removable plates with sectoral cuts for lengthening the dentition. Removable plates with sectoral cuts for lengthening the dentition. When the screw is unscrewed in the plate with a sectoral cut in the anterior section, mesial movement (or vestibular deviation) of the incisors and distal movement of the lateral teeth occur under the influence of the adjacent parts of the apparatus, plate, clasps, springs and other devices. A plate with a sectoral cut in the lateral area is designed to move the lateral teeth in the distal direction and (if indicated) the anterior teeth in the mesial direction, which is achieved depending on the location of the screw. SCHWARTZ PLATE WITH VESTIBULAR RETRACTION ARCH The plate differs from the Katz bite plate in that instead of flip-over clasps for each anterior tooth, it has a vestibular retraction (posteriorly retracting) arch with semicircular activation loops. They also make isolation behind the moved teeth. The device has arrow-shaped or other clasps for fixing and an inclined plane made of plastic. The vestibular arch is bent as described above. On the labial surface of the crowns of the anterior teeth, the arc can be located in the middle, closer to the neck or to the cutting edge of the teeth, depending on the degree of inclination of the axis of the teeth being moved. Further work is carried out in the same way as in the manufacture of the Katz plate. If necessary, simultaneous expansion of the dentition is inserted into the screw. It should be emphasized that the inclined plane of any apparatus should not be a rough monolith. It is necessary to model its rear-facing surface with a notch for the tip of the tongue, which greatly facilitates the development of the apparatus and its use. 7. "Cross" bite (occlusion). Classification, etiology, clinic. Crossbite is a transversal anomaly in the relationship of the dentition, which is one of the most severe, requiring long-term active treatment and a long retention period. Classification : Given the diversity of the clinical picture of crossbite, it is advisable to distinguish the following forms of it (Uzhumetskene I.I., 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 the 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. 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 mid-sagittal plane or diagonally). The listed varieties of crossbite can be unilateral, bilateral, symmetrical, asymmetric, and also combined (Fig. 16.38). Filed by L.V. Ilyina-Markosyan (1959), A.P. Kibkalo (1971), G. Korkhaus (1939), E. Reichenboch and H. Bruckl (1957), crossbite more often (77%) is associated with lateral displacement of the lower jaw.  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. The function of the temporomandibular joints is often disturbed, especially in case of malocclusion with a displacement of the lower jaw to the side. Etiology: The development of a crossbite can be caused by the following reasons: heredity, 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 temporary 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 masticatory muscles, violation of calcium metabolism in organism, facial hemiatrophy, trauma, inflammatory processes and jaw growth disorders caused by them, ankylosis of the temporomandibular joint, unilateral shortening or growth of the jaw body, growth retardation, residual defects in the sky after uranoplasty, neoplasms, etc. Clinical picture: 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 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 parallel to the midsagittal plane, the mandible can move diagonally to the side. The position of the articular heads of the lower jaw in the joint with its lateral displacement changes, which is reflected in the mesiodistal ratio of the lateral teeth in the occlusion. On the side of the displacement, a distal ratio of the dental arches appears, on the opposite side - a neutral or mesial one. On palpation of the area of the temporomandibular joints during opening and closing of the mouth on the side of the displacement of the lower jaw, 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 according to Ilyina-Markosyan and Kibkalo are used; the patient is asked to open his mouth wide and examine the facial signs of abnormalities. Facial asymmetry increases, decreases or disappears, depending on the cause that determines 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). In all forms of crossbite, chewing function is significantly impaired, which is due to a decrease in the area of occlusal contacts, biting of the mucous membrane of the cheeks. 8. "Cross" bite (occlusion). Methods of treatment of dentoalveolar forms in different age periods. Prevention. Treatment: Cross bite should be eliminated as early as possible (especially buccal, with a displacement of the lower jaw to the side) in order to avoid asymmetric formation and development of the facial skeleton and temporomandibular joint.  It is necessary to treat all forms of crossbite at any age in order to improve the functions of chewing, breathing, swallowing, speech, changing the appearance and creating conditions for rational prosthetics for dentition defects. In order for the result of correction of the anomaly to be more stable, if the treatment is carried out in the milk bite. The child should be taught to chew intensively on the deformed side, if possible, eliminate bad habits. With a unilateral crossbite, the cusps of the primary molars can be abraded in order to remove the dentition from the wrong closure. This can be done with a slight reverse overlap. With a symmetrical narrowing of the upper dentition, the child usually shifts the lower jaw laterally when closing the mouth to obtain contacts of the posterior teeth on one side, resulting in a unilateral crossbite. It is enough to measure the width between milk canines and molarsto determine the narrowing. During the period of milk teeth with lingual crossbite, due to excessive growth of the upper jaw, it is possible to apply a pressure extraoral bandage to this area, expand the lower dentition (with its narrowing) with simultaneous bite separation. During the period of milk bite, the use of large forces is undesirable, since forcing, rapid expansion can affect the structural elements of the nose. In case of an overdose of the force of the device, unpleasant sensations may occur in the region of the nose. With an inverse ratio of the lateral teeth, when the buccal tubercles of the upper teeth articulate with the longitudinal intertubercular fissure of the lower ones, expansion of the dentition of the upper jaw without separation is impossible, since it is necessary to overcome the slope of the tubercles of the lower teeth. When there is no closure of the dentition, under the action of the apparatus, the upper jaw will expand, but with each contact, the teeth will begin to move back according to the principle of an inclined plane. It is necessary to perform deocclusion using a mouthguard with a smooth chewing surface on the lower teeth, or with the addition of a bite pad to the expanding plate on the upper jaw. In case of bilateral lingual crossbite, it is necessary to make a mouth guard on the lower teeth with a widened platform, which will create conditions for expanding the lower dentition and possibly narrowing the upper one. When the cause of the cross bite is unilateral underdevelopment of the upper jaw, then on the side of the incorrect closure, a mouth guard is made for the lower jaw with an inclined plane that goes under the upper teeth from the palatine side and, when closed, contributes to their displacement to the buccal side, while