Prosthetics for pathological abrasion of teeth pursues both therapeutic and prophylactic goals. The former means improving the function of chewing and the appearance of the patient, the latter - preventing further erasure of hard tissues of the teeth and preventing diseases of the temporomandibular joint. What specific tasks are solved during the prosthetics of a particular patient depends on the characteristics of the clinical picture.

With localized and diffuse forms of abrasion without lowering the height of the lower third of the face, prosthetics are preventive in nature, preventing further abrasion of the teeth.

Preiswerk (Preisswerk) in 1904 used for these purposes metal inlays in antagonistic teeth located in three points: in the front teeth and in the lateral teeth of the left and right sides. You can also use counter crowns made of stainless steel. Gold crowns are unsuitable for this because of their softness.

With pathological abrasion, accompanied by a decrease in the height of the lower third of the face, the tasks of prosthetics are complicated. Here it is necessary not only to improve the function of chewing and to prevent further abrasion of the teeth. At the same time, it is required to increase the bite height. This will change the appearance of the patient and normalize the position of the articular head in the articular cavity.

An increase in the height of the bite is achieved by restoring the shape and height of the worn crowns of natural teeth, for which they are covered with porcelain, plastic, metal or combined crowns. When choosing a material for crowns, both the aesthetic side of the issue and the possibility of erasing the substance of the artificial crown should be taken into account. Full metal crowns are not aesthetically pleasing. Plastic ones are the most beneficial, but they wear out quickly. Preference should be given to porcelain or combined crowns, the chewing surface of which is cast.

Prosthetics is carried out in the following order. First, natural teeth are prepared, taking into account the type of future artificial crowns (porcelain, plastic or metal). After that, the height of the occlusion is determined, for which the height of the lower third of the face is measured in a state of rest of the lower jaw. Then a wax or other thermoplastic mass is placed between the teeth and the desired bite height is fixed. The occlusal height of the lower third of the face should be less than the resting height, but not more than 2-3 mm. The correctness of determining the bite height can be checked by radiography of the temporomandibular joint. With a correctly defined bite height, the joint space is the same width in both the anterior and posterior sections. If these ratios are violated, the height of the occlusion should be changed by reducing or increasing the bite ridge.

Then casts of the dentition are taken and models are cast on them. Using a bite roller, the models are made in the position of central occlusion, they are plastered into the articulator and proceed to the modeling of the crowns.

With a large difference in the height of the lower third of the face when the teeth are closed and in the resting position (6-8 mm), the height of the bite can be increased in two steps. Initially, the bite is raised with a temporary removable mouthguard to a normal height. If at the same time there are no disorders in the activity of the temporomandibular joint, then after 2-3 weeks the final prosthetics is performed in the manner described above. If there are pains in the joint, the bite should be lowered, and after a while it should be raised again, bringing it to the desired value.

When imposing ready-made hollow metal crowns, the following should be borne in mind. Since artificial crowns are longer than a tooth, when applied, it is easy to push them deeper into the gum pocket than necessary, and thereby damage the mucous membrane of the gum pocket. The height of the bite will be lowered. Hollow crowns are also inconvenient because when they are rubbed, saliva gets into the holes formed. It dissolves the cement, and the cavity in the crown is filled with food debris, which subsequently decomposes.

In order to prevent these complications, crowns should be applied in two steps. First, the crowns are fixed, for example, on the right, and in order not to push their edge deep under the gum, a stencil bite roller should be placed on the left side, with which the desired bite height was fixed. After strengthening the crowns on the right, do the same on the left side. Only in this case, the role of the limiter is played by the crowns of the right side.

A more convenient method of prosthetics is metal combined crowns. In this case, only caps are made on the teeth at first. They are fixed on the teeth with artificial dentin and determine the bite height. Impressions are taken, models are cast, they are made in the position of central occlusion and plastered into the occluder. The missing part of the crown (chewing surface, cutting edge) is modeled on wax caps. Then the wax is replaced with metal in the usual way, and parts of the crowns are soldered to the caps. Molded occlusal crowns are more advantageous than stamped full crowns because they can prevent lowering of the bite when they are applied; in addition, they are less erased when chewing.

It is also possible to restore the shape of worn crowns and increase the bite height with the help of removable plastic caps. To do this, impressions are taken from both jaws and combined models are cast: teeth from fusible metal, and the rest from plaster. Before taking the impression, the bite height is determined. Models are plastered in the position of central occlusion in the occluder. After that, a wax kappa is modeled and the latter is replaced with plastic. The finished kappa is fitted in the oral cavity. The inaccuracies that have appeared in its fit to the teeth are eliminated with quick-hardening plastic.

