Determination of the central relationship of the jaws with complete loss of teeth. Possible errors and complications when determining and fixing the central relationship of the jaws

A significant number of errors in prosthetics for patients with complete secondary adentia occurs at the stage of determining the central relationship of the jaws.

When determining the central relationship of the jaws using wax bases with rollers, the most common errors are overestimating or underestimating the height lower section of the face, fixation of the ridges in an anterior or lateral relationship, which ultimately leads to disruption of the function of chewing, speech, aesthetic standards and facial harmony. The listed errors, as a rule, occur at the moment of fixing the upper wax roller to the heated lower wax roller. Even if incorrect fixation of the jaws is directly detected, the entire procedure, starting with fitting wax rollers in the oral cavity, determining the height of the lower third of the face, etc., has to be repeated.

In order to eliminate these errors, we proposed new technique(RF Patent No. 2200501) fixation of the central relationship of the jaws using a metal plate, 0.5-0.7 mm thick, attached with molten wax to the occlusal surface of the lower wax roller and corresponding in shape.

After the final adjustment of the wax rollers (determining the prosthetic plane, the height of the lower third of the face and the formation of the vestibular oval), a uniform layer of wax corresponding to the thickness of the plate is removed from the lower wax roller. The plate is placed on the occlusal surface of the lower wax ridge so that it covers the vestibular perimeter by 1-2 mm, and is strengthened on it with molten wax. Wax base with roller upper jaw and a roller with a metal plate of the lower jaw is fitted in the oral cavity and the central relationship of the jaws is determined. This is not always possible on the first try, but in the method we propose, this procedure can be repeated until the desired result is obtained, without fear of deformation of the wax rollers.

At the moment of fixing the jaws in central occlusion Using a pencil, outline the perimeter of the upper wax roller on the protruding part of the plate. Clinical guide lines for placing artificial teeth are drawn on the upper wax ridge and these lines are transferred with a pencil to the horizontal protruding edge of the metal plate of the lower jaw. Then the wax bases with rollers are installed on the model, they are compared in a central ratio according to the outlines and landmarks printed on the plate and fixed to each other with molten wax with inside models. After plastering the models into the articulator, the artificial teeth of the upper jaw are placed on a metal plate, which replaces the method of setting teeth on glass according to M.E. Vasilyev. Thus, the stage of manufacturing a plaster table with glass on the lower frame of the articulator is eliminated.

An important advantage this method fixation of the central relationship of the jaws is that using a metal plate, it is possible to carry out anatomical alignment of teeth on the sagittal curve, using the Christensen phenomenon. To do this, after fitting the fitted wax rollers with a metal plate in the oral cavity, the patient is asked to push the lower jaw forward.

In this case, the ridges in the area of ​​the molars form a wedge-shaped gap, facing an acute angle forward. In this position, the distal edges of the plate on the right and left are folded up until they come into contact with the upper wax roller, and the resulting space is filled with softened wax and fixed to the lower roller with a hot spatula. Next, the cooled rollers are again placed in the mouth and the patient is asked to close the jaws in the position of the central jaw ratio. Thus, disocclusion is obtained in the anterior section. The wax is cut from the distal part of the upper wax ridge until it makes tight contact with the metal plate along its entire length and an individual patient curve is obtained.

Using the proposed method of fixing the central relationship of the jaws when complete absence Dental treatment was performed on 43 patients. All of them successfully use manufactured removable dentures, and note their individual naturalness at rest and while chewing food.

Thus, using the above-described technique, it is possible to avoid errors in determining the central relationship of the jaws and obtain a sagittal plane individually for each patient, which will allow the restoration of impaired functions of the dentofacial system and faster adaptation to removable dentures.