simultaneously stimulating the growth of the alveolar process of the upper jaw. In the process of treatment, the inclined plane is corrected if necessary. During this period, activators of various designs can be used, in particular, the Andersen activator with occlusal pads on the side of correctly interlocking teeth. To the activator, you can add springs, screws to move the lateral teeth. In this case, the bite is normalized without opening the palatine suture, by correcting the position of the teeth, shifting the lower jaw (if any), the growth of its articular process and branches. The dentoalveolar shape of the cross can be practically corrected by any removable or non-removable apparatus of the appropriate design. One-sided crossbite or backbite of individual teeth can be corrected by using elastic bands fixed to the palatal surface of the upper tooth and the vestibular-lower tooth, where braces with buttons or hooks are glued. During the period of milk and early removable dentition, the opening of the median palatine suture can be performed using an apparatus such as a four- loop palatine clasp ( Quad helix ). This apparatus produces slower expansion than expanders. It is possible to use non- removable devices during this period, but with very weak and slow activation. Successful correction of transverse misalignments requires sufficient vestibular tilt of the roots of the maxillary first molars and palatal tilt of their crowns to prevent occlusal layering. Otherwise, premature contacts may occur, which in turn cause dysfunction of the temporomandibular joints. Strict control over the operation of the devices is necessary, since when correcting a lingual crossbite by any method at some point, as noted by R. G. _ Alexander the tubercles of the upper teeth "jump" over the tubercles of the lower ones. And at the same time, the “opening” of the bite often occurs, and it is necessary to take action for the introduction (intrusion) of the first upper molars. The most suitable method for this is R. G. _ Alexander considers the use of a facebow to be high thrust. In the second period of mixed dentition (9-11 years) after the eruption of the lateral teeth, preference should be given to mechanically acting devices. In particular , the V - shaped arch of Herbst , which is strengthened in the area of the first permanent molars, and its processes are directed anteriorly and expand the dentition of the lower jaw, in the area of canines, premolars and molars, or the Merschon arch. Fixed devices with expanding screws or dilating- expanding plates with median or sectoral cuts and screws can be used. The main element in them are orthodontic screws. 9. Teleroentgenography. Imaging technique, Schwartz analysis. In the book. 10. Photostatic shots. Obtaining method. Image analysis. diagnostic value.  Facial profile analysis and photostatic analysis in orthodontics serve to analyze the patient's clinical picture before and after orthodontic treatment. Inclusion of a person in the overall study avoids potential orthodontic or surgically conditioned unweighted decisions and influences the diagnosis, treatment plan, therapy and, finally, the quality of the treatment outcome. The camera must have a 2:1 zoom function (enlargement of parts, e.g. anterior and posterior anterior bites, intraoral images), 1:1 for facial profile shots, and a zoom ratio of up to 1:4. What is important is the repeatability of the images and thus the placement of the patient in a sitting position and the same scale. Compliance with the above facilitates comparative measurements on the images of a given patient. In this case, the use of a shallow depth of field is fundamental. These requirements are best met by reflex cameras with optically high- quality macro lenses with an ideal focal length of 100 mm and special circular flash systems. The finished picture should have a format of 9 x 13 cm, so that later auxiliary lines can be applied to it. It doesn't matter if the picture is color or black and white. The small format reflex camera (24mm x 36mm) has taken its place in dental photography. Medium format cameras (60 mm x 60 mm) are inferior to it in terms of weight and ease of use. The instant shot is notable for its lack of color consistency, duplication, sharpness, contrast, and choice of high quality lenses. As a photographic material, the products of the Diafilm company are recommended. Usually in orthodontic practice, a face profile image is taken from the side (en lateral) and from the front (en face). In addition, special frontal images, a semi-lateral profile image and the opposite side of the face for symmetry comparison are taken to evaluate the smile line. Pictures are taken with the natural position of the head, in the central ratio and the position of the lips at rest. For illustrative documentation of the occlusion situation and occlusal relationships, in addition to external oral images, a number of intraoral images are taken, such as, for example, an image of the teeth of the upper and lower jaws, and occlusal images of the dentition from the front and side. When taking a profile picture, the camera is placed parallel to the middle of the body. The head is oriented along the Frankfurt horizontal, the eyes are open, the gaze is straight. The auricles must be open (symmetry comparison, ear canal entry point). When taking a full-face shot, the camera is installed parallel to the frontal plane of the head at the height of the patient's eyes. There are different options for technically taking full-face and profile shots: — Performing frontal and lateral images with one camera in two different positions of the patient — Performing two images with one camera at the same position of the patient using the mirror method — Simultaneous side and front shots using two cameras. 11. Anomalies in the shape of the dentition. Etiology, clinic, prevention. Methods of treatment. In relation to three mutually perpendicular planes, the following anomalous forms of dentition are distinguished: - in the transversal direction - narrowing and expansion of the dentition, - in the sagittal - lengthening and shortening of the dentition, - in the vertical - dentoalveolar shortening and dentoalveolar elongation in separate segments of the dentition. Anomalies of the dentition in the transversal plane Abnormal forms of dentition in the transversal plane are distinguished by the following types (Fig. 100): 1) V - shaped, when the dentition is narrowed in the lateral sections, the rotation of the central and sometimes lateral incisors around the longitudinal axis and the protruding front section; 2) trapezoid, when the dentition is narrowed in the lateral sections, and the anterior one is flattened; 3) a generally narrowed dentition, when both the anterior and lateral teeth are located closer to the median plane than it should be in the norm; 4) saddle shape, when the narrowing is most pronounced in the region of the second premolar and first molar; 5) asymmetric shape, when the location of the lateral teeth to the median plane of one and the other side is different, 6) anomalies of the dentition in the presence of several supernumerary teeth (Fig. 68). Narrowed teeth. Narrowed dentitions are characterized by a change in their shape due to a decrease in the distance between the median plane and the teeth located laterally from it. The narrowing of the upper dentition is determined in relation to the mid-sagittal suture, the lower - in relation to the median plane of the face and jaw. The main etiological factors for the narrowing of the dentition, the alveolar arch and the apical base are: 1) difficulty in nasal breathing, predominant breathing through the mouth; 2) sucking the thumb, several fingers or foreign objects; 3) dysfunction of swallowing, speech; 4) parafunctions of facial and chewing muscles and muscles of the tongue.  