Methods for determining and fixing central occlusion. Central jaw ratio

Among the common manipulations that have to be addressed when designing various prostheses is the definition of central occlusion. Without taking it into account, not a single structure can function normally (from crowns to complete removable dentures).

The central closure of the dentition ( central occlusion) is characterized by a certain relationship of the jaws in the vertical, sagittal and transversal directions. The relationship in the vertical direction is usually called the height of the central occlusion, or the height of the occlusion, the relationship in the sagittal and transversal directions is called the horizontal arrangement mandible in relation to the top.

When determining central occlusion in persons with partial loss of teeth, three groups of defects in the dentition are distinguished. The first group is characterized by the presence in the oral cavity of at least three pairs of articulating teeth located symmetrically in the frontal and lateral parts of the jaws. The second group is characterized by the presence of one or more pairs of interlocking teeth located in one or two parts of the jaw. In the third group of defects in the oral cavity, there is not a single pair of antagonizing teeth, i.e., despite the presence of teeth in both jaws, the central occlusion is not fixed on them.

With the first group of defects, the jaw models can be installed in the central closure (occlusion) along the ground occlusal surfaces of the teeth. In the second group of defects, the articulating teeth fix the height of the central occlusion and the horizontal position of the lower jaw, therefore, these relationships of the teeth must be transferred to the occluder using bite rollers made in the prosthetic laboratory, or gypsum blocks. Depending on the clinical conditions, templates with bite ridges are made for one or both jaws. Templates with rollers are introduced into the oral cavity, cut or built up until the opposing teeth close as they did without rollers. A heated strip of wax is glued to the occlusal surface of one of the rollers, the roller is inserted into the oral cavity and the patient is asked to close his teeth in central occlusion. On the occlusal ridges, imprints of teeth that do not have antagonists are formed. Templates with bite ridges are removed from the oral cavity, transferred to the models, and according to the impressions of the teeth in the bite ridges, the jaw models are folded in the central occlusion.

It is also possible to fix the central occlusion in this group of defects by introducing a plaster test with closed teeth into the areas of the jaws that are free from antagonizing teeth.

After crystallization of the gypsum, the patient is asked to open his mouth and gypsum blocks are removed from the mouth, on which alveolar areas and teeth of the upper jaw are fixed on one side, and opposite areas of the lower jaw are fixed on the other side. The blocks are cut, laid on the corresponding places of the jaw models, and then the models are folded over them and plastered in the occluder.

In the third group of defects, the definition of central occlusion is reduced to determining the height of the central occlusion and the horizontal position of the teeth.

The most common anatomical and physiological method for determining the height of the central occlusion. Its measurement is made on the basis of facial anatomical features (nasolabial folds, closing of the lips, corners of the mouth, height of the lower third of the face), which are evaluated after some functional tests(speech, opening and closing of the mouth). These tests are carried out in order to distract the patient from protruding the lower jaw anteriorly and set it in a state of relative physiological rest, when the lips are closed without tension, the nasolabial folds are moderately pronounced, the corners of the mouth are not lowered, lower third the face is not shortened.

The distance between the jaws in a state of physiological rest of each jaw is 2-3 mm greater than when the teeth are closed in central occlusion, which underlies the anatomical and physiological method, which consists in the following: between two arbitrarily marked points on the upper and lower jaws (on tip of the nose, in the area upper lip and chin) at the moment of physiological relative rest of the muscles, points are marked, the distance between which is measured with a spatula or ruler. Subtracting 2.5-3 mm from the obtained distance, the height of the central occlusion is obtained.

The bite block templates are inserted into the mouth and trimmed to the desired height. If the jaw has 3-4 teeth located in its various parts, you can limit yourself to one template with a bite roller made for the opposite jaw.

The anthropometric method for determining the bite height based on the law of the golden section (using Hering's compass) is only of historical importance, because ancient faces are rare, especially in old age. Therefore, it is necessary to determine not the conditional height of the central occlusion, but the one that the patient has at the time of the loss of the last pair of antagonistic teeth.

The horizontal position of the teeth or the neutral position of the lower jaw is determined various methods. Some patients adjust the lower jaw into the correct position without any effort on the part of the doctor. You can also suggest that the patient reach the back edge of the upper template with the tip of the tongue or swallow the saliva while closing the mouth. For the same purpose, the doctor inserts the thumb and forefinger of the left hand into the patient's mouth, fixing the upper template with a roller on the jaw. Wherein right hand impose on the chin and the lower jaw lead to the upper until the rollers are tightly closed. Then the rollers are removed from the oral cavity, lowered into cold water and reintroduced into the mouth. To connect the bite rollers to each other, that is, to fix the central occlusion, a heated strip of wax is used attached to one of the rollers. In places where there are no teeth, recesses are made on a hard roller, into which, when the jaws are compressed, heated wax is pressed, forming locks. It is better to apply a heated strip of wax not over the entire bite roller, but in several pieces in places where there will be imprints of the teeth of the opposite jaw or recesses are cut out. The rollers glued together are removed from the oral cavity, cooled and separated, then they are applied to the models and the tightness of the templates to the models is checked. Again, the templates with rollers are inserted into the mouth, the coincidence of the recesses with the protrusions is checked, as well as the coincidence of the teeth with their prints on the wax roller.

After fixing the central occlusion, the models are plastered in the occluder and dentures are constructed on them.

With the fourth group of defects, in addition to the indicated parameters, a prosthetic plane is constructed.

Muscular signs: muscles that lift the lower jaw (chewing, temporal, medial pterygoid) simultaneously and evenly contract;

Articular signs: articular heads are located at the base of the slope of the articular tubercle, in the depths of the articular fossa;

Dental signs:

1) between the teeth of the upper and lower jaws there is the most dense fissure-tubercular contact;

2) each upper and lower tooth is connected with two antagonists: the upper one with the lower one of the same name and behind it; the lower one - with the upper one of the same name and in front of it. The exceptions are the upper third molars and the lower central incisors;

3) the middle lines between the upper and lower central incisors lie in the same sagittal plane;

4) the upper teeth overlap the lower teeth in the anterior region no more than ⅓ of the crown length;

5) the cutting edge of the lower incisors is in contact with the palatine tubercles of the upper incisors;

6) the upper first molar merges with the two lower molars and covers ⅔ of the first molar and ⅓ of the second. Medial buccal cusp top first the molar enters the transverse intertubercular fissure of the lower first molar;

7) in the transverse direction, the buccal tubercles of the lower teeth are overlapped by the buccal tubercles of the upper teeth, and the palatine tubercles of the upper teeth are located in the longitudinal fissure between the buccal and lingual tubercles of the lower teeth.

Signs of anterior occlusion

Muscular signs: this type of occlusion is formed when the mandible moves forward by contraction of the external pterygoid muscles and horizontal fibers of the temporal muscles.

Articular signs: articular heads slide along the slope of the articular tubercle forward and down to the top. The path they take is called sagittal articular.

Dental signs:

1) the front teeth of the upper and lower jaws are closed by cutting edges (butt);

2) the midline of the face coincides with the midline passing between the central teeth of the upper and lower jaws;

3) the lateral teeth do not close (tubercle contact), diamond-shaped gaps form between them (deocclusion). The size of the gap depends on the depth of the incisal overlap with the central closure of the dentition. More in deep bite individuals and absent in straight bite individuals.

Signs of lateral occlusion (on the example of the right one)

Muscular signs: occurs when the lower jaw is displaced to the right and is characterized by the fact that the left lateral pterygoid muscle is in a state of contraction.

Articular signs: in joint on the left, the articular head is located at the top of the articular tubercle, shifts forward, down and inwards. In relation to the sagittal plane, articular path angle (Bennett's angle). This side is called balancing. Offset side - right (working side), the articular head is located in the articular fossa, rotating around its axis and slightly upward.

With lateral occlusion, the lower jaw is displaced by the size of the tubercles of the upper teeth. Dental signs:

1) the central line passing between the central incisors is “broken”, displaced by the amount of lateral displacement;

2) the teeth on the right are closed by tubercles of the same name (working side). The teeth on the left are joined by opposite cusps, the lower buccal cusps are merged with the upper palatine cusps (balancing side).

All types of occlusion, as well as any movement of the lower jaw, are performed as a result of the work of the muscles - they are dynamic moments.

The position of the lower jaw (static) is the so-called state of relative physiological rest. At the same time, the muscles are in a state of minimal tension or functional balance. The tone of the muscles that lift the lower jaw is balanced by the force of contraction of the muscles that lower the lower jaw, as well as the weight of the body of the lower jaw. The articular heads are located in the articular fossae, the dentition is separated by 2–3 mm, the lips are closed, the nasolabial and chin folds are moderately pronounced.

Bite

Bite- this is the nature of the closing of the teeth in the position of central occlusion.

Bite classification:

1. Physiological bite, providing a full-fledged function of chewing, speech and aesthetic optimum.

a) orthognathic- characterized by all signs of central occlusion;

b) straight- also has all the signs of central occlusion, with the exception of the signs characteristic of the frontal section: the cutting edges of the upper teeth do not overlap the lower ones, but are butt-joined (the central line coincides);

in) physiological prognathia (biprognathia)- the front teeth are tilted forward (vestibularly) along with the alveolar process;

G) physiological opistognathia- front teeth (upper and lower) tilted orally.

2. Pathological bite, in which the function of chewing, speech, and the appearance of a person are impaired.

a) deep

b) open;

c) cross;

d) prognathism;

e) progeny.

The division of bites into physiological and pathological ones is conditional, since with the loss of individual teeth or periodontitis, teeth are displaced, and a normal bite can become pathological.

Occlusion of teeth- this is the closing of the dentition or individual teeth for a short or long period of time. Occlusion is divided into the following types: central, anterior and lateral.

Central occlusion. This type of occlusion is characterized by the closing of the teeth with the maximum number of interdental contacts. With this disease, the head of the lower jaw is very close to the base of the articular tubercle. It should also be noted that all the muscles of the jaws contract evenly and simultaneously. These muscles move the lower jaw. Due to this position, lateral movements of the lower jaw are very likely.

Anterior occlusion. With anterior occlusion, the lower jaw moves forward. With anterior occlusion, it can be observed completely. If the bite is normal, then the midline of the face coincides with the midline of the central incisors. The anterior occlusion is very similar to the central one. However, there is a difference in the location of the head of the lower jaw. With anterior occlusion, they are closer to the articular tubercles and slightly pushed forward.

Lateral occlusion. This type Occlusion occurs when the lower jaw moves to the left or right. The head of the lower jaw becomes mobile. But remains at the base of the joint. At the same time, on the other hand, it shifts upward. If posterior occlusion occurs, then a displacement of the lower jaw occurs. In doing so, it loses its central location. During this, the heads of the joints are shifted upward. The posterior temporal muscles suffer. They are in constant tension. The functions of the lower jaw are partially violated. She stops moving sideways.

These types of occlusions are called physiological and in some cases are considered the norm. However, there is also pathological occlusion in dentistry. Pathological occlusions are dangerous because when they occur, absolutely all functions of the masticatory apparatus are violated. Such conditions are characteristic of some diseases that can cause occlusion of the teeth: periodontal disease, loss of teeth, malocclusion and jaw deformity, increased tooth wear.

It should be noted that occlusion is directly related to the bite of the teeth. You could even say that they are the same concept. In this regard, it is necessary to analyze the types and causes of pathological bites or occlusions.

Distal bite

This type of bite is very different. A distinctive feature is the overdeveloped upper jaw. It is not good. The fact is that with such a bite, the distribution of the chewing load is disturbed. It is more convenient for a person to bite off food with the side teeth. In this regard, it is the lateral teeth that are very susceptible to caries. In order to hide a non-aesthetic flaw, the patient in most cases pulls the lower lip up to the upper one. To eliminate this type of bite, many experts advise to completely remove the teeth in the upper jaw with the further installation of implants. However, now there are, which gives very positive results.

Causes of occlusion

genetic predisposition.
Chronic ENT diseases that arose in childhood. At the same time, they were accompanied by the fact that the child did not breathe through the nose, but through the mouth.
Bad habits, such as thumb sucking as a child, can lead to such an overbite.

Level bite

The level bite is very similar to the physiological one, so it is difficult to distinguish it. However, there are differences. Teeth in a direct bite are in contact with each other with cutting edges. And normally they should go for each other. Doctors sometimes say that this is absolutely normal. Although, this is not true. the fact is that the contacting cutting surfaces further lead to pathological abrasion of the teeth. Over time, teeth begin to wear out. This leads to a change in the joints, and then there may be restrictions on opening the mouth. Such a bite necessarily requires appropriate treatment. And the treatment consists in the fact that special silicone mouth guards are placed on the cutting interacting surfaces of the teeth.

Deep bite

With a deep bite, there is an overlap of the lower teeth with the upper ones by more than half. Such a bite can be developed not only on the front of the jaw, but also on the lateral parts. This type of bite (occlusion) is dangerous because a disease such as periodontal disease can develop very early. In addition, such patients may face the appearance of periodontitis (). The mucous membrane of the mouth suffers greatly, as it is constantly damaged by the teeth. In addition, the volume of the oral cavity decreases, and this leads to violations of swallowing food and breathing. In most cases, some groups of anterior teeth are erased. Patients complain of crunching, clicking and pain in the joints. Prosthetics of such a bite is very difficult.

Open bite

In an open bite, the patient's teeth do not meet at all. Accordingly, they do not contact each other in any way. This bite can occur in the front and in the sides. In addition, both single teeth and entire groups of teeth can be involved in such a process. In places where the teeth cannot be closed, the process of chewing food is disrupted. From this it follows that the more teeth do not close, the harder it is to chew food. As a result, there are problems with the digestive system. In addition, patients with such an overbite suffer from speech disorders.

The reasons:

Prolonged pacifier use and thumb sucking in childhood.
Almost all ENT diseases.
Incorrect swallowing function during the formation and growth of teeth in childhood.

Occlusion of the teeth should be detected on early stages. Accordingly, treatment should be started on time. Basically, these ailments are “laid” from childhood due to bad habits child. That's why. To prevent the occurrence of occlusion, it is worth monitoring your children very closely.

Occlusion is the most complete closure between the cutting edges or chewing surfaces of the teeth, which occurs simultaneously with evenly contracted chewing muscles. This concept also includes dynamic characteristics that make it possible to determine the work of the muscles of the face and the temporomandibular joint.

