central occlusion. Determination of the central relationship of the jaws in case of complete loss of teeth Control of occlusion

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

The main concepts of applying knowledge of occlusion in clinical practice include the ability to identify common problems and violations of occlusal relationships, as well as changes associated with them in the temporomandibular joint (TMJ), which further helps to use the obtained data in the course of patient management. 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 technique for determining the sliding effect is to have the patient clench the teeth together in the position of maximum intercuspidation, while the clinician determines whether the jaw moves significantly in any direction upon reaching this position. 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 greater 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 it is definitely necessary to warn the patient about the possible consequences.

Thorough diagnosis before starting treatment

Before the clinician begins the treatment process, a complete diagnosis of the patient must be made. 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 diagnosis. 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 is observed. 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 on the joint area, determining the threshold of 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 can be used. 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 the use of the new T-scan technology.

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. In this case, the doctor must also observe possible deviations and biases. 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 disc displacement disorders 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 ratio. In the presence of muscle pain without disc displacement and difficulty in determining the central ratio, a rigid full-coverage splint is a 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 bite, 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 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 diagnostic stage.

conclusions

Effective application of diagnostic methods and differential diagnosis of occlusal changes involves early identification of occlusal pathologies by assessing the state of the intermaxillary relationships, TMJ function and associated pain sensations. 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 the general practice of a dentist.

An integral clinical stage of prosthetics is the calculation of central occlusion.

From this article, you will learn about all the important factors that should be taken into account in order to correctly fix the AC, which steps of the procedure and methods of determination are applied, which means correctness control.

signs

It is possible to characterize the central occlusion by muscular, articular and dental signs.

For muscle signs characterized by uniform tension at the same time several muscle groups (chewing, temporal, medial).

For articular signs the adjoining of the articular convexity of the lower dentition to the posterior slope of the articular tubercle is characteristic.

For dental signs certain features of jaw compression are characteristic in comparison with all teeth, as well as frontal and lateral.

Features of contact for all teeth are as follows:

• the middle line between the frontal incisors corresponds to the line of the face;
• a large number of fissure-tubercular connections of both jaws;
• contact of the teeth with the corresponding antagonistic pairs.

Signs of connection of the anterior teeth:

• the presence of connecting contacts between the edges of the lower incisors and the palate of the upper ones;
• overlapping with the upper frontal teeth about a third of the lower ones;
• placement of the anterior teeth of both jaws in an identical sagittal plane during their compression.

Signs of contact of the lateral incisors:

• overlapping of the buccal tubercles of the upper (left or right) incisors of the identical tubercles of the lower ones;
• the transverse arrangement of the palatine bulges of the upper teeth between the oral bulges of the lower ones.

Ways

In case of incomplete absence of teeth, prosthetics are performed, which provides for the determination of central occlusion. Incorrect fixation of the central proportions can lead to many undesirable aesthetic and functional consequences.

The CO can be defined in the following ways:

1. If antagonistic pairs are present on both sides, then occlusal rollers made of wax are used to calculate the central ratio.

   In order to install the CO, the wax roller is carefully placed on the lower dentition and fitted to the upper one. Then the mesiodistal position of the jaws is determined.

2. If antagonists are in three occlusal points(front, left and right).

   Since the lower chin line is fixed with natural teeth, the central proportions are set without the use of occlusal ridges.

   This technique for calculating the CO is to fix the maximum number of chewing contacts. It is permissible to use this technique in the absence of two lateral or four frontal teeth.

3. If there are no antagonistic pairs at all, then occlusion is not traced. Therefore, in order to find out the CO, it is necessary to establish and fix such parameters - determining the lower point of the face, measuring the mesiodistal location of the jaws and the occlusal surface.

To determine the correct position of the teeth in the central comparison, the following technique is used:

• if antagonistic pairs are present, occlusion is checked by closing the jaw.

  To do this, a softened warm strip of wax is glued to the chewing surface of the fitted roller and inserted into the growth cavity, after which the patient quickly squeezes his jaw until the wax has cooled.

