Determination of the location of the temporomandibular joint disc during magnetic resonance imaging visualization

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Introduction

The temporomandibular joint (TMJ) is a combined paired joint that ensures optimal occlusal relationships between the dental arches, phonetic capabilities, and aesthetics of the human facial skull. Anatomical and functional disturbances in the jaw relationship are one of the main causes of degenerative-dystrophic lesions of the TMJ bone-cartilaginous structures, tendon-muscle attachments, and ligaments, leading to persistent morphological changes in the joint components, disability, and a reduced quality of life [1–3].

The dynamic development of technical capabilities for visualizing TMJ elements is outpacing improvements in methods for analyzing static and dynamic images. To improve the accuracy of TMJ image craniometry (computed tomography, cone beam computed tomography, magnetic resonance imaging), along with the development and improvement of methods and techniques for obtaining images, it is necessary to focus efforts on the development of methods for analyzing the images obtained, based on the use of anatomical landmarks that meet the criteria of the craniometric point [4–6]. At the same time, image analysis should be based on modern morphofunctional data on TMJ elements [7–9].

Consequently, optimizing methods for obtaining and analyzing images of anatomical structures of the TMJ remains one of the most pressing diagnostic tasks in formulating a final diagnosis and planning treatment for TMJ disorders [10–12].

The aim of the study is to optimize the conditions for determining the location of the TMJ disc during magnetic resonance imaging.

Materials and Methods

We analyzed MRI images of the TMJ obtained from 11 patients. MRI examinations were performed using a 1.5-ton unit (Magnetom Vision, Siemens, Erlangen, Germany) with a dual surface coil for the temporomandibular joint. For each patient, a multi-second examination was performed with nine slices for each joint in several planes (slice thickness 2.5 mm). All patients had bilateral oblique sagittal T₁-weighted spin echo sequences [repetition time (TR) = 550 ms, echo time (TE) = 13 ms, field of vision (FOV) 14×14 cm] with the mouth open and closed. Other images available for review included T₂-weighted spin echo images in the oblique sagittal plane (TR = 3570, TE = 67) with the mouth open and closed.

The weighted sagittal plane in both closed and open positions was obtained based on image density with a spin echo sequence (TR = 3570, TE = 22). T1-weighted coronal images were obtained only with the mouth closed (TR = 550 ms, TE = 13 ms). Analysis of the MRI images of the TMJ was performed by two independent radiologists with appropriate certification.

Results and Discussion

The proposed method for diagnosing the anatomical and functional state of the TMJ is based on the analysis of TMJ images obtained by magnetic resonance imaging (MRI) of the TMJ in the oblique sagittal projection, which corresponds to the frontal plane of the caput mandibulae (CM), in two joint positions—mouth closed and maximum mouth opening—based on which a comprehensive criterion for the condition of the TMJ is determined*. The originality of the complex criterion of the TMJ condition is that it combines three types of data (tables).

These include angular values:

1. The indicator of the displacement of the rear pole of the disc relative to the upper pole of the caput mandibulae CM in the polar coordinate system, which is calculated from the geometric center of the CM in the range from 90° to 180° at maximum intercuspal contact of the dental arches.
2. Disc shape indicator, accepting values: undeformed and deformed.
3. Disc movement synchrony index, which can be: complete, partial, absent (see table) at maximum possible mouth opening.

 

Comprehensive TMJ condition criteria indicators based on MRI imaging data

Rear pole dislocation index of the disc	Disc shape index	Disc movement synchronisation index
90о15о	Undeformed. Deformed	Complete. Partial. Absent
120о15о
150о15о
180о15о

 

Fig. 1. Angular values of the rear pole dislocation index relative to the upper pole of the CM in the polar coordinate system in the rear pole position range from 90° to 180°: a – angular value 90°; b – angular value 120°–2°; c – angular value 150°–15°; d – angular value 180°

 

Angular values indices of the posterior pole dislocation of the articular disc relative to the upper pole of the CM, interpreted in digital form (Fig. 1).

The indices of disc position and disc repositioning are elements of the sets: {undeformed, deformed}, {complete, partial, absent}.

During diagnosis, the angular value of the posterior pole dislocation index relative to the upper pole of the CM is determined in a polar coordinate system with its origin at the geometric center of the condylar process of the lower jaw in the range of the posterior pole position of the disc from 90° to 180° in the position of multiple intercuspal contact of the teeth, the physical condition of each articular disc is determined, taking the following values: undeformed and deformed, identify the possibility of disc repositioning with wide mouth opening, determining the repositioning index of each articular disc when opening the mouth, which takes the following values: complete, partial, absent, for diagnosis, a comprehensive TMJ condition criterion is used, including:

1) the index of displacement of the posterior pole of each articular disc relative to the upper pole of the articular head in a polar coordinate system with its origin at the geometric center of the condylar process of the lower jaw in states of intercuspal contact of the teeth in the range from 90° to 180°;

2) the index of the physical condition of each joint disc, taking the values: undeformed and deformed;

3) the index of repositioning of each articular disc when opening the mouth, taking the following values: complete, partial, absent.