Correct occlusion is extremely important for the correct functioning of the entire dentition. It provides the necessary load on the teeth and alveolar processes, eliminates periodontal overload, is responsible for the correct functioning of the temporomandibular joint and all facial muscles. With its anomalies, which are observed in the absence of teeth in a row, periodontal diseases and other functional disorders dental system, not only the aesthetics of the face suffer. They can also cause increased tooth wear, joint inflammation, muscle strain, and gastrointestinal disturbances. That is why any anomalies of occlusion of the teeth require treatment.

Types of occlusion of teeth

All movements of the lower jaw are provided by the work of the muscles, which means that the types of occlusion should be described in dynamics. There are static and dynamic, some researchers also distinguish occlusion at rest, which is determined by closed lips and teeth open by a few millimeters. Static occlusion characterizes the position of the jaws with their usual compression relative to each other. Dynamic describes their interaction during movement.

Different sources emphasize different aspects of central occlusion. Some look primarily at the location of the mandibular joint, others consider the state (full contraction) of the masticatory and temporal muscles to be of paramount importance. However, in orthopedics and restorations, where it is important to correctly calculate the ratio of teeth in the rows, dentists prefer characteristics that can be assessed visually, without the use of complex devices. We are talking about the maximum area of \u200b\u200bclosure in compliance with the formulas:

the sagittal central line of the face lies between the anterior incisors of the upper and lower jaws;
the lower incisors rest against the palatine tubercles of the upper ones, and their crowns overlap by one third;
the teeth have close contact with two antagonists, except for the third molars and the anterior lower incisors.

A slight protrusion of the mandible forms an anterior occlusion. An imaginary vertical median line separates the anterior upper and lower incisors, which, in turn, touch incisally.

The upper and lower molars may meet unevenly, forming a cusp contact.

Posterior occlusion is characterized by the movement of the lower jaw towards the back of the head.

With lateral occlusion, the sagittal line is broken with an offset to the right or left, the teeth of one, the working side, touch the same-named tubercles of their antagonists, while on the other, the balancing one, the opposite ones (upper palatine with lower buccal).

Some characteristics of the occlusal system have genetic causes, others are produced in the process of growth. The hereditary factor can affect the shape, size of the jaws, muscle development, teething, and the functional apparatus is formed under the influence of various internal and external factors during jaw development.

Understanding occlusion is very important in restorative and orthopedic work in dentistry so that the function of the masticatory apparatus is restored as fully as possible.

Central occlusion- This is a type of articulation in which the muscles that lift the lower jaw are evenly and maximally tense on both sides. Because of this, when the jaws are closed, the maximum number of points touch each other, which provokes the formation. In this case, the articular heads are always located at the very base of the slope of the tubercle.

Signs of central occlusion

The main signs of central occlusion include:

each lower and upper tooth tightly closes with the opposite one (except for the central lower incisors and three upper molars);
in the frontal section, absolutely all the lower teeth overlap with the upper ones by no more than 1/3 of the crown;
the right upper molar connects to the lower two teeth, covering them by 2/3;
the incisors of the lower jaw are in close contact with the palatine tubercles of the upper ones;
buccal tubercles, located on the lower jaw, overlapped by the upper ones;
palatine tubercles of the lower jaw are located between the lingual and buccal;
between the lower and upper incisors, the middle line is always in the same plane.

Definition of central occlusion

There are several methods for determining central occlusion:

Functional technique- the patient's head is thrown back, the doctor puts his index fingers on the teeth of the lower jaw and puts special rollers in the corners of the mouth. The patient raises the tip of the tongue, touches the palate and swallows at the same time. When the mouth closes, you can see how the dentition closes.
Instrumental technique- involves the use of a device that records the movements of the jaws in a horizontal plane. When determining central occlusion with partial absence of teeth, they are forcibly displaced by hand, pressing on the chin.
Anatomical and physiological technique- determination of the state of physiological rest of the jaws.

This term originates from Latin and means "closing".

Central occlusion is a state of evenly distributed tension of the jaw muscles, while ensuring a one-time contact of all surfaces of the elements of the dentition.

The need to determine the central occlusion is to correctly make a partial or removable prosthesis.

Main features

Experts have identified the following indicators of central occlusion:

Muscular. Synchronous, normal contraction of the muscles responsible for the functioning of the lower jawbone.
Articular. The surfaces of the articular heads of the lower jaw are located directly at the bases of the slopes of the articular tubercles, in the depth of the articular fossa.
Dental:

full surface contact;
opposite rows are brought together so that each unit is in contact with the same and the next element;
the direction of the upper frontal incisors and the similar direction of the lower ones lie in a single sagittal plane;
overlapping elements of the upper row of fragments of the lower one in the front part is 30% of the length;
the anterior units are in contact in such a way that the edges of the lower fragments rest against the palatine tubercles of the upper ones;
the upper molar comes into contact with the lower one so that two-thirds of its area is combined with the first, and the rest with the second;

If we consider the transverse direction of the rows, then their buccal tubercles overlap, while the tubercles on the palate are oriented longitudinally, in the fissure between the buccal and lingual lower rows.

Signs of proper row contact

the rows converge in a single vertical plane;
incisors and molars of both rows have a pair of antagonists;
there is a contact of the same units;
the lower incisors in the central part of the antagonists do not have;
the upper eighths have no antagonists.

Applies to front units only:

if we conditionally divide the patient's face into two symmetrical parts, then the line of symmetry should pass between the front elements of both rows;
overlapping of the upper row of fragments of the lower one in the anterior zone occurs to a height of 30% of the total size of the crown;
the cutting edges of the lower units are in contact with the tubercles of the inner part of the upper ones.

Applies only to the side

the buccal distal tubercle of the upper row is based in the interval between the 6th and 7th molars of the lower row;
the lateral elements of the upper row merge with the lower ones in such a way that they fall strictly into the intertubercular furrows.

Methods Used

Central occlusion is determined at the stage of manufacturing prosthetic structures with the loss of several units.

Of great importance in this case is the height of the lower third of the face. However, in the absence a large number units, this indicator may be violated and it must be restored.

If the patient has partial adentia, several options for determining the indicator are used.

The presence of antagonists on both sides

The method is used when antagonists are present in all functional areas of the jaws.

In the presence of a large number of antagonists, the height of the lower third of the face is preserved and is fixed.

The occlusion index is determined based on the largest possible number of contact zones of the same-named units of the upper and lower rows.

This option is the simplest since it does not require the additional use of occlusal rollers or specialized orthopedic templates.

The presence of three occlusal points between antagonists

This method is used if the patient has retained antagonists in the three main contact areas of the rows. At the same time, a small number of antagonists does not allow normal positioning of plaster casts of the jaw in the articulator.

In this case, the natural height of the lower third of the face is violated, and occlusal wax or thermoplastic polymer ridges are used to correctly compare the casts.

The roller is placed on the bottom row, after which the patient reduces the jaws. After the roller is removed from oral cavity, imprints of the contact zones of antagonists remain on it.

These impressions are subsequently used by technicians in the laboratory to position the impressions and create a fully functional and correct, from an orthopedic point of view, prosthesis.

Absence of antagonistic pairs

The most time-consuming variant of the development of events is the complete absence of elements of the same name on both jaws.

In this situation, instead of the position of central occlusion determine the central ratio of the jaws.

The procedure includes the following steps:

Work on the formation of the prosthetic plane, which is positioned along the chewing surfaces of the side units and is parallel to the beam. It is built from the lower point of the nasal septum to the upper edges of the auditory canals.
Determination of the normal height of the lower third of the face.
Fixation of the mesiodistal ratio of the upper and lower jaw due to wax or polymer bases with occlusal rollers.

Checking the central occlusion with the existing pairs of elements of the same name is performed by closing the teeth and is carried out as follows:

a thin strip of wax is placed on the already prepared and fitted contact surface of the occlusal roller, glued;
the resulting structure is heated until the wax softens;
heated templates are placed in the patient's mouth;
after bringing the jaws together, the teeth leave imprints on the wax strip.

It is these prints that are used in the process of modeling central occlusion in the laboratory.

If the surfaces of the upper and lower rollers meet during the determination of occlusion, the specialist corrects their contact surfaces.

On the top, wedge-shaped cuts are made, and a certain amount of material is cut off from the bottom, after which a wax strip is glued onto the treated surface. After the rows are brought together again, the strip material is pressed into the cutouts.

Products are removed from the patient's oral cavity and sent to the laboratory for the subsequent manufacture of the prosthesis.

Calculations for orthopedic purposes

In the process of creating prosthetic structures for malocclusion, an orthopedic specialist measures the heights of the lower third of the patient's face using the anatomical and physiological method.

To do this, the bite height is measured in a state of complete reduction of the jaws, with central occlusion and in a state of physiological rest.

Calculation procedure:

At the bottom of the nose, at the level of the nasal septum, the first mark is placed strictly in the center. In some cases, the specialist puts a mark on the tip of the patient's nose.
In the center of the chin, a second mark is placed in its lower zone.
Measurement is performed between the applied marks height in a state of central occlusion of the jaws. To do this, bases with bite rollers are placed in the patient's oral cavity.
Re-measuring between marks, but already in a state of physiological rest of the lower jaw. To do this, the specialist must distract the patient so that he really relaxes. In some cases, the patient is offered a glass of water. After a few sips, the muscles of the lower jaw really relax.
The results are recorded. However, the standardized normal bite height, which is 2-3 mm, is subtracted from the resting height. And if after that the indicators are equal, we can talk about the normal bite height.

If, when measuring the height, according to the results of the calculations, a negative result is obtained - the lower third of the patient's face is understated. Accordingly, if the result deviates in a positive direction - overbite.

Receptions for the correct setting of the lower jaw

Correct positioning of the patient's jaw in the position of central occlusion involves the use of two methods of setting: functional and instrumental.

The main condition for correct setting is myorelaxation of the jaw muscles.

Functional

Order of conduct this method next:

the patient takes his head back a little until the muscles of the neck tense, which prevents the protrusion of the jaw;
touches the tongue to the back of the palate, as close to the throat as possible;
at this time, the specialist places the index fingers on the patient's teeth, slightly pressing on them and at the same time slightly pulling the corners of the mouth in different directions;
the patient imitates swallowing food, which in almost 100% of cases leads to muscle relaxation and prevents jaw protrusion;
when reducing the jaws, the specialist touches the surfaces of the teeth and holds the corners of the mouth until it is completely closed.

In some cases, the procedure is repeated several times until complete muscle relaxation and correct convergence of both rows is achieved.

Instrumental

It is performed using specialized devices that copy the movements of the jaw. It is used only in extremely serious situations, when bite deviations are significant and it is necessary to correct the position of the jaw using the physical efforts of a specialist.

Most often, this method the apparatus Larina is used and special orthopedic rulers that allow you to fix the movements of the jaw in several planes.

Permissible mistakes

The creation of a prosthetic structure in conditions of malocclusion is the most complex orthopedic procedure, the quality of which is 100% dependent on the qualifications of a specialist, a responsible approach to work.

Violations in determining the position of the central occlusion can lead to the following problems:

overbite

The folds of the face are smoothed out, the relief of the nasolabial zone is weakly expressed;
the patient's face looks surprised;
the patient feels tension when closing the mouth, during the reduction of the lips;
the patient feels that during communication the teeth knock against each other.

underbite

The folds of the face are strongly pronounced, especially in the chin area;
the lower third of the face becomes visually smaller;
the patient becomes like an elderly person;
the corners of the mouth are lowered;
lips sink;
uncontrolled salivation.

Permanent anterior occlusion

There is a noticeable gap between the front incisors;
the lateral elements do not contact normally, tubercular convergence does not occur.

Permanent lateral occlusion

overbite;
offset side clearance;
shifting the bottom row to the side.

Reasons for such problems

Incorrect preparation of wax templates.
Insufficient softening of the material for taking impressions and impressions.
Violation of the integrity of wax forms due to their premature removal from the oral cavity.
Excessive jaw pressure on the rollers during impression taking.
Errors and violations on the part of a specialist.
Errors in the work of the technician.

The video presents Additional Information on the topic of the article.

conclusions

The procedure for determining the position of the central occlusion is only one step in a complex and lengthy procedure for creating a prosthetic structure for the patient. But this stage can certainly be called the most significant and responsible.

It is on the qualifications, professionalism and experience of an orthopedic specialist that the comfort of further operation of the product by the patient and the absence of problems from the temporomandibular joint depend.

After all, various violations in his work, although they can be treated, take a significant period of time, causing discomfort, pain and inconvenience to the patient.

Take care of your teeth, contact your dentist’s office for help in a timely manner in order to maintain the health of the oral cavity and dentition for many years. In addition, taking care of your teeth and gums will help you avoid such unpleasant procedures described in our article.

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The central closure of the dentition (central occlusion) is characterized by a certain relationship of the jaws in the vertical, sagittal and transversal directions. The relationship in the vertical direction is usually called the height of the central occlusion, or the height of the occlusion, the relationship in the sagittal and transversal directions is the horizontal location of the lower jaw in relation to the upper.

It is also possible to fix the central occlusion in this group of defects by introducing a plaster test with closed teeth into the areas of the jaws that are free from antagonizing teeth.

In the third group of defects, the definition of central occlusion is reduced to determining the height of the central occlusion and the horizontal position of the teeth.

The most common anatomical and physiological method for determining the height of the central occlusion. Its measurement is made on the basis of facial anatomical features (nasolabial folds, lip closure, mouth corners, height of the lower third of the face), which are evaluated after some functional tests (speech, opening and closing of the mouth). These tests are carried out in order to distract the patient from protruding the lower jaw anteriorly and set it in a state of relative physiological rest, when the lips are closed without tension, the nasolabial folds are moderately pronounced, the corners of the mouth are not lowered, the lower third of the face is not shortened.

The distance between the jaws in a state of physiological rest of each jaw is 2-3 mm greater than when the teeth are closed in central occlusion, which underlies the anatomical and physiological method, which consists in the following: between two arbitrarily marked points on the upper and lower jaws (on tip of the nose, in the region of the upper lip and chin) at the moment of physiological relative rest of the muscles, points are marked, the distance between which is measured with a spatula or ruler. Subtracting 2.5-3 mm from the obtained distance, the height of the central occlusion is obtained.