The narrowing of the dentition and the lack of space for the front teeth can be explained by the weak pressure on the teeth of the inactive tongue with its short frenulum and the prevailing action of the muscles of the lips and cheeks. Anomalies in the shape of the dentition Sluggish chewing or chewing of food on one side does not have a stimulating effect on the growth of the jaw bones and is one of the etiological factors for the narrowing of the dentition. Narrowed dentition, in turn, impedes lateral chewing movements of the lower jaw and a “vicious circle” is formed, which aggravates the anomaly in the development and formation of both dentition and occlusion. Premature loss of temporary teeth, especially molars, significantly reduces chewing pressure, which is one of the main factors stimulating the physiological and proportional development of the jaw bones, which also causes their narrowing. General diseases of the body - rickets, dyspepsia, infectious and other diseases that affect the metabolism, weaken the body and can cause narrowing of the dentition. Narrowing of the dentition can often be a symptom of almost all malocclusion. It is customary to distinguish between the narrowing of the dental, alveolar and basal arches, which is detected on the control and diagnostic models of the jaws. The narrowing of the dentition can be unilateral or bilateral, symmetrical or asymmetrical, on one or both jaws, without violating the closure of the dentition and with violation. There are narrowing of the dentition with protrusion of the front teeth without three between them, with protrusion of the front teeth and their crowded position, with protrusion of the front teeth and the presence of a diastema and three between them. Of all these options, the crowded position of the front teeth is more often observed with the rotation of some teeth around the longitudinal axis, partial or complete retention of individual teeth. The diagnosis is established on the basis of clinical and radiographic examination, as well as the study of control and diagnostic models of the jaws. The width of the dentition in the area of premolars and molars is determined by the Pont method, adjusted according to Linder-Hart, by the Snagina method and the width of the apical basis (according to Howes). Comparison of the data obtained with the individual norm allows you to determine the severity of the dentition and choose a rational method of treatment. This takes into account: 1) the closing of the lateral teeth (according to 1, 2 and 3 Angle class); 2) narrowing of the dental arch, alveolar, basal; 3) the position of the lateral teeth, i.e. whether the crowded position of the front teeth is a consequence of underdevelopment of the basis of the jaw or other reasons; 4) whether the active period of jaw growth has ended; 5) whether it is possible to eliminate the anomaly by the orthodontic method or a preliminary compact osteotomy is required (surgical - orthodontic method), or only a surgical method. Treatment consists in expanding the dentition and their apical base, determining possible options for establishing individual teeth in the correct position, determining orthodontic indications for the removal of less functionally and aesthetically valuable teeth in order to create a place in the dentition or determine the volume of other surgical interventions (plasty of the frenulum of the lip or tongue, compactosteotomy, etc.). The expansion of the dentition is achieved using various designs of removable and non-removable orthodontic appliances. Removable plate expanding orthodontic appliances. One of the first orthodontic devices for expanding the dentition was proposed in 1882 by Coffin - a plate device with a wire spring located in the center of the base and a sagittal cut. In 1886, Kingsleyy put a screw in the basis of the orthodontic apparatus. AND I. Schwartz improved the expansion plates by adding arrow-shaped clasps, retraction arches, various springs and devices for moving teeth. Kalvelis D.A. modified the Coffin expansion spring. More often, a removable plate apparatus with a screw is used to uniformly expand the dentition, in the basis of which an expanding screw is placed (Fig. 38, a). In permanent occlusion, for expansive opening of the median palatine suture, skeletonized (large and small sizes) screws with a closed body are used (Fig. 38, b). The greatest narrowing of the dentition is usually observed in the region of the premolars, therefore, when cutting the basis of the plate apparatus sagittally, the screw is installed between the premolars. The distance between the model and the screw should be 0.5 - 0.7 mm. The cut of the basis is oriented to the position of the central incisors, to the base of the frenum of the tongue and the place of attachment of the frenulum of the lips. A plate apparatus with a vestibular arch and an expanding screw is used to simultaneously expand and shorten the dentition.  Asymmetric expansion of the dentition is achieved with the help of plate devices with a screw and shaped sectoral cuts. In the area of the lateral teeth subject to vestibular movement, the dentitions are separated. For this purpose, on the opposite side, occlusal overlays are made on the lateral teeth with imprints of the chewing surface of the lower teeth. For uneven expansion of the upper dentition, larger in the front section and smaller in the lateral ones, special screws are used. When they expand, both halves of the base diverge in a fan-like manner, which is achieved using a screw with a restrictive hinge located in the distal section of the plate for the upper jaw, in addition, uneven expansion of the upper dentition is achieved with a plate orthodontic appliance with a single or double Coffin spring or with a clasp spring, as well as with a screw and a sectoral cut of the basis (Fig. 101). Anomalies in the shape of the dentition The design of the expanding plate apparatus for the lower jaw with a significant narrowing of the dentition and lingual inclination of the lateral teeth has some features. The lower edges of the base of the apparatus must be thickened, since during fitting it is necessary to cut the plastic from the inner surface. In order to better fix the plate apparatus and prevent it from slipping towards the bottom of the mouth, wire occlusal pads on the lateral teeth are recommended. The screw should be loosened weekly by ¼ - ½ turn (1 - 2 movements). Instead of a screw to expand the dentition, you can use the Kofin spring - single or double. A plate with two Coffin springs serves to uniformly expand the upper dentition. The springs are bent from orthodontic wire with a diameter of 0.6 - 0.8 mm, the ends are given a zigzag shape to ensure their secure fixation in the plastic base. When the finished apparatus is inserted into the oral cavity, the springs are compressed. They tend to straighten up and transfer pressure to the teeth through the base of the apparatus. The springs are activated by extension. The active element of the expanding plate apparatus for the lower jaw is an orthodontic screw or spring with additional semicircular bends. Standard Koller springs with a W-shaped loop 30 - 35 mm wide are also used. In the manufacture of the clasp, the springs are not covered with plastic, it is located under the lower edge of the base, departing from it by 0.5 mm. To expand the dentition, in addition to