  As a result of such actions, an impression is formed on the wax strip, according to which the design of the prosthesis is made in the central comparison;

• when the chewing surfaces of the upper and lower rollers come into contact, produce wedge-like cuts on the upper roller.

  A small layer is cut from the lower roller, then a warm strip of wax is applied on top. When the patient clenched his teeth, the wax lining of the lower roller in the form of wedge-like bulges is inserted into the cuts of the upper one.

Measurements for orthopedic purposes

The height of the lower point of the face is of great importance in orthopedic dentistry.

Measurements of this area are necessary to achieve the best aesthetic results, to improve dental contacts under normal functioning conditions, and to create space in the vertical plane.

Dentists are required to determine the size of the lower face using the following methods:

1. Anatomical. The essence of this method is to measure the outlines of the face. With the loss of a fixed bite, deformation of the anatomical structures around the oral cavity occurs.

   To return the correct outlines of the face, one should take into account the fact that during the measurement of the interalveolar height, the patient must completely close his lips, while not straining them. This method is usually used in conjunction with the other two.

2. Anthropometric. This method consists in measuring the proportions of individual parts of the face. In practice, it is rarely used. It can only be used if the patient has a classic face type.
3. Anatomical and physiological. This method is based on the study of anatomical and physiological data.

   To measure the height of the lower point of the face, the patient needs to move the lower jaw, and then lift it and slightly close the lips.

   In this position, the specialist takes the necessary measurements and subtracts three millimeters from the resulting figure. This sets the height of the bottom point of the face in the central juxtaposition.

Receptions for the correct setting of the lower jaw

Many specialists use certain techniques to accurately calculate the lower jaw in the CO.

For example, it is required that the patient clench his jaw and swallow saliva. The second technique is that the patient should touch the tongue to the soft palate.

In addition, the patient needs to touch his chin with his right hand (palm), close his mouth, and while doing this, try to push his jaw back (without fixing the CO).

When the patient closes his mouth, imprints formed by antagonistic pairs remain on the bite roller, on which prosthesis designs are subsequently created.

Permissible mistakes

Errors in the calculation of the CO are classified into groups.

Errors in the vertical plane (increase or decrease in bite)

With an increase in bite, the patient has a tense clenching of the lips, a slightly surprised facial expression, an elongated chin, and tapping of teeth when talking.

To eliminate this error, with an increased bite height due to the lower teeth, it is necessary to redo the rollers only for the lower row.

If the height is increased by the upper incisors, new rollers are required only for the upper jaw. Next, you need to calculate the CO again and do the setting of the teeth.

When the bite is lowered, the patient has pronounced nasolabial wrinkles, chin skin folds, sunken lips, lowered mouth tips, and a slight shortening of the chin.

When underestimated only due to the lower teeth, rollers are redone for the lower jaw. But if the height is underestimated due to the upper incisors, both rollers are redone. After that, the CO is redefined.

Errors in the transversal plane

If the lower jaw is fixed not in the central comparison, but in the frontal, posterior or lateral (right, left).

With frontal position there is a prognathic bite, tubercular contact of the lateral incisors, a small gap between the frontal teeth.

When placed on the side- increased bite, a slight gap between the displaced teeth.

Errors with the extended lower jaw

The most common mistake is fixing the protruding lower jaw when measuring the CO.

To correct it, converted rollers are installed on the sides of the lower jaw. If the lower jaw is displaced back, new rollers are installed on the entire lower surface of the teeth.

Due to the fact that patients often fix the jaw in an incorrect position, it is not so easy to establish an accurate COA.

If there is no contact between some antagonistic pairs, this can be explained by the following factors:

1. Incorrect fitting of wax rolls or their uneven softening. Most often, the occurrence of defects occurs due to uneven closing of the rollers during the installation of the central heating.

   The main signs of these shortcomings is the lack of contact between the lateral teeth on one or both sides.

   You can eliminate them by applying a not too heated wax strip to the chewing surface of the teeth. After that, it is necessary to fix the bite again.

2. Deformation of wax rollers. When they are removed from the oral cavity and installed on the model, loose contact with the latter is monitored.

   Signs of this error are an increase in bite, a gap between the frontal teeth, an uneven tubercular connection of the chewing teeth. Eliminate the error with bite rollers with rigid bases.