The horizontal position of the teeth or the neutral position of the lower jaw is determined by various methods. Some patients adjust the lower jaw into the correct position without any effort on the part of the doctor. You can also suggest that the patient reach the back edge of the upper template with the tip of the tongue or swallow the saliva while closing the mouth. For the same purpose, the doctor inserts the thumb and forefinger of the left hand into the patient's mouth, fixing the upper template with a roller on the jaw. In this case, the right hand is placed on the chin and the lower jaw is brought to the upper one until the rollers are tightly closed. Then the rollers are removed from the oral cavity, lowered into cold water and reintroduced into the mouth. To connect the bite rollers to each other, that is, to fix the central occlusion, a heated strip of wax is used attached to one of the rollers. In places where there are no teeth, recesses are made on a hard roller, into which, when the jaws are compressed, heated wax is pressed, forming locks. It is better to apply a heated strip of wax not over the entire bite roller, but in several pieces in places where there will be imprints of the teeth of the opposite jaw or recesses are cut out. The rollers glued together are removed from the oral cavity, cooled and separated, then they are applied to the models and the tightness of the templates to the models is checked. Again, the templates with rollers are inserted into the mouth, the coincidence of the recesses with the protrusions is checked, as well as the coincidence of the teeth with their prints on the wax roller.

After fixing the central occlusion, the models are plastered in the occluder and dentures are constructed on them.

With the fourth group of defects, in addition to the indicated parameters, a prosthetic plane is constructed.

Lesson 7. Determination of the height of the lower part of the face. Methods for determining and fixing central occlusion. Occluders and articulators. Production of wax bases with occlusal rollers.

Determining the height of the lower face

Anatomical method- descriptive, the basis for determining the height is the restoration of the correct configuration of the face according to the appearance of the patient (the degree of severity of nasolabial folds, non-falling lips, their calm closing)

Anthropometric method- based on the principle of proportionality of parts of a person's face.

Zeising found a number of points that divide the human body according to the principle of the "golden section" ( The whole always consists of parts, parts of different sizes are in a certain relationship to each other and to the whole. ZS - the division of a continuous quantity into two parts in such a ratio in which the smaller part relates to the larger one as much as the larger one to the entire value; the form, which is based on a combination of symmetry and the golden ratio, contributes to the best visual perception and the appearance of a sense of beauty and harmony. Zeising did a great job. He measured about two thousand human bodies and came to the conclusion that the golden ratio expresses the average statistical law. The division of the body by the navel point is the most important indicator of the golden ratio. The proportions of the male body fluctuate within the average ratio of 13: 8 = 1.625 and approach the golden ratio somewhat closer than the proportions of the female body, in relation to which the average value of the proportion is expressed in the ratio 8: 5 = 1.6. In a newborn, the proportion is 1: 1, by the age of 13 it is 1.6, and by the age of 21 it is equal to the male. The proportions of the golden section are also manifested in relation to other parts of the body - the length of the shoulder, forearm and hand, hand and fingers, etc. When the numbers expressing the lengths of the segments were obtained, Zeising saw that they constituted a Fibonacci series - a sequence of numbers in which each subsequent number is equal to the sum of the previous two numbers.)

Finding these points on a person's face is accompanied by complex calculations and constructions. Facilitated by the use of Hering's compass, which automatically determines the interalveolar height.

Method of determination according to Wadsworth-White: equality of distances from the middle of the pupils to the line of closing of the lips and from the base of the nasal septum to the lower part of the chin.

The easiest way is to divide the face into 3 parts: upper, middle and lower. It is believed that with age remains relatively unchanged middle department, with which the lower section is compared.

Anatomical and physiological- determination of the height of the relative physiological rest of the lower jaw and the presence of a free interocclusal gap. Methodology: the patient is involved in a conversation, asked to count. Upon completion, the lower jaw is set in the resting position of the masticatory muscles, and the lips, as a rule, close freely. In this position, the doctor measures the distance between two points applied to the skin at the base of the nasal septum and on the protruding part of the chin. The wax templates are then inserted into the mouth and the patient is asked to close them. The distance is measured again - it should be less than the resting height by 2-3 mm.

Central occlusion- multiple fissure-tubercular contacts of the dentition with the central position of the TMJ heads in the articular fossae.

- a state of relative physiological rest (minimal masticatory tone and complete relaxation of facial muscles; occlusal surfaces of the teeth are separated by 2-4 mm)

- anterior occlusions (sagittal movements of the lower jaw)

- lateral occlusions (right and left)

- distal contact position of the mandible.

Signs of central occlusion

Main:

1) dental - closing of teeth with the greatest number of contacts

2) articular - the head of the condylar process of the lower jaw is located at the base of the clivus of the articular tubercle of the temporal bone

3) muscular - simultaneous contraction of the temporal, chewing and medial pterygoid muscles (muscles that lift the lower jaw)

Additional:

1) the midline of the face coincides with the line passing between the central incisors

2) the upper incisors overlap the lower ones by 1/3 of the crown (with orthognathic bite)

3) each tooth has two antagonists: the upper one is of the same name and distal (except for 11, 21), the lower one is of the same name and medially (except for 38, 48)

Directly related to the central occlusion are the interalveolar height and the height of the lower third of the face. The interalveolar height is understood as the distance between the alveolar processes of the upper and lower jaws in the position of central occlusion. With existing antagonists, the interalveolar height is fixed by natural teeth, and when they are lost, it becomes unfixed and should be determined.

From the point of view of the difficulty in determining the central occlusion and interalveolar height, A.I. Betelman identified four options for the complexity of determining central occlusion:

In the first variant, when there are three or more pairs of antagonist teeth in the alveolar processes of the upper and lower jaws, located as follows: at least one in the front, and the other two, in the lateral areas. In this case, as a rule, only the height is determined from the position parameters of the CO. Plaster models of prosthetic beds at the laboratory stage are compared in the position of the CO according to dental features and facets of the worn occlusal surfaces of antagonist teeth or using occlusal impressions;

Starting from the second variant of the complexity of determining the position of the CO, when less than three pairs of antagonists are located in the alveolar processes of the upper and lower jaws, it is necessary to first make bite patterns at the laboratory stage and determine the position of the CO at the clinical stage.

And only then, with the help of bite patterns, compare the models of prosthetic beds in the position of central occlusion (central ratio);

The most difficult option for determining the position of the CA of the jaws is the third, when there is not a single pair of antagonists or they are located only in two areas of the jaws) and the fourth (with complete adentia) options for the location of dentition defects.

In the second, third and fourth variants of the location of defects in the dentition of the upper and lower jaws, in order to determine the position of the CA, it is necessary in all cases to always make bite templates

The definition of central occlusion is one of the most important points in prosthetics. In the complete absence of teeth, the central ratio of the jaws is determined.

To determine the central occlusion (the central ratio of the jaws) means to determine the position of the lower jaw in relation to the upper in three mutually perpendicular planes: sagittal, vertical and transversal. That is, the doctor must convey to the dental technician as accurately as possible the conditions that this particular patient has.

Used in daily practice anatomical and physiological method for determining the central occlusion (the central ratio of the jaws). The physiological basis of this method is the fact that the occlusal height is less than the height of relative physiological rest by 2-4 mm.

The doctor does the following:

a wax base with an occlusal roller is made. In it, the basis is the basis of the future prosthesis. And the roller is future teeth.

The upper base is put on and the occlusal ridge is formed as follows: The upper lip does not protrude or recede. Depending on the length of the upper lip, the edge of the upper ridge can protrude from under it by 2 mm, be at its level, or be located 2 mm above the edge of the upper lip. In general, the cutting edges of the upper central incisors, when the mouth is closed, coincide with the line of closing of the lips, and when speaking, they protrude from under the edge of the upper lip by 1-2 mm. A person looks older than his age if the cutting edges of the upper incisors are not visible when smiling. The height of the upper occlusal ridge is determined based on these considerations. After introducing the template into the oral cavity, the patient is asked to close his lips - the closure line is marked on the roller. Check the height of the roller with a half-open mouth - the edge should protrude by 1-2 mm.

A prosthetic plane is formed on the upper roller (a plane that imitates the cutting edges and the occlusal surface): in the frontal section, the prosthetic plane is formed parallel to the pupillary line, in the lateral sections - parallel to the nasal line (Camper horizontal). For this, two rulers are taken: one is installed on the occlusal surface of the roller, the other is placed on the pupillary line (frontal section) and nasal (the base of the wing of the nose - the middle of the ear tragus) lines (lateral section). Check the parallelism of the rulers, if necessary, adjust the rollers.

The height of the lower part of the face in a state of relative physiological rest is determined (it is approximately equal to the height of the middle part of the face). To determine the state of relative physiological rest, anatomical landmarks are also used: the lips close freely, without tension, the nasolabial and chin folds are slightly pronounced, the corners of the mouth are slightly lowered.

Approximately calculated the height of the lower part of the face in the position of central occlusion (height at rest minus 2-4 mm).

Wax bases with rollers are inserted into the mouth and the lower roller is adjusted to the upper one until the calculated height of the lower face in the position of central occlusion is reached.

The fixation of the central occlusion is carried out (the rollers are fastened together).

Anatomical landmarks are applied that indicate the technique of how to position artificial teeth: The median line is drawn as a continuation of the central line of the face, the line of fangs is drawn vertically from the wings of the nose, horizontal line carried out along the border of the upper lip with a smile.

The bases are put on the model and sent to the laboratory in a fastened form.

ADD.1 Production of wax templates with bite ridges in the complete absence of teeth.

Methodology:

1. Cut off a piece of wax from the plate with a warm spatula, required in size, according to the model.

2. Moisten the model with water.

3. Heat up the cut wax plate on one side.

4. Attach the reverse unmelted side to the model.

5. Very accurately squeeze the model with your fingers, starting on the upper jaw from the palate, and on the lower jaw - from the lingual side and further outward.

6. Strengthen the bases with an orthodontic wire with a diameter of 0.8 mm and a length of 2 cm, bending it along inside and according to the shape of the alveolar processes, heat up and immerse in the base, topping up with boiling water.

7. Heat up the second plate of wax and roll it tightly into a roller.

8. Attach the resulting roller strictly in the center of the alveolar process to the wax template.

9. Pour the roller to the base with boiling wax, forming sheer vestibular surfaces, adhering to the dimensions: height - 1.5 cm, width = 1 cm.

10. Make the surface of the rollers smooth, make a bevel in the distal sections.

11. Trim the wax base along the appropriate borders.

12. Remove from the model and smooth the wax along the borders.

Bite Roll Requirements:

1. The borders of the wax templates must match the borders of the prostheses.

2. Templates should fit snugly on models.

3. The wax roller should be located strictly in the middle of the alveolar process, the width in the frontal section is 0.8 - 1.0 mm, in the lateral section 1 - 1.5 cm.

Method for determining the central ratio of the jaws in the complete absence of teeth on both jaws:

1. Check that the bite block wax templates meet the requirements.

a. The borders of the wax templates must match the borders of the prostheses.

b. Templates should fit snugly to models.

c. The wax roller should be located strictly in the middle of the alveolar process, the width in the frontal section is 0.8 - 10.0 mm, in the lateral section 1 - 1.5 cm, 2 - 3 mm above the remaining teeth.

2. Determine the interalveolar height by the anatomical and physiological method:

a. Use paper or a ruler. An arbitrary point is applied to the patient's chin.

b. Then, in a state of physiological rest, this point is transferred to a piece of paper or a ruler.

c. On a ruler or paper, from 1 to 4 mm are taken away, depending on the age of the patient (the tone of the masticatory muscles), to obtain the bite height.

3. With a dental spatula, the frontal section of the upper bite ridge is cut parallel to the pupillary line, making sure that it is 0.5–1 mm below the edge of the upper lip.

4. Cut the side sections of the bite roller parallel to each other and the tragonasal line.

5. We make locks on the surface of the roller.

6. We cut the lower bite roller, achieving its contact over the entire plane with the upper roller, the height of the rollers should correspond to the height of physiological rest (that is, 2-3 mm higher than the bite height) - we control it with a ruler.

7. Using a dental spatula and an alcohol burner, the bite rollers are heated by 2–3 mm.

8. Heated bite rollers are introduced into the oral cavity and close the dentition in the position of central occlusion.

9. After the wax has hardened, and after checking the correct fixation of the bite height and the central ratio of the jaws, reference lines are applied to the rollers: the median line, the line of closing of the teeth, the canine line, the smile line.

10. Wax patterns are removed from the mouth.

Requirements for bite ridges after determining the central occlusion:

1. Bite ridges should fit snugly on models.

2. Bite blocks must be securely glued together.

3. Bite blocks should securely fix the models in the position of central occlusion.

4. On the bite rollers, reference lines should be clearly drawn: the median line, the line of closing of the teeth, the line of fangs, the line of a smile.

ADD.2 use wax templates with bite or, as they are sometimes called, occlusal rollers. On plaster models, along the boundaries marked with an indelible pencil, templates, or bases, are first made from dental wax. In the area of defects in the dentition, rollers are installed, the width of which in the lateral sections should be no more than 1-1.2 cm, and in the area of the front teeth - 0.6-0.8 cm. The height of the rollers in the area of \u200b\u200bthe front teeth is about 1.5 cm , in the region of the molars 0.8 cm and should be 1-2 mm more than the height of the teeth. And the occlusal surface is formed approximately along the occlusal plane of the entire dentition.

With a fixed bite and the presence of antagonists at the occlusal roller, the central occlusion is determined as follows. Wax templates with bite rollers are treated with alcohol, rinsed in cold water, inserted into the mouth and the patient is asked to slowly close his teeth. If the rollers interfere with the closing of the antagonist teeth, the amount of separation of the teeth is determined and the wax is cut off by about the same amount. If, when the teeth are closed, the rollers turn out to be disconnected, then, on the contrary, wax is layered on them until the teeth and rollers are in contact. The position of the central occlusion is assessed by the nature of the closing of the teeth, typical for each type of bite. To accurately establish the lower jaw in the central ratio, special functional tests are used. The best results are obtained by swallowing. However, in some patients with restless behavior, it is useful to insure this test as follows. Before asking the patient to make a swallowing movement, it is necessary to achieve relaxation of the muscles that lower and raise the lower jaw. For this, the patient is asked to open and close his mouth several times, relaxing the muscles as much as possible. At the moment of closing, the lower jaw should move easily, and the teeth should be set exactly in the position of central occlusion. After preliminary training and achieving the usual closure, strips of wax are placed on the occlusal rollers, glued to the roller and heated with a hot dental spatula. Wax rollers with bases are introduced into the oral cavity and the patient is asked to close his teeth in the same way as during training, i.e. the muscles that lift the lower jaw should be relaxed, and in the final phase of closing the patient should make a swallowing movement. On the softened surface of the wax, impressions of the teeth of the opposite jaw are obtained, which serve as a guide for setting plaster models in the position of central occlusion.