mechanically removable and functionally operating orthodontic appliances and devices, non-removable ones are also used. Of the fixed devices for expanding the dentition, the Ainsworth apparatus, the Simon beam apparatus, the Angle spring apparatus, the Begg technique, the Mershon, Herbst lingual arch, with auxiliary springy ends are used. Devices Nord, Derichsweiler, Brun for accelerated opening of the median palatine suture, Levkovich kappa apparatus with removable expanding springs, etc. The Mershon lingual arch is fixed with special locks soldered on the palatal surface of crowns or rings on the first permanent molars. It expands the dentition in the region of molars and premolars. The V-shaped lingual Herbst arch is fixed from the oral surface of the crowns of the first molars and is able to expand the dentition in the region of the molars, premolars and canines. In the period of permanent occlusion, depending on the severity of the narrowed dentition and the apical base, one of the following methods is selected: 1. When narrowing the dental or dentoalveolar arch to 5 mm compared to the individual norm, orthodontic treatment is indicated using plate devices with screws or springs of Coffin, Kalvelis or fixed arc devices. 2. When narrowing the dental or dentoalveolar arch by more than 5 mm compared to the individual norm, combined treatment is indicated - preliminary surgical preparation in the form of compact osteotomy or extraction of the tooth (teeth) and subsequent orthodontic treatment. 3. When the apical base of the upper jaw is narrowed by 37% or more compared to the individual norm (according to Howes), combined treatment is carried out - the extraction of individual teeth, compact osteotomy and subsequent orthodontic treatment. In severe forms of narrowing, the median palatal suture is opened using non- removable expanding orthodontic appliances (Fig. 102). Apparatus for tearing the median palatine suture The first group is the devices proposed by Stenton, Schroder - Bousler, Nord, Levkovich and others. These are rings or crowns fixed on the side teeth, interconnected by a cast intermediate part and a screw. The first designs of devices designed to open the palatine suture include the Nord apparatus, the kappa apparatus with a Brun screw, the Levkovich kappa apparatus with a Coffin spring, etc. The supporting part of such devices are rings or crowns for the second premolars and molars, to which from the palatal surface soldered rods adjacent to the first premolars and canines, transferring pressure to these teeth in the process of unwinding the expansion screw. When using this device, the entire load is transferred to the supporting teeth, which can lead to overload of the teeth.  The second group is the devices proposed by Derichsweiler, Chateau, Khoroshilkina and others. These are rings or crowns fixed on the first premolars and molars, interconnected by cast or wire fittings, with a screw and a plastic base resting on the alveolar process. When the screw is untwisted, its pressure is transferred to the alveolar process, lateral teeth, which ensures not only a more equal distribution of the screw force on the teeth and alveolar process, but also a change in the shape of the arch of the hard palate. Extended dentition Extended dentition is characterized by an increase in the distance between the median plane and the teeth located laterally from it. The main etiological factors of extended dentition and their apical basis are as follows: 1) With dentoalveolar forms - abnormal laying of the follicles of the teeth, bad habits, parafunction of the muscles of the maxillofacial region, delay in the physiological change of teeth; 2) With gnathic forms - hereditary or acquired macrognathia, tumors, etc. An extended dental arch is observed with neutral, distal or medial closure of the posterior teeth and vertical bite anomalies. It occurs much less frequently than narrowed. An extended dental arch can be unilateral, bilateral, symmetrical, asymmetric, on one jaw, on both jaws, without violation of the closure of the dentition or with violation. Treatment may be orthodontic or combined with surgery. To correct the shape of the dental arch, they are often used mechanically - Angle's operating single-jaw arc devices, edgewise technique or rings of the dental arches of the upper and lower jaws with intermaxillary traction. On the expansion side, the archwires are bent so that it exerts pressure on the support and movable archwires in the oral direction. To narrow the upper dentition, a fixed frame apparatus is used. It consists of support rings for the upper lateral teeth (usually the first premolars and molars). From the vestibular side, rods are soldered to them, touching the crowns of the upper lateral teeth and transferring pressure to them in the oral direction. From the palatine side, 3-4 pieces of flattened wire with a diameter of 1.2 mm are soldered to the crowns along the midline of the palate, an untwisted orthodontic screw. The metal elements of the device should be 1 - 3 mm from the sky. The apparatus is fixed on the teeth with phosphate cement or bisphat cement. A day later, they begin to twist (twist) the screw, which leads to oral (to the mid-sagittal plane) dentoalveolar movement of the lateral fragments of the dentition. In the case of the use of functional devices, for example, the Frenkel function regulator, on the side of the dentoalveolar expansion, the side shield must be adjacent to the teeth and to the alveolar process. In case of violation of transversal contacts between the dentition, the treatment corresponds to the principle of treatment of crossbite. Anomalies of the dentition in the sagittal plane Elongated dentition. Elongated dentitions are determined by their total length and the length of their anterior segment. The reasons for such anomalies can be: 1) dysfunction - nasal breathing, swallowing (preserved infantile type of swallowing), articulation of the tongue during speech function; 2) violations of motor reactions - sucking fingers, tongue, lips, and other foreign objects; 3) anatomical predisposition - the presence in the dentition of one or more supernumerary teeth, preserved temporary teeth in the presence of all complete ones, the presence of diastemas and "three primates", etc. In most cases, the anterior teeth protrude from under the lip and there are no contacts between them; a sagittal gap of various sizes is formed depending on the etiological factor and the duration of its exposure. At a younger age, during the period of temporary occlusion, the elimination of bad habits, the normalization of the functions of the dentoalveolar system contribute to the self-regulation of the disorders that have arisen. According to the indications, vestibular plates (Schoenher's plate), Frenkel function regulators, Andresen-Goipl activator, open Klamt activator, etc. can be used. In the period of removable and permanent occlusion, in addition to the above measures, orthodontic appliances with various types of dental arches are used to retract the front teeth, and individual teeth are removed according to indications. To shorten the dentition, mechanically acting orthodontic appliances with intermaxillary and extraoral traction, a removable plate appliance with an expanding screw and a vestibular arch, fixed on the molars with Adams or Schwartz clasps, are used. A good therapeutic result is achieved by using non-removable arc devices, including edgewise technology. The protrusion of the teeth is eliminated by an arc with closing loops. On the opposite jaw, it is possible to strengthen the oral (ligual) arch, connected to the supporting crowns or rings on the molars, on the vestibular surface of which hooks are soldered to fix the rubber rings that provide intermaxillary traction.  