3. Anatomical defects in the oral cavity. In such cases, it is advisable to determine the CO using rollers made on rigid bases.

The video provides additional information on the topic of the article.

conclusions

In conclusion, it can be noted that a qualified specialist should determine the central occlusion, taking into account the anatomical and physiological features of the dentition.

Only after a thorough check of the AC, detection and correction of errors, can wax casts be plastered into the articulator and sent to the laboratory for the manufacture of prostheses.

If you find an error, please highlight a piece of text and click Ctrl+Enter.

Identification of occlusion is a mandatory step before prosthetics.

The article will talk in detail about the signs of CO, how to determine it and measure the parameters necessary for an orthodontist.

signs

Signs of CO are manifested in the muscles, teeth and joints. In the first case, the central occlusion is judged by the state of the muscles responsible for raising the jaw. The masticatory and temporal structures must contract simultaneously.

The main articular signs are the heads on the lower jaw adjacent to the articular fossa.

Features of contact between all dental units:

• the presence of tight contact when closing the elements of the upper and lower rows;
• the closure of all pairs of antagonists (with the exception of the upper sixes and the front lower ones);

Features of the bite of the frontal elements:

• units of the upper jaw overlap the elements of the lower jaw by no more than 1/3 of the length;
• the cutting side of the lower central units is in contact with the tubercles located on the upper incisors;
• the midlines located between the central elements of the lower and upper jaws are located in the same sagittal plane.

Signs of closing of the lateral teeth:

• the upper quad is in contact with the antagonist and the quintuple on the lower jaw, covering about 2/3 of the length of the first and 1/3 of the second molar;
• overlapping of the buccal tubercles of the lower elements by the upper tubercles.

Commonly Known Methods

Determination of CO is an important step before installing a prosthesis for adentia. The orthodontist must determine the ratio of units in the sagittal and transversal directions. In addition, the height of the lower part of the face is determined.

If the antagonist teeth are preserved, then the bite height is fixed in a natural way. With the loss of antagonists, a displacement of the lower point of the face occurs.

CO is determined depending on the presence or loss of antagonist teeth. Calculations are carried out according to the following scheme:

1. Presence of antagonists in three occlusal planes. The length of the lower part of the face is fixed by natural elements.

   For this reason, the central heating is established by fixing the maximum number of contact surfaces. The manufacture of wax occlusion rollers is not required.

   The method is used when the patient loses 2 lateral or 4 frontal units.

2. Presence of antagonist teeth in two planes. To install the prosthesis in the correct anatomical position, a special wax roller is made.

   In order to determine the required orthodontic parameters, the product is attached to the elements in the bottom row and fitted to the teeth in the upper jaw.

3. There are no pairs of antagonists in the oral cavity. Determining the CO consists of 3 successive stages - identifying the lower point of the face, fixing the medial ratio of bone structures and determining the prosthetic surface.

The position of the central occlusion is determined as follows:

1. In the presence of the same teeth on both jaws the parameter is checked by closing the bone structures. To do this, use fitted rollers, on the chewing side of which warm wax strips are applied.

   Products are inserted into the patient's oral cavity. The person should quickly close their jaws before the wax strips cool down.

   As a result of manipulations, an impression of the teeth remains on the wax strip. Based on this impression, a prosthesis is made in a central comparison.

2. If the chewing planes of the rollers are in contact, then perform wedge-shaped cuts in that area of ​​​​the upper jaw.

   A small layer of material is removed from the lower roller, and instead a warm strip with wax is fixed. By compressing the jaws, the wax strip comes into contact with the serifs of the upper jaw ridge.

   After the manipulations, the products are removed from the patient's oral cavity and sent to the laboratory to create a future prosthesis.

Calculations for orthopedic purposes

When creating prostheses, determining the size of the lower point of the face is of great importance. In a healthy person who does not have bite problems, all thirds of the face are approximately equal.

