RU2844623C1 - Method for diagnosing dentoalveolar anomalies depending on changes in craniovertebral joint in frontal plane - Google Patents

Abstract

FIELD: medical science.

SUBSTANCE: invention refers to medicine, namely to X-ray diagnostics and dentistry, and can be used in diagnosing dentoalveolar anomalies (DAA). CBCT is carried out and 3D images of the maxillofacial region are obtained. Molars and heads of the temporomandibular joint (TMJ) position is assessed in the frontal plane with reference points applied to the CBCT sections to obtain reference planes, namely the horizontal reference plane – the infraorbital plane Or-Or and the vertical reference plane. In the craniovertebral region, cephalometric points are applied on the CBCT cuts, and the planes drawn through the applied cephalometric points are used for analysis, the craniovertebral junction is assessed in the transversal plane and abnormal angles of the reference planes and the obtained cephalometric planes are assessed. Deviation of angles between planes indicates presence of dentoalveolar anomalies.

EFFECT: method provides the more reliable and accurate diagnosis of the DAA that enables providing the more predictable therapeutic effect ensured by assessing the changes in the craniovertebral joint.

1 cl, 14 dwg, 4 tbl, 3 ex

Description

The invention relates to the field of medicine, namely to CBCT (cone beam computed tomography) diagnostics in dentistry for assessing dental anomalies (DMA) depending on changes in the craniovertebral joint in the frontal plane and establishing the relationship between the tilt of the occlusal plane, the position of the heads of the TMJ (temporomandibular joint) and the position of the cervical vertebrae C1 and C2, related to the craniovertebral joint.

In the last decade, an increasing number of studies have been devoted to the biomechanical and neurological relationships of the dental system with other parts of the body. The increasing occurrence of combined occlusion and posture anomalies has become a pressing issue.

Reviews of foreign and domestic literature indicate that there is a need to improve the methodological quality of research, as well as to consider more specific clinical issues.

In particular, the relationship between occlusion and posture should be assessed from the point of view of a possible two-way effect, namely: occlusion influences posture and vice versa. At present, the literature data have been mainly based on the influence of dental occlusion on the position of the head and body, while there is very little information on the inverse influence of postural balance on the state of the dental system (1).

When studying osteopathy in relation to the vertical plane, the concepts of descending, ascending and mixed postural adaptation are considered. The descending type is characterized by initial changes in the jaw and face (as a result of various dental treatments, tooth loss, muscle changes or disorders in the temporomandibular joint), which then leads to compensation of the musculoskeletal and muscular system, causing deformations of the spine and feet. The ascending type indicates changes that begin in the foot (for example, flat valgus foot), after which there is an imbalance of the back muscles, rotation of the lumbosacral bones, scoliosis, lordosis and kyphosis of the thoracic or cervical spine. There are also changes in the position of C1 - the first cervical vertebra (atlas), spheno-basilar synchondrosis and an effect on the closure of the dental arches (2, 3).

As a result of posture studies in patients with occlusal plane tilt, it was found that lateral displacement of the lower jaw is accompanied by an elevation of the occlusal plane in the direction of the lower jaw displacement. The consequence of the tilt of the occlusal plane in the lateral part of the dental arches will be disturbances in the cervical spine, which lead to a change in the distribution of stress in this area and cause asymmetry, affecting the postural balance (4-5).

The stomatognathic system is an integral component of the upper body and may play an important role in postural control. Changes in body posture may affect the development of the maxillofacial region. According to various scientific sources, spatial relationships between the jaws may affect muscle balance and cause postural adaptation of the body (6).

Based on the above, it is possible to trace the presence of a certain relationship between disorders of the musculoskeletal system and dentoalveolar anomalies, which can be generalized into the concept of postural imbalance. Effective diagnostics and treatment of postural balance disorders should be carried out comprehensively by an orthodontist and osteopath. Osteopathic correction of posture disorders together with dental treatment increases the adaptation of the body to new occlusal relationships of the dental arches (7).

Currently, CBCT is the method of choice for an orthodontist, as it is the most informative in comparison with other studies (8).

At present, there is no single algorithm for diagnosing dental anomalies in the dental community, which, in turn, affects the course of treatment and the occurrence of relapses (9).