Removable plastic mouth guards, which are very aesthetically advantageous, have a big drawback. Under them, despite careful hygienic care, systemic enamel necrosis develops. To avoid this, worn teeth should first be covered with metal caps, and then prosthetized with a removable mouthguard. In this case, it is possible to achieve a satisfactory aesthetic effect, facilitate the fitting and insertion of the mouthguard, and also prevent its harmful effect on dental tissues.

Partial loss of teeth can occur against the background of already developed pathological abrasion of teeth. On the other hand, the loss of, for example, molars can lead to pathological abrasion of the front teeth from their mixed function. The clinical picture in this case is very complex, since the symptoms of partial loss of teeth are superimposed on the pathological abrasion. In this regard, the tasks of prosthetics are also expanding. To the tasks that are pursued in the prosthetics of pathological abrasion, the replacement of defects resulting from the loss of teeth is added.

The designs of prostheses used in resolving the latter task are determined by the specific clinical picture. With included defects without lowering the bite height of the lower third of the face, fixed dentures can be used. When lowering the height of the lower third of the face, prosthetics provides, in addition to replacing defects, and increasing the height of the bite.

With end defects (unilateral or bilateral), the use of various designs of removable dentures (arc and plate) is shown. An increase in the height of the bite is made on fixed dentures or on removable arc ones, equipped with special metal linings for worn teeth.

Details

Deep (reduced) bite

Deep bite belongs to the group of anomalies of hereditary origin. Its occurrence is facilitated by: excessive development of the premaxillary bone, early loss of the upper milk incisors (the lower permanent incisors, without meeting antagonists, reach the mucous membrane of the palate, and the incisors of the upper jaw, erupting, are set in front of the lower ones and deeply overlap them) or milk and permanent molars, the predominance of the muscles-elevators of the lower jaw over the muscles that push it forward, and other factors [Yu.L. Obraztsov, 1991].

There are various clinical variants of deep bite, which is due to its combination with other anomalies (see Table 11).

The occurrence of a reduced bite causes various pathologies of the masticatory apparatus: pathological abrasion of natural teeth against the background of intact dentitions, dentition defects in the lateral sections, periodontitis and secondary deformations of the dentition, as well as prosthetic errors, including excessive preparation of natural teeth that articulate with each other, for prosthetics.

The relationship between the dentition with a deep (reduced) bite is characterized by the overlap of the upper front teeth of the lower ones by more than 1/3 of the height of the crowns of the latter. With this pathology, often the cutting edges of the lower front teeth reach the mucous membrane of the palate and injure it, and the cutting edges of the upper incisors often injure the mucous membrane of the gums of the alveolar arch of the lower jaw. The occlusal curve has an atypical shape, and the level of the occlusal plane of the anterior teeth of the lower jaw is higher than the level of the lateral teeth. The prevailing are the vertical movements of the lower jaw, which determines the crushing nature of the chewing movements and the degree of violation of the grinding of food products in the oral cavity. With a reduced bite (in the absence of parafunctions and pathological abrasion of hard tissues of the teeth), a decrease in the force of compression of the masticatory muscles is noted. Often diction is broken. During articulation, patients complain of rapid “fatigue” of the masticatory muscles.

Such patients have an aesthetic defect of the face due to shortening of the lower third, deepening of the nasolabial and submental folds, "excess" of the lips, etc. The aesthetic center of the jaws is often displaced.

Patients may involuntarily bite the mucous membrane of the cheeks, lips and tongue and complain of a decrease in the volume of the oral cavity. When you open your mouth, you can hear a click that occurs when the back of the tongue “sticks off” from the mucous membrane of the palate.

Often there is pain or discomfort in the TMJ area, especially during articulation. Such pain intensifies at the moment of complete closure of the dentition. Crepitus, clicking and crunching in the TMJ also appear, which indicates the presence of dystrophic changes in them. It is possible to join the listed sensations with the so-called "ear" symptoms: noise, hearing loss, the desire to "ventilate the Eustachian tubes" and others, although the examination of the organ of hearing often does not reveal pathology.

Neurological symptoms often join: headache, pain in the TMJ and in the parotid-masticatory region with irradiation to various parts of the head, which is associated with the involvement of the TMJ in the pathological process due to a violation of the optimal combination of motor reactions of the TMJ and changes in the position of the articular heads in relation to the articular fossae and articular tubercles.

By reducing the bite height and changing the tone and volume of the masticatory muscles proper, the outflow of saliva from the parotid glands may be disturbed due to a decrease in the diameter of their excretory ducts, since the latter are associated with the activity of these muscles. Sometimes there is dryness in the mouth.

Underbite is often complicated by distal mandibular displacement and protrusion of the upper anterior teeth. Then, in the lateral areas of the dentition, a clinical picture of the false Hodon phenomenon occurs, which requires an appropriate differential diagnosis.

