No abstract available.
Masticatory Muscles* ; Trismus*

No abstract available.
Masticatory Muscles* ; Spasm* ; Tetanus*

OBJECTIVETo study the mechanism in masticatory muscle dysfunctional induced by hemimastication.

METHODSCa2+ contents were measured with atomic absorption spectrometry; calcinuerin were measured with colorimetric method; muscle fiber types were measured with adenosine-triphosphate (ATPase) staining.

RESULTS(1) Compared with the controls, Ca2+ contents in experimental group had the higher level except 8 weeks (P < 0.05). (2) The ratio of slow fiber in experimental group increased, higher than the match groups (P < 0.05). (3) With Ca2 contents rise, the activities of calcinuerin present a bell-like shape. (4) The ratio of slow-type fiber was positively correlated to the activities of calcinuerin (r = 0.876, P < 0.05).

CONCLUSIONThe signal way of muscle fiber growth and fiber transformation were activated by high concentration of calcium, then, muscle fiber transferred from fast to slow type. It may play an important role in the mechanism that hemimastication result in masticatory muscles dysfunction.

OBJECTIVE: To analyze characteristics of mandibular movement in patients with unilateral mastication.
 METHODS: Undergraduate students in oral medicine from Grade 2011 and 2012 in Wannan Medical College were enrolled for this study by cluster sampling method, which include 30 people with unilateral mastication and 30 people with bilateral mastication. The surface electromyogram (sEMG) of masseter muscle and anterovent of digastric muscle were recorded and the trajectory of mandibular incisor point was recorded simultaneously in the maximum opening and closing movement. The results were analyzed by SPSS 19.0 software.
 RESULTS: Average electrical peak of left anterior digastric muscle and right anterior digastric muscle in the unilateral chewing group was lower than that in the bilateral chewing group (P<0.05). The jaw tangent point trajectory was separate in the unilateral chewing group. There were significant differences at the opening type between the 2 groups. The vertical displacement and the sagittal displacement in the unilateral chewing group were significantly lower than those in the bilateral chewing group (P<0.01). There was significant positive correlation between the average peak potential of masseter muscle and displacement on the right side.
 CONCLUSION Average electrical peak of left masseter muscle, left anterior digastric muscle, and right anterior digastric muscle decreases in the unilateral chewing group. Jaw tracking in most people deflects to the working side. Opening and closing jaw tracking is separate in 50% unilateral chewing individuals with the decreased opening degree. Unilateral chewing leads to changes in muscle performance accompanied by trajectory anomalies.
Electromyography ; Humans ; Mandible ; Mastication ; Masticatory Muscles ; Movement

PURPOSE: To compare the size of the masseter and lateral pterygoid muscle between the affected and the unaffected side of the patients who have the chief complaints of the mandibular asymmetry. MATERIALS AND METHODS: Twenty two patients (male: 4, female: 18, average age: 21.3 year-old) were radiographed using posterior-anterior (P-A) cephalography and computed tomography (CT). On P-A cephalography, the degree of deviation was determined by the distance from the mentum to the vertical reference line through the crista galli and the anterior nasal spine. On the scanned tracing papers of the maximum cross-sectional area of the masseter and lateral pterygoid muscle using axial CT images, the pixel number was measured. The ratio of the affected : unaffected sides were obtained. For the masseter and lateral pterygoid muscle, the relationship between the muscular volume and degree of skeletal hypoplasia was studied. RESULTS: The half cases showed no skeletal asymmetry. The lateral pterygoid muscle of the affected side was larger significantly than unaffected side (p.0.05). However, there was no significant difference between two sides in the cases of skeletal asymmetry. There was only significant difference in the cases without skeletal asymmetry (p.0.05). CONCLUSIONS: To some extent, the slight mandibular hypoplasia could affect the growth of some masticatory muscles.
Chin ; Facial Asymmetry ; Female ; Humans ; Masticatory Muscles* ; Pterygoid Muscles ; Spine