In the field of technology, patent for invention RU 2694175 is known, published on 07/09/2019 "A method for comprehensive diagnostics of occlusion", i.e. the closure of dental arches or individual groups of antagonist teeth. X-ray examinations are performed sequentially: teleradiography (TRG) of the head in the lateral plane, orthopantomography (OPG), CT of the temporomandibular joint (CT TMJ) to identify anatomical changes in the articular head, glenoid cavity and disturbances in the relationship of bone structures. Based on the data of OPG, TRG and CT TMJ, the presence or absence of anatomical changes in bone structures is established and a preliminary diagnosis is formulated. The method ensures a definitive diagnosis in a short time, taking into account the anatomical and functional disorders of occlusion, allows for a comprehensive treatment plan to be drawn up and the percentage of complications and relapses of diseases to be reduced.

The disadvantages of this method include its complexity and the use of various examination methods and their subsequent combination.

The closest in technical essence and taken as a prototype is patent RU 2117444 “Method for diagnosing diseases of the craniovertebral region”, published on 20.08.98.

An X-ray examination is performed in direct and lateral projections of the skull and upper cervical spine in the patient's physiological position, and an additional X-ray is taken in the lateral plane with the patient's head flexed and the chin brought to the chest. When taking pictures in lateral projections, the central X-ray beam is directed at the sella turcica. Then, on the resulting pictures, angular and linear indicators are determined, as well as the condition of the cranial vault and the entire cervical spine according to a unified diagnostic scheme. If the patient has physiological features, a picture is also taken in the anterior nasofrontal projection.

The disadvantage of this method is the need to take several pictures in different projections to obtain an image, which increases the radiation load on the human body and is quite labor-intensive. In this analysis, calculations are made on planar pictures that have an overlap of other bone structures, the emphasis is primarily on the sagittal plane without assessing dental anomalies.

The problem addressed by the invention is the development of a method for diagnosing dentoalveolar anomalies depending on changes in the craniovertebral joint in the frontal plane using CBCT to develop a unified diagnostic algorithm.

The technical result consists in creating a more reliable and accurate diagnosis of dentoalveolar anomalies depending on changes in the craniovertebral joint in the frontal plane according to CBCT, which will improve the predictability of the treatment outcome.

The essence of the developed method is that an X-ray examination is carried out - cone-beam computed tomography of the patient's head in the usual closure of the dental arches. As a result of this study, a digital 3D-volume image of the facial and cerebral sections of the skull and the upper cervical spine is obtained. The result of the study (CBCT) is assessed in 3 planes - frontal (coronal), sagittal and axial planes.

When implementing the method in the frontal plane, changes in the craniovertebral joint are assessed relative to the position of the molars and heads of the TMJ (temporomandibular joint) as follows:

Reference points are applied to the CBCT sections in the frontal plane to obtain reference planes. To describe the characteristics of the first permanent molars of the upper jaw, the heads of the TMJ and the cranivertebral region, cephalometric points are applied to the CBCT sections in the frontal plane, and cephalometric planes drawn through the specified points are used for analysis.

Deviation from the norm of the angles between the plane of the upper first molars and the reference plane indicates the presence of dental anomalies, that is, the tilt of the occlusal plane, which leads to uneven abrasion of tooth enamel and asymmetrical tone of the masticatory muscles.

Deviation of the angle between the reference plane and the cephalometric plane in the TMJ area from the norm indicates different heights of the TMJ heads, which leads to the development of TMJ dysfunction.

The craniovertebral joint in the frontal plane and deviations from the norm of angles between the reference planes and the obtained cephalometric planes are assessed.

In this way, dental anomalies and the presence of changes in the craniovertebral joint in the frontal plane are diagnosed.

A study of the craniovertebral region (CVR) was conducted in the frontal plane using CBCT in natural occlusion with TMJ.

The reference (standard) points and reference planes used in the analysis are presented in Tables 1, 2 and in Fig. 1, which shows a CBCT slice in the frontal plane.

Table 1 - Points used to define reference planes

Designation Name Definition Paired dots Or orbital The lowest point on the lower edge of the orbit Unpaired dots N nation the point of intersection of the nasofrontal suture with the median Cg Crista Galli the middle of the base of the cockscomb, the narrowest point ANS anterior nasalis spina anterior nasal spine

Table 2 - Reference planes used in the analysis

Designation Name Definition Or-Or Horizontal reference plane
(infraorbital plane) The plane drawn through the points Or on the right and left MP Midsagittal reference plane
(middle plane) median plane drawn through points N, Cg, ANS

In this analysis, 1 known point and 11 new cephalometric points were used to describe the characteristics of the maxillary first permanent molars in the craniovertebral region.