Shortened teeth. Shortened dentitions are determined by their total length and the length of their anterior portion. The shortening of the dentition may be the result of anomalies in the shape, size, number and location of the teeth, underdevelopment of the jaw, bad habits of sucking or biting the lips, tongue or any other foreign objects. The shortening of the dentition due to the medial displacement of the premolars and molars can be due to several reasons: 1) carious destruction of the proximal surfaces of the crowns of the teeth, 2) early loss of temporary or permanent teeth, 3) partial adentia, 4) retention of teeth, 5) incorrect location of the rudiments of permanent teeth or their eruption outside the dental arch. Often there is a crowded position of the teeth, displacement of individual teeth from the dentition, more often in the oral direction, retention of some teeth (usually canines and second premolars). The violation can be unilateral or bilateral. There is a retraction of the lip, with deep incisal overlap - shortening of the lower third of the face. A shortened lower dentition is often observed with distal occlusion, a shortened upper dentition - with mesial. For the purpose of treatment, removable orthodontic appliances are used: Schwarz plate appliances with screws, springs, lingual arches and other devices, as well as sectoral cuts. When the screw is untwisted in a plate with a sectoral cut, the vestibular deviation of the incisors and the distal movement of the lateral teeth occur under the influence of the protrusions of the plastic base adjacent to them, clasps and other devices. The long axis of the screw is set in the direction of movement of the teeth. The cut is made at the level of the middle of the canine crowns. When sawing a sector in plastic equal to the width of the crowns of the moving teeth, it is important to ensure that the sides of the cut are parallel - this prevents the moving sector from jamming when the screw is unscrewed. With a direct and open bite, the oral surface of the moved upper front teeth is covered with plastic. With reverse incisal overlap, the anterior teeth are separated using occlusal plastic overlays on the lateral teeth. The sectoral cut in the posterior-lateral section allows, with sufficient support of the apparatus, to move the lateral teeth in the distal direction, as well as in the distal-vestibular, oral, which depends on the location of the longitudinal axis of the screw. Movement of the posterior teeth in the distal direction, i.e. towards the wider part of the dental arch, contributes not only to elongation, but also to the expansion of the upper dentition. To lengthen the dentition due to the distal movement of the lateral teeth, a plate apparatus with two screws is made (Fig. 33). They are located, according to indications, between the canines and the first premolars, between the premolars or between the second premolar and the first molar, depending on the specific situation. After sawing the base of the apparatus, a large supporting sector is formed for the anterior teeth and two smaller sectors for the lateral teeth. With this design of the orthodontic apparatus, it is possible to carry out both uniform on both sides and uneven lengthening of the dentition. It is recommended to activate the screws of the device screws not simultaneously, but alternately, with a break of two days. Such an activation mode preserves the condition of a larger area of the fulcrum and a smaller area of the force application point, which vary among themselves depending on the alternation of the activation period of each screw. Elongation of the dentition is also achieved through the use of functionally active devices (Andresen-Goipl activator, Frenkel function regulator, etc.), which stimulate the growth of the jaw in the sagittal direction. Screws, springs, levers and other devices are attached to these devices to act on individual teeth or groups of teeth. In addition to removable single- and double-jaw devices, non-removable devices of Crozat, Gerling-Gashimov, Kalamkarov and others are used to lengthen the dentition (Fig. 34). For the distal movement of canines, premolars and molars, edgewise is effective - a technique in combination with springs pushing the teeth apart, as well as intermaxillary traction. If the extraction of individual teeth is indicated, then after the last one it is possible to complete the treatment with the edgewise technique. The combined non-removable apparatus is effective, consisting of rings for the first premolars and first molars of the upper jaw with locking devices, sectoral arches and tension springs worn on these arches. Pieces of wire are soldered to the palatal surface of the rings on the first premolars, the ends of which are placed in the dentoalveolar pad adjacent to the palatal surface of the incisors. On the pelota, a bite pad is made for the incisors of the lower jaw. The force of the tension springs provides the distal movement of the molars and the vestibular movement of the incisors. In recent years, non-removable arc devices with fixation of braces from the palatal surface of the crowns of the teeth have been used. For the same purpose, special braces are offered. Such devices perform all the necessary functions, but have significant advantages from an aesthetic point of view, since they are invisible to others. For bilateral distal movement of the upper lateral teeth, a facial arch with an extraoral support on the back of the head or on the neck is often used. Distal movement of premolars and molars with permanent occlusion (after the end of the period of active growth of the jaw bones) presents significant difficulties, in such cases, the extraction of individual teeth may be the method of choice. 12. "Open" bite (vertical incisal disocclusion). Etiology, clinical forms. This type of occlusion anomaly is characterized by the absence of teeth closure with central occlusion in the vertical direction, i.e. with respect to the horizontal plane. There may be an open bite not only in the anterior but also in the region of the lateral teeth - one-sided, two-sided, although very rarely. An open bite can be an independent form with a neutral ratio of the sixth teeth or combined with other anomalies (sagittal and transversal). Etiology: D.A.Kalvelis distinguished two forms of open bite by origin: a) true, or rachitic, b) traumatic (from prolonged trauma - sucking fingers, tongue, lips, cheeks, other objects). Clinic: With an open bite, as a rule, biting and chewing food is difficult, articulated movements of the lower jaw predominate, therefore, when chewing, the tongue takes an active part, helping to knead food. The pronunciation of labial, lingual-labial and hissing sounds is impaired: “p”, “b”, “c”, “m”, “f”. Attention should be paid to swallowing, which, with an open bite, resembles infantile or infantile. Breathing changes, becoming predominantly oral, which causes dryness of the mucous membrane. On external examination, there is often an oval face, elongated due to the lower third, often compressed lips from the patient's desire to hide the existing flaw. The study of the structural features of the facial skeleton and soft tissues, depending on the shape of the face, showed that the severity of the open bite increases precisely with a narrow face. The upper lip may be elongated or vice versa shortened and flaccid from the constant gaping of the mouth opening. When the mouth is open, from under the upper lip, the cutting edges of the front teeth and the tongue can be seen, which closes the gap between the dentition. The lower lip may be tensed and the chin crease flattened out with a seemingly retracted chin. Chewing efficiency is significantly reduced. The severity of the anomaly is determined by the distance between non-contacting teeth and the number of non- contacting teeth: 1st degree - up to 5mm, 2nd degree - up to 9mm, 3rd degree - large 9 mm and can be up to 1.5 cm. The localization of dentoalveolar shortening should be taken into account and three types of open bite, characterized by dentoalveolar shortening, should be distinguished: the first - in the area of the upper teeth; the second - in the region of the lower teeth; the third - in the area of the upper and lower teeth. 