If the antagonists are the occlusal ridges of the upper and lower jaws, you should first achieve simultaneous closing of the teeth and ridges, pre-cutting or layering the wax. It is necessary to pay attention to the location of the occlusal plane of the ridges. It should coincide with the occlusal plane of the dentition or be their continuation. The occlusal plane of the ridges is a guideline when modeling the surface of the closure of prostheses. After determining the height of the rollers on the occlusal surface of the upper roller, I do "?: wedge-shaped cuts at an angle to each other. A thin layer of wax is cut off from the lower roller and a new, preheated strip is glued in its place. The patient is asked to close his teeth, controlling the accuracy of setting the lower jaw to the position of central occlusion. The heated wax of the lower roller fills the cuts on the upper one and takes the form of wedge-shaped protrusions. The rollers are removed from the oral cavity, cooled, the clarity of the resulting imprints is assessed and reintroduced into the mouth for a control check of the accuracy of determining the central ratio of the jaws. If the protrusions enter the wedge-shaped notches, and the signs of closing of the teeth correspond to the position of the central occlusion, therefore, the clinical reception satisfies all the necessary requirements.Convinced of this, the doctor removes the rollers from the oral cavity, cools and installs on the model.Before plastering in the articulator, the models are made in position of the central occlusion and compare the resulting ratio with the nature of the closing of the teeth in the oral cavity. Once again making sure of the accuracy of the manipulations, the models are fixed in the articulator for the next stage of manufacturing a partial removable lamellar denture.

The technician fixes the models in an articulator or occluder.

An occluder is a device that reproduces only the vertical movements of the lower jaw (opening and closing the mouth).

Occluders consist of two wire or cast frames hinged to each other. The lower frame is bent at an angle of 100 - 110 degrees and imitates the angle and branch of the lower jaw. In the rear section of the frame there is a platform for the stop of the pin holding the interalveolar height.

The upper frame is located in a horizontal plane and has a vertical pin resting against the platform on the lower frame. Plastering models in the occluder is performed as follows.

Preparing the model for plastering: making cuts on their base and soaking in water, create a gypsum slide on the table, lower the lower frame of the occluder into it, and, covering it completely with gypsum, place the models in the space of the occluder. At the same time, attention is paid to the position of the models relative to the front edge of the occluder frames, its middle line and the plane of the table. Having covered the lower model with gypsum, a gypsum slide is created on the basis of the upper model and the upper frame of the occluder is lowered. With non-fixed bite height, it is necessary to ensure that the height pin is supported on the platform of the lower frame of the occluder. When the plaster hardens, cut off its excess, remove the wax strips that hold the models together, and open the occluder. Then the wax bases with occlusal rollers are removed, and the relative position of the models in the central occlusion remains fixed in the occluder.

Articulators - these are mechanical devices that are designed to reproduce the movement of the lower jaw relative to the upper jaw.

There are various articulators, but they all fall into four main types:

Simple articulated articulators;

Mid-anatomical or linear-planar;

Semi-adjustable;

Fully adjustable or universal.

In a simple articulated articulator, only articulated movements can be performed, and any lateral movements are excluded. Therefore, such an articulator can only be used as a visual aid for students.

In the mid-anatomical articulators, the value of the articular and incisal angles is fixed. You can change the relationship of the incisors, but there is no way to adjust the lateral displacements. Mid-anatomical articulators can be used to fabricate single crowns and, if necessary, to fabricate a complete denture for edentulous jaws.

The Girrbach mid-anatomical articulator has a fixed Benet angle of 20*, a set angle of the sagittal articular path is 35*.

Semi-adjustable articulators allow adjustment of the Bennett angle and the angle of the sagittal articular path. The intercondylar distance is usually 110 mm. Semi-adjustable articulators contain mechanisms that reproduce the articular and incisal paths, which can be adjusted according to averaged data, as well as according to the individual angles of these paths obtained from patients.

Fully adjustable or universal articulators - adjusted according to individual data of the position of the jaws, which are transferred to the articulator using the facial bow.

Muscular signs: muscles that lift the lower jaw (chewing, temporal, medial pterygoid) simultaneously and evenly contract;

Articular signs: articular heads are located at the base of the slope of the articular tubercle, in the depths of the articular fossa;

Dental signs:

1) between the teeth of the upper and lower jaws there is the most dense fissure-tubercular contact;

3) the middle lines between the upper and lower central incisors lie in the same sagittal plane;

4) the upper teeth overlap the lower teeth in the anterior region no more than ⅓ of the crown length;

5) the cutting edge of the lower incisors is in contact with the palatine tubercles of the upper incisors;

6) the upper first molar merges with the two lower molars and covers ⅔ of the first molar and ⅓ of the second. The medial buccal tubercle of the upper first molar falls into the transverse intertubercular fissure of the lower first molar;

Signs of anterior occlusion

Muscular signs: this type of occlusion is formed when the mandible moves forward by contraction of the external pterygoid muscles and horizontal fibers of the temporal muscles.

Articular signs: articular heads slide along the slope of the articular tubercle forward and down to the top. The path they take is called sagittal articular.

Dental signs:

1) the front teeth of the upper and lower jaws are closed by cutting edges (butt);

2) the midline of the face coincides with the midline passing between the central teeth of the upper and lower jaws;

Signs of lateral occlusion (on the example of the right one)

Muscular signs: occurs when the lower jaw is displaced to the right and is characterized by the fact that the left lateral pterygoid muscle is in a state of contraction.

With lateral occlusion, the lower jaw is displaced by the size of the tubercles of the upper teeth. Dental signs:

1) the central line passing between the central incisors is “broken”, displaced by the amount of lateral displacement;

All types of occlusion, as well as any movement of the lower jaw, are performed as a result of the work of the muscles - they are dynamic moments.

Bite

Bite- this is the nature of the closing of the teeth in the position of central occlusion.

Bite classification:

1. Physiological bite, providing a full-fledged function of chewing, speech and aesthetic optimum.

a) orthognathic- characterized by all signs of central occlusion;

in) physiological prognathia (biprognathia)- the front teeth are tilted forward (vestibularly) along with the alveolar process;

G) physiological opistognathia- front teeth (upper and lower) tilted orally.

2. Pathological bite, in which the function of chewing, speech, and the appearance of a person are impaired.

a) deep

b) open;

c) cross;

d) prognathism;

e) progeny.

The beauty of our smile depends on the health of the dentition. This is an important part, but it is not enough. Even healthy teeth can be placed incorrectly in the oral cavity, forming a malocclusion. The upper and lower jaws, namely the movement of the latter, are involved in the process of human life. Chewing, swallowing, pronunciation of sounds - all this is impossible without its normal work. First and last action has its own peculiarity, which is directly related to the correct closure of the teeth of the upper and lower jaws. This phenomenon is called occlusion.

Occlusion of teeth

What is occlusion?

This is a Latin name, translated means closing, clutch. Occlusion in dentistry refers to the work of the upper and lower jaw, their connection. For the common man it is familiar. But it's not quite the same thing. The concepts of functional occlusion intersect with each other and intersect in dental practice. The development of bite and occlusion depends on the genetic predisposition. If such developmental anomalies are not observed in the closest blood relatives, then parents need to monitor their child at the time of the development of the dentition, to prevent the occurrence of bad habits. Factors contributing to the developmental anomalies of the jaw cannot be ignored. These include:

long sucking of a pacifier by a child;
diseases of the nasopharynx;
thumb sucking habit.

Quite often, at the age of 4 years, a child develops the skills of improper swallowing. Dentists often associate such changes with various diseases of the upper respiratory tract. Such an incorrectly formed reflex leads to the development of an incorrect occlusion. If changes are noticed, you should immediately consult a doctor. He will find out the cause, which will prevent abnormal development.

The dentist notices in the early stages of its development. The prescribed treatment should be started as soon as possible. elimination initial changes occlusion is very important, since improper contact of the teeth of the upper and lower jaw affects the chewing process.

Dentists often argue over the definitions of articulation and occlusion. The question is moot. Some argue that articulation represents the process of contact of rows during conversation, chewing and other actions. And occlusion, in their opinion, is the location of the jaws at rest.

Another opinion speaks of the relationship of concepts. So, in their opinion, articulation is the main concept, and bite occlusion is its manifestation. But everyone agrees on one thing, that the processes are the interconnection of the rows of the upper and lower jaws, facial muscles, and joints.

Varieties of occlusion

The dental system is fully formed by the age of 16. But its main formation is associated with the period between 4-6 years of a baby's life. It is during this period that the child develops the functions of chewing, talking, swallowing. The rudiments of the third molar are actively developing. Therefore, it is very important to monitor the development and, if necessary, prescribe the treatment of occlusion in time. Avoid the formation of persistent childhood bad habits associated with the oral cavity. In the process of development in dentistry, temporary and permanent occlusion of teeth is distinguished.

Temporary

There is also another gradation of types of occlusion. Each of them has its own set of characteristics. Types of occlusion are determined by the features of the work of the jaw muscles, joints. Usually, the work of the lower jaw is taken into account.

central occlusion. The muscle groups that are responsible for the closure and position of the jaw bones work correctly. Their actions are coordinated, uniform and smooth. The central occlusion and the central ratio of the jaws determine the arrangement of the rows in the oral cavity. The connection of the teeth occurs with the maximum number of contact. The head and tubercle of the joint are characterized by close proximity to each other. The proximity of the head of the lower jaw to the articular tubercle is characteristic.
Anterior occlusion involves the coincidence of the position of the incisors so that it coincides with the central facial line. It is characterized by a visual protrusion of the lower jaw. This is due to the work of the pterygoid muscles. The front teeth are in close contact with the cutting edges. There is a tubercular touch of the dentition. With anterior occlusion, bite is normally common. Its main difference from the central one is the close location of the head of the lower jaw to the articular tubercles and its forward displacement.
distal occlusion. It is characterized by the position of the rows, in which visually the upper jaw looks larger than the lower. This is an anomaly in many cases. There is underdevelopment of the lower jaw. The nose visually increases, the lips do not close, the chin fold is noticed. Such occlusion of the dentition is of two subspecies: dentoalveolar and skeletal.
Lateral occlusion of the jaw. It is divided into right and left. Judging by the name, it is clear that this form of the disease is characterized by the departure of the lower jaw to one side. When shifting the lower row to the right or left, they contact with the same zone of the upper jaw. The head of the jaw is mobile, does not hold at the base of the joint on the one hand, on the other hand it moves up. This violation of occlusion is accompanied by compression of the pterygoid lateral muscle. The central line of the face and front incisors is shifted to one side.
Deep incisal occlusion has two degrees of developmental anomalies. The first is characterized by cutting tubercular contact between the incisors of the jaws. Deep incisal occlusion in the second stage is marked by a clear lack of contact between these teeth.

Deep bite

Incorrect formation of the dentoalveolar system is diagnosed in early childhood Therefore, it is possible to identify a defect and correct it even at the development stage. This will allow the child to form the correct skills of swallowing, chewing, speaking.

The correct one implies the contact of the upper and lower row. Bite is directly related to occlusion. The upper incisors cover the lower ones. Lateral bite makes the row shift to the side. Often this goes along with lateral occlusion. They also observe if there is an oblique bite. When correct - the arrangement of the teeth in a row correspond to each other. There are such types of bites in dentistry: physiological and pathological groups.

Level bite

It belongs to the physiological group. This is a kind of direct occlusion, when the incisors take the position of being on top of each other. This leads to rapid abrasion of the enamel and gradual destruction of the tooth. With the right bite, the teeth are on top of each other and the upper ones cover the lower ones by 1/3 of the visible part.

Pathological abrasion with a direct bite does not occur immediately, for a person to notice this, a lot of time must pass. But with such an anomaly, there are a number of side defects:

reduction of a third of the lower part of the face;
incorrect or incomplete functioning of the temporal mandibular joint;
violation of diction.

Treatment is determined by the dentist together with the orthopedist. Basically, the unstarted stages of the direct bite are easily corrected in childhood with the help of the installation of braces.

Physiological or correct bite

This is a variation of the natural proportion of the rows of the upper and lower jaws. It provides:

lack of chewing and speech dysfunction;
correct features of the lower part of the head;
healthy condition of teeth and periodontium;
full functioning of the jaw system.

Correct bite

The physiological bite has subspecies that differ in certain deviations from the norm, but are characterized by a physiological occlusal ratio of the upper and lower jaws. These include bites:

progenic;
bioprogenic;
orthognastic;
direct bite.

The last two subspecies are considered in dentistry to be the closest deviations from the norm. Therefore, often a dentist, having examined the oral cavity, may not prescribe treatment, since minor discrepancies with the norm are not a problem and do not require a solution.

Deep bite

It has a pronounced visual defect, when the upper row of teeth overlaps the lower row by more than half of the crown. A deep bite makes it difficult to bite and chew food. The oral cavity is reduced, which leads to difficulty swallowing.

Such a bite leads to abrasion of the upper row of teeth, since a large load falls on them in the process of eating. The work of the temporomandibular joint is also modified. When the jaw moves, characteristic clicks appear in it. There are frequent headaches.

But the most frequent Negative consequences incorrect deep bite is an injury to the mucous membrane of the oral cavity. Such pathological changes often lead to inflammation of the gums, which leads to loss of teeth.

It should not be forgotten that it is easier to correct occlusion while the jawbone is being formed. Therefore, it is important that the diagnosis occurs on time and timely treatment will give its positive results. Dentistry today has a mass of tools and techniques that are used for one purpose, to make your smile healthy.

In the central ratio of the jaws, there is a physiological relative position of the articular heads, discs, fossae and a uniform load on all structures of the TMJ.

Determination of the central ratio of the jaws is necessary when:

Occlusal analysis and evaluation of the topography of the TMJ elements before orthodontic and orthopedic treatment.
terminal defects of the dentition;
decrease in occlusal height;
suspicion of displacement of the lower jaw into the position of "forced" occlusion;
loose ligamentous apparatus of the temporomandibular joint;
prosthetics of edentulous jaws;
non-fixed bite, when there are not enough antagonistic teeth;
wear of teeth for drawing up a plan for occlusal reconstruction;
before and after the preparation of a large number of teeth in order to reconstruct the occlusion;
to detect supercontacts in the rear contact position.

Central ratio of the jaws and the hinge axis of the articular heads

articulated axle- a starting point for determining the central ratio of the jaws and installing the jaw models in the articulator.