The points used in the analysis are presented in Table 3 and Table 4 and in Fig. 2 CBCT section in the frontal plane, where the OR plane is indicated, drawn through the MsP points on the right and left, and in Fig. 3 CBCT section in the frontal plane (TMJ with paired Co points)

Table 3 - Cephalometric points used in the analysis

Designation Name Definition Molars of the upper jaw - paired points (Fig. 2 CBCT section in the frontal plane.) MSP molar superior palatine tubercle palatal cusp of the upper first molar (point of contact of the upper molar with the lower ones) Temporomandibular joint - paired points (Fig. 3 CBCT section in the frontal plane) With condylion the uppermost point of the condylar process of the mandible Craniovertebral region (Fig. 4. CBCT section in the frontal plane with cephalometric points indicated) Paired dots PrTr1 C1 transverse process inferior point of the transverse process of the C1 vertebra PrTr2 C2 transverse process inferior point of the transverse process of the C2 vertebra AOu atlant - os occipitale upper point superior point of the joint space of the atlantooccipital joint AOl atlant - os occipitale lower point inferior point of the joint space of the atlantooccipital joint AAU atlant-axis upper point superior point of the joint space of the atlantoaxial joint AAl atlant-axis lower point inferior point of the joint space of the atlantoaxial joint LMC1 lateral mass C1 the most convex point of the lateral masses of the C1 vertebra Unpaired dots AD apex dentis apex of the C2 vertebral tooth CV vertebral body the lower point of the middle of the body of the C2 vertebra m the point of intersection of the line drawn through LMC1 from the right and from the left with the line AL

Figure 5 shows a CBCT section in the frontal plane with an image of the planes used for analysis.

The name and definition of the planes of the craniovertebral region are presented in Table 4.

Table 4 - Cephalometric planes used in the analysis

Designation Name Definition Molars of the upper jaw (Fig. 2 CBCT section in the frontal plane.) OR occlusal plane plane drawn through points MsP on the right and left Temporomandibular joint (Fig. 3) So-So TMJ plane plane drawn through points Co on the right and left Craniovertebral region (Fig. 5) CBCT in the frontal plane. Cephalometric planes of the craniovertebral region. PrTr1- PrTr1 plane of transverse processes of vertebra C1 plane drawn through points PrTr1 on the right and left PrTr2- PrTr2 plane of transverse processes of vertebra C2 plane drawn through points PrTr2 on the right and left AOu - AOl R plane of the joint space of the atlanto-occipital joint on the right plane drawn through points AOu and AOl on the right AOu - AOl L plane of the joint space of the atlanto-occipital joint on the left plane drawn through points AOu and AOl on the left AAu - AAl R plane of the joint space of the atlantoaxial joint on the right plane drawn through points AAu and AAl on the right AAu - AAl L plane of the joint space of the atlantoaxial joint on the left plane drawn through points AAu and AAl on the left AL axis line - plane of the C2 vertebra plane drawn through points AD and CV

After this, the angles between the reference plane Or-Or (Fig. 1) and the planes OR (Fig. 2), Co-Co (Fig. 3), PrTr1- PrTr1 (Fig. 5), PrTr2- PrTr2 (Fig. 5) are measured separately.

Normally these angles should be equal to 0 degrees, with an error of 0.5 degrees.

Deviation from the norm of the angle between the Or-Or and OR planes indicates a tilt of the occlusal plane, which leads to uneven wear of tooth enamel and asymmetrical tone of the masticatory muscles.

Deviation of the angle between the reference plane Or-Or and the plane Co-Co from the norm indicates a different height of the TMJ heads, which can lead to the development of TMJ dysfunction.

Deviation from the norm of the angle between the planes Or-Or and PrTr1- PrTr1 and the angle between the planes Or-Or and PrTr2- PrTr2 indicates the presence of tilt of the vertebra C1 and C2, respectively. In rare cases, such a deviation may be a feature of the development of these vertebrae.

Next, the angle between the MP plane (reference line) and the AL plane (plane of the C2 vertebra) is measured.

Normally, this angle should be equal to 0 degrees, a possible normal variant has a variability of 1 degree.

Deviation from the norm of the angle between the MP and AL planes indicates rotation and tilt of the C2 vertebra (axis), which can lead to the development of neurological symptoms.

The next step is to evaluate the position of the intersection points of the AOu - AOl R and AOu - AOl L planes and the Au - AAl R and AAu - AAl L planes relative to the AL plane.