13. "Open" bite (vertical incisal disocclusion). Methods of treatment depending on the form and age. Prevention. Treatment of an open bite depends on its type, severity and period of formation. When planning the treatment of an open bite, first of all, all the possibilities for improving the patient's appearance are taken into account, and then the ratio of the dentition. The period of temporary bite. At this age, active treatment is not indicated. The main task at this stage is to eliminate the cause (bad habit), an obstacle to the growth of the dentition. Worms et al report that dental open bite closes spontaneously and in 80% of cases by 7 to 10 years of age if the habit stops. Also an important event at this age is preventive prosthetics. An important role is played during this period by myogymnastics, which consists of exercises for the lips and biting soft, elastic sticks. Exercises are carried out 5 times a day from 1 to 5 minutes. The exercises themselves do not cause any changes in growth, they help control the vertical factor of jaw development in combination with the devices used: vestibular, vestibulo-oral plates, plates with occlusal pads on the lateral group of teeth and a barrier for the tongue. Early signs of skeletal hyperdivergence may be an indication for treatment, but they are very rare at this age. Early mixed bite. Is the optimal age for the treatment of frontal deocclusion. The main intervention is aimed at eliminating the cause - an obstacle to the eruption of the incisors. The most commonly used devices are tongue protectors. The effectiveness of their application is 85 - 90%. Tongue guards can be removable or non-removable. If the reason is in the tongue, it is better to use removable plates. A feature of the manufacture of such structures is the presence of retention points (balls, grooves made of plastic) in the basis of the plate in the region of the palate slope. Reflexively, the child finds them with the tongue, which helps the tongue to take the correct position at rest. The shape of the retention points should be changed once every 2-3 weeks, as the tongue adapts when swallowing when using such plates. If deocclusion develops due to a bad habit - thumb sucking, non-removable protectors are used. Rings are made for the first permanent molars or the last milk molars with a palatine arch with a wire diameter of 0.8-1 mm with 3-4 loops soldered in the anterior section, limiting the laying of the tongue in the anterior section between the incisors. After normalization of the occlusion (overlap), it is necessary to wear the device as a retention device for another 3 to 6 months. Tongue shield In the presence of signs of skeletal hyperdivergence, the goal of treatment is vertical control in the lateral areas. The concept of treatment is as follows - the earlier treatment of deocclusion is started, the more successful the result will be. For early treatment of gnathic frontal deocclusion, an apparatus is used that includes a Hirex screw in its design, occlusal pads on the lateral teeth 2–3 mm high. The device includes abutment rings for the first permanent molars, rings or linings of composite material for the first premolars or first primary molars, a Hirex expansion screw with a metal frame for quick opening of the palatal suture. The frame is soldered to the support rings, the structure is fixed with glass ionomer cement. The device gives symmetrical force to both halves of the upper jaw, teeth and alveolar process. The frequency of rotation of the screw depends on the age of the patient. For early treatment of deocclusion, it is 2 turns every day for 4 to 5 days, and then 1 turn if further treatment is needed. After the end of the activation, the face is strengthened. 14. Clinical and laboratory stages of the manufacture of mechanical devices (with a screw, with a Coffin spring, with various wire elements). Apparatuses of mechanical action (active) They are characterized by the fact that the power of their action is inherent in the design of the device itself. The source of power is the active part of the device: the elasticity of the arc, springs, elasticity of rubber traction and ligatures, the force developed by the screw. The intensity of the devices is regulated arbitrarily by the doctor who uses their active part. It should be said that the applied force of pressure or traction should be purely individual, depending on the characteristics of the periodontium and tissues of the dentoalveolar system. In order to avoid complications, it is advisable to apply small forces of action, approaching natural forces, and activate the devices no more than once a week in order to create an appropriate rest period. The action of mechanical equipment and the creation of a new form are manifested regardless of the function of chewing. Non-removable devices of mechanical action include the devices of Angle, Ainsworth, Mershon, the high-labial arc of Luri, etc. They are strengthened with crowns or rings. Crowns or rings are placed on unprepared teeth (milk or permanent). Usually they reach only to their necks. In order for rings and crowns to be placed, a so-called physiological separation must be carried out. For this purpose, a bronze-aluminum ligature is used, which is inserted between the teeth and left there for 3-4 days or more, depending on the density of interdental contacts. To increase the height of the bite, crowns are used. If it is not necessary to increase the bite, they use rings or grind off points on the chewing surface of the crown that prevent closure. These crowns are called orthodontic. Angle's apparatus is called universal, since it can be used to treat various types of anomalies of the dentition (Fig. 257). The main part of this apparatus is the vestibular arch made of elastic metal. It is made of stainless steel wire 0.8- 1 mm thick. At both ends of the arc, screw cuts are made and nuts are screwed on. Crowns or rings with tubes located horizontally on the buccal side of the teeth are put on the abutment teeth. An arc curved according to the shape of the dentition is inserted into the tubes. Nuts make it possible to set the archwire in any sagittal position: from contact with the teeth to a certain distance from them. The first permanent molars are usually used as supporting teeth. The Angle apparatus is used to expand the dentition. Depending on in which area it needs to be expanded (in the region of molars or premolars), an arc is set accordingly. To expand the dentition in the region of the molars, the arc is expanded (straightened) and, by bringing its ends together under tension, is inserted into the tubes (Fig. 257, a). To expand the dentition in the region of premolars and canines, the same arch is used, bent according to the desired shape of the dentition, and the teeth