There are 4 ways to determine the orthodontic parameters required in the process of making a prosthesis:

1. Anatomical. The specialist measures the facial features of the patient. To do this, he asks to close his lips tightly, without straining them. After that, the alveolar height is measured. For measurement accuracy, the anatomical method is supplemented by anthropometric and anatomical-physiological methods.
2. Anthropometric. The methodology is based on the equality of third parties. It is used only if the patient has ideal facial contours. The anthropometric method gives small errors - an overestimation of the bite height.
3. Anatomical and physiological. The essence of the method is that the lower point of the face in the state of bite is 2-3 mm higher than in the state of physiological rest.

   First, the doctor asks the patient to close his lips tightly, draws two points on the upper and lower jaw and measures the distance between them.

   It is important that the marks are located on the center line of the face. 2-3 mm is subtracted from the obtained value, since it is this value that distinguishes the state of physiological rest from CO.

   The disadvantage of the method is its inaccuracy, since not every person has a difference taken as a basis for 2-3 mm. In some cases, this value can be 5 mm.

4. Functional. The idea of ​​this method is that the muscles are able to develop the greatest strength in the CO position.

   To do this, doctors use rigid spoons, created taking into account the individual characteristics of the patient. Pins are attached to the lower spoon, preventing the jaws from closing tightly together. With the help of pins, the bite is measured, and the sensors on them determine the load of the masticatory muscles.

   First, to determine the load, a pin is used, the dimensions of which exceed the patient's bite. Then the parameter is determined using a pin, shorter than the first by 0.5 mm, etc.

   The index of chewing load decreases sharply when using a pin, the length of which is slightly shorter than the optimal one. The desired parameter is equal to the length of the previous used pin.

Setting of the lower jaw

There are several ways to set the lower jaw in the CO position:

• Functional. To do this, the doctor asks the patient to tilt his head slightly back. There are several more techniques that eliminate the forward protrusion of the lower bone structure.

  This is touching the distant parts of the palatine region with the tongue and performing swallowing movements. The patient performs the described manipulations until the specialist reveals the correct closure of the dentition.

• Instrumental. Special devices are used that record the movements of the lower bone structure relative to the horizontal plane. The instrumental method is rarely used to set the jaw in the CO position with adentia.

With a significant loss of teeth or with the loss of antagonists, the fixation of the occlusal surface occurs using the Larin apparatus.

Permissible mistakes

When measuring orthopedic parameters of the face, the doctor can make a number of mistakes. All of them are classified into groups:

Overbite

If the parameter is incorrectly defined, the patient's teeth will constantly be in contact with each other, causing overstrain of the masticatory muscles.

In this state, the prosthetic bed is also subjected to overload. When speaking, the patient will experience difficulty. A dangerous consequence after the installation of prostheses for overbite - jaw joint injury.

You can determine that the value of the lower third is overestimated by the symptoms:

• the difference between the state of physiological rest and CO is less than 2 mm;
• sensation in the patient of constant tension in the lips;
• no nasolabial fold.

To correct the error, prostheses are removed from the lower jaw, a new roller is created. The proportions of the face are determined by the anatomical and physiological method.

If the maxillary prosthesis is incorrectly positioned, the constructions of both jaws are removed and 2 new products are made.

By mistake, the doctor may underestimate the bite. In this case, all complications in the patient will be associated with insufficient load on the masticatory muscles. The main signs of underestimation of the upper third of the face:

• lip retraction;
• excessive severity of the nasolabial fold;
• pushing the chin forward.

Defects are eliminated according to the same algorithm as in the case described above.

Errors in the transversal plane

The doctor may make a mistake when fixing the CO, determining the anterior or lateral occlusion. It will be difficult for the patient to wear the prosthesis due to the fact that the product is constantly shifting in the oral cavity.

With erroneous fixation of the anterior occlusion, there is a lack of closure between the incisors. To eliminate the defect, the teeth are removed from the lower roller and the necessary orthodontic parameters are re-fixed.

A competent specialist can correctly determine the central occlusion. At the same time, he takes into account the anatomical and physiological characteristics of the patient.

After determining the CO and rechecking the data obtained, the doctor plasters the resulting wax models and poisons them to the laboratory for the manufacture of prostheses.