S.I. Abakarov, K.S. Adzhiev

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Possible errors in determining the central ratio of toothless jaws

Errors that are made when determining and fixing the central relationship of the jaws can be identified and eliminated at the stage of checking prosthetic structures. They can be divided into four main groups:
1) fixation of the lower jaw not in the central, but in the anterior or lateral (right, left) relationship;
2) fixation of the central ratio at the moment of overturning one of the wax bases;
3) fixation of the central ratio with simultaneous crushing of the wax base or occlusal ridge;
4) fixation of the central ratio when one of the wax bases is displaced in the horizontal plane.
To check the design of the prosthesis, the wax base and teeth are wiped with alcohol, introduced into the oral cavity and the correct determination of the interalveolar height and other components of the central relationship of the jaws is checked. The interalveolar height is controlled by the anatomical and functional method using a speaking test, if fixation of wax bases allows this.
With an increase in interalveolar height, error correction is possible in two ways. If upper teeth stand in the right attitude to the upper lip and their occlusal plane is not broken, the interalveolar height should be reduced using the teeth of the lower denture. They are removed, a new bite block is placed on the wax base, and the interalveolar height and central position of the mandible are re-determined. After this, the upper model is separated from the articulator, combined with the lower one in a new position and plastered into the articulator for placement lower teeth. An increase in interalveolar height can be combined with incorrect calculation of the height of the upper bite ridge in the anterior region. Then the upper teeth protrude excessively from under the lip, making the smile unattractive. To correct such an error, artificial teeth are removed from both the upper and lower wax bases. Bite ridges are placed on the bases and the central relationship of the jaws is again determined.
When the interalveolar height decreases, if the upper dentition is positioned correctly, proceed as follows. A strip of softened wax is placed on the lower row of teeth and the patient is asked to close his teeth until the desired height is established. Once the wax has hardened, the dentures are removed. The upper model is separated from the articulator, placed in a new position and plastered again.

When checking central occlusion, two errors may be revealed: the anterior or one of the lateral occlusions were fixed with bite ridges. In the first case, when the teeth are closed in the position of central occlusion, only the lateral teeth come into contact, and a gap is formed between the incisors. The reason for this error is the habit of patients who have lost all their teeth to push their lower jaw forward. If such an error is discovered, it is necessary to remove teeth from the lower wax base, make a bite ridge, and re-determine the central relationship of the jaws.
If one of the lateral occlusions was fixed with bite ridges, a crossbite occurs when the teeth are closed in the central position. In this case, the determination of the central relationship of the jaws should be repeated.
Incorrect determination and application of the line of the center of the face on the rollers leads to a violation of not only the symmetry of the arrangement of artificial teeth on the right and left sides, but also occlusal contacts and aesthetic standards. This error is most often due to the fact that this landmark is determined not by the center of the face, but by the position of the frenulum upper lip. In some cases, the frenulum of the upper lip does not coincide with the line of the center of the face.

Diseases of the teeth, tissues surrounding the teeth, and damage to the dentition are quite common. Abnormalities in the development of the dental system (developmental anomalies) are no less often observed, which arise as a result of the most various reasons. After transport and production damage, operations on the face and jaws, when damaged or removed a large number of soft tissues and bones, after gunshot wounds Not only are there disturbances in form, but function is also significantly affected. This is due to the fact that the dental system mainly consists of the bony skeleton and the musculoskeletal system. Treatment of lesions of the musculoskeletal system involves the use of various orthopedic devices and dentures. Establishing the nature of the injury, disease and drawing up a treatment plan is a section of medical practice.

The production of orthopedic devices and dentures consists of a number of activities that are performed by an orthopedic surgeon together with a dental laboratory technician. The orthopedic doctor carries out all clinical procedures (preparing teeth, taking impressions, determining the relationships of the dentition), checks the designs of prostheses and various devices in the patient’s mouth, places the manufactured devices and prostheses on the jaws, and subsequently monitors the condition of the oral cavity and dentures.

The dental laboratory technician does everything laboratory works for the production of prostheses and orthopedic devices.

The clinical and laboratory stages of manufacturing prostheses and orthopedic devices alternate, and their accuracy depends on the correct execution of each manipulation. This necessitates mutual control of the two persons involved in the implementation of the intended treatment plan. Mutual control will be the more complete, the better each performer knows the technique of making prostheses and orthopedic devices, despite the fact that in practice the degree of participation of each performer is determined by special training - medical or technical.