are pulled to it with ligatures (Fig. 257, a, b). In order to correct the incorrect position of the front teeth and to move them (vestibularly), the arch is set with nuts at a certain distance from the front teeth and the teeth in the wrong position are tied to it with ligatures. The entire group of anterior teeth is displaced by tightening the nuts and moving the arc forward (Fig. 257, c). Often in these cases, the Angle apparatus is combined with crowns or rings that are put on incorrectly located teeth. Vertical rods or hooks are soldered to the crowns or rings, and the teeth, under the action of rubber traction or ligatures, move in the desired direction (mesially, distally, vertically) or rotate along the axis. The arc usually protects the gingival mucosa from damage by the rubber ring, prevents rotation along the axis of the moving teeth, and, if necessary, directs the tooth into the dentition with its pressure. To tilt the anterior teeth to the palatal side, the arch is turned into a sliding one: the nuts are removed, and medially open hooks are soldered to the arch in the area of the canines. After the arc is inserted into the reinforcing tubes, rubber rings are put on the hooks on both sides and fixed at the rear end of the tube (Fig. 257, d). The rubber band displaces the archwire distally and thus exerts pressure on the anterior teeth. In order for the archwire not to slip from the teeth to the gum, it is advisable to solder flip hooks in its anterior section, and put rings or crowns with threads on the central incisors to fix it. In the treatment of vertical bite anomalies (to stretch the teeth or dip them), the arc is set at the level of the normal position of the teeth and, using its elasticity, is fixed to the moving teeth (Fig. 257, e, f). The Angle apparatus is also used to align the sagittal relationships of the dentition by using an oblique intermaxillary rubber traction. In this case, Angle's arcs are used simultaneously on the upper and lower jaws with hooks on one of them. If the hook is located on the arch of the upper jaw in the region of the canine-premolar, then the force of the rubber traction displaces the upper dentition backward, and the lower one forward (Fig. 257, g). When the hook is located on the arch of the lower jaw, the reverse action takes place (Fig. 257, h). Becker is considered the inventor of the oblique intermaxillary rubber traction. Engle only improved his method. The Angle apparatus, despite its versatility, has a number of disadvantages: 1. It develops great strength, which can cause tissue damage to the periodontium and a sharp mobility of the moving and supporting teeth. To avoid this, it is advisable to use soldered crowns for two molars or solder cast rods to the crowns of the abutment tooth, which fit snugly against the palatal surface of two adjacent teeth. The use of a sliding arc can cause compression of the lateral sections. 2. In many cases, the teeth are pulled to the arch with a wire ligature, which injures the mucous membrane of the gums, especially its papillae. Ligatures loosen quickly and need to be reactivated frequently. 3. The arc is located on the vestibular side, preventing the growth and development of the jaws. Therefore, the Angle apparatus is not indicated for the treatment of anomalies in milk and early mixed dentition. 4. The device makes it difficult to clean the oral cavity and disturbs the appearance. The first improvement in ligature tooth movement is the use of lingual beams (rods) for group movement of teeth. An example of it is the apparatus of Ainsworth (Ainsworht, 1904). It consists of two rings worn on the first premolars, first primary molars or canines, depending on which part of the jaw needs to be expanded. Round tubes are soldered vertically to the rings from the vestibular side, and tangent beams from the oral side, equal in length to the expanding jaw area. The operating force is developed by a round arc, which is introduced with curved ends into the tubes (Fig. 258, a). Simon's "spring-beam" apparatus is also known, which consists of a labial arc and beams 0.6 mm thick (Fig. 258, b). When using Angle arcs and other similar devices, the force of action is carried out in the form of thrust. A more appropriate way to apply force is considered to be free pressure in the area of the neck of the tooth. The advantage of this method is that during the load the tooth retains a free natural position. Functional stimuli during articulation, movements of the tongue, cheeks during eating and talking stimulate jaw growth. This way of applying force is provided by lingual arches. The first lingual arch was described by Lefulon (1839). Subsequently, many different types of lingual arches were created, but among them the lingual arch of Mershon (1909) attracted special attention (Fig. 259). The Mershon apparatus consists of a supporting lingual archwire 0.7–1 mm thick, which is fixed on the first permanent molars using rings with special locks. The operating force is developed by finger-shaped springs made of elastic metal with a thickness of 0.4–0.5 mm. These springs are attached to the lingual surface of the teeth in the cervical region with a very small pressure force (1-5 g). The apparatus of this design is designed to expand the dentition (Fig. 259, a). Subsequently, Mershon introduced auxiliary springs, mounted on the main arch, for all kinds of movement of both individual and groups of teeth. To move the front teeth in the labial direction, springs were used, mounted on the front of the main arc of the apparatus (Fig. 259, b). With the help of special springs, the teeth can be moved mesially (Fig. 259, c) or distally (Fig. 259, d). With a certain installation of the springs, the teeth move in combination (mesially and around the axis) (Fig. 259, e); with the help of two springs, it is possible to rotate the tooth around the longitudinal axis (Fig. 259, e). The group of weakly functioning orthodontic appliances includes the high-labial arch Luri (1930), which consists of a main wire arch 0.9-1 mm thick, reinforced with locks on the rings. The peculiarity of the shape of this arch is that its frontal part is high in the vestibule of the oral cavity, approximately at the level of half the length of the roots of the teeth. This is quite beneficial from an aesthetic point of view. Springy processes (0.5-0.6 mm thick) extend vertically downwards from the arch, directed to those teeth that are to be moved to the palatal side (Fig. 260) Fixed devices of mechanical action include a screw device for expanding the upper jaw (Fig. 261, a, b). It consists of rings soldered together, bushings soldered to them, into which an expansion screw is inserted. The action of this apparatus is very strong, and during its application there is a rupture of the palatal suture, changes in the apical basis (its expansion in the transversal and to some extent in the sagittal direction), as well as in the region of the nasal septum. On the x-ray, a dark strip is visible in the region of the palatine suture. This old method of treatment has recently been improved by Derichsweiler. The author proposed a screw apparatus, which consists of a plate with crowns welded into it and a screw. Crowns are fixed on premolars and molars with phosphate cement. If the screw is actuated frequently (2/4 to 3/4 turns per day), the palatal suture also breaks. After the expansion of the jaw, such an apparatus is left in the oral cavity for another 6 months to consolidate the results achieved, that is, it is used as a retention one. According to the author, this method is the leading one in orthodontics and