Normally, they should be located on this plane. Deviation from the norm indicates rotation and/or tilt of the C1 and C2 vertebrae relative to each other and the occipital bone (os occipitale).

Next, the distance between point LMC1 on the right to point m and point LMC1 on the left to point m is measured.

Normally, these distances should be equal to each other or have a difference of no more than 0.5 mm. An increase in the difference between these parameters means rotation and/or tilt of the C2 vertebra relative to the C1 vertebra.

Based on these deviations from the norm, it is possible to judge the relationship between changes in the craniovertebral joint with the inclination of the occlusal plane, which leads to tooth wear, and with the inclination of the plane of the TMJ heads, which can lead to the development of TMJ dysfunction.

Clinical example #1

Patient female, 27 years old. According to CBCT data, the same height of the palatal cusps of the first permanent upper molars is noted (Fig. 6 - CBCT section in the frontal plane in the area of the first permanent molars. In the figure, the green line indicates the plane of the upper molars OR, the blue line indicates the reference planes Or-Or and MP.)

In this clinical case, these planes are parallel to each other, which indicates the absence of inclination of the occlusal plane.

On the CBCT section in the frontal plane in the TMJ area, parallelism of the plane of the TMJ heads, drawn through the Co-Co points, with the Or-Or reference plane is noted, which indicates the symmetry of the position of the TMJ heads. (Fig. 7 CBCT section in the frontal plane in the TMJ area. In the figure, the Co-Co plane of the TMJ heads is indicated by the green line, the Or-Or (infraorbital) reference planes are indicated in blue Or-Or plane) and MP.)

When assessing the craniovertebral articulation, it is noted that the main axis of the C2 vertebra (AL) corresponds to the reference median plane (MP). The C2 vertebra is located symmetrically relative to the C1 vertebra, as evidenced by the fact that the distance between the LMC1 point on the right to the m point (10.33 mm) and the LMC1 point on the left to the m point (10.55 mm) are almost identical. The intersection of the planes drawn along the articular surfaces of the atlas-occipital articulation (AOu - AOl R and AOu - AOl L) and the atlas-axial articulation (Au - AAl R and AAu - AAl L) is symmetrical and is located on the plane of the main axis of the C2 vertebra (AL). The plane drawn through the transverse processes of the C2 vertebra (PrTr2- PrTr2) is parallel to the infraorbital plane (Or-Or). The plane drawn through the transverse processes of the C1 vertebra (PrTr1- PrTr1) has a slight deviation from the infraorbital plane. Since all other parameters are normal, this deviation is a structural feature and not a sign of C1 vertebra rotation. (Fig. 8 CBCT section in the frontal plane in the craniovertebral region. In the figure, the green lines indicate the planes PrTr1- PrTr1, PrTr2- PrTr2 and AL, the green arrows indicate the distance between the point LMC1 on the right to the point m and the point LMC1 on the left to the point m, the orange lines indicate the planes AOu - AOl R and AOu - AOl L, the purple lines indicate the planes Au - AAl R and AAu - AAl L, the blue color indicates the reference planes Or-Or and MP and their planes).

Thus, with a symmetrical position of the C2 vertebra relative to the C1 vertebra, the absence of rotation and tilt, parallelism of the planes of the upper molars (OR) and the heads of the TMJ (Co-Co) with the reference plane Or-Or is noted, which indicates the absence of tilt of the occlusal plane, that is, this dentoalveolar anomaly.

Clinical example #2

Patient m., 23 years old. According to CBCT data, there is a deviation of the plane drawn through the palatine tubercles of the first permanent molars of the upper jaw (OR) from the infraorbital plane Or-Or by 2.7 degrees - the right molar is located below the left (Fig. 9), which indicates a tilt of the occlusal plane to the right.

Fig. 9. CBCT section in the frontal plane in the area of the first permanent molars. In the figure, the green line indicates the plane of the upper molars OR, the blue color indicates the reference planes Or-Or and MP. In this clinical case, we see that the right molar is lower than the left, the angle between the planes Or-Or and OR is 2.7 degrees - there is a tilt of the occlusal plane to the right.

On the CBCT section in the frontal plane in the TMJ area, it is noted that the right head of the TMJ is lower than the left, the angle between the Or-Or and Co-Co planes is 1.9 degrees - there is a tilt of the plane of the TMJ heads to the right, an asymmetrical position.

Fig. 10 CBCT section in the frontal plane in the TMJ area. In the figure, the green line indicates the plane of the TMJ heads Co-Co, and the blue line indicates the reference planes Or-Or and MP.