Denture technology is the science of the designs of dentures and methods of their manufacture. Teeth are necessary for grinding food, i.e. normal operation masticatory apparatus; in addition, teeth are involved in the pronunciation of individual sounds, and, therefore, if they are lost, speech can be significantly distorted; finally, good teeth decorate the face, and their absence disfigures the person, and also has a negative impact on mental health, behavior and communication with people. From the above, it becomes clear that there is a close connection between the presence of teeth and the listed functions of the body and the need to restore them in case of loss through prosthetics.

The word “prosthesis” comes from the Greek prothesis, which means an artificial part of the body. Thus, prosthetics aims to replace a lost organ or part of it.

Any prosthesis that is essentially foreign body, must, however, restore the lost function as much as possible without causing harm, and also repeat the appearance of the replaced organ.

Prosthetics have been known for a very long time. The first prosthesis, which was used in ancient times, can be considered a primitive crutch, which made it easier for a person who had lost a leg to move around and thereby partially restore the function of the leg.

The improvement of prostheses went both along the line of increasing functional efficiency and along the line of approaching the natural appearance organ. Currently, there are prostheses for legs and especially for arms with quite complex mechanisms, more or less successfully meeting the task. However, prostheses are also used that only serve for cosmetic purposes. An example would be ocular prostheses.

If we turn to dental prosthetics, we can note that in some cases it gives greater effect than other types of prosthetics. Some designs of modern dentures almost completely restore the function of chewing and speech, and at the same time, in appearance, even in daylight, they have a natural color, and they differ little from natural teeth.

Dental prosthetics has come a long way historically. Historians testify that dentures existed many centuries BC, as they were discovered during excavations of ancient tombs. These dentures consisted of frontal teeth made of bone and secured with a series of gold rings. The rings apparently served to attach artificial teeth to natural ones.

Such prostheses could only have cosmetic value, and their manufacture (not only in ancient times, but also in the Middle Ages) was carried out by persons who did not have direct relationship to medicine: blacksmiths, turners, jewelers. In the 19th century, specialists involved in dental prosthetics began to be called dental technicians, but in essence they were the same artisans as their predecessors.

The training usually lasted several years (there were no set deadlines), after which the student, having passed the appropriate exam at the craft council, received the right to independent work. Such a socio-economic structure could not but affect the cultural and socio-political level of dental technicians, who were at an extremely low stage of development. This category of workers was not even included in the group of medical specialists.

As a rule, no one cared then about improving the qualifications of dental technicians, although individual workers achieved high artistic perfection in their specialty. An example is a dentist who lived in St. Petersburg in the last century and wrote the first textbook on dental technology in Russian. Judging by the contents of the textbook, its author was experienced specialist and an educated man for his time. This can be judged at least by his following statements in the introduction to the book: “A study begun without theory, leading only to the proliferation of technicians, is worthy of reproach, because, being incomplete, it produces workers - merchants and artisans, but will never produce a dentist - an artist as well as an educated technician. The art of dentistry, practiced by people without theoretical knowledge, cannot in any respect be equated with that which would constitute a branch of medicine.”

The development of denture technology as a medical discipline has taken a new path. In order for a dental technician to become not only a performer, but also a creative worker capable of raising denture equipment to the proper height, he must have a certain set of special and medical knowledge. The reorganization of dental education in Russia is subordinated to this idea, and this textbook is based on it. Dental prosthetic technology has the opportunity to join the progressive development of medicine, eliminating handicrafts and technical backwardness.

Despite the fact that the object of study of dental technology is mechanical equipment, we should not forget that the dental technician must know the purpose of the equipment, its mechanism of action and clinical effectiveness, and not just its external forms.

The subject of study of denture technology is not only replacement devices (prostheses), but also those that serve to influence certain deformations of the dentofacial system. These include the so-called corrective, stretching, and fixing devices. These devices, used to eliminate all kinds of deformities and consequences of injuries, acquire especially great importance in wartime, when the number of injuries to the maxillofacial region increases sharply.