The nature of the severity of the described symptoms is influenced by the patient's age, his psychosomatic state, the size and topography of defective dentition, the state of the periodontium of the remaining teeth, morphological changes in the TMJ, the nature of the kinematics of the lower jaw, etc.

There are two ways to normalize the value of the interalveolar distance: one-stage and two-stage. Clinical practice has shown that in the absence of clear indications for the use of a single-stage method, its unreasonable use can lead to complications, especially those associated with the occurrence or exacerbation of the existing periodontal and temporomandibular joint pathology. The use of a two-stage method based on the restructuring of myostatic reflexes [IS Rubinov, 1965] gives fewer complications. However, when it is used to change the value of the interalveolar distance, there are significant differences in tactics, volume and rate of normalization of the height of the reduced bite [A.V. Tsimbalistov, 1996]. In particular, the distance between the articulating teeth is very individual, the knowledge of the value of which is necessary for the anatomical and physiological method of determining the central ratio of the jaws, establishing the position of the physiological rest of the lower jaw. According to various authors, the distances between the articulating teeth are: 1-6 mm (A. Gizi), 1-2 mm (B.N. Bynin), 2 mm (A.I. Betelman), 2-4 mm (A.Ya. Katz), 2-5 mm (V.Yu. Kurlyandsky), 4 mm (P. Kantorovich), 4-6 mm (A.K. Nedergin). According to L.M. Perzashkevich (1961), this distance ranges from 1.5 to 9 mm and is 2-3 mm in 70%, 1.5-2 mm in 12%, and 3-4 mm in 7%. . At the same time, the author observed extreme cases when this distance was equal to 7 mm in orthognathic bite and 9 mm in prognathic bite and normal development of the crown parts of the teeth.

Traditionally, when diagnosing a deep (reduced) bite, before rational dental prosthetics, it is necessary to determine the constructive bite and carry out functional preparation of the oral cavity for dental prosthetics, which provides the necessary conditions for the latter and is a test for preparing the correct choice of "bite height".

To perform functional preparation of the oral cavity for dental prosthetics (orthodontic preparation), bite-dissolving devices (bite plates, supragingival mouth guards) are used, which are made in three clinical stages:

1) getting a cast;.

2) definition of constructive bite;

3) fitting and application of the apparatus.

At the first stage, it is necessary to plan the design features of the future bite plate or mouth guard, at the second stage - to determine the height of the bite, as well as the width and shape of the slope of the area of ​​the bite plate that separates the bite. The latter is carried out depending on the specific clinical situation, which is determined by the nature of the pathology - the type of deep (reduced) bite (see Table 11).

At the same time, bite plates have common design features that help prevent the occurrence of other deformations of the masticatory apparatus.

When planning a bite block, one should keep in mind the need to include a retraction arch in its design, which allows you to evenly distribute chewing pressure on the teeth, keep the bite block from sinking and avoid displacement of the anterior teeth of the upper jaw from possible increased pressure on them. For aesthetic reasons, the retraction arch can be replaced with flip-over clasps in the area of ​​the anterior teeth. The latter can be combined with occlusal onlays, which are appropriately placed in the mesial fissures of the first premolars on both sides. Sometimes the cutting edges of the front teeth are covered with the plastic of the bite plate, which should be selected according to the color in this area according to the color of the enamel of natural teeth. With the protrusion arrangement of the anterior teeth of the upper jaw, the presence of a retraction arc in the design of the bite plate makes it possible to eliminate this pathology.

The dissociating platform must be located (in width) in the region of the front teeth: from 13 to 23. The question of the magnitude of bite separation (“bite height”) is decided individually. As a rule, they try to ensure that the anterior teeth of the upper jaw overlap the coronal part of the lower anterior teeth by 1/3. The length of the bite pad is mainly determined by the maximum distal shift of the mandible. This is necessary to prevent the development of forced prognathia. If it is necessary to normalize not only the height of the occlusion, but also the mesiodistal position of the lower jaw, the dissociating platform should be modeled in the form of an inclined plane. The angle of the inclined plane is determined by the magnitude of the distal shift of the lower jaw (the greater the distal shift, the greater the angle of the inclined plane) and averages 60°.

In all cases, the occlusal surface of the bite site must be smooth, ensuring normal lateral movements of the lower jaw and uniform contact with its anterior teeth. This is finally achieved at the stage of fitting and application of the bite block by using carbon paper.

It is important when modeling the disconnecting platform to combine the aesthetic center of the jaws, which helps to keep the lower jaw in the correct position and has a positive effect on the function of the TMJ.

The terms for patients to wear bite plates are strictly individual and depend on the purpose of their use: functional preparation of the oral cavity for prosthetics or correction of malocclusion.