When assessing the craniovertebral articulation, it is noted that the main axis of the C2 vertebra (AL) is deviated from the reference midline (MP) to the right, the angle is 6.2 degrees. The C2 vertebra is displaced to the right relative to the C1 vertebra, as evidenced by the difference in the distance between the LMC1 point on the right to the m point (7.4 mm) and the LMC1 point on the left to the m point (9.9 mm). The intersection point of the planes drawn along the articular surfaces of the atlas-occipital articulation (AOu - AOl R and AOu - AOl L) is to the right of the plane of the main axis of the C2 vertebra (AL); the intersection point of the planes drawn along the articular surfaces of the atlas-axial articulation (Au - AAl R and AAu - AAl L) is to the left of the plane of the main axis of the C2 vertebra (AL).

The plane drawn through the transverse processes of the C1 vertebra (PrTr1- PrTr1) has a slope to the right relative to the infraorbital plane (Or-Or), the angle is 1.1 degrees. The plane drawn through the transverse processes of the C2 vertebra (PrTr2- PrTr2) PrTr2 has a slope to the right relative to the infraorbital plane (Or-Or), the angle is 3.3 degrees.

Fig. 11. CBCT section in the frontal plane in the craniovertebral region. In the figure, the green lines indicate the planes PrTr1- PrTr1, PrTr2- PrTr2 and AL, the green arrows indicate the distance between the point LMC1 on the right to the point m and the point LMC1 on the left to the point m, the orange lines indicate the planes AOu - AOl R and AOu - AOl L, the purple lines indicate the planes Au - AAl R and AAu - AAl L, the blue color indicates the reference planes Or-Or and MP and their planes.

Thus, in the presence of changes in the craniovertebral region, namely the tilt of the C2 vertebra to the right, its rotation relative to the C1 vertebra to the right, there is a tilt of the occlusal plane to the right and a tilt of the plane of the TMJ heads to the right, which can lead to uneven abrasion of the teeth and dysfunction of the TMJ, which is related to dentoalveolar anomalies.

Clinical example 3.

Patient female, 32 years old.

According to CBCT data, there is a deviation of the plane drawn through the palatine tubercles of the first permanent molars of the upper jaw (OR) from the infraorbital plane Or-Or by 1.2 degrees - the left molar is located below the right (Fig. 12), which indicates a tilt of the occlusal plane to the left.

Fig. 12. CBCT section in the frontal plane in the area of the first permanent molars. In the figure, the green line indicates the plane of the upper molars OR, and the blue line indicates the reference planes Or-Or and MP.

On the CBCT section in the frontal plane in the TMJ area, it is noted that the left head of the TMJ is located lower than the right, the angle between the Or-Or and Co-Co planes is 1.9 degrees - there is a tilt of the plane of the TMJ heads to the left, an asymmetric position (Fig. 13).

Fig. 13 CBCT section in the frontal plane in the TMJ area. In the figure, the green line indicates the plane of the TMJ heads Co-Co, and the blue line indicates the reference planes Or-Or and MP.

When assessing the craniovertebral articulation, it is noted that the main axis of the C2 vertebra (AL) is deviated from the reference midline (MR) to the left, the angle is 4.5 degrees. The C2 vertebra is located almost symmetrically relative to the C1 vertebra, as evidenced by the fact that the distances between the LMC1 point on the right to the m point (8.2 mm) and the LMC1 point on the left to the m point (8.6 mm) are almost identical. The intersection point of the planes drawn along the articular surfaces of the atlas-occipital articulation (AOu - AOl R and AOu - AOl L) is to the right of the plane of the main axis of the C2 vertebra (AL); the intersection point of the planes drawn along the articular surfaces of the atlas-axial articulation (Au - AAl R and AAu - AAl L) is on the plane of the main axis of the C2 vertebra (AL).

The plane drawn through the transverse processes of the C1 vertebra (PrTr1- PrTr1) has a leftward slope relative to the infraorbital plane (Or-Or), the angle is 2.3 degrees. The plane drawn through the transverse processes of the C2 vertebra (PrTr2- PrTr2) PrTr2 has a leftward slope relative to the infraorbital plane (Or-Or), the angle is 1.6 degrees.