From the above it follows that denture technology should be based on a combination of technical qualifications and artistic skill with basic general biological and medical principles.

The material on this site is intended not only for students of dental and dental engineering schools, but also for old specialists who need to improve and deepen their knowledge. Therefore, the authors did not limit themselves to one description technological process manufacturing various designs of prostheses, and considered it necessary to also give the basic theoretical prerequisites for clinical work at the level of modern knowledge. This includes, for example, the question of the correct distribution of chewing pressure, the concept of articulation and occlusion, and other points that link the work of the clinic and laboratory.

The authors could not ignore the issue of workplace organization, which has become of great importance in our country. Safety precautions were also not ignored, since work in a dental laboratory is associated with occupational hazards.

The textbook provides basic information about the materials that a dental technician uses in his work, such as gypsum, wax, metals, phosphorus, plastic, etc. Knowledge of the nature and properties of these materials is necessary for a dental technician in order to properly use them and further improve them .

Currently, in developed countries there is a noticeable increase in people's life expectancy. In this regard, the number of people with complete loss th teeth. A survey conducted in a number of countries revealed a high percentage of complete tooth loss in the elderly population. Thus, in the USA the number of toothless patients reaches 50, in Sweden - 60, in Denmark and Great Britain it exceeds 70-75%.

Anatomical, physiological and mental changes in elderly people complicate the prosthetic treatment of edentulous patients. 20-25% of patients do not use complete dentures.

Prosthetic treatment of patients with toothless jaws is one of the important sections of modern orthopedic dentistry. Despite the significant contribution of scientists, many problems in this section of clinical medicine have not received a final solution.

Prosthetics for patients with toothless jaws aims to restore normal relationships between the organs of the maxillofacial area, providing an aesthetic and functional optimum so that eating is enjoyable. It is now firmly established that the functional value of complete dentures mainly depends on their fixation on edentulous jaws. The latter, in turn, depends on taking into account many factors:

1. clinical anatomy toothless mouth;

2. a method for obtaining a functional impression and modeling a prosthesis;

3. features of the psychology of patients undergoing primary or repeated prosthetics.

When starting to study this complex problem, we first focused our attention on clinical anatomy. Here we were interested in the relief of the bone support of the prosthetic bed of toothless jaws; relationships various organs toothless oral cavity with varying degrees of alveolar process atrophy and their applied value(clinical topographic anatomy); histotopographic characteristics of toothless jaws with varying degrees atrophy of the alveolar process and surrounding soft tissues.

In addition to clinical anatomy, we had to research new methods for obtaining a functional impression. The theoretical prerequisite for our research was the position that not only the edge of the prosthesis and its surface lying on the mucous membrane of the alveolar process, but also the polished surface, the discrepancy of which with the surrounding active tissues leads to a deterioration in its fixation, is subject to targeted design. Systematic study clinical features prosthetics for patients with toothless jaws and accumulated practical experience have allowed us to improve some ways to improve the effectiveness of complete dentures. In the clinic, this resulted in the development of a three-dimensional modeling technique.

The debate has not been settled that acrylate base materials have a toxic, irritating effect on the tissue of the prosthetic bed. All this makes us wary and convinces us of the need for experimental and clinical trials manifestations side effects removable dentures. Acrylic bases break unreasonably often, and finding out the reasons that cause these breakdowns is also of some practical interest.

For more than 20 years we have been studying the listed aspects of the problem of prosthetics for toothless jaws. The site summarizes the results of these studies.

At the time of applying the prosthesis or after some time of using it, mistakes are discovered. The most common errors are:

1) the central relationship of the jaws was incorrectly determined or changed during the laboratory production of dentures;

2) the height of the lower part of the face is incorrectly set;

3) the boundaries of the prosthesis are incorrectly determined or changed during laboratory production of prostheses.