The functional method of preparing the oral cavity for dental prosthetics according to I.S. Rubinov is indicated with a reduced bite (with a deep bite only in cases where it has deepened due to loss of teeth and other reasons). The essence of this preparation lies in the restructuring of myostatic reflexes, the development of a new, greater length of the muscles of the lifting lower jaw (mm. masseters, temporales, pretygoidei medialis), which allows you to increase the interalveolar space and excludes the possibility of its use with a small incisal overlap and direct bite to eliminate dentoalveolar lengthening . With a deep bite, which occurs in a patient from birth, a slight increase in the height of the bite is possible, but not to orthognathic, since in adults tissue restructuring in the TMJ region will not occur, which will lead to pain in the TMJ, other neurological symptoms and recurrence of the anomaly.

With an increase in the bite height in a patient in the first week, there is an increase in the rest tone of the masticatory muscles proper up to 80-100 g (physiological rest tone - 40 g) while reducing their compression tone to 50-70 g (physiological compression tone - 180-220 g) . In the second week, stabilization of these indicators is noted, followed by normalization of the resting tone and compression tone of the masticatory muscles proper, which by the end of the third to fifth weeks come to the initial data. Thus, as a result of using a bite plate (occlusion disengaging apparatus), static and dynamic reflexes of bite disengagement are restructured, which ensures an increase in the interalveolar space, that is, a new state of functional rest of the lower jaw. Clinically, the completion of the functional preparation of the oral cavity for prosthetics can also be judged by the patient's feelings: it is convenient to hold the lower jaw in a new position, including in the absence of a bite block or mouth guard in the oral cavity, the previous position of the lower jaw is inconvenient for the patient (he is looking for it, but does not find), the absence of discomfort in the TMJ area, the appearance of a mixed type of chewing.

It is generally accepted that it is possible to separate the occlusion up to 6-10 mm at once (if the patient does not have pronounced diseases of the cardiovascular and nervous systems) or to achieve the specified separation of the occlusion in stages, by gradually layering plastic in the area of ​​the bite pad, which separates the bite of the plate. The completion of functional training should be judged on the basis of the clinical data described above, as well as myotonometry indices of the masticatory muscles proper. Functional training was completed when the tone of rest and compression of the masticatory muscles proper came to the initial data and remained at this level for several days.

It is possible to make dentures with a one-time restoration of the bite height only for those patients who, with extreme disconnection after 30-40 minutes, do not have an acute reaction in the form of a noticeable increase in the tone of the masticatory muscles proper, up to about 50 g [L.M. Perzashkevich, S.B. Fishchev, 1987].

In case of bite anomalies, deformations of the dentition, the wearing of the bite plate will be longer and is determined by the timing of the anomaly elimination.

After completion of the functional preparation of the oral cavity and orthodontic treatment, rational dental prosthetics are carried out. In such cases, it is possible to use more widely supported dentures with the inclusion of various occlusal overlays in their designs, since the bite is still divided. It is also important to restore the optimal shape of the occlusal curve with multiple occlusal contacts. This ensures the prevention of recurrence of the pathology and favorable long-term results of dental prosthetics. After preliminary orthopedic treatment by restructuring bite disengagement reflexes, the time for adaptation to dentures is reduced, as with repeated use of dentures (L.M. Perzashkevich). In the process of using such dentures, the compression tone of the chewing muscles proper increases within 12 months. up to 31.3%. This suggests that the normalization of the height of the occlusion puts the masticatory muscles in optimal conditions of function (Z.P. Latiy, E.D. Volova).

Practically significant are the studies of A.V. Tsimbalistov (1996) on the development of a functional-physiological approach to the rehabilitation of patients with a secondarily reduced bite. The prerequisite for the emergence of these studies was the work of I.S. Rubinov (1965, 1970), L.M. Perzashkevich (1961, 1975), Z. Platiy (1967), B.K. Kostur (1970), W.B. Eressmeyer and A. Manys (1985) and others, which show that the maximum jaw compression force and the bioelectrical activity of the masticatory muscles occur in the position of central occlusion. The masticatory muscle can develop maximum force only in the case of an optimal ratio of its points of attachment [V.N. Kopeikin, 1993].

In the clinical aspect, the existing difficulties in the treatment of patients with reduced bite come down precisely to the impossibility of accurately and confidently determining the central ratio of the jaws.

Conducted by A.V. Tsimbalistov (1996) studies on the rehabilitation of patients with partial or complete loss of teeth and reduced bite and assessment of the integral force of compression of the jaws made it possible to identify three types of distribution of power characteristics depending on the size of the interalveolar state. In the complete absence of teeth, a single-peak distribution occurred in 51%, a two-peak distribution in 26%, and a peakless distribution in 23% of cases. At the same time, the maximum jaw compression force with a two-peak distribution was significantly higher than with a different nature of the dependence (see Table 9).