The video provides additional information on the topic of the article.

conclusions

From the foregoing, it is clear that the adequacy of creating a prosthesis that is convenient for the patient directly depends on the competent definition of central occlusion, and, in general, on the professionalism of the doctor.

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Requirements for wax bases with occlusal rollers:

bases should fit snugly to the models throughout;

the edges of the wax bases must be rounded, without sharp protrusions, they must be precisely “pressed” on the model;

wax bases must be reinforced with wire to prevent their deformation;

occlusal ridges should be monolithic and not delaminate;

the height of the roller should be 2 cm, width 8-10 mm;

the upper occlusal ridge in the area of ​​the second molars should be cut at an angle towards the maxillary tubercles.

In the event that the bite rollers are located opposite the natural teeth of the opposite jaw, then wax is cut from the occlusal surface of the bite roller to the thickness of the wax plate, which is heated and placed on the occlusal surface.

For the manufacture of wax bases, base wax is used, which is heated and pressed very tightly around the model.

With the help of bite recorders.

This type of fixation is carried out using high-viscosity silicone impression materials. The representatives of the latter are: Voco Register (Germany), Reprosil (USA), Regisil (USA), Garant Deception.

Methodology: The patient closes the teeth in the position of central occlusion. Using a syringe-gun, the paste is squeezed into the interdental spaces along the occlusal surface of the teeth, starting from the distal sections. After the paste has hardened, the patient is asked to open his mouth and the silicone template is removed.

2 Clinical stage

Determine the central ratio of the jaws.

Methods for establishing the lower jaw in the position of central occlusion.

Functional -

To establish the lower jaw in a central position, the patient's head is tilted slightly back. At the same time, the cervical muscles tense slightly, preventing the lower jaw from moving forward.

Then the index fingers are placed on the occlusal surface of the lower teeth or the roller in the region of the molars so that they simultaneously touch the corners of the mouth, slightly pushing them to the sides.

After that, the patient is asked to raise the tip of the tongue, touch the posterior parts of the hard palate and at the same time make a swallowing movement. This technique almost always ensures that the lower jaw is placed in a central position.

Some manuals on orthopedic dentistry recommend for this purpose on the upper wax template, along its posterior edge, to make a tubercle of wax, which the patient should get with his tongue before he swallows saliva, closing his mouth (Walkoff). When the patient closes his mouth, the bite ridges or occlusal surfaces of the teeth begin to approach, the index fingers lying on them are removed in such a way that they do not interrupt the connection with the corners of the mouth all the time, pushing them apart. Closing the mouth using the techniques described should be repeated several times until it is clear that proper closure is taking place.

violent

Instrumental(provides a number of devices that help establish the lower jaw in central occlusion), but they are rarely used, only in difficult cases of clinical practice. At the same time, the lower jaw is forcibly displaced posteriorly by the pressure of the doctor's hand on the patient's chin.

Central occlusion and its signs (articular, muscular, dental). Method for determining central occlusion. Various methods of fixing the position of the dentition in the central occlusion. Plastering models in the occluder and articulator.

Central occlusion - multiple fissure-tubercular contacts of the dentition, in which the articular heads are located in the thinnest avascular part of the articular discs in the anterior superior section of the articular fossae opposite the base of the articular tubercles, the chewing muscles are simultaneously and evenly contracted.

Signs of central occlusion:

I. Muscular sign - bilateral uniform contraction of the muscles that raise the lower jaw.

II. Articular sign - the articular head is located on the basis of the slope of the articular tubercle.

III. Dental sign - the maximum number of contact points.

Signs of clenched teeth:

1. Relating to all teeth:

Each tooth has two antagonists, with the exception of the lower central incisors and upper eighth teeth;

The dentitions of the upper and lower jaws end on the same vertical plane;

2. Signs of closure related to the anterior teeth:

The midline of the face coincides with the lines passing through the central incisors;

The upper anterior teeth overlap the lower ones of the same name by 1/3 of the height of the crowns;

Cutting-tubercular contact;

3. Signs related to the lateral teeth:

In the medio-distal direction - the medial buccal cusp of the first upper molar is located between the medial and distal cusps of the first lower, and the distal buccal cusp is located in the interval between the 6th and 7th lower;

In the vestibular-oral direction - the upper lateral teeth overlap the lower ones, the palatine teeth are located in the intertubercular groove of the lower ones.