Methods for correcting inaccuracies in the centric relation of edentulous jaws. When determining the central ratio of toothless jaws, the following errors are possible:

1) the mesiodistal relationship of the jaws is fixed with a sagittal or lateral shift of the lower jaw;

2) the vertical relationships of the jaws in various departments(front or side). This can also be a technical laboratory error if, when pressing plastic or rubber, the plaster is pressed through or the cuvette is unevenly pressed.

To check for clinical or laboratory errors in a particular case, it is necessary to preserve wax bases with occlusal ridges, which were used to establish the central relationships of the jaws.

Correction of inaccuracies in determining the central ratio of toothless jaws is carried out as follows. During sagittal or lateral shift, teeth are removed from the base of the finished prosthesis of the lower jaw and instead of them, an occlusal ridge is formed from wax, on which they are installed correct ratios jaws. The dentures in this new position are plastered into the articulator or occluder and the teeth are positioned in a new way on the base of the lower jaw prosthesis. We emphasize once again that the dentition on the upper jaw prosthesis is not subject to any changes, since it displays a plane parallel to the nasal-auricular plane of the prosthetic.

If an error is detected in the vertical ratios separate groups teeth, which is expressed in the absence of occlusal contact between them (most often this is observed in the area of ​​chewing teeth on one or both sides), a small amount of heated wax is placed on artificial teeth where there is no contact, which is used to fix correct position jaws. The dentures in the established position are plastered in an articulator or occluder and the alignment of the teeth on the lower jaw prosthesis is corrected.

In case of errors in establishing the height of the lower part of the face, all corrections are also carried out by correcting the dentition of the lower jaw. In cases where the lower part of the face is set at a higher height than required, teeth are removed from the lower jaw prosthesis and the height is determined on a newly applied wax roll. If the height of the lower part of the face is underestimated, a wax plate is applied to the dentition of the lower jaw prosthesis, the correct height is determined and the teeth are rearranged after plastering the dentures in an articulator or occluder.

Corrections to the basis of the prosthesis boundaries. Certain deficiencies in the bases of the prosthesis for toothless jaws are usually identified in the very first days of using the prostheses. Most often they are expressed as follows:

1) the edge of the prosthesis base is elongated;

2) there is a discrepancy between the relief of the prosthesis base (from the side adjacent to the mucous membrane) and the relief of the palate or alveolar process;

3) the base of the prosthesis injures the mucous membrane on the sharp bony protrusions of the jaw;

4) the base of the prosthesis is shortened.

Shortening the edges of the prosthesis base. When the edges of the prosthesis base are elongated on the vestibular, palatal or lingual side, the prosthesis is pushed away from the toothless jaw and this disrupts the valve system. In addition, bedsores (tissue necrosis) form in the area of ​​the elongated edge. When bedsores form, sudden painful sensations, forcing the prosthetic wearer to remove the prosthesis.

Correcting the elongated edge of the prosthesis is a rather important operation, since if the edge of the prosthesis is not removed sufficiently, the defects of the prosthesis are not eliminated, and if the edge is removed excessively, the valve system is disrupted.

The presence of elongated edges of the base is established several hours after using the prosthesis and is expressed in the fact that, corresponding to the elongated edge of the prosthesis, strictly defined hyperemia appears on the mucous membrane.

Shortening the edges of the prosthesis base should be done as follows. Some harmless white powder (plaster can be used) is applied to the entire area of ​​the hyperemic mucous membrane, after which the prosthesis is installed on the jaw and immediately removed and removed from the oral cavity. The white powder goes to the edge of the prosthesis base and precisely indicates the area and its extent where it is necessary to make corrections within the boundaries of the prosthesis base. With longer use of a prosthesis with elongated edges, continued traumatization of the mucous membrane causes the development of bedsores with inflammatory infiltration surrounding tissues. The occurrence of an inflammatory infiltrate, in turn, leads to the formation of bedsores along a significant extent of the edge of the prosthesis. As a result, the boundaries defining the area of ​​the elongated edge of the prosthesis are erased.