Thus, in the process of determining the central ratio of the jaws by the functional-physiological method, the use of a device for determining the central ratio of the jaws of the AOCO type, equipped with a mechanism for smooth regulation of the interalveolar distance, the gnatodynamometer "Vizir-E" and the electromyogram drive, allowed A.V. Tsimbalistov to design dentures for each the patient, taking into account the indicator of the maximum force of compression of the jaws. A comparative assessment of the use of the anatomical-physiological and functional-physiological methods for determining the central ratio of the jaws, carried out by the author, indicated a more effective adaptation to dentures in cases where a higher level of jaw compression force develops during chewing (Fig. 30). It should also be noted that when using the functional-physiological method for determining the central ratio of the jaws, the author noted a shorter correction period and a relatively smaller number of corrections (Fig. 31).

The results of studies by A.V. Tsimbalistov (1996) are fully consistent with the results of previous fundamental studies on the study of the features of the chewing function depending on the bite height in dentures [L.M. Perzashkevich, 1961] and the possibility of restoring the normal bite height in edentulous patients with habitual reduced occlusion [Z.P. Latiy, 1967], which also took into account the reaction of the masticatory muscles proper, depending on the method of increasing the occlusion.

The data of physiological chewing tests indicate that with a normal bite height in the process of getting used to full dentures, the chewing efficiency increases from 25% on the day the dentures are delivered to 90% after a year of using them. An increase in bite by 5-8 mm significantly complicates adaptation to dentures, reduces the chewing efficiency by 14-19%. Decreased occlusion by 3-8 mm does not subjectively affect the process of adaptation, but weakens the effectiveness of the chewing function by 6-14% compared to the norm [L.M. Perzashkevich, 1961]. That is why among people using full dentures, a reduced bite height occurs in 35.7% of cases, which is due to the relatively easy adaptation of patients to dentures with a reduced bite, atrophic processes in the underlying tissues, abrasion of plastic teeth, as well as the mistakes of doctors who take habitual convergence of edentulous jaws for a state of physiological rest [Z.P. Latiy, 1967].

The use by A. Tsimbalistov of the functional-physiological method for determining the central ratio of the jaws with partial loss of teeth and with a secondary reduced bite made it possible to develop an algorithm for managing such patients with different types of distribution of the power characteristics of the masticatory apparatus (Table 10).

These studies are of particular relevance today, when expensive technologies for the manufacture of dentures are increasingly used in clinical practice. Until now, the question of a one-time method of restoring the occlusion due to the possibility of serious complications of prosthetics has made its use in wide clinical practice very problematic. After the fundamental research of AV. Tsimbalistov (1996), one-stage method of occlusion restoration can be considered an alternative to the two-stage method of managing patients with a secondarily reduced occlusion that has developed as a result of partial loss of teeth.

Konstantin Ronkin, DMD

From time to time in our professional activity we come across situations when this or that method of diagnostics or treatment is based more on an opinion previously expressed and repeated over decades than on scientifically substantiated facts. Such opinions acquire the status of laws over time, and sometimes it is difficult to distinguish them from the truth. In fact, they are nothing but myths that have filled our specialty.
Another category of myths is the results of insufficiently carefully performed or not fully verified studies. So, for example, a not entirely correct study conducted in England in the nineties of the last century showed the negative impact of the whitening procedure on the hard tissues of the teeth, which threw the dentistry of this country back 20 years in the issue of teeth whitening. A few years later, the study was repeated, the results of the initial tests were not confirmed, but the myth about the dangers of whitening still hovers in dental circles, despite hundreds of positive results of scientific work conducted in many countries of the world.
Myths related to the field of aesthetic and functional dentistry are extremely common and tenacious. I must say that they interest me more than any other. Let's try to deal with some of them in this article.

Myth one - bite height

According to this myth, it is impossible to increase the bite height by more than 2 mm at a time when constructing occlusion during orthopedic, therapeutic or orthodontic treatment. This myth is undergoing some correction today. Some doctors have expanded the frames to 4 and even 6 mm.
However, in general, there is a certain figure within which we are allowed to increase the bite. Let's figure it out. The movement of the jaw is carried out along a certain trajectory (Fig. 1).

Rice. 1. The movement of the lower jaw is carried out along the usual pathological trajectory due to the presence of supercontacts in the region of the upper front teeth, which can cause muscle hypertonicity.

The position of this trajectory in the space of the skull is influenced by many factors. Congenital pathology of the joints and jaws, malocclusion, dysfunction of the temporomandibular joints, abrasion of teeth as a result of bruxism or clenching, ascending problems associated with poor posture, narrowing of the airways. A special group is made up of factors that we create: incorrectly made composite or ceramic restoration, not carried out selective grinding after orthodontic treatment, not made device to prevent displacement of neighboring teeth in case of early loss of a molar, untreated crowded position of teeth or deformation of the dentition, etc. - all this can lead to the appearance of supercontacts.
Through proprioceptive transmission, the central nervous system receives a signal about the presence of such premature contact. The CNS sends an impulse back to the muscles, causing them to change the position of the jaw so that when they close, the teeth do not bump into these supercontacts. This phenomenon has been called "negative impact avoidance syndrome". Thus, the neuromuscular system, controlling the movement of the lower jaw in order to bypass the supercontact, moves it along an altered - pathological - trajectory (Fig. 2).