When finding the hinge axis, the laws of mechanics are taken into account, which determine that the movement of any body (in this case, the lower jaw) in three planes can only be studied if the axis of rotation of the body is established and can be reproduced. The articulating axis of the articular head meets these requirements.

Hinged axis - an imaginary fixed horizontal axis connecting the centers of the articular heads with their simultaneous and uniform hinge movement. Such movements of the articular heads occur at the beginning of the opening of the mouth, if the lower jaw is in a central relationship with the upper jaw. In this case, the median point of the central incisors describes an arc about 12 mm long - the arc of the articulation of the lower jaw (Fig. 8.1).

With a greater opening of the mouth, the lower jaw shifts forward, and its trajectory of movement curves forward. If the mouth closes from this anterior position, then an error occurs in determining the central ratio - the mesial displacement of the lower jaw.

Rice. 8.1. Trajectory of mouth opening in the sagittal plane.
a - the arc of the articulation of the lower jaw when opening the mouth up to 12 mm (A); b - deviation of the trajectory of the movement of the lower jaw with a greater opening of the mouth (AO anteriorly and displacement of the articular head (H).

Thus, in the central ratio, the articular heads rotate around a fixed axis. At the same time, the lower jaw descends and rises, being in a central relationship with the upper jaw. When the hinge axis is shifted forward or backward, the lower jaw is not in a central relationship with the upper jaw.

If the occlusion is reconstructed when the mandible is moved forward or backward (an error in determining the central ratio), the articular heads also move in the corresponding direction.

The hinge axis is determined arbitrarily or with the help of special devices: axiographs, hinge axis localizers, rotographs. Such devices are an integral part of many devices for recording movements of the lower jaw.

The hinge axis is projected onto the skin of the face along a line from the middle of the ear tragus to the corner of the eye, 11 mm anterior to the tragus and 5 mm below this line. The projection of the hinge axis on the skin of the face is used when installing the facial bow in order to orient the models of the jaws between the frames of the articulator, which is an important condition for the movements of the patient's lower jaw to be similar to those in the articulator.

Central jaw relation, central and "habitual" occlusion

Central occlusion- multiple fissure-tuberous contacts of the dentition with the central position of the articular heads in the articular fossae during contraction of the muscles that lift the lower jaw.

The central position of the articular heads is the symmetrical position of both heads with the physiological mutual arrangement of the head-disk-fossa complex.
Pathological processes in the dentition (caries, wear of hard dental tissues, secondary deformations after tooth loss, etc.) lead to the loss of central occlusion and the formation of “forced”, “habitual” occlusion with the maximum possible contact of teeth. In this case, the articular heads are displaced, there is no correct position of the head-disc-fossa complex, and in determining the central relationship of the jaws, occlusion is a secondary factor in obtaining optimal positioning of the mandible in relation to the maxilla.

According to modern ideas If there are no complaints in the presence of "habitual" occlusion, it is not necessary to change the position of the articular heads, especially with a large amount of work and in older people.

Central relation of jaws and temporomandibular joint

In the central ratio of the jaws, the articular heads are located at the base of the slopes of the articular tubercles. The articular discs are located between the articular surfaces, even out the discrepancy between the sizes and shapes of the articular elements (heads and fossae), absorb masticatory pressure, the vector of which is directed upward and forward, towards the articular tubercle.
The central region of the disk, which carries the load, is formed by dense fibrous tissue, has no vessels and sensitive nerve endings.

In the tissues along the periphery of the “supporting” zone of the disc, there are vessels and sensitive nerve endings. Pressure on these tissues causes discomfort and pain. If the articular head and disc are not in the correct position, then the lower jaw is not in a central relationship.

Discoordination of masticatory muscle function, dislocation of the articular disc, deformation of the articular surfaces, internal damage to the elements of the temporomandibular joint prevent the determination of the central ratio of the jaws. In these cases, preliminary treatment is necessary (occlusive splints, physiotherapy, selective grinding, etc.).

Signs of a violation of the relative position of the head and disk:

Clicking in the joint when opening and closing the mouth;
pain when trying to put the lower jaw in the position of the central ratio;
unable to achieve muscle relaxation.

Muscle relaxation- the main condition under which the central ratio can be correctly determined. The exception is the registration of the Gothic angle by the intraoral method, when the recording is needed for diagnosis and the use of "temporary" medical devices.

All modern methods definitions of central ratio are based on the fact that in a relaxed patient, the articular heads are self-centered by a neuromuscular mechanism, if there are no symptoms of musculo-articular dysfunction.

Methods for determining the central ratio of the jaws

Considering the emergence of methods for determining the central ratio of the jaws in historical terms, one can see a trend in the transition from static methods to functional ones. The most famous static method is anthropometric, based on the principle of proportional division of the face into 3 parts.

Functional methods are based on the principle of using speech, swallowing, chewing load.

The phonetic method involves conducting phonetic tests: the reference point is the size of the interocclusal space at the time of pronouncing speech sounds (for example, the sound “s”). However, this value varies over a wide range.

When the tip of the tongue is touched to the palate, the tension of the muscles that protrude the lower jaw is reflexively removed, and it is set to the correct mesiodistal position. Multiple opening and closing of the mouth (amplitude up to 12 mm) along the articulated arch contributes to the establishment of the lower jaw in a central relationship.

The electrophysiological method is difficult for everyday clinical practice, and the results obtained are difficult to evaluate. The position of the physiological rest of the masticatory muscles depends on many factors and, like the other methods mentioned above, can be used as an additional guide.

The method for determining the central ratio is a combination of gnathodynamometry, indicating an increase in the force of compression of the jaws, and graphic registration of the movements of the lower jaw using a bite device. The authors of this method [Tsimbalistov A.V. et al., 1996] developed the AOCO device, which includes a capacitive strain gauge, an amplifying and measuring unit, a battery pack, a charger and parts of an intraoral device (support plates, pins 6 to 23 mm long).

By changing the length of the pin, the doctor determines the maximum value of the compression force, the interalveolar distance, and then records the trajectory of the lower jaw from its extremely posterior position forward, to the right and to the left. Anterior to the apex of the resulting angle, a pin is installed and the central ratio of the jaws is fixed in this position. The authors called this method functional-physiological and use it to determine the central ratio in edentulous patients with non-fixed occlusion. The absence of a spring pin, however, does not allow using the method with preserved dentitions, where separation of the latter is not required. There is also an opinion that the maximum jaw compression force is recorded not during, but before the onset of maximum contact. This prevents excessive stress on the periodontium and TMJ.

If there are four reference zones (between premolars and molars, two zones on the left and on the right), it is possible to compare the jaw models in a central relationship without bite blocks.
If there are three or fewer support zones and there is no musculoskeletal dysfunction, the central ratio is determined by plastic bases and hard wax rollers. Bases are refined with eugenol paste to reduce pressure on the mucous membrane.

For symptoms of musculoskeletal dysfunction alternative method determining the central relationship is funktsiography using a bite device.

Before determining the central relationship of the jaws, supercontacts in centric and eccentric occlusions should be identified and eliminated.

If at the first contact of the teeth in the central ratio, for example, a supercontact is detected, then this area of the occlusal surface is marked with articulation paper and ground off.

Determining the central ratio of the jaws involves the following tasks:

Set the lower jaw in the position of the central relationship with the upper jaw (manual techniques);
correctly make interocclusal blocks;
correctly fix the jaw models in the articulator using the obtained blocks.

Prerequisites for the correct determination of the central ratio: relaxation of the masticatory muscles, fixation of the patient's head on the headrest, vertical position of the head.

Light touching of the chin with a vertical position of the head contributes to the non-muscular orientation of the position of the lower jaw. At the same time, they do not exert pressure on the jaw, the masticatory muscles should be completely relaxed, and iatrogenic compression of the articular structures is excluded.

Manual tricks. To set the lower jaw in the central ratio, various manipulations are used (passive methods).

The doctor stands in front of the patient. The patient's head rests on the headrest. Thumb doctor's hands - on the chin or on the alveolar process at the lower central incisors, index finger - under the chin or at the lower edge of the body of the lower jaw. Articulated opening-closing movements are made within 12 mm without contact of the teeth and without pressure on the chin. The doctor's finger controls unwanted movements of the lower jaw forward or to the side. If the articulated movements occur in the same way and without lateral displacements, then the central ratio of the jaws is set correctly. If the lower jaw is set in different positions, then additional techniques are used: the patient is asked to swallow saliva, reach the sky with the tip of the tongue, etc. (Fig. 8.2, a).

The doctor stands behind the patient, places his thumbs on his chin, and the rest - in the area of \u200b\u200bthe corners of the lower jaw on the right and left. The thumbs exert a slight downward pressure to separate the teeth, and the remaining fingers direct the angles of the jaw up and slightly forward (P. Dawson's technique) (Fig. 8.2, b).

Rice. 8.2. Manual techniques for setting the lower jaw in the position of the central ratio of the jaws.
a - the correct position of the fingers of the doctor's hand, which controls the movement of the lower jaw along the hinged arc of opening and closing the mouth (there is no hand pressure!); b - the Dawson technique orients the articular head in the anteroposterior position, preventing its displacement backwards.

In this case, the patient makes small hinged movements of opening and closing the mouth.

Rice. 8.3. Bite blocks that pre-program job rework.

If using the above manual techniques it is not possible to put the lower jaw in the central ratio, then this may be due to the tension of the masticatory muscles, muscular-articular dysfunction.

To relax the chewing muscles, you can use:

Cotton rolls that are placed between the premolars on the left and right and force the patient to bite them for 5 minutes. This causes muscle fatigue and subsequent muscle relaxation;
hard blocks in the area of the front teeth (made of plastic, hard wax), separating the lateral teeth;
relaxation splints;
physiotherapy;
biofeedback method;
myogymnastics, autotraining;
drug therapy(small tranquilizers).

To fix the central ratio can be used:

Biting plates made of refractory wax and other thermoplastic materials;
front bite blocks made of plastic, which are installed in the area of the incisors, separating the lateral teeth;
plastic bases for terminal, included defects in the dentition of a large extent;
bite devices.

Materials for fixing the central ratio of the jaws. Determination and fixation of the central relationship of the jaws is the basis for the successful manufacture of prostheses and occlusal splints. The use of base soft wax, one-sided bite blocks, impression silicone (Fig. 8.3) “programs” occlusion correction on finished prostheses and their rework in advance. Impression silicone "clears" fissures that are not reproduced on the model, therefore, using blocks of this material, it is impossible to accurately establish models in the occlusion.

Good results are obtained by:

Refractory wax ("Beauty Pink wax", "Bite wax Moyco", "Aluwax", etc.);
occlusal A-silicones ("Futar occlusion", "Kettenbach", "Regidur", "Bisico", etc.);
self-hardening plastics;
light curing composites.

Refractory wax softens at 52°C. The wax plate is folded 2 times, applied to the model of the upper jaw. The edges of the plate are cut with scissors so that it is 3 mm to the teeth, they are pressed along the occlusal surface, inserted into the oral cavity, the lower teeth slightly bite the plate.

Thus, a basis for registering the central ratio is obtained. Then the plate is slightly warmed up, the fit to the upper teeth is specified. The aluvax plate is divided lengthwise into parts, preheating it in warm water. A flagellum is made from one strip. The end of the flagellum is heated on fire and the mass is applied to the imprints of the lower teeth from canine to canine on the main wax plate.

If a uniform imprint is not obtained, aluvax is added. Aluvax is then applied to the area of the premolars and the imprints of the lower teeth are obtained again. For the third time imprints of molars are obtained. The plate is removed, the excess mass is cut outward from the fissures so as not to damage the contact points of the teeth. Uniform imprints of the tops of the tubercles should remain on the plate. chewing teeth and cutting edges of incisors.

It is possible to use the method of two-stage obtaining of imprints of teeth. A plate of wax, folded in two layers, is placed between the upper fangs, biting with the lower teeth. After the frontal wax block hardens, a softened strip of wax is placed between the teeth in the lateral areas, the patient closes the jaws again without manual intervention by the doctor.

Gradual obtaining of occlusal impressions is necessary, since, given the articulation in the joint when closing the mouth, the distance between the jaws in the region of the posterior teeth is less than in the region of the anterior teeth. Therefore, while obtaining occlusal prints, the bite material is crushed in the region of the lateral teeth and loose contact in the region of the anterior teeth.

The moment of determining the central ratio of the jaws with a plate of refractory wax is shown in fig. 8.4.

In addition to hard wax, individual plates made of self-hardening plastics (Pekatrey, Formatrey, Ostron 100, Unifast, etc.) can be used.

These plates are made in an articulator with minimal separation of the teeth and held for at least 24 hours to eliminate the residual stress that occurs during the polymerization process.

Rice. 8.4. Determination of the central ratio of the jaws.

Any blocks should be as thin as possible, not be deformed and fit exactly on the model.

Zinc-eugenol paste, "Temp Bond" or aluvax is applied to the plastic plate to obtain impressions of the teeth. The impressions of the teeth should be small in area, uniform and obtained without pressure. First, the accuracy of the fit of the plate on the upper jaw of the patient is checked, inaccuracies are eliminated. Then, imprints of the teeth of the lower jaw are obtained in a central ratio with a vertical position of the head and body. After hardening of the imprints of the teeth, the patient is asked to close the jaws several times in a central ratio. The doctor assesses whether there is no lateral displacement of the lower jaw, whether the actual masticatory muscles are evenly tensed when closing. Registration material should not have perforations.

In the absence of a large number of teeth, plastic bases are used to determine the central ratio of the jaws.

Rice. 8.5. Rigid bite front block to determine the central ratio of the jaws (scheme).

The central ratio of the jaws is fixed with wax, zinc-eugenol paste (for example, Temp Bond, Kerr), self-hardening composite mass (for example, Luxatemp Automix, DMG). The bases should fit exactly on the palatal/lingual side of the teeth and, if possible, overlap the occlusal surface.

Front hard block. To control the correct installation of the lower jaw in the position of the central ratio, before using manual techniques, it is recommended to make front rigid blocks in the area of the incisors that prevent the closing of the lateral teeth - “Jig of Lucia”) (Fig. 8.5). After the material has hardened and the block has been corrected, the central relationship of the posterior teeth can be fixed with bite blocks of occlusion registration materials. The sequence of manufacturing rigid anterior bite blocks: a small ball of dough-like plastic is pressed against the upper central incisors so that the plastic completely covers the palatine and partially vestibular surfaces. The lower jaw is set in the position of the central ratio, while the lower incisors are imprinted on the lower surface of the block.