The correction of the edge of the prosthesis carried out in this case according to the size of the bedsore, as a rule, leads to shortening of the edges of the prosthesis and to disruption of the valve system. With such advanced cases Correction of the prosthesis base should not be carried out on the day of the patient’s visit. It is necessary to first cure bedsores, and then apply a prosthesis and correct it in the stage of tissue hyperemia.

Treatment of bedsores. Bedsore (decubital stomatitis) occurs as a result of mechanical irritation of various parts of the oral mucosa; it is most often caused by a denture. The disease begins with a small but painful erosion, which then, developing under the influence of unresolved irritation, can turn into a decubital ulcer. At the onset of the disease, there is usually a shallow abrasion, redness of the mucous membrane, sometimes necrosis, and desquamation of the surface layers of the epithelium. If the irritating agent is eliminated during this period, the erosion usually heals on its own and quickly. If a significant decubital ulcer occurs, the prosthesis cannot be used until the process has completely reversed.

Drug treatment consists of prescribing antiseptic rinses and lubrication with astringents.

Antiseptic rinses:

1. 3% hydrogen peroxide solution, 1 tablespoon per glass of water.

2. Potassium permanganate solution.

3. Rivanol solution.

4. Chloramine solution.

Astringents:

1. Lugol's solution.

2. Iodine mixture according to A.I. Evdokimov.

Correction of inaccuracies in the relief of the prosthesis base. The presence of a discrepancy between the relief of the base of the prosthesis and the relief of the mucous membrane located under the prosthesis, most often the result of a technical error in the manufacture of the prosthesis (chips or breakage of the plaster model), is established by the occurrence of a hyperemic area or bedsore located away from the edge of the prosthesis.

Correction of the prosthesis base is also carried out based on the imprint white powder. Amendments can be made both in the stage of hyperemia and in the stage of bedsore.

Grinding the base more than necessary in the area of ​​the bedsore in this case does not lead to a deterioration in the fixation of the prosthesis on the jaw.

The same procedure for correction should be carried out in cases where trauma to the mucous membrane is a consequence of the presence of acute painful bony protrusions on the toothless jaw.

Lengthening the shortened edge of the prosthesis. It is much more difficult to correct the base of the prosthesis if its edges are shortened, due to which the valve necessary for fixing the prosthesis is not formed.

Several methods can be used to lengthen the edges of the denture.

Correction of the base and edges of the prosthesis with plastic. In those cases; When the prosthesis base is made of plastic, it can be corrected directly with plastic. The method is as follows. Before applying a new layer of plastic in those places where the edge of the prosthesis is shortened, it is extended with a strip of plastic 1 mm thick, which is glued to the prosthesis with nitro varnish (a solution of cellophane in acetone).

A layer of freshly prepared self-hardening plastic is applied to the prosthesis base prepared in this manner, pre-lubricated with monomer.

The prosthesis prepared in this way is inserted into the mouth, pressed to the jaw and the patient is asked to close his teeth, squeeze them, and after some time speak, swallow saliva, etc. At the same time, the edge of the prosthesis is formed. Once the plastic has hardened, the prosthesis is removed from the mouth, the accuracy of the imprint is checked, excess plastic is removed, the prosthesis is finished and polished.

In the absence of self-hardening plastic, the edge of the prosthesis can be lengthened using other, albeit more painstaking, methods.

A method of lengthening the edge of a denture with wax and then replacing the wax with plastic. A softened piece of wax is attached to the shortened edge of the prosthesis, the fingers give it the appropriate shape, after which the wax is additionally heated and the prosthesis is inserted into the mouth and placed on the jaw. Then they begin to form: wax. In cases where the edge of the prosthesis is lengthened on the vestibular side, wax formation is carried out by pressing soft fabrics, cheeks to the area of ​​the prosthesis where wax is applied. If the edge of the prosthesis lengthens on the lingual side, then, having installed the prosthesis on the jaw, the wax is pressed with the fingers to the jaw and the patient is asked to lift the tongue up and push it forward. Movements of the tongue shape the edge of the prosthesis according to the valve zone. In cases where it is necessary to lengthen the palatal edge of the prosthesis, the boundaries of line A are established based on the principles described previously. It should be remembered that when lengthening the palatal edge of the prosthesis, it must be formed with some compression of the soft tissues along line A.