Rice. 2. Pathological trajectory of the movement of the lower jaw on axiography. The intersection of the curves indicates the occlusal reasons for the change in the trajectory.

Why pathological? Because some muscles must constantly work with overvoltage in order to move the jaw along a changed trajectory (Fig. 1). As a result, their hypertonicity occurs, over time, spasm and, finally, chronic fatigue. The TMJ as a result of such a displacement of the lower jaw from the physiological trajectory also undergoes changes, which can be expressed in the displacement of the articular head from the central position, joint deformity, and disc displacement (Fig. 3).

Rice. 3. Joint pathology with anterior disc displacement and its morphological changes.

If in such a patient, as a result of abrasion, the height of the bite has decreased and the vertical Shim-bachi index is 3 mm (Fig. 4), then restoring the height of his bite “by eye” by more than 2 mm can cause unpleasant symptoms and aggravate the existing one. pathology. And in this case, the supporters of the myth of 2 mm will be absolutely right.

Rice. 4. Change in the position of the patient's lower jaw as a result of pathological abrasion and dysfunction of the TMJ: Shimbachi index = 3 mm, planned width of the central incisors = 8 mm, LVI index = 17.75 mm.

First of all, let's find out how much it is necessary to increase the height of the lower third of the face and, accordingly, the bite (I apologize in advance to those of you who are used to other terminology, but I hope to be understood). According to the LVI esthetic index, if the width of the central incisors is 8 mm, the vertical index should be 17.75 mm. That is, ideally, we need to “open” the bite by more than 14 mm. Oh! And I assure you that if such a patient, whose lower jaw moves along a pathological trajectory, is increased in height by 14 mm, you risk getting full symptoms of TMJ dysfunction.
Another method for determining the correct position of the lower jaw when restoring the height of the bite is to relax the muscles using the J5 myomonitor (Myotronics company) - fig. 5.

Rice. 5. Electroneurostimulation using a myomomonitor.

As a result of such relaxation, the lower jaw is shifted to the true position of physiological rest and the physiological neuromuscular trajectory of the movement of the lower jaw is restored (Fig. 6).

Rice. 6. Axiography of the movement of the lower jaw. As a result of muscle relaxation, the lower jaw moves from the habitual (blue and green lines) to the neuromuscular trajectory (dashed line), and under the action of electrical impulses from the myomonitor
moves from the position of physiological rest (red dot) to the planned neuromuscular occlusion (black dot). The neuromuscular trajectory in this case is 3.5 mm anterior to the habitual occlusion, and the neuromuscular occlusion is at a point located 3.5 mm sagitally, 3.6 vertically, and 0.5 mm horizontally to the left of the habitual occlusion.

With the help of axiography and myography, we can determine the individual distance of physiological rest (the distance from the position of physiological rest to the central occlusion) - fig. 7.

Rice. 7. Axiography allows you to determine the individual distance of physiological rest.

However, you can use the average value, which is 1.5 - 2 mm. Having risen along the neuromuscular trajectory to this distance from the position of physiological rest, we will find the point where the lower jaw should be in the vertical dimension (Fig. 6). As a rule, the LVI index and the method based on determining the position of physiological rest coincide. The main thing is that the jaw moves along a neuromuscular trajectory, which in some cases can be a few millimeters from the usual one. The movement of the lower jaw along the neuromuscular trajectory is provided by ultra-low-frequency electrical nerve stimulation using a myomotor.
In such a situation, we can increase the height of the bite by 10 and 15 mm, and it becomes possible to move the lower jaw to a position in which the muscles will feel comfortable, be in a relaxed, balanced state. The K7 system allows you to monitor the state of the muscles on the computer screen in any position of the lower jaw in real time (Fig. 7). Therefore, we can see the state of the muscles at a point that we have determined on the neuromuscular trajectory according to the LVI index or relative to the position of physiological rest. And if the muscles are relaxed with a light bite on the bite register at this point, then this confirms the correctness of our choice (Fig. 8).

Rice. 8. Myography of masticatory muscles. The left part shows muscle tone in a relaxed state, the middle part - with light biting on the bite register at the point of neuromuscular occlusion, the right part - light biting in habitual occlusion. Muscle tone when biting in habitual occlusion is higher than when biting on the register in the position of neuromuscular occlusion.

