Evaluation of the relationship between the attachment type of lateral pterygoid muscle and the position of temporomandibular joint disc in patients with temporomandibular joint disorders based on wireless amplified MRI detector high resolution imaging / 中华口腔医学杂志

Objective: To explore the correlation between the attachment type of lateral pterygoid muscle (LPM) and the position of temporomandibular joint (TMJ) disc in patients with temporomandibular disorders (TMD) by using wireless amplified magnetic resonance imaging detector (WAND) coupled with conventional head and neck joint coil for high resolution imaging of TMJ. Methods: Eighty-five patients with TMD diagnosed by oral and maxillofacial surgeons of Guizhou Provincial People's Hospital from October 2019 to January 2022 were collected. A total of 160 TMJ were included. There were 16 males and 69 females, aged (32.7±14.2) years. All patients were scanned with open, closed oblique sagittal and coronal WAND coupled head and neck coils with bilateral TMJ. Based on TMJ and LPM high resolution imaging, to explore the correlation between LPM attachment types and the position of TMJ disc in TMD patients, and to evaluate the potential clinical value of LPM attachment types in TMD patients. χ2 test and Pearson correlation analysis were used to evaluate the correlation between LPM attachment type and TMJ disc location. Results: There were three types of LPM attachment: type Ⅰ in 51 cases [31.9% (51/160)], type Ⅱ in 77 cases [48.1% (77/160)] and type Ⅲ in 32 cases [20.0% (32/160)]. There was a significant correlation between the type of LPM attachment and the position of articular disc (χ2=28.20, P=0.002, r=0.776). There was no statistical significance between the type of LPM attachment and the reversible displacement of articular disc (χ2=0.24, P=0.887, r=0.825). Conclusions: There is a correlation between the attachment type of LPM and the position of the disc in TMD patients. WNAD coupled with conventional head and neck joint coil TMJ high resolution scan can provide reliable imaging evidence for TMD patients in evaluating the type of LPM attachment and the location of disc.

Prevalence of the third head of the lateral pterygoid muscle: a magnetic resonance image study / Prevalencia de la tercera cabeza del músculo pterigoideo lateral: estudio con imaenes de resonancia magnética

The lateral pterygoid muscle (LPM) is important in the physiology and dysfunction of the temporomandibular joint (TMJ), which has described the presence of a third head in the lateral pterygoid muscle (THLPM). The purpose of this study was to evaluate the prevalence of THLPM and its relationship with the TMJ disc through magnetic resonance imaging (MRI). It was evaluated 178 MRI of the TMJ of healthy individuals, in images that presented THLPM, and these were defined and measured at the surface inserted into the disc. The prevalence of THLPM was 20.22 percent (n = 36). Insertion of THLPM was made entirely on the TMJ disc, the average area of insertion was 4.14mm (SD 1.35) in women and 4.67 (SD 2.68) in men, but these differences were not significant. We concluded that the LPM has a complex structure, and that a THLPM could contribute in the development of TMJ disc function alterations and anterior disc displacement.

El músculo pterigoideo lateral (MPL) tiene importancia en la fisiología y en la disfunción de la articulación temporomandibular (ATM), se ha descrito la presencia de una tercera cabeza en el músculo pterigoideo lateral (TCPL). El propósito de este estudio fue evaluar mediante resonancia nuclear magnética (RNM) la prevalencia de la TCPL y su relación con el disco de la ATM. Se evaluaron 178 RNM de ATM de individuos sanos. En las imágenes que presentaron TCPL éstos fueron delimitados y se midió la superficie inserta en el disco. La prevalencia de la TCPL fue del 20,22 por ciento (n=36). La inserción de la TCPL se realizó completamente en el disco de la ATM, la media del área de inserción fue de 4,14mm (DS. 1,35) en mujeres y 4,67 (DS. 2,68) en hombres, estas diferencias no resultaron significativas. Concluimos que el MPL presenta una estructura compleja y que una TCPL podría participar en el desarrollo de alteraciones en la función discal y en la presencia de desplazamiento anterior del disco.

Etiopathogenesis of disk displacement of the temporomandibular joint: A review of the mechanisms.

Disk displacement of the temporomandibular joint (TMJ) is a clinically important condition, showing a high prevalence in both patient and non-patient populations. Despite its clinical importance, there is incomplete understanding of the etiopathogenic mechanisms leading to disk displacement. A number of possible risk factors have been identified. This article analyzes the etiopathogenesis from both the clinical and the biomechanical viewpoints and also reviews the literature on the association between disk displacement and the main risk factors (i.e., trauma, altered disk shape and/or dynamic properties, occlusal abnormalities, steepness of the articular eminence, hyperactivity of the lateral pterygoid muscle, joint hypermobility, etc.). According to our interpretation of available data, an impairment of joint lubrication may be a common finding in cases of disk displacement, thus suggesting the need for future studies addressing both local and systemic neuroendocrine aspects influencing the friction coefficient of the TMJ. A full comprehension of the etiopathogenesis of disk displacement is far from being achieved, and clinicians must take into account this consideration when treating patients with temporomandibular disorders.

Masseter muscle hypertrophy: case report

Masseter muscle hypertrophy is characterized by unilateral or bilateral enlargement of the masseter muscles affecting both males and females after puberty. Its etiology remains unknown. Limitations on mouth opening and also tension in the region of the hypertrophied muscle are symptoms reported. This paper reports a case of masseter muscle hypertrophy diagnosed using imaging modalities such as conventional radiography, computed tomography and magnetic resonance imaging scans. The familiarity with this condition is important to settle the differential diagnosis with other pathologies such as parotid gland tumors and dental infection.

A hipertrofia dos músculos masseteres caracteriza-se aumento uni ou bilateral dos músculos masseteres, atingindo igualmente homens e mulheres depois da puberdade. Sua etiologia é desconhecida. Os sintomas incluem limitação da abertura bucal e tensão na região dos músculos hipertrofiados. Este artigo apresenta um caso de hipertrofia de músculo masseter, com várias modalidades imagens, tais como radiografia convencional, tomografia computadorizada e ressonância magnética. É muito importante um conhecimento profundo desta condição para estabelecer o diagnostico diferencial de outras patologias, como tumores da glândula parótida e infecção dental.