After the first formation, the prosthesis with applied wax is removed from the mouth and checked, excess wax is removed, and where the edge of the prosthesis remains shortened, wax is added and again: the edge of the prosthesis is formed. Lengthening the edge of the prosthesis is considered sufficient if the prosthesis is well fixed on the jaw when lever pressure is applied to the anterior and lateral teeth.

After the edge of the wax prosthesis is formed, it must be immediately plastered. since otherwise the wax may become deformed under the influence of temperature.

Method of lengthening the edge of the prosthesis with plaster and then replacing the plaster with plastic. In contrast to the method of deforming the edge of the prosthesis with wax, the method of performing the same operation with plaster requires preliminary preparation of the edge of the prosthesis for an impression. This preparation consists of removing all protrusions protruding from the inside edge of the prosthesis and removing a small layer of base material from the same side, resulting in a rough surface. This is necessary so that the layer of plaster restoring the edge of the prosthesis is of sufficient thickness and can be installed in its place in the event of breakage when removing the prosthesis from the oral cavity. Having prepared the edge of the prosthesis, a layer of liquid plaster is applied to its base, the prosthesis is inserted into the mouth and, placed on the jaw, supported by fingers right hand, and with the left hand they form the edge of the plaster, pressing the soft tissue of the cheek to the prosthesis. When forming the lingual edge on the lower jaw prosthesis, the patient is asked to lift the tongue up and push it forward.

If it is necessary to lengthen the edge on the palatal side along lines A, before applying plaster, the edge of the prosthesis is lengthened with wax, and the possibility of some compression of the soft tissues along line A is provided. After preliminary lengthening of the edge of the prosthesis with wax, the base of the prosthesis is covered with liquid plaster, and the prosthesis is installed on the jaw. Once the plaster has hardened, the prosthesis is removed from the mouth and a plaster model is cast. The prosthesis and the plaster that formed the edge are removed, after which the prosthesis is installed on the model. The area occupied by plaster is filled with wax. The prosthesis prepared in this way is plastered into a ditch and the wax is replaced with the base material.

Lengthening the edge of the prosthetic wall with subsequent replacement of the wall with plastic. WITH inner surface a layer of 1-1.5 mm is cut out of the prosthesis, heated to the wall and placed on a milled surface, the prosthesis is inserted into the mouth, installed on the jaw and its edges are formed in the same way as when taking an impression, with the only difference being that to correct the base of the prosthesis, an impression is made removed when jaws closed, i.e. under careful control of central occlusion. After cooling the stanza and removing the prosthesis from the oral cavity, the imprint is checked and, if necessary, it is corrected. Stens is replaced with plastic using the usual method.

After the laboratory stage of setting the teeth, a wax model of the future prosthesis is checked in the patient’s mouth to verify the correctness of all previous clinical and laboratory stages making a prosthesis.

The clinical stage of checking the placement of artificial teeth is the last stage, when it is still possible to correct errors or inaccuracies made at the preliminary stages of prosthetics.

Checking the design of the prosthesis in the clinic consists of:

1) inspection of plaster models of jaws;

2) correct placement of teeth in the articulator;

3) checking the wax structure of the future prosthesis in the oral cavity.

When assessing the quality of models, attention is paid to their integrity: the presence of chips, pores, traces of injury from a technical spatula used when setting teeth. In this case, one should be guided by the rule - it is better to take a functional impression again than to use models that raise doubts.

After examining the models, the position of the teeth in the articulator should be carefully checked before the wax bases are artificial teeth will be introduced into the oral cavity. Pay attention to the color, size, shape of the teeth, and the size of the incisal overlap. The numbers of the color, size and style of the teeth must correspond to the preliminary entries in the production order. All changes are possible only taking into account the opinions of the doctor and the patient, with mandatory registration in the order and medical history.