In addition, we can determine the occlusal comfort zone for each patient. This zone looks like a cylinder located along the neuromuscular trajectory. In most patients, the height of the cylinder exceeds its length and averages 5-7 mm, with the exception of the group of patients with clenches (Fig. 9).

Rice. 9. The comfort zone looks like a cylinder with a large vertical dimension.

Within the comfort zone, you can find the optimal position of the lower jaw for a given patient, corresponding to the objectives of the treatment. The position of the jaw determines the tone of the muscles, and not the average derived numerical value. Of course, the position of the jaw must be confirmed radiographically by the correct position of the articular head.
Thus, the state of the muscles and the neuromuscular trajectory determine how much we can increase the height of the bite at one time, and not the average value, and in practice we can see an increase in height up to 15 - 18 mm.

Myth two - ceramic restorations in the lateral area

The above data allow us to debunk another myth, according to which it is impossible to make ceramic restorations in the molars.
First of all, modern pressed ceramics (Empress) are as strong as ceramic-to-metal bonding in metal-ceramic restorations, not to mention restorations made of high-strength E-max material by Ivoclar. Secondly, if the patient is prosthetized in optimal occlusion, in which the muscles are in a balanced relaxed state, when the lower jaw functions on a neuromuscular trajectory and optimal microocclusion is created according to all the rules of gnatology, then the load on the restorations in the lateral parts of the dentition makes it possible to use ceramic restorations . The experience of using material restorations in the complete reconstruction of the dentition at our institute showed the effectiveness of the use of ceramic restorations on the posterior teeth. When checking the long-term results (8-15 years) in a group of 43 patients after complete reconstruction with ceramic restorations, 89% of patients did not observe any chips, breakages, facets, abrasion, decementation or loss of teeth (Fig. 10).

Rice. 10. Restoration of teeth using crowns, veneers and onlays made of material
Empress

Conclusion

Of course, we must use the achievements of modern science and introduce high technologies into everyday practice in order not to be captive to such and many other myths.

Article provided by the Boston Institute of Aesthetic Dentistry

PhD, CEREC-trainer, dentist

Today, CEREC debunks the myth that increasing the height of the lower third of the face and, accordingly, the bite is a laborious task that can only be done in collaboration with the laboratory. With the availability of CEREC equipment, total reconstruction of teeth with an increase in bite height can be performed within one visit.

This is possible thanks to the latest software. Options such as smile design, virtual articulator and virtual tooth contact marking make total bite reconstruction easy and fun. In the presented clinical case, a technique for increasing the bite height in a patient in one visit with occlusal abrasion facets is described. The technique described below, I am sure, is not new, and although not described in the literature, it is used by many clinics equipped with CEREC technology. In particular, in the author's clinic of Tamara Prilutskaya, this technique has been successfully used for several years.

It should be understood that it is necessary to carry out the reconstruction of teeth in the absence or subsidence of clinical manifestations of dysfunction of the temporomandibular joint. And after reinstalling the lower jaw in a new correct position, if necessary, relative to the initial one with the help of, for example, an orthotic, in the future, with the help of CEREC Omnicam, you can simulate a new bite in one visit.

Materials and methods

CEREC Omnicam , Trilux Forte Vita ceramic blocks , Duo Cement Kit .

Clinical case

Smile design, virtual articulator and virtual tooth contact marking make total bite reconstruction a fun challenge.

The patient complained of abrasion of the teeth of the upper jaw and, accordingly, a decrease in the height of the upper incisors to such an extent that they were no longer visible when smiling. As a result of a clinical examination of the maxillofacial region, no muscular-fascial tensions were detected, the movements of the lower jaw were in full, symmetrical, no pathological changes in the TMJ joint were detected. The bite is straight (Fig. 1). On the anterior teeth of the upper jaw 13-23, occlusal abrasion facets, wedge-shaped defects in the area of ​​24 and 25 teeth are determined (Fig. 1, 2). It was not planned to change the height of the lower teeth, although they also had occlusal abrasion facets, but with a slight loss of tissue (Fig. 3, 15), therefore, the bite increased without transversal and sagittal movements of the lower jaw, namely, in habitual occlusion only due to an increase the height of the upper teeth.

Treatment plan

Total prosthetics and increased bite by increasing the height of the teeth of the upper jaw. On the first visit - the manufacture and fixation of ceramic restorations of 9 teeth of the upper jaw. In subsequent appointments, it was planned to complete the prosthetics of the remaining teeth, and in fact it took the following two visits: on the second visit - 11 teeth, 3 teeth of the upper jaw: 15, 16, 27 - and 7 teeth of the lower jaw: 44-31 and 34-36. On the third visit - the remaining two teeth of the lower jaw, 32 and 33.