The odontogenic keratocyst (OKC) is a developmental odontogenic cyst typically occurring in the jaws. Since the first description of OKC was published in 1956, the lesion has been of particular interest because of its specific histopathologic features, high recurrence rate, and aggressive behavior. Recurrences most commonly arise within bone at the site of the original cyst. However, as lining cells may find their way into surrounding tissues either from implantation during surgery or from cortical perforation recurrences may arise at a distance from the original cyst. Here, we report a rare case of recurrent OKC which was first developed in mandible and recurred within the masticatory space.
Diagnostic Imaging ; Jaw ; Mandible ; Masticatory Muscles ; Odontogenic Cysts ; Recurrence

In cases of extensive prosthetic restoration, correction of occlusal contact is often needed, as it is the essential component for a successful restoration. If occlusal contact is given incorrectly, various symptoms of occlusal trauma can occur of which temporomandibular joint disorder (TMD) is one of them. As one of the common symptoms of TMD, patients may suffer with masticatory muscle disorder and temporomandibular joint pain. This case presents satisfactory results for the improvement of masticatory muscles and temporomandibular joint pain of a TMD patient, caused by incorrect occlusal contact of the restoration, by replacing the prosthesis after occlusion correction.
Humans ; Masticatory Muscles ; Prostheses and Implants ; Temporomandibular Joint Disorders* ; Temporomandibular Joint*

OBJECTIVETo investigate the characteristics in the topographic distribution of the muscle spindles in human masticatory muscles.

METHODSThe muscle spindles of the masticatory muscles on both sides of 3 human corpses fixed in formalin for more than 1 year were observed histologically and analyzed quantitatively using an image analysis system.

RESULTSThe mean muscle spindle density was 32.11/g in the masseter, significantly higher in the deep muscular fibers (70.76/g) with high proportion of spindle complexes than in the superficial layers of the muscle belly (P<0.05). The mean spindle density in the temporalis was 5.44/g, higher in the anterior portion (7.44/g) than in the posterior portion (3.78/g, P<0.01). The medial pterygoid had a mean spindle density of 4.43/g.

CONCLUSIONThese results indicate a heterogeneous distribution of muscle spindles in the masticatory muscles with different morphologies or in different portions of the same muscle, depending on muscle fiber type and muscular architecture.

PURPOSE: To determine the clinical correlation of magnetic resonance imaging (MRI) findings of temporomandibular joint internal derangements. MATERIALS AND METHODS: The MR images of 150 TMJs in 75 patients were analyzed. The clinical symptoms were pain in the preauricular area and masticatory muscles and TMJ sounds. RESULTS: There was a statistically significant relationship between the MRI diagnoses of different types of disc displacements and clinical findings of pain, clicking, and crepitus. The risk of TMJ pain was increased when the disc displacement without reduction occurred at the same time in combination with the osteoarthrosis and effusion. CONCLUSION: Regardless of the results, the data indicate that each of these MR imaging variables may not be regarded as the unique and dominant factor in defining TMJ pain occurrence.
Diagnosis ; Humans ; Magnetic Resonance Imaging* ; Masticatory Muscles ; Osteoarthritis ; Temporomandibular Joint*

OBJECTIVETo analyze changes of myoelectrical activity of anterior funicle of temporal muscle (TA) and masseter muscle (MM) after raising vertical distance of occlusion by flat bite plate during treatment of deep overbite in order to approach an optimal raised vertical distance.

METHODSA total of 70 persons were selected and divided into two groups: Experiment group (36 patients) with deep overbite and control group (34 persons) with individual normal occlusion. The experiment group was subdivided into three groups that were respectively raised D, D+2 mm and D+4 mm (D means free way space, mm). Electromyologram (EMG) was utilized to measure the average peak potential of TA and MM on quiescent condition before treatment and two weeks after wearing flat bite plate.

RESULTS1) Before treatment, the average peak potential of experiment group was obviously higher than that of the control group (P<0.05). 2) After two weeks the potential of TA and MM of all persons in experiment group was obviously lower than before (P<0.05), the degree between the group D+2 mm and the group D+4 mm was not manifestly different, but both of the two groups were more obvious than the group D.

CONCLUSIONThe raised vertical distance of occlusion by flat bite plate, which exceeded free way space, was favourable to the functional recovery of masticatory muscles.