In accordance with the comprehensive criterion calculated on the basis of the values of the above indicators, the position of the TMJ disc in relation to the head of the lower jaw is determined by its belonging to one of the sets (Fig. 2):

1) reversible dislocation = {(90° ± 15°, undeformed, complete), (90° ± 15°, undeformed, partial)};

2) borderline dislocation = {(90° ± 15°, undeformed, absent), (90° ± 15°, deformed, complete), (90° ± 15°, deformed, partial), (90° ± 15°, deformed, absent), (120° ± 15°, undeformed, complete), (120° ± 15°, undeformed, partial), (120° ± 15°, undeformed, absent), (120° ± 15°, deformed, complete), (120° ± 15°, deformed, partial), (120° ± 15°, deformed, absent)};

3) irreversible dislocation = {(150° ± 15°, undeformed, complete), (150° ± 15°, undeformed, partial), (150° ± 15°, undeformed, absent), (150° ± 15°, deformed, complete), (150° ± 15°, deformed, partial), (150° ± 15°, deformed, absent), (180° ± 15°, undeformed, complete), (180° ± 15°, undeformed, partial), (180° ± 15°, undeformed, absent), (180° ± 15°, deformed, complete), (180° ± 15°, deformed, partial), (180° ± 15°, deformed, absent)}, where the first element is the index of dislocation of the posterior pole of the disc relative to the upper pole of the CM in the polar coordinate system with its origin at the geometric center of the condylar head of the joint, the second element is the index of the physical condition of the articular disc, the third element is an index of disc repositioning when opening the mouth, and based on the data obtained, the indices of the complex criterion of the condition of each TMJ disc and the possibility of further treatment are compared.

The proposed method has been implemented in practice and is supported by clinical examples.

Female patient 1. 29 years old, visited a dental clinic on the recommendation of a surgeon, where she is undergoing treatment for post-traumatic pain syndrome in the TMJ area on the right and left sides.

Medical history: About 10 years ago, the patient complained of pain in her left joint and limited mouth opening. No treatment was administered. Over time, the intensity of pain decreased, the range of mouth opening was restored, and clicking sounds appeared in the TMJ area. A month ago, while playing with a child, she received a blow to the chin, causing my lower jaw to shift backward and upward, accompanied by sharp pain in the right TMJ area. After that, she experienced limited mouth opening.

 

Fig. 2. A comprehensive criterion for determining the state of TMJ

 

After that, she experienced limited mouth opening. At the time of consultation, external examination revealed facial asymmetry, moderate pain when opening the mouth up to 30 mm, and a 2 mm deviation of the lower jaw to the right. Palpation of the masticatory muscles was painless. On the cone beam computed tomography scan, there are no changes in the bone structures of the TMJ on the right side, while on the left side, the anterior surface of the condylar head is flattened. Against the background of anti-inflammatory treatment and splint therapy, pain, clicking, and deviation of the lower jaw have decreased.

Magnetic resonance imaging of the temporomandibular joint was performed in the position of multiple intercuspal contact of the teeth and with the mouth wide open. Sagittal sections on the right side in the position of multiple intercuspal contact of the teeth and with the mouth wide open are shown in Fig. 3, a, b, respectively.

 

Fig. 3. Patient 1. Magnetic resonance imaging of the temporomandibular joint on the right (a – in the position of central occlusion; b – with the mouth wide open) and on the left (c – in the position of central occlusion; d – with the mouth wide open)

 

Sagittal sections on the left side in the position of multiple intercuspal contact of the teeth and with the mouth wide open are shown in Fig. 3, c, d, respectively.

According to the data presented (see table, Fig. 2), when evaluating the patient's magnetic resonance imaging in accordance with the comprehensive criteria, the following indicators of the condition of the TMJ on the right side were determined: borderline dislocation (120° ± 15°, undeformed, complete) and on the left side: irreversible dislocation (150° ± 15°, undeformed, complete). That is, asymmetrical changes in the condition of the intra-articular structures on the right and left sides were detected: the articular discs are not deformed, partially dislocated (the posterior pole of the articular disc is 120° ± 15° on the right and 150° ± 15° on the left) and can be fully reduced.

As a result of the examination, the following diagnosis was made: K 07.6 dysfunction of the temporomandibular joint, borderline dislocation of the articular disc on the right and irreversible dislocation on the left. When planning orthodontic and orthopedic treatment, it is recommended to create conditions for improving the position of the articular condyle and repositioning the disc on the right and improving the position of the articular condyle without repositioning the disc on the left, creating protective occlusal support to reduce compression of the intra-articular structures.

Female patient 2. 20 years old, referred to a dental clinic by a dental surgeon for treatment of exacerbation of chronic subluxation of the left TMJ.

