OBJECTIVETo study the effects of repeated + Gz forces on masticatory muscles.

METHODS48 male Wistar rats were randomly divided into 4 groups. Group A was normally fed. Group B was only fixed with rat-kept devices for 5 minutes. Group C was borne + 1 Gz for 5 minutes. Group D was repeatedly exposed + 10 Gz (each for 30 s, onset rate about 0.5 G/s, 5 times/d with + 1 Gz 1 minute intervals, 4 d/wk, 3 weeks in total). The histological changes of the masseter, temporal and lateral pterygoid muscles were observed.

RESULTSNo abnormal changes were observed in Group A, B and C. But pathological changes could be found in group D. The wrench and deformation of muscular fibers, the dissolution of partial myofibril, the swelling of mitochondria, the reduce of hepatin from the masseter and lateral pterygoid muscles could be found.

CONCLUSIONSRepeated + Gz stresses could induce the damage of masticatory muscles in different degrees.

Animals ; Hypergravity ; Male ; Masseter Muscle ; pathology ; ultrastructure ; Masticatory Muscles ; pathology ; ultrastructure ; Microscopy, Electron ; Pterygoid Muscles ; pathology ; ultrastructure ; Rats ; Rats, Wistar ; Temporal Muscle ; pathology ; ultrastructure ; Time Factors

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.
Male ; Female ; Humans ; Temporomandibular Joint Disc/pathology* ; Pterygoid Muscles/pathology* ; Joint Dislocations ; Temporomandibular Joint Disorders/diagnostic imaging* ; Magnetic Resonance Imaging/methods* ; Temporomandibular Joint/pathology*

Running through the infratemporal fossa is the lingual nerve (i.e. the third branch of the posterior trunk of the mandibular nerve). Due to its location, there are various anatomic structures that might entrap and potentially compress the lingual nerve. These anatomical sites of entrapment are: (a) the partially or completely ossified pterygospinous or pterygoalar ligaments; (b) the large lamina of the lateral plate of the pterygoid process; and (c) the medial fibers of the anterior region of the lateral pterygoid muscle. Due to the connection between these nerve and anatomic structures, a contraction of the lateral pterygoid muscle, for example, might cause a compression of the lingual nerve. Any variations in the course of the lingual nerve can be of clinical significance to surgeons and neurologists because of the significant complications that might occur. To name a few of such complications, lingual nerve entrapment can lead to: (a) numbness, hypoesthesia or even anesthesia of the tongue's mucous glands; (b) anesthesia and loss of taste in the anterior two-thirds of the tongue; (c) anesthesia of the lingual gums; and (d) pain related to speech articulation disorder. Dentists should, therefore, be alert to possible signs of neurovascular compression in regions where the lingual nerve is distributed.
Cranial Fossa, Middle ; Foramen Ovale ; pathology ; Humans ; Ligaments ; pathology ; Lingual Nerve ; pathology ; Nerve Compression Syndromes ; complications ; pathology ; Ossification, Heterotopic ; pathology ; Paresthesia ; etiology ; Pterygoid Muscles ; pathology ; Sphenoid Bone ; pathology ; Tongue ; innervation

OBJECTIVETo analyze the relationship between Class III malocclusion and pathological changes in temporomandibular joint (TMJ) structures using magnetic resenonce imaging (MRI).

METHODSTwenty-four Class III malocclusion adult patients and 10 normal control cases were included in the study. The characteristics of lateral pertygoid muscle (LPM) in the sample group and the control group were assessed.

RESULTSMore pathological changes of LPM were found in Class III malocclusion adult patients (36 TMJ). The changes included hypertrophy, atrophy and contracture. And there was no relation between the pathological changes of LPM and the symptom of temporomandibular disorders (TMD).

CONCLUSIONSThe frequency of pathological changes of LPM was greater in patients with Class III malocclusion than in the control group.

Adolescent ; Adult ; Atrophy ; pathology ; Case-Control Studies ; Contracture ; pathology ; Female ; Humans ; Magnetic Resonance Imaging ; methods ; Male ; Malocclusion, Angle Class III ; complications ; pathology ; Pterygoid Muscles ; pathology ; Temporomandibular Joint ; pathology ; Temporomandibular Joint Disorders ; complications ; pathology ; Young Adult