The upper teeth along the entire perimeter of the dental arch overlap the lower teeth of the same name.

Method for determining central occlusion.

For the manufacture of prostheses, it is necessary to set the dentition in the central occlusion and transfer the appropriate landmarks to the model. The establishment of models in the central occlusion is carried out taking into account the presence and location of antagonistic teeth. There are three typical variants of the state of the dentition in the presence of defects in them, in which central occlusion is established in different ways.

First option. Dental rows with a large number of antagonistic teeth on the right and left. Central occlusion is established based on the maximum number of contact points between the dentition, without the use of wax templates with bite ridges.

Second option. It is characterized by the presence of three occlusal points between antagonistic teeth, however, the number of antagonistic teeth and their topography do not allow placing plaster models in the position of central occlusion without the use of wax bases with bite ridges. The prepared wax base with an occlusal roller is placed on the jaw and the patient is asked to close the dentition. In this way, imprints of antagonist teeth are obtained. If there is no occlusal contact between natural teeth, then the wax roller is cut off until there is uniform contact between them and the occlusal roller in the places of missing antagonist teeth. Formed on the occlusal roller contact points contribute to the precise establishment of models in the central occlusion of the dentition.

Third option. It is characterized by the absence of antagonistic pairs of teeth. In this case, the central ratio of the jaws is set as follows. First, the height of the lower part of the face is set in a state of relative rest (height of physiological rest). To do this, the prosthetist is asked to lower the lower jaw so that the facial muscles are completely relaxed and the lips close without tension. This position is fixed with a spatula or ruler and proceed to determine the central occlusion. A wax base with an occlusal roller is introduced into the oral cavity and the patient is asked to slowly close the dentition. When closing the dentition, patients often set the lower jaw incorrectly - they shift it forward or to the side.

In order to fix the correct position of the dentition in central occlusion, various methods are used:

In the presence of antagonistic teeth, the position of the central occlusion is checked by closing the teeth. After that, a strip of wax is placed on the occlusal surface of the fitted roller, glued, and then softened hot. Without allowing the wax to cool, the templates are inserted into the oral cavity and the patient is asked to close his teeth. On the softened surface of the wax, imprints of the teeth remain - they serve as a guide for compiling models in a central ratio.

If the occlusal surface of the upper and lower bite rollers closes, then wedge-shaped cuts are made on the occlusal surface of the upper bite roller. A thin layer is removed from the lower roller, opposite the cuts, and a heated strip of wax is attached to it. Then the patient is asked to close his jaws, and the heated wax of the lower roller enters the cuts on the upper one in the form of wedge-shaped protrusions. The rollers are removed from the oral cavity, cooled, installed on the model.

For orthopedic purposes, it is important to know two measurements of the height of the lower face:

The first is measured with the dentition closed in the central occlusion, while the height of the lower part of the face is called morphological, or occlusal;

The second is determined in a state of functional rest of the masticatory muscles, when the lower jaw is lowered and a gap appears between the teeth, this is the functional height.

The anatomical and physiological method for determining the interalveolar height is as follows: the patient makes various movements of the lower jaw, then raises the lower jaw until the upper and lower lips lightly touch. In this position, the orthopedist measures the lower part of the face (in a state of physiological rest). Subtract 2-3 mm from the obtained value - this is the interalveolar height with central occlusion.

To correctly establish the lower jaw, the following techniques are used:

1) ask the patient to swallow saliva while closing the jaws;

2) ask the patient to rest against the soft palate with the tip of the tongue.

In addition to these techniques, it is necessary to place the palm of the right hand on the chin and, while closing the oral cavity, push the jaw backwards, trying not to fix the central occlusion. When the dentition closes, the antagonistic teeth leave imprints on the occlusal ridge, which serve as reference points in the preparation of models.

Then check the occlusal height: it should be less than the height of physiological rest by 2-3 mm. After establishing the central occlusion, the models are plastered in an occluder or articulator.