After the plastic has hardened, the block is corrected: a horizontal platform is formed at the point of contact of the lower incisors with the block. After checking the correctness of determining the central ratio of the jaws, bite blocks are made for the lateral teeth from refractory wax or silicone (Fig. 8.6).

A hard anterior block can be refined with a thin layer of paste ("Super Bite", "Temp Bond") to fit more closely to the upper teeth.

Instead of rigid front blocks, graduated plastic wedges can be used, which are connected to cardboard templates (Sliding-Guide, Girrbach). The wedges create the necessary separation of the posterior teeth, and the templates serve to hold the recording material (Fig. 8.7).

Rice. 8.6. Bite front block made of plastic and side blocks made of occlusal silicone (a). Blocks outside the mouth (b).

After determining the central ratio of the model of the jaws, they are installed in the articulator using the facial arch: first, the model of the upper jaw, and then with the help of occlusal blocks, the model of the lower jaw.

For accurate transfer of models from one articulator to another, it is necessary to set in all articulators (in the clinic and laboratory) the same distance between the mounting plates to which the models of the upper and lower jaws are attached. To do this, use a calibration device (Fig. 8.8).

Graphic methods for determining the central ratio of the jaws. Extraoral graphic methods are carried out using axiographs, rotographs. The essence of such methods is shown in fig. 8.9. The definition of the central ratio is based on finding the points of the hinge axis of the articular heads on the right and left - fixed points during the hinge movements of the lower jaw when opening and closing the mouth.

The axiograph scribe is set perpendicular to the paper template along the hinge axis of the articular head on the left and right at the intersection of two perpendicular lines. When articulating movements of the lower jaw, the end of the writing pin must always be located at the intersection of these lines.

The scribe is fixed on the lower jaw with the help of a para-occlusive spoon, which does not interfere with the contact of the teeth. If the patient has a "habitual occlusion", then by setting the lower jaw in this occlusion, it is possible to determine the direction of displacement of the lower jaw in the sagittal plane. On the axiogram, the points of the hinge axis of the articular heads and the trajectory of the displacement of the lower jaw to the position of habitual occlusion are determined.

Rice. 8.7. A device for determining the central ratio of the jaws, consisting of graduated wedges (to create the necessary separation of the teeth) and cardboard templates (to hold the recording material) ("Girrbach", Germany).
a - device in the oral cavity; b - outside the oral cavity.

Intraoral methods of graphic registration of the central ratio are carried out using bite devices - "Gnatometer M" ("Bottger", "Ivoclar"), centrofix ("Girrbach").
General principle the use of these devices is a recording of the Gothic angle, at the top of which the desired central ratio of the jaws is determined.

Rice. 8.8. Calibration device for setting the same distance between the mounting plates (and frames) of the articulator.
a - calibration device; b - articulator with installed calibration device.

The recording of the Gothic angle is carried out on a plate fixed on the lower jaw (on teeth, hard bases), using a pin fixed on the upper jaw. If the bite device pin is located at the top of the gothic angle, then the articular heads are centered in the TMJ pits, and the lower jaw is located in a central relationship with the upper.

Rice. 8.9. Graphic registration of the central ratio of the jaws by axiography in the sagittal plane.
The line connecting the centers of the articular heads is the hinge axis. The arrow indicates the point of the central ratio of the jaws - the starting position for the start of all movements of the lower jaw. P - anterior movement of the articular head; RL - movement of the articular head to the right; LL - movement of the articular head to the left.

Let us give an example of the use of graphical methods for determining the central ratio of the jaws.

Patient P., 35 years old, complained of inconvenience when chewing and closing the jaws, sometimes pain in the parotid-masticatory region on both sides, more in the evening. These phenomena were associated with the manufacture of bridge prostheses.

Objectively: there are bridges on the upper and lower jaws on the left and right, supported by premolars and molars (Fig. 8.11, A). When opening the mouth - displacement of the lower jaw to the left (deflection). Palpation of the masticatory muscles proper and external pterygoid muscles is painful (more on the right).

In habitual occlusion, there are multiple even contacts of the teeth on the right and left, functional occlusion without features. The bite device was mounted in the Gnatomat articulator (Fig. 8.11, B). The ratio of the jaws was determined with a rigid pin (recording of the Gothic angle with separation of the dentition). Then, the occlusal movements of the lower jaw were recorded with a spring pin (Fig. 8.11, B).

The functionograph's pin is mounted on the top of the Gothic corner and fixed in this position by a perforated plate. The central relationship of the jaws with the functionograph before and after the introduction of the Regidur occlusal silicone into the region of the posterior teeth is shown in Fig. 8.11, G.

Two casts were sent to the laboratory, an adapter with a fork of the facial bow, as well as bite blocks (Fig. 8.11, E) for the manufacture of new prostheses.

Features of determining the central ratio of the jaws in the complete absence of teeth. Since the central ratio of the jaws is the location of the jaws in three mutually perpendicular planes, the following tasks are posed at this stage in the manufacture of prostheses:

Determination of occlusal height (interalveolar distance);
finding the position of the lower jaw in the horizontal and sagittal planes.

To solve the first problem, an anatomical and physiological method is used, based on the fact that the distance between the subnasal and mental points during the physiological rest of the lower jaw is 2-4 mm greater than the same distance when the jaws are closed in a central ratio. This task, like the second, is performed using wax rollers on individual rigid spoons or on prosthesis bases made on jaw models after taking impressions with individual spoons.

When determining the central ratio of the jaws using wax bases and rollers, numerous errors are observed (deformation of the bases, displacement of the lower jaw, displacement and departure of the rollers), which is inevitably detected at the stage of checking the design of prostheses and requires re-determination of the central ratio of the jaws.
The anatomical-physiological method, based on the position of the lower jaw during physiological rest, depends on muscle tone, and therefore does not give stable results.

Of particular difficulty are cases of long-term tooth loss, when patients long time used prostheses with a reduced interalveolar distance, the usual anterior or lateral position of the lower jaw.

In the oral cavity, it is difficult to shape the surface of the upper ridge along the Camperian horizontal at the same level on the right and left. A common mistake is the lengthening of the ridges in the distal sections, which leads to a forced shortening of the boundaries of the lower bases in the region of the mandibular tubercles. When determining the position of the lower jaw in the sagittal and transversal directions using traditional methods, errors are also observed, which are detected at the next stage of checking the design of prostheses - the stage of setting the teeth.

Many mistakes can be avoided by using the biofunctional prosthetic system for edentulous patients proposed by Ivoclar. Determination of the central ratio of the jaws is an important part of this system, carried out using the bite device "Gnathometer M" (according to N. Bottger).

Rice. 8.11. Determination of the central ratio of the jaws with a bite device - a functiograph in patient P. A - habitual occlusion. Bridges in the area of molars and premolars on both jaws; B - installation of the functionograph in the "Gnatomat" articulator: a - a recording plate with an adapter is installed on the model of the lower jaw; b - on the model of the upper jaw, a plate with a writing pin located at the level of the first molars (mastication center); c - view of the functionograph from the distal side; C - preparation for registration of the central ratio of the jaws by a functionographer: a - a Gothic angle and a Gothic arc are recorded on the mandibular plate; b - at the top of the Gothic corner there is a hole of a transparent plate for orienting the pin in the central ratio of the jaws; D - the central ratio of the jaws with the functionograph before (a) and after (b) the introduction of occlusal silicone into the region of the lateral teeth; E - two casts, a transition device with a fork of the front arch and bite blocks for the manufacture of new prostheses.

The design of the "Gnathometer M" (Fig. 8.12) differs from that of the functionograph only in the features of fixation on the bases of removable dentures. The one-point contact of the support pin with the mandibular plate provides reflex centering of the lower jaw according to the principle of stable three-point contact: two contacts in the TMJ area and a third contact between the support pin and the recording plate.

The method of intraoral recording of movements of the lower jaw can be used not only to find and fix the central ratio of the jaws, but also as diagnostic method studying the movements of the lower jaw (vertical, horizontal type of chewing, restriction and / or curvature of trajectories).

Advantages of using a bite device to determine the central relationship of the jaws:

The support pin of the bite device, installed in the "center of mastication" (at the level of the second premolars and first molars), ensures reliable centering of the articular heads, uniform distribution of chewing loads on the edentulous alveolar processes, and stabilization of the prosthesis;

Along with determining the central ratio, the bite device makes it possible to record the Gothic angle and thereby assess the state of the masticatory muscles and TMJ.

Rice. 8.12. "Gnathometer M" ("Bottger", "Ivoclar").
1 - plastic mounting plate;
2 - a metal plate on the upper jaw for recording the Gothic angle; 3 - metal plate on the lower jaw with a supporting screw-shaped pin; 4 - patch plates for bite rollers.

Disadvantages of the method:

The lower base with a registration plate limits the space for the tongue;
the manufacture of a bite device requires time and materials.

Contraindications: diseases of the TMJ in the acute stage, neurological diseases, macrolossia.

Installation of "Gnathometer M" is carried out in the following order (Fig. 8.13):

Rice. 8.13. Installation of "Gnathometer M" in the articulator "Biokop".
a - installation of the mounting plate on the model of the lower jaw, on top of this plate - a metal plate for recording; b - metal plates before fixing on plastic bases of the upper and lower jaws; c - white plastic pads are installed in place of the mounting plate in order to maintain the interalveolar distance; d - after fitting the spoons, casts of toothless jaws with a bite device were made; e - record of the Gothic corner, a hole in the transparent plate at the top of the Gothic corner; e - to fix the central ratio of the jaws between the metal plates, an occlusal mass was introduced.

Orient the position of the mounting plate between the frames of the articulator: in the distal section at the upper third of the mandibular tubercle, and in anterior section at half the interalveolar distance of the models of the upper and lower jaws. bilateral symmetry is maintained. Plastic is applied to the lower spoon, an arcuate metal lower plate is laid on it, then an arcuate upper plate of the bite device is placed on top and then an assembly plate. Plastic is also applied to the upper spoon and the articulator is closed.
after the plastic has hardened, white plastic pads are installed in place of the mounting plate, the thickness of which is equal to the thickness of the mounting plate. Thus, the interalveolar distance is maintained;
spoons with a bite device are introduced into the oral cavity, if necessary, they are corrected. The white lining of the upper and lower spoons are in contact, providing a uniform load on the mucous membrane of the alveolar processes. Functional impressions with individual trays can be taken when the bite device is mounted on them;
remove white plastic overlay plates, instead of them install metal registration ones;
the support screw is unscrewed to the desired value. A full turn of the screw increases the interalveolar distance by 1 mm. It is necessary to warn the patient that the tongue is behind / or under the plate. If functional casts are taken with a bite device at this stage, then by adjusting the screw in height, the interalveolar distance is reduced by several millimeters (thickness of the impression mass), and at the stage of registering the central ratio, the desired distance is set with the screw;
check the distance between the distal edges of the spoons. These edges should not touch and interfere with the movements of the lower jaw;
the upper registration plate is covered with black wax or soot, introduced into the oral cavity and the following movements are carried out (it is recommended to test them before registering the Gothic angle): the lower jaw is shifted forward and backward (several times), right and back to its original position, to the left and to its original position.
The patient holds the head straight (without tilt). The bite device is removed from the oral cavity.

Rice. 8.14. Diagnostic evaluation of Gothic angles.
1 - norm; 2 - predominance of lateral movements; 3 - smoothed corner vertex; 4 - asymmetric angle; 5 - a sharp limitation of the amplitudes of movements; 6 - the path of displacement of the lower jaw back from the top of the angle.

If there is no clear record, then everyone repeats. A transparent plate is installed so that its hole coincides with the top of the gothic angle both in the articulator and in the oral cavity.

To fix the central relationship between the plates of the bite device, an occlusive mass is placed. The facial arch is fixed to the protrusions of the metal arcuate plate of the upper jaw. After installing the models in the articulator, they begin setting the teeth.

Diagnostic evaluation of Gothic corners (Fig. 8.14). The classic acute angle, symmetrical sides indicate the absence of disorders of the TMJ and masticatory muscles. The classic obtuse angle is a sign of the predominance of lateral movements of the articular heads. The smoothed top of the angle is a sign of deforming arthrosis of the TMJ, anomalies of the articular heads, a pronounced posterior component of the jaw movement. Asymmetric angle - restriction of mobility of one articular head or their different mobility. A slight amplitude of all movements is possible in cases where the bite device causes pain under the base plates, if the patient has not used prostheses for a long time or the prostheses were of poor quality in terms of functionality. In difficult cases, the Gothic angle may not be recorded, indicating a vertical type of chewing.

As an example of finding the "therapeutic" position of the lower jaw - the central ratio - with the help of intraoral registration of the movements of the lower jaw, we present an observation.

Patient A., 64 years old, has been using it for many years complete dentures for both jaws. Recently there were pains in the parotid region, the left cheek when chewing. Palpation revealed a sharp soreness of the TMJ and the masticatory muscle proper on the left.

On the tomograms in the usual occlusion on the right - the centric position of the articular heads, on the left - the narrowing of the posterior articular gap. Bone changes in the articular surfaces were not detected.

Rigid bases were made, on which a bite device is mounted in the articulator. By changing the length of the support pin, the vertical ratio of the jaws is established. It was not possible to get a clear record of the Gothic corner, it was noted in different places of the plate, the sides of the corners were different lengths. This indicates stretching of the ligamentous apparatus, compression of the joint, displacement of the lower jaw. The apex of the Gothic angle was set according to the recording of the occlusal field. The patient noted discomfort and pain when holding the lower jaw in this position. Then the lower jaw was moved back - the pain intensified, forward - the pain decreased, to the right - comfortable, to the left - uncomfortable.

The treatment position of the mandible was found in front of and to the right of the top of the Gothic angle. In this position, convenient for the patient, X-ray control was performed: the centric position of the articular heads. Splints on prostheses were made in the new central ratio. After 4 months, the pain disappeared. During this time, there were minor tire corrections. After 10 months, a "Gnatometer M" was installed on the prostheses and the Gothic angle was recorded. The recording was clear, the top of the gothic angle was in the middle line of the record. The prostheses were made in the new position of the lower jaw. Long-term results were evaluated after 1.5 years. There were no complaints.

Graphical methods for determining the central ratio of the jaws are not indicated for deforming arthrosis. On fig. 8.15 - radiographs, functionograms and axiograms of a patient with a pronounced deformity of the right articular head of unclear etiology, in which the central relationship could not be determined using functiography.

Checking the correctness of determining the central ratio of the jaws

In the manufacture of extensive restorations, it is desirable to repeatedly determine the central ratio of the jaws and obtain two or three occlusal blocks.