Medical history: a year ago, the patient first experienced acute pain, which was more pronounced in the left TMJ area. No treatment was provided. Over time, the intensity of the pain decreased, and clicking sounds appeared in the TMJ area, more pronounced on the left side. At the time of consultation, external examination revealed facial asymmetry, painless mouth opening up to 40 mm, 1 mm deviation of the lower jaw to the left, and early TMJ clicking, more pronounced on the left side. Palpation of the masticatory muscles was painless. On the CBCT on the right there are no changes in the bone structures of the TMJ; on the left side, the condylar head has bone spurs on the anterior surface, and the posterior surface of the head is flattened.

After clinical examination, magnetic resonance imaging of the temporomandibular joint was performed on the right and left sides in a position of multiple intercuspal contact of the teeth and with the mouth wide open. Sagittal sections on the right side in the position of multiple intercuspal contact of the teeth and with the mouth wide open are shown in Fig. 4, a, b, respectively.

Sagittal sections on the left side in the position of multiple intercuspal contact of the teeth and with the mouth wide open are shown in Fig. 4, c, d, respectively.

Magnetic resonance imaging of the patient revealed asymmetrical changes in the condition of the intra-articular structures on the right and left sides: the articular discs on the right and left are not deformed, there is no dislocation on the right (the posterior pole of the articular disc is at 90° ± 15°), the disc is fully reduced, on the left the disc is completely dislocated (the posterior pole of the articular disc is at 180° ± 15°), there is no reduction.

That is, according to the comprehensive criterion: on the right: reversible dislocation (90° ± 15°, undeformed, complete), on the left: irreversible dislocation (180° ± 15°, undeformed, absent).

This indicates asymmetric destruction of intra-articular structures: the presence of irreversible dislocation of the left articular disc.

 

Fig. 4. Patient 2. Magnetic resonance imaging of the temporomandibular joint on the right (a – in the position of central occlusion; b – with the mouth wide open) and on the left (c – in the position of central occlusion; d – with the mouth wide open)

 

After examination, the diagnosis was made: K 07.6 – dysfunction of the temporomandibular joint, reversible dislocation of the articular disc on the right and irreversible dislocation on the left. When planning orthodontic treatment, it is recommended to create conditions for preserving the position of the articular condyle and repositioning the disc on the right and improving the position of the articular condyle without repositioning the disc on the left, creating protective occlusal support for this purpose.

Conclusions

The proposed method, based on the use of a comprehensive criterion for assessing the condition of the TMJ and visualizing it in the form of a diagram of the intra-articular structures, allows for rapid and reliable diagnosis of the condition of the intra-articular structures of the TMJ and, accordingly, quick planning of orthodontic and orthopedic treatment for patients. An additional advantage is the ability to reposition the disc with a wide mouth opening, as well as the use of the disc displacement index in relation to the upper pole of the articular head in a polar coordinate system with its origin at the geometric center of the condylar process of the lower jaw in states of intercuspal contact of the teeth in the range of the posterior pole of the disc from 90° to 180°, significantly increasing the accuracy and reproducibility of the results obtained.

 

*Afanasyeva O.E., Koledov A.S., Postnikov M.A., Yumatov A.Yu., Yumatov S.Yu. Method for rapid diagnosis of the condition of intra-articular structures of the temporomandibular joints: invention application No. 2023129747; MKI A 61 B 5/055: Application dated 16.11.23. Decision to grant a patent dated 27.09.24

About the authors

Michael A. Postnikov

Samara State Medical University

Email: postnikovortho@yandex.ru
ORCID iD: 0000-0002-2232-8870
SPIN-code: 6696-8870

DSc (Medicine), Professor, Head of the Department of Therapeutic Dentistry

Russian Federation, Samara

Oksana E. Afanasieva

Dental Clinic “Orthostudio”

Email: afanasieva@list.ru
ORCID iD: 0009-0007-8741-1265

Orthodontist

Russian Federation, Moscow

Alexander M. Nesterov

Samara State Medical University

Email: nesterov003@rambler.ru
ORCID iD: 0000-0001-8487-7392

DSc (Medicine), Professor, Head of the Department of Prosthodontics

Russian Federation, Samara

Oleg V. Slesarev

Samara State Medical University

Email: o.slesarev@gmail.com
ORCID iD: 0000-0003-2759-135X
SPIN-code: 4507-6276

DSc (Medicine), Associate Professor of the Department of Maxillofacial Surgery and Dentistry

Russian Federation, Samara

Elizaveta M. Postnikova

I.M. Sechenov First Moscow State Medical University

Email: postnikova.e.m@gymn1sam.ru
ORCID iD: 0000-0002-5989-1704

5^th-year Student

Russian Federation, Moscow

Iuliia V. Aleshkova

ESPO Clinic

Email: al-julia@mail.ru
ORCID iD: 0009-0003-8368-809X

Orthodontist

Russian Federation, Saint-Petersburg

Karina T. Sargsyan

Samara State Medical University

Author for correspondence.
Email: sukasyan_karina@mail.ru
ORCID iD: 0009-0004-1076-9961
SPIN-code: 2297-3180

Postgraduate Student of the Department of Maxillofacial Surgery and Dentistry

Russian Federation, Samara

References

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