Treatment

On the first visit, a minimally invasive preparation of 9 teeth of the upper jaw was performed, which took no more than 60 minutes, that is, about 7 minutes per tooth, which, in our opinion, is a lot, since the preparation was minimally invasive (Fig. 4). The bite is fixed in habitual occlusion with the first layer of silicone impression material. In the frontal region, the impression mass was removed before it hardened, which allows visual control of the position of the lower jaw in relation to the upper jaw and, subsequently, optical bite registration (Fig. 4) .

With the help of a light-cured composite, a direct temporary restoration of the lost tissues of the two central teeth of the upper jaw was performed, after which the patient was asked to close his mouth. The teeth of the lower jaw entered the grooves of the impression material before the composite contact with the lower teeth, and the new position of the jaws was recorded virtually. Thus, the position of the lower jaw in relation to the upper one remained stable, without deviation from the usual occlusion, and the height increased by the size of temporary restorations (Fig. 5) .

Virtual modeling of teeth is a simple procedure, since everything happens automatically and only in some cases the intervention of a doctor is required. In this case, modeling time for 9 teeth took no more than an hour, milling of 9 restorations - a little more than two hours, glaze firing - twice for 15 minutes, fixation, occlusal correction and polishing of the occlusal surface - a little more than two hours: total time - six seconds half an hour, if you add one hour for preparation. But the patient's reception time is reduced due to the fact that all stages, except for preparation, do not occur sequentially, but in parallel; the fact that the dentist has two assistants, who are well trained, also reduces the time of reception.

For example, tooth 26 is virtually modeled, a ceramic block of the required size and color is inserted into the milling machine, and the milling process begins. Meanwhile, the 25th and 24th teeth are modeled (Fig. 6), after milling the 26th tooth, it is tried on, the proximal and distal contacts are checked, and the restoration of the 25th tooth is milled in parallel.

When 3-4 restorations are ready, with approximal contacts adjusted, the application of the glaze is carried out, and these restorations are sent to the Glaze firing. At the same time, the stages of virtual modeling, milling, fitting and fixation of the remaining restorations continue (Fig. 7) .

After the Glaze firing, the restorations are cemented with DUO CEMENT VITA. After fixing all the restorations, the teeth are ground along the occlusion and the corrected areas are polished.

Thus, in this clinical case, the total time of the first appointment was 4 hours 45 minutes (Fig. 8). To control the parallelism of the line of occlusion - the line of pupils, the "smile design" option was used (Fig. 9, 10) .

VITABLOCS TriLuxe forte 2M 2 were chosen for restoration. These blocks consist of four layers that differ in color intensity. In this clinical case, this made it possible to create natural color shades, as in the structure of a natural tooth, due to a subtle color transition from enamel to the cervical layer with a more accentuated color in the lower dentin and neck (Fig. 11, 12) .

At the second visit, it was planned to complete the prosthetics, but when the appointment time exceeded 5 hours, it was decided to transfer the restoration of the two remaining teeth, 32 and 33, to the next appointment. The preparation was also minimally invasive (Fig. 13-15) . On the third visit, the work was completed (Fig. 16, 17).

Conclusion

Rapid patient recovery is not the primary criterion for the CEREC technique. Still, the precision quality of the fit of restorations, minimally invasiveness and informativeness remain in the foreground: the dentist constantly sees a virtual model of the restored tooth with a high magnification and can prevent his mistakes in a timely manner, because the patient is sitting in a chair. Dentistry today is aggressive, often the patient is offered to remove all teeth or completely prepare the remaining ones. In my opinion, dentistry more often harms than helps, the patient loses money, but does not get health. The CEREC technique changes the main thing: the patient still loses money, but gains health for many years.

Raising the height of the bite by increasing the height of the crown part with the help of filling material. We use modern light composites that effectively fill in the shape of the tooth.

To create precise restorations and constructions, we use face bow. An instrument that attaches to your head to record the movement of your jaw in different directions to make a personal impression. The latter is then transferred to articulator– a device that reproduces the trajectory and helps to design a suitable restoration, taking into account individual characteristics, even at the stage of treatment planning.

Bracket systems

We will return you the correct ratio of the jaws with the help of braces. In our dentistry, 4 reliable methods are presented - classic and innovative. They can handle the toughest orthodontic challenges.

Which treatment method is right for you? The choice largely depends on the clinical indications and the condition of the jaw and teeth. Make an appointment at a convenient time for a detailed consultation and diagnosis.

It is possible to restore the harmonious and anatomically correct position of the dentition! We are like Innovation Center of the Dental Association of Russia, we will help you with the recognized competence of doctors and next-generation technologies. Contact Dent-a-med dentistry (Cheboksary) for high-quality care any day of the week.

Crowns made of metal-free ceramics

Reconstruction of the bite using ceramic crowns, which is as close as possible in structure to natural teeth. Designs are created in our own digital laboratory individually for you.