Practice shows that normally the use of blocks that fix the correct position of the lower jaw gives the same results, even if the blocks were made at different times and by different doctors.

To verify the definition of the central ratio by different occlusal blocks, the “method of model control bases” (A. Lauritzen) is used.

The essence of the method is that the model of the upper jaw is connected to the upper frame of the articulator not by a single plaster block, but by two blocks (“double base of the model” - split-cast), corresponding to each other.

Rice. 8.15. Right-sided deforming arthrosis of the temporomandibular joint.
a - radiographs; b - functionogram: flattening of the top of the Gothic corner, the path of the front movement is curved to the left; c - axio-grams on the right (R): 1 - the forward movement is shortened: 2 - the opening-closing movement of the mouth has a bulge upward (reverse bend); 3 - mediotrusion movement is flattened and shortened. The axiogram on the left (L) does not differ from the norm.

If, when installing occlusal blocks on the dentition, a gap forms between the parts of the gypsum block, then an error has occurred in determining the central ratio of the jaws. If there is no gap, the central ratio is correct. In the first case, it is necessary to abandon the occlusal restoration and use the methods of relaxation, deprogramming of muscle function, as well as documenting the existing symptoms of masticatory muscle dysfunction and TMJ. The manufacture of permanent prostheses is possible only after the correctness of the determination of the central ratio of the jaws has been confirmed.

In addition, this method is used to compare the positions of the mandible in central relation and in habitual occlusion.

Preparing models for this method is greatly simplified if the articulator has magnetic bases for mounting models. The base of the upper jaw model must be without a magnet. A metal plate (for fixing the magnet) can be covered with a sticky patch. In the absence of magnetic bases, it is necessary to first install the model of the lower jaw in the articulator, then put the model of the upper jaw with the occlusal block to the model of the lower jaw. On the base of the model of the upper jaw, make wedge-shaped notches and, after isolating this base, apply plaster between it and the upper frame of the articulator. When the plaster hardens, a double base of the model of the upper jaw is formed. Now, having installed the occlusal block, you can close the plaster parts of the base of the upper jaw model and check if there is a gap between these parts. Then install another occlusal block on the dentition and check again for the presence or absence of a gap. If it is not there, then both occlusal blocks fixed the same position of the lower jaw. If there is a gap, then, therefore, there are violations of the dentoalveolar system and masticatory muscles, which must be eliminated, and then the central ratio of the jaws should be determined again.

If the method is used if there is a suspicion of an existing habitual occlusion, then the direction of displacement of the lower jaw can be determined by the size and location of the gap.

Additional information is provided by tomograms of the TMJ when the jaws are closed in the position of habitual occlusion and in the central ratio (with occlusal registers).

The displacement of the lower jaw, and consequently, the articular heads can be determined by the following features:

If the model of the upper jaw is displaced forward, then the articular heads in the usual occlusion are displaced backward;
if the model is displaced backward, the articular heads are displaced forward;
if the model is not displaced along the sagittal, but there is a gap increasing anteriorly - distraction in the joint (expansion of the joint space);
if the situation is similar, but the gap increases posteriorly, then there is compression in the joint (narrowing of the joint space);
lateral displacements of the model indicate a transversal displacement of the articular heads.

We give an example of using double control bases of the upper model.

Patient 3., aged 47, complained of pain in the parotid-masticatory region (more on the right). She has repeatedly redone crowns and a removable prosthesis for the lower jaw.

Rice. 8.16. The method of control (separated) bases of jaw models to assess the correctness of determining their central relationship.
a - the central ratio of the jaws was determined by means of a bite device and fixed with occlusal silicone; b - the bite device is removed; c - the central ratio of the jaws was determined without a bite device with bite blocks made of impression silicone and the same models were installed in the articulator. The decrease in the interalveolar distance is greater on the left and behind, determined by the gap between the base of the upper model and the mounting plate of the upper frame of the articulator.

The examination revealed included (right) and terminal (left) defects in the dentition of the lower jaw. In the area of the front teeth on the left - straight, on the right - progenic occlusion. Incisors and canines have pathological wear of hard tissues.

The central ratio of the jaws was determined using a bite device and fixed with a blue occlusal mass. After installing the models in the articulator, the blocks were removed and the interalveolar distance in the region of the lateral teeth on the right and left is clearly visible (Fig. 8.16, a, b).

Then the central ratio of the jaws is fixed without a bite device, the model of the upper jaw is installed in the same articulator using new blocks. On fig. 8.16, in
a gap is visible between the base of the upper model and the mounting plate of the upper frame, the protrusions of which do not coincide with the wedge-shaped notches of the base of the plaster model of the upper jaw. In relation to the plate of the upper frame of the articulator, the model of the upper jaw is displaced downward (more on the left side and in the distal sections). Consequently, when determining the central ratio of the jaws, there was a decrease in the interalveolar distance, more at the back.

The control base method can be used to establish the correct definition of the hinge axis. To do this, use the "high registration method", obtained with a large separation of the dentition (about 1 cm). If the articulation axis is correctly defined, there is no gap between the base of the upper model and the mounting plate on the upper frame of the articulator when the “high register” is installed on the occlusal surface.

An additional way to check the correctness of determining the "occlusal height" in an edentulous patient is to measure the distance between the most deep dots transitional folds on the sides of the frenulums of the upper and lower lips. Studies by many authors have shown that this distance is 34 + 2 mm. If it is very different from 34 mm, you need to check the correctness of the definition of "occlusal height".

V.A. Khvatova
Clinical gnathology

Muscular signs: muscles that lift the lower jaw (chewing, temporal, medial pterygoid) simultaneously and evenly contract;

Articular signs: articular heads are located at the base of the slope of the articular tubercle, in the depths of the articular fossa;

Dental signs:

1) between the teeth of the upper and lower jaws there is the most dense fissure-tubercular contact;

3) the middle lines between the upper and lower central incisors lie in the same sagittal plane;

4) the upper teeth overlap the lower teeth in the anterior region no more than ⅓ of the crown length;

5) the cutting edge of the lower incisors is in contact with the palatine tubercles of the upper incisors;

Signs of anterior occlusion

Muscular signs: this type of occlusion is formed when the mandible moves forward by contraction of the external pterygoid muscles and horizontal fibers of the temporal muscles.

Articular signs: articular heads slide along the slope of the articular tubercle forward and down to the top. The path they take is called sagittal articular.

Dental signs:

1) the front teeth of the upper and lower jaws are closed by cutting edges (butt);

2) the midline of the face coincides with the midline passing between the central teeth of the upper and lower jaws;

Signs of lateral occlusion (on the example of the right one)

Muscular signs: occurs when the lower jaw is displaced to the right and is characterized by the fact that the left lateral pterygoid muscle is in a state of contraction.

With lateral occlusion, the lower jaw is displaced by the size of the tubercles of the upper teeth. Dental signs:

1) the central line passing between the central incisors is “broken”, displaced by the amount of lateral displacement;

All types of occlusion, as well as any movement of the lower jaw, are performed as a result of the work of the muscles - they are dynamic moments.

Bite

Bite- this is the nature of the closing of the teeth in the position of central occlusion.

Bite classification:

1. Physiological bite, providing a full-fledged function of chewing, speech and aesthetic optimum.

a) orthognathic- characterized by all signs of central occlusion;

in) physiological prognathia (biprognathia)- the front teeth are tilted forward (vestibularly) along with the alveolar process;

G) physiological opistognathia- front teeth (upper and lower) tilted orally.

2. Pathological bite, in which the function of chewing, speech, and the appearance of a person are impaired.

a) deep

b) open;

c) cross;

d) prognathism;

e) progeny.

Introductory concepts of occlusion

Search for central occlusion

Photo 3. Sheet calibrator.

Photo 5. Chewing muscle.

Photo 6. Temporal muscle.

Tires with full coverage

Hybrid devices

When bite is not a problem

conclusions

Basic concepts of applying knowledge of occlusion in clinical practice include the ability to identify common occlusal problems and disorders, as well as associated changes in the temporomandibular joint (TMJ), which further helps to use the obtained data in the course of patient treatment. In the presence of muscle pain, patients can be treated through the use of full or partial plates, which help to deprogram the muscles. At the same time, it is important to understand when and what types of devices are best used. This article will describe the main approaches to the analysis and analysis of occlusion parameters, and methods for their implementation in clinical practice.

Introductory concepts of occlusion

When applying occlusal concepts during a restoration, the difference between central relation and maximum fissure-cusp position (MIP) must be clearly understood. At the same time, in some cases, the doctor manages to determine the so-called "guiding" tooth. This tooth allows the jaw to adapt and guides it into the proper position for occlusion when in contact with it in the central occlusion stage. If the tooth changes in some way during treatment, the occlusion is no longer stable and the overall rehabilitation procedure is noticeably worse. It is logical that it is best to avoid any iatrogenic interventions in the area of the "guide" tooth, because the chain of changes can lead to a change in the position of the joint and the location of the disc. In such cases, to restore occlusion, it is necessary to collect the entire set of additional diagnostic data, which will be extremely useful in the course of further rehabilitation.

Definition of central ratio

The central ratio is the position of the joint at which it is in the maximum upper and anterior position in the glenoid fossa. Central relation should not be confused with central occlusion, maximum intercuspidation, adaptive central posture, centric sliding, or centric stop. The Glossary of Orthopedic Terms defines the central ratio as the ratio of the maxilla and mandible, in which the articular process interacts with the thinnest avascular part of the disc, and this complex of components is in the anterior superior position opposite the corresponding shape of the articular tubercle. Thus, the central ratio is in no way dependent on the contact of the teeth. Essentially, the joint should be in the anterior position, and how the teeth close together is the second question. Frank Spear defines centric ratio as the position of the condyle in which the lateral pterygoid muscle is relaxed and the levator muscles converge with a properly positioned disc. The muscles try to pull closer and closer to the center, which, in principle, is quite normal and correct, if there are no violations in the area of the joint as a whole, or the disc specifically. A central ratio is a position that is self-centering. For example, if a marble ball falls anywhere inside a cup, it will eventually roll into the center of the cup. If the patient has inflammation of the pterygoid muscle, which prevents the centering of the condyle, then this is the same as replacing the ball in the cup with a metal one, and attaching a magnet to the bottom of the cup - thus the position of the ball in the cup turns out to be predisposed. Similar processes take place in the area of the inflamed lateral pterygoid muscle.

Finding a central ratio

The central ratio can be defined in several different ways.

The simplest, but also the least accurate method is for the patient to place the tongue on the back of the palate while biting. Such an approach is useful for quick analysis, but in the opinion of the author, the accuracy of such an approach may be poor.

Another method for determining the central relationship is bilateral manipulation of the jaw (bilateral guide). This technique is very sensitive to perform. It is necessary to create a C-shape between the thumb and other fingers, while placing them on the lower jaw and chin. The patient is then asked to gently open and close his mouth, thus allowing him to adapt to the movement. After several cycles of opening and closing, the dentist asks the patient to relax and, being careful not to provoke muscle activation, repeats the movements. It is also important not to provoke distal positioning of the condyle, because the purpose of this manipulation is to achieve its anterior and superior medial position.

The third method of finding the center ratio involves the use of an anterior deprogrammer. An instrument, such as a Lucia or a quicksplint, is placed in the mouth with bite registration material. It is attached to the central incisors. The patient begins to move the lower jaw back and forth on the Lucia jig, relaxing the muscles. After relaxing the muscles, the patient is directed to bite on the distal plane. When the patient's jaw returns to its starting point, the condyle should sit strictly in the fossa. Similar to this approach is the technique using a sheet calibrator. The sheet calibrator allows you to open the jaw to different sizes by removing or inserting one or more sheets of the same thickness between the teeth. Whether the sheet calibrator can actually provide jaw distalization is not yet known, but its use itself is already more than useful. If the joint is healthy, the disc does not move and the muscles do not hold it in place. Therefore, the muscles can self-center the joint. A well-adjusted kappa, which promotes muscle relaxation, also helps to find the central relationship. After registering the central relationship, it is important to determine the point of first contact. It is inherently the starting point for further treatment, but it can not be detected in all patients. This point should always be marked, but not always literally (not always with a pencil, in other words). Photo 1 shows teeth No. 2 and No. 3. In this situation, the point of first contact is on the mesiolingual cusp of tooth No. 2, on which the strongest mark is noted. However, a small, but all mark, is visualized on the distobuccal cusp of tooth No. 3. Again, the central ratio is the position of the joint and does not depend on the contact of the teeth. However, when the antagonist teeth in a state of central relation are in contact, then this position is already referred to as central occlusion.

Photo 1. First contact points.

Search for central occlusion

Maximum intercuspidation is the term used for habitual occlusion when the patient has the maximum number of antagonistic tooth contacts. Central occlusion can be determined using bilateral manipulations, a bilateral guide (photo 2) or using a sheet calibrator (photo 3).

Photo 2. Bimanual direction.

Photo 3. Sheet calibrator.

Thus determined, the central occlusion may or may not coincide with the position of maximum contact of the antagonist teeth. When planning the treatment of a tooth in the area of which there is a first contact, it is necessary to determine the presence or absence of a sliding effect. The author's preferred method for determining the sliding effect is for the patient to compress the teeth together in the position of maximum intercuspidation, while the clinician determines whether the jaw moves significantly in any direction when reaching this provision. Before determining sliding, the dentist must measure the level of vertical and sagittal overlap, for which a periodontal probe can be used. If the level of sagittal (horizontal) overlap is greater than the level of vertical overlap, considerable care must be taken during further treatment (Figure 4).

Photo 4. Definition of vertical and sagittal (horizontal) overlap.

For patients with sliding in the central occlusion, a change in the vertical overlap parameters is more characteristic than horizontal ones. In this case, in most patients, sliding will be noted to the right, left, vertically, forward or backward. Sliding more than 1.5-2 mm with a predominant horizontal component over the vertical component indicates a potential problem that may be related to the "guide" tooth. The term "guide tooth" is used because its presence is the key to achieving archwire stability, and is a significant determinant of existing occlusal function. Restoration of this tooth may lead to unpredictable changes in occlusion. The only way to understand the possible consequences of such interventions is to establish changes in the central ratio to determine what changes are noted in the bite after the occlusion in the area of the "guide" tooth has been changed. Due to the unique properties of physiology, as soon as the patterns of (1) what partially held the occlusion, (2) the direction in which the patient was biting, and (3) what held the disc in place, is forgotten, the reverse loop begins: from teeth to muscles, from muscles to teeth. If the feedback loop is interrupted, it will not be possible to return the patient to his usual bite. Therefore, it is important to determine the possibility of developing such a problem before fixing the crown. No modifications should be made to the tooth structure until its full role in the occlusal process has been determined. If the teeth continue to maintain good contact after treatment, and there is no change in the central ratio, then there is nothing to worry about. But if new points of first contact are found that articulate “not quite well”, or there is a deficiency of the occlusal space between the “guide” tooth and the antagonist, it is necessary to explain the possible consequences of such violations to the patient. At the same time, it is impossible to determine whether the restoration will provoke a problem that the patient will not be able to endure, or whether it will be within the limits of the compensation potential. But warn the patient about possible consequences clearly necessary.