can be used starting from childhood in cases where there is an uneven development of the jaws, if necessary, to expand the dentition by more than 5 mm or in cases where jaw compression is the prevailing symptom of the anomaly. The disadvantage of the described method is the impossibility of expanding the apical basis of the lower jaw. The group of non-removable devices of mechanical action includes devices used to eliminate the diastema (crowns with hooks and vertical rods, acting on the principle of rubber traction, as well as with spring loops), fixed metal (from soldered crowns) or plastic trays with hooks for vertical displacement of teeth under the action of the force of rubber traction, devices for body movement of teeth in case of their incorrect location (vertical or horizontal annular - Angle's bandage arch, Schwartz's loop-shaped arch, Griffin's springy arch, Johnson's double arch). Apparatus Korkhauz, Schwarz, retaining a place in the dentition after the early extraction of milk teeth, various retention devices are also fixed orthodontic appliances. Begg's method, which consists in using the Angle arc system to apply small forces for body movement of teeth, has received great recognition. For this, the author used a thin, very elastic, so-called Australian wire, which is a stainless steel wire with a diameter of 0.4 mm. Auxiliary springs cannot be soldered to such a wire, and therefore additional hooks for rubber traction are bent on the arc itself. In order to make the action of the vestibular arch more gentle, Begg applied vertical loops. They even out the force of action between misaligned teeth. The length of the arc increases due to the loops, and thus the effect of the force is reduced. The number and type of loops depend on the irregularity of the dentition. Loops are usually applied at the beginning of treatment. Begg's technique does not use locks and large forces. Begg's treatment includes three stages (Fig. 262). In the first stage, depending on the clinical picture, the space is cleared, rotations are corrected along the axis, the inclination of the upper front teeth to the palatal side, the distal bite is eliminated by mesial movement of the lower jaw to its neutral position, deep overlap is eliminated, etc. In the second stage, the existing gap after the removal of premolars due to the palatine and lingual inclination of the anterior teeth. In the third stage, the direction of the axes of the incisors, canines and premolars is corrected. Thus, in the first and second stages, the teeth tilt, and in the third, the direction of their tilt is corrected. Removable devices of mechanical action include plate devices in combination with. screws, springs, vestibular arches, levers. The use of plate devices became possible at the beginning of the second half of the last century, after the discovery of rubber vulcanization. In the 1960s, Kingslay designed a plate in which the acting force was a screw. In the future, the already almost forgotten Kingsley record was used and modified by Nord (Nord, 1929). He proposed a screw of his own design. Further improvement of Nord's idea belongs to A. M. Schwartz. Currently, removable plate devices are used with different screw arrangements, according to the area that needs to be expanded or removed vestibularly (Fig. 263). Screws of various designs and sizes are used depending on the jaw (upper or lower), its size and the number of screws required. In order to create greater stability of plate devices, various clasps are used: conventional holding, crossover Jackson, swept Schwartz, Adams clasps, etc. For the manufacture of these clasps, wire of various thicknesses and elasticity is used. Holding and Jackson clasps are made of hard wire with a thickness of 0.7-1.1 mm, swept - from hard wire 0.7 mm thick (it is bent with special tongs or simple pliers), Adams clasps - from hard or hard springy wire with a diameter of 0.6 or 0.7 mm. In orthodontics, removable devices with springs and vestibular arches are widely used, the predecessor of which is considered to be Coffin's expanding plate (1882) (Fig. 264). The action of these devices is carried out by extension or compression of the corresponding loops. The location of the springs, the shape of their bend and the vestibular arch depend on the clinical picture (Fig. 265). For vestibular arches, a rigid wire 0.7-0.8 mm thick is usually used, for springy processes - 0.5-0.6 mm, for the Coffin spring - 1.0-1.5 mm. In addition to devices located in the oral cavity, the so-called buccal, or vestibular, plates proposed by Fronkel are used to expand the lower dentition. The advantage of these devices is that there is free space for the tongue and speech is less disturbed, the possibility of damage to the gingival mucosa on the lingual side during the activation of screws or springs is excluded. The lamellar part of the apparatus removes the soft tissues of the lips and cheeks from the dentition and thereby eliminates their not always favorable influence (Fig. 266). Describing the above-described removable devices, it should be noted that they work well and cause fewer negative effects compared to non-removable devices. The action of the devices is carried out with less force, with interruptions, irritation is transmitted to a greater extent to the bone tissue of the jaw than to the teeth. They are more hygienic and burden the sick in society (especially adults) to a lesser extent. These devices are indicated for the treatment of anomalies of the dental system at any age with their individual design in each individual case. 15. 16. Anthropometric methods for the study of models of jaws (method of Pohn, Korghaus, Gerlach). Pohn-Linder-Hart method The method is used to determine the width of the dentition in children in mixed and permanent dentition. Pont established a relationship between the sum of the mesiodistal dimensions of the incisors and the width of the dentition in the region of the first premolars and molars, which he expressed by premolar and molar indices: 80 and 64. This relationship is reflected in the following formulas: The measuring points on the upper jaw are: the middle of the longitudinal fissures of the first premolars and the anterior point of intersection of the longitudinal and transverse fissures of the first molars. Rice. 8. Measuring points for studying jaw models Measuring points on the lower jaw - the distal point of the first premolar, which is in contact with the second premolar (the point between the premolars), and the median point on the vestibular surface or the distal-buccal tubercle of the first premolar (Fig. 8, a, b). These measuring points, according to Pona, are used for permanent occlusion. In the interchangeable bite, instead of the measuring points of the premolars, the distal dimples of the first temporary molars on the upper jaw or their distal-buccal tubercles on the lower jaw are taken. In cases where not all upper incisors have erupted (or are missing), the sum of their width can be determined by the sum of the transverse dimensions of the lower incisors, using the Tone index (1.35), according to which the sum of the width of the upper incisors is related to the sum of the lower incisors as 4/3.  For practical purposes, Pont compiled a table of distances between premolars and molars with different widths of the four upper incisors. For the lower jaw, the sum of the transverse dimensions of the four incisors and the corresponding distances between premolars and molars are taken from the table of the upper jaw (Table 3). The German orthodontists Linder and Hart checked Pohn's data and found that it