Fig. 14. CBCT section in the frontal plane in the craniovertebral region. In the figure, the green lines indicate the planes PrTr1- PrTr1, PrTr2- PrTr2 and AL, the green arrows indicate the distance between the point LMC1 on the right to the point m and the point LMC1 on the left to the point m, the orange lines indicate the planes AOu - AOl R and AOu - AOl L, the purple lines indicate the planes Au - AAl R and AAu - AAl L, the blue color indicates the reference planes Or-Or and MP and their planes.

Thus, in the presence of changes in the craniovertebral joint, namely rotation of the entire craniovertebral joint to the left, there is a tilt of the occlusal plane and the plane of the TMJ heads to the left, which can lead to uneven abrasion of the teeth and dysfunction of the TMJ, which is related to dentoalveolar anomalies.

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Claims (9)

A method for diagnosing dental anomalies, characterized by the fact that a cone-beam computed tomography of the patient's head is performed, a volumetric 3D image of the facial and cerebral sections of the skull and the upper cervical spine in the frontal plane is obtained, reference planes are marked on the CBCT section - the infraorbital plane Or-Or and the midsagittal plane MSP, then cephalometric points are marked: paired points: MsP - the palatine tubercle of the upper first molar, namely the point of contact of the upper molar with the lower ones; Co - the uppermost point of the condylar process of the mandible; PrTr1 - the lower point of the transverse process of the C1 vertebra, PrTr2 - the lower point of the transverse process of the C2 vertebra, AOu - the upper point of the joint space of the atlanto-occipital joint, AOl - the lower point of the joint space of the atlanto-occipital joint, AAu - the upper point of the joint space of the atlanto-axial joint, AAl - the lower point of the joint space of the atlanto-axial joint, LMС1 - the most convex point of the lateral masses of the C1 vertebra; unpaired points: AD - the apex of the tooth of the C2 vertebra, CV - the lower point of the middle of the body of the C2 vertebra, m - the point of intersection of the line drawn through LMC1 on the right and left with the line AL-drawn through the points AD and CV; then define the planes: OP - occlusal plane drawn through points MsP on the right and left, Co-Co - plane drawn through points Co on the right and left, PrTr1-PrTr1 - plane of transverse processes of vertebra C1 drawn through points PrTr1 on the right and left, PrTr2-PrTr2 - plane of transverse processes of vertebra C2 drawn through points PrTr2 on the right and left, AOu - AOl R plane of joint space of atlanto-occipital articulation on the right drawn through points AOu and AOl on the right, AOu - AOl L - plane of joint space of atlanto-occipital articulation on the left drawn through points AOu and AOl on the left, AAu - AAl R - plane of joint space of atlanto-axial articulation on the right drawn through points AAu and AAl on the right, AAu - AAl L - the plane of the joint space of the atlantoaxial joint on the left, drawn through points AAu and AAl on the left, AL axis line - the plane of the C2 vertebra drawn through points AD and CV; then, the angles between the reference plane Or-Or and the planes OP, Co-Co, PrTr1- PrTr1, PrTr2- PrTr2 are measured separately, taking 0 degrees as the norm; if the angle between the planes Or-Or and OP deviates from the norm, the inclination of the occlusal plane is determined; if the angle between the planes Or-Or and Co-Co deviates from the norm, the asymmetric position of the heads of the temporomandibular joint (TMJ) is determined; if the angle between the planes Or-Or and PrTr1- PrTr1 and the angle between the planes Or-Or and PrTr2- PrTr2 deviates from the norm, the presence of an inclination of the vertebra C1 and C2, respectively, is determined, leading to an inclination of the occlusal plane and an asymmetric position of the heads of the TMJ; measure the angle between the MSP plane and the AL plane, taking 0 degrees as the norm; if there is a deviation from the norm, determine the rotation and tilt of the C2 vertebra, leading to the tilt of the occlusal plane and an asymmetric position of the TMJ heads; assess the position of the intersection points of the planes AOu - AOl R and AOu - AOl L and the planes AАu - АAl R and AAu - АAl L relative to the plane AL; normally, the intersection points should be located on the plane AL; if there is a deviation from the norm, the rotation and/or tilt of the C1 and C2 vertebrae relative to each other and the occipital bone is determined, leading to the tilt of the occlusal plane and an asymmetric position of the TMJ heads; measure the distance between point LMC1 on the right to point m and point LMC1 on the left to point m, normally these distances should be equal to each other or have a difference of no more than 0.5 mm; if the difference between these parameters increases, determine the rotation and/or tilt of the C2 vertebra relative to the C1 vertebra, leading to a tilt of the occlusal plane and an asymmetric position of the TMJ heads.