Thorough diagnosis before starting treatment

Before the clinician begins the treatment process, it is necessary to complete diagnostics patient. The clinician must devote time to understanding the specifics of occlusion, bite, muscle interaction, and TMJ. Ideally, the doctor should identify all possible risk factors that may compromise the outcome of treatment in the future. The goal of diagnosis is to clearly categorize patients in whom treatment should not cause significant changes from those in whom treatment may trigger the development of potential complications. A comprehensive diagnostic process begins with an analysis of the history, including the collection of data on the facts of previous trauma, or the occurrence of pain symptoms. It is also necessary to familiarize yourself with the general somatic condition of the patient, confirm or exclude the presence of obstructive sleep apnea, snoring, gastroesophageal reflux disease, the fact of taking antiangiotic / antidepressant drugs, and the presence / absence of headaches. Patients with sleep apnea may not be aware of their presence, so the Epworth scale or similar diagnostic classification algorithms should be used to determine the likelihood of risk.

Modifying the degree of invasiveness of interventions

After collecting an anamnesis, the doctor proceeds to a thorough clinical diagnostics. The dentist should ask patients about his own attitude towards occlusion: for example, the patient may show signs of pathological abrasion, but he does not complain about the change in their shape. In this case, the diagnosis should be carried out from the outside to the inside, starting from the assessment of less personal zones of the maxillofacial apparatus and moving towards more personal ones. In this case, it is necessary to diagnose all eight muscles of the study area, namely a pair of masticatory muscles (photo 5), a pair of temporalis muscles (photo 6), a pair of medial and a pair of lateral pterygoid muscles (photo 7).

Photo 5. Chewing muscle.

Photo 6. Temporal muscle.

Photo 7. Medial and lateral pterygoid muscles.

The digastric, sternocleidomastoid, trapezius and splenius muscles of the head can also be causes of TMJ disorders, but diagnosis of these in the absence of visible TMJ dysfunctions is not necessary. The first step in the diagnosis is palpation of the masticatory muscle with a pressure of about 3-5 pounds. In order to determine the strength of palpation, you can test it on a scale in a regular store. By palpating the masticatory muscle along its entire length, the doctor can easily determine in which area pain. A similar palpation technique is used for the temporal muscles. Both pterygoid muscles are usually palpable inside the mouth, but this diagnostic process can be difficult for the lateral pterygoid muscle. A simpler method of assessment is to evaluate muscle activity with the dentist's hand on the chin, after which he asks the patient to move him forward, resisting pressure. After that, the doctor instructs the patient about the need to move the jaw to the left and right.

Joint condition and range of motion

It is also extremely important to collect information about the joint, evaluating its range of motion and data obtained by palpation. To do this, the dentist puts his finger on the side, and then asks the patient to open and close his mouth. The patient should continue to make this movement until the doctor feels that his finger is moving slightly to the right in front of the ear. After that, the doctor must apply some pressure to the joint area, determining the threshold pain sensitivity. This technique can also be performed directly in the patient's ear in the absence of any hearing impairment. After the doctor has already felt the specifics of the movement of the joint when opening and closing the mouth, the dentist can press his finger slightly down and forward, as if leaving the joint, assessing the patient's pain response. In the presence of pain, the patient must evaluate them on a numerical scale. Range of motion can be measured with a ruler, triangle, or any other tool designed specifically for changing distances. The range of motion should be determined in the open and closed position of the mouth, taking into account the parameters of vertical overlap. In addition, it is necessary to assess the range of motion of the jaw to the left and right.

Stress test and joint response

After diagnosing the muscles and joint, proceed to the analysis of occlusion, central relationship and central occlusion. With the help of a load test, the condition of the joint is checked. This test is performed by placing an object in the oral cavity, like a sheet calibrator, after which the patient moves the jaw back and forth, and then bites. If during the diagnosis it is painful for the patient to move the jaw forward, then the problem is not in the load, but in the muscles and tissues behind the articular disc. After the patient moves the jaw back and bites, the presence or absence of pain allows the doctor to assess the degree of disc displacement. The dentist may conclude that the patient has only lateral displacement, or that there is also medial displacement, which is much more difficult to treat. After that, the clinician moves from the stress test to the examination of the oral cavity itself. The presence of signs of wear, vibration and fractures of the teeth are signs that may indicate problems with occlusion. To evaluate the analysis of their etiology, it is important to analyze the specifics of articulatory excursions and the interaction of teeth in the distal area. In order to perform this procedure, articulation paper of two different colors. First, the doctor uses very thin paper and instructs the patient to move his jaw left-right-forward-backward, chew on the paper, and then move his jaw in any direction he can. At this stage, if abnormalities are present, most patients already show signs of clenching or bruxism. After the patient "chewed" the previous piece of paper, he should have a bite in the maximum fissure-tubercle ratio, while using articulating paper of a darker color. Thus, by analyzing the light markings on the teeth, the doctor can assess the interference of articulatory movement, and the darker ones - the contact in the state of maximum intercuspidation. But such an approach does not help the doctor to determine the existing pathologies of the TMJ. On the other hand, the results obtained can be used in planning restorative treatment and predicting the functional state of the periodontium. An alternative to the above technique is to use new technology T-scan.

Methods for studying the state of the articular disc

The gold standard for disc examination is magnetic resonance imaging (MRI), which can be used to visualize various positions of the structural element of the joint. But given that MRI is not a routine diagnostic method, in clinical practice, a doctor can use the “open, look, listen and feel” test. The clinician should listen for sounds as the patient opens and closes the mouth while eating and lightly palpating the joint. The physician must also observe possible deviations and offsets. Deviations are observed when the disc moves to the side and then re-centers, that is, deviates to the left or right, but the final position is still marked in the middle. Displacements are characterized by the movement of the disk to one side or the other, in which it remains at this angle. Additionally, you can listen to the joint with a stethoscope, thus it is possible to study the disc popping out of the joint. After comparing the data obtained with the preliminary data recorded during the stress test and related manipulations, the doctor can make a working diagnosis. In some cases, the Doppler method may be used. It allows you to broadcast audio sounds when the joint moves, so that not only the doctor, but also the patient can hear. The disadvantage of the method is the need to use a lubricating gel, the sensation of which is unpleasant for some patients. Joint vibration analysis (JVA) can also be used. The JVA is a sophisticated measurement device containing a small microphone attached to the earphones that passes through the area of the joint. This device registers frequency and cataloged joint noises, but its disadvantage is its excessively high price. Adequate diagnosis of chronic or acute disorders disc displacement will ensure the prevention of complications in the future, leveling the risk of failure of clinical interventions.

Diagnosis based on joint disorders

The classification of changes in the joint area can be carried out according to the system proposed by Mark Piper. This approach involves the categorization of violations in 5 main stages. Stage I is the normal state of the joint. Stage II is a loose state of the ligament (weakness of the ligament). The ligament is like a rubber band: it can stretch and become "doughy", causing noise when moving. Stage III usually involves lateral disc displacement. The reason for this may be a traumatic effect on the joint area, but often the presence of pain is not a sign of the bone form of the disorder. Stage IV disc suggests medial disc displacement (acute or chronic). Stage V develops with changes in the anatomy of the disc in the area behind the underlying tissues (early/acute or chronic perforation). To use this classification, a deep understanding of the joint is required.

Devices for the treatment of muscle pain

The success of the treatment of patients with muscle pain may depend on the choice of the appropriate apparatus. The choice of the latter depends on the etiology of disorders. If the patient shows signs of pathological abrasion, there are ceramic restorations in the oral cavity, and no violations are registered from the point of view of the joint, then the goal of treatment is to protect the teeth from pathological abrasion. For this purpose, you can use a night opening mouth guard. Similar mouthguard designs may be used in the treatment of muscle pain, but in this case they are called splints or splints, or other types of mouthguards. The splint is designed to change the position of the jaw in any direction, and to correct the vector of acting forces to eliminate the symptoms of muscle pain.

Tires with full coverage

When the disc is displaced and there is pain, the patient needs a kappa that takes into account the etiology of the disorder. For normal protection of teeth from abrasion, mouthguards with full overlap are used. It can also be used to assess the severity of the pathology of bruxism or clenching. A mouthguard of this design can be made directly in the dental chair, but its range of use is limited. The use of individual modification of these kappas should even be avoided in the presence of disc displacement. A rigid full coverage splint performs the same function (protecting the teeth) but also provides the stable position of the joint that is designed. When the joint is stabilized, muscle relaxation is achieved, which provides opportunities for determining the central relationship. In the presence of muscle pain without disc displacement and difficulty in determining the central ratio, a rigid full-coverage splint is good choice for treatment. Such splints also make it possible to minimize or avoid deformation of the ligament. At the same time, both the patient and the doctor must understand that there is no universal mouthguard design for all occasions. There are many types of hard mouthguards with full coverage. For example, the Pankey/Dawson splint is a mandibular plane device without angles that does not cause posterior displacement of the disc or joint. The Maxillary Anterior Orthopedic (Michigan) Splint is a solid acrylic mouth guard covering the maxillary teeth with a ramp over the structure. The theory behind its use is to exclude distal teeth from the insertion route. The Tanner kappa allows you to slightly separate the jaws while maintaining the position of the disc and joint, thus achieving muscle relaxation, which significantly determines the presence or absence of joint pathology.

Hybrid devices

Hybrid devices are characterized by the possibility of multitasking. The most common is the anterior bite plane, which is fairly easy to create. When the anterior bite plane is combined with the lingual ramp behind the teeth, the appliance can already be classified as a Farrar appliance. The latter is used in the treatment of patients with obstructive sleep apnea. The Farrar apparatus does not provoke distalization of the joint, maintaining the vertical parameters of the occlusion, but at the same time does not allow the lower jaw to slide back, holding it with the tongue ramp. The use of the distal Gelb apparatus allows only distal occlusion to be formed. But using it for more than 12 hours a day or more than 3 months is not recommended, since the formation of an anterior bite can lead to the development of pathological abrasion. The use of a Hawley apparatus with front stop markers was first proposed by Kois. The advantage of the Kois splint is that it can be used to equilibrate occlusion during restorative treatment. In addition, this mouthguard can also be used as a guide. In the course of persistent tire biting, the clinician can identify distal stop areas and lower bite zones around which appropriate modifications need to be made. The tricky part of the jaw balancing process is that it can reduce the vertical bite parameter, causing changes in the joint as well. The nociceptive trigeminal inhibitory splint (NTI) is essentially an anterior bite plane, but smaller, which also expands its range of applications. It is important to remember that hybrid devices cannot be worn 24 hours a day. Especially devices with distal support, which provoke a change in occlusion, which could easily be corrected through orthopedic or orthodontic treatment. If the likelihood of bite change is high, the dentist should discuss this with the patient in advance, informing him of the possible results of the treatment. At the same time, it must be remembered that the goal of all hybrid devices is to relieve the patient from pain.

Critical steps in the use of mouthguards

When making a diagnosis and choosing a treatment method, choosing the appropriate mouth guard should not be problematic. Before fixing, such a doctor should be aware that he has all the necessary tools: burs, rubber bands, polishing systems, and, of course, knowledge. When fixing the mouth guard, start from the stage of drying the teeth before applying markings to them. For this purpose, a layer of tissue can be placed on the articulating paper fixators. After that, they begin to use first the red articulation strip, and then the blue one. The red one is mainly used to analyze lateral displacements, and the blue one is used to analyze changes in the vertical direction. After that, the necessary modifications are carried out with the help of boron.

When bite is not a problem

In the dental community, more and more attention is paid to the problem of bruxism during sleep every year. In 2005, the American Academy of Sleep Medicine (AASM) defined sleep bruxism as a sleep-related movement disorder similar to restless leg syndrome or parafunctional dentition. This is usually associated with waking up during sleep. As of 2014, the understanding of sleep bruxism has changed somewhat. The AASM now defines this disorder as "repetitive jaw muscle activity characterized by clenching or abrasion of the teeth and/or repositioning of the mandible." In a 2014 study, Hosoya and colleagues found a correlation between obstructive sleep apnea and a high risk of developing sleep bruxism. Therefore, patients should be screened for risk factors associated with sleep bruxism. If this pathology is suspected, the patient should be examined by an appropriate doctor who can provide individual advice and a proper diagnosis. Patients diagnosed with sleep bruxism are characterized by the presence of hypersensitivity of the teeth, the presence of bites in the tongue and cheeks, a burning sensation in the masticatory muscles and noises, and a blocking function of the TMJ. Sleep apnea is also commonly associated with fatigue and snoring. Factors indicating the presence of sleep apnea and associated bruxism should be identified during the history taking or during the preliminary stage of diagnosis.

conclusions

Effective application of diagnostic methods and differential diagnosis occlusal changes involves early identification of occlusal pathologies by assessing the state of intermaxillary relations, TMJ function and pain associated with disorders. A thorough understanding of the concepts of “guide” tooth, muscular fixation, and sleep bruxism is also part of the clinician’s general knowledge set required to conduct an adequate diagnostic process. During the diagnosis, the doctor analyzes the central ratio and central occlusion, the state of the masticatory muscles, their range of motion and the level of joint displacement. This information is based on a comprehensive preliminary diagnosis, using not only clinical techniques, but also additional instrumental methods. Diagnosis of the patient should be carried out "from outside to inside", necessarily starting with palpation of the masticatory, temporal, medial and lateral pterygoid muscles. The load test allows the clinician to determine if the load on the joint causes pain, and a classification system is used to categorize the results of diagnosing a displaced disc. Treatment of disc displacement and muscle pain depends on the choice of mouthguards of different designs, from rigid counterparts to hybrid designs. Ultimately, it is critical to identify the difference between problems due to malocclusion and due to sleep bruxism. The combination of all these factors is critical to the successful restoration of functionally stable occlusion in general practice dentist.