It is necessary to pay attention to the overlap of the lower incisors with the upper ones, which should be within 1-2 mm depending on the size of the teeth used. Significant overlap can interfere with the fixation of the prosthesis; absence of it worsens the aesthetic optimum. You should also avoid large overlap of the lower cheek cusps of the chewing teeth with the same upper ones. It is advisable to grind off pronounced cusps, especially those of the canines, so that the lateral and anterior movements of the lower jaw are sliding. The position of the teeth in relation to the top of the alveolar ridge must correspond to the method of placing artificial teeth, which is chosen by the doctor according to the clinical conditions of the oral cavity at the preliminary stages of prosthetics. A change in the way teeth are positioned during the testing phase indicates rough medical errors in prosthetic planning. An important condition for stabilizing a plate prosthesis is the presence of a gap between the anterior group of teeth, i.e. the cutting edges of the lower incisors should not touch the palatal surface of the upper ones and be at a distance of 1.5-2.5 mm.

Stabilization of a plate prosthesis means holding it on the jaw during functional movements of the lower jaw.

Then you should check the occlusal contacts of the lateral teeth on both the buccal and palatal sides, paying attention to the modeling of the wax base, the volume of its edges, and the tight fit to the model. All noticed deficiencies are eliminated.

To check the design of the prosthesis in the oral cavity, the wax base and teeth are disinfected, introduced into the oral cavity, and the tightness of the wax base to the mucous membrane of the prosthetic bed is monitored both with the mouth open and closed. Next, they check the correctness of determining the height of the lower part of the face, as well as the adequacy of the choice of color, shape and size of the teeth, their placement in relation to the midline of the face and other landmarks, and their relationship in central and lateral occlusions.

The height of the lower part of the face is controlled by the anatomical and functional method using a speaking test, if the degree of fixation of the wax rollers allows.

The patient is asked to pronounce several syllables or letters (“o”, “i”, “e”, “m”, “p”), while monitoring the degree of separation of the rollers. With normal height of the lower part of the face, this separation reaches 5-6 mm. If the separation of the ridges is more than 5 mm, then the height of the lower part of the face is reduced; if the separation is less than 5 mm, then it is increased.

The line passing between the central incisors should coincide with midline faces. When the mouth is opened slightly, only the cutting edges of the incisors should be visible, and when smiling, the front teeth can be seen almost to the equator, and in some cases to the neck.

As the height of the lower part of the face increases, the nasolabial and chin folds are smoothed, the contours of the face, and mainly the lips, are tense, and teeth chattering is possible during a conversational test. The distance between the teeth in the anterior region during the speaking test will be less than 5 mm. With a significant increase in the height of the lower part of the face, there may be no gap between the teeth, which in a state of physiological rest is 2-3 mm.

This error is eliminated as follows: if the placement of the upper artificial teeth is made correctly in relation to the Camper horizontal, then the reduction in the height of the lower part of the face should be done at the expense of the lower artificial teeth. They are removed, a new bite block is placed on the wax base and the central relationship of the jaws and the height of the lower part of the face in particular are re-determined. After this, the upper model of the jaw is separated from the articulator, combined with the lower one in a new position and plastered in the articulator. The lower teeth are placed again.

If there is an error in the positioning of the upper teeth, especially when the prosthetic plane is not maintained, it is necessary to re-make bite ridges for the upper and mandible and again determine the central relationship of the jaws. Next, the teeth are repositioned.

When the height of the lower part of the face decreases, if the upper teeth are set correctly, proceed as follows: a heated strip of wax is applied to the lower dentition and the central relationship of the jaws is redefined, bringing the height to normal. If the cause of the low height is also the upper teeth, then it is necessary to redefine the jaw relationship using new upper and lower bite ridges.

In addition to checking the correctness of determining the central relationship of the jaws, the density of contacts of artificial teeth is controlled. If there are no contacts between individual antagonist teeth, they are restored.

After checking the design of the prosthesis in the clinic, the wax compositions of the prostheses are sent to dental laboratory for final modeling of wax bases and replacing them with plastic ones.