OBJECTIVES: This study aimed to evaluate the repeatability and reliability of a self-developed domestic wireless surface electromyography (sEMG) system (Oralmetry) in assessing the activity of the temporalis and masseter muscles to provide theoretical support for its clinical application. METHODS: Twenty-two volunteers were recruited. Through multiple repeated measurements, the sEMG signals of bilateral anterior temporalis and masseter muscles during maximum voluntary clenching were collected using the self-developed sEMG device, Oralmetry, and two commercial sEMG devices (Zebris and Teethan), filtered, screened, and standardized. Seven sEMG indicators for assessing masticatory muscle function were calculated. The intraclass correlation coefficient (ICC) was used to evaluate the repeatability of the measurements from the three sEMG devices, and statistical analysis was conducted to compare the consistency of the seven sEMG indicators obtained from the devices. RESULTS: Among the 22 participants, the ICC values of the repeated measurements from the three sEMG devices ranged from 0.88 to 0.99. The measurements of three sEMG indicators (antero-posterior coeffificient, percentage overlapping coeffificient_MM, and percentage overlapping coeffificient_TA) obtained by Zebris were significantly different from those obtained by Oralmetry and Teethan (P<0.05). No significant differences in the measurements of the seven sEMG indicators were found between Oralmetry and Teethan. CONCLUSIONS Oralmetry and the two commercial sEMG devices demonstrated good repeatability in capturing sEMG indicators for evaluating masticatory muscle function. In particular, Oralmetry showed the highest ICC values. All three devices also exhibited good consistency in measuring sEMG indicators, and a high agreement was observed between the two wireless sEMG devices (Oralmetry and Teethan). These findings provide theoretical support for the clinical application of Oralmetry.
Humans ; Electromyography/methods* ; Masseter Muscle/physiology* ; Masticatory Muscles/physiology* ; Wireless Technology ; Reproducibility of Results ; Temporal Muscle/physiology* ; Male ; Adult ; Female ; Young Adult

The purpose of this study was to evaluate whether the cranial and circumaxillary sutures react differently to maxillary expansion (ME) and alternate maxillary expansions and constrictions (Alt-MEC) in a rat model. Twenty-two male Sprague-Dawley rats (6 weeks old) were used and divided into three groups. In ME group (n=9), an expander was activated for 5 days. In Alt-MEC group (9 animals), an alternate expansion and constriction protocol (5-day expansion and 5-day constriction for one cycle) was conducted for 2.5 cycles (25 days total). The control group comprised 4 animals with no appliances used, each of two sacrificed on day 5 and day 25 respectively. Midpalatal suture expansion or constriction levels were assessed qualitatively and quantitatively by bite-wing X-rays and cast models. Distances between two central incisors and two maxillary first molars were measured on cast models after each activation. Circumaxillary sutures (midpalatal, maxillopalatine, premaxillary, zygomaticotemporal and frontonasal suture) in each group were characterized histologically. Results showed that midpalatal suture was widened and restored after each expansion and constriction. At the end of activation, the widths between both central incisors and first molars in Alt-MEC group were significantly larger than those in ME group (P<0.05). Histologically, all five circumaxillary sutures studied were widened in multiple zones in Alt-MEC group. However, only midpalatal suture was expanded with cellular fibrous tissue filling in ME group. Significant osteoclast hyperplasia was observed in all circumaxillary sutures after alternate expansions and constrictions, but osteoclast count increase was only observed in midpalatal suture in ME group. These results suggested that cranial and circumaxillary sutures were actively reconstructed after Alt-MEC, while only midpalatal suture had active reaction after ME.
Animals ; Male ; Mandible ; anatomy & histology ; physiology ; Masticatory Muscles ; anatomy & histology ; physiology ; Maxilla ; anatomy & histology ; physiology ; Range of Motion, Articular ; physiology ; Rats ; Rats, Sprague-Dawley

The aim of this study was to design a simple, economic, with high Common Mode Rejection Ratio (CMRR), preamplifier and multi-channel masticatory muscle surface electromyography (sEMG) signal acquisition system assisting to diagnose temporomandibular disorders (TMD). We used the USB interface technology in the EMG data with the aid of the windows to operate system and graphical interface. Eight patients with TMD and eight controls were analyzed separately using this system. In this system, we analyzed sEMG by an optional combination of time domain, frequency domain, time-frequency, several spectral analysis, wavelets and other special algorithms under multi-parameter. Multi-channel sEMG System of Masticatory Muscles is a simple, economic system. It has high sensitivity and specificity. The sEMG signals were changed in patients with TMD. The system would pave the way for diagnosis TMD and help us to assess the treatment effect. A novel and objective method is provided for diagnosis and treatment of oral-maxillofacial disease and functional reconstruction.
Algorithms ; Computer Graphics ; Data Collection ; Electromyography ; Humans ; Masticatory Muscles ; physiology ; physiopathology ; Sensitivity and Specificity ; Signal Processing, Computer-Assisted ; Temporomandibular Joint Disorders ; diagnosis ; User-Computer Interface

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.

Humans ; Masticatory Muscles ; innervation ; physiology ; Muscle Spindles ; anatomy & histology ; physiology

OBJECTIVETo evaluate trigeminal function of patients with chronic masticatory muscle pain (MMP) using trigeminal somatosensory evoked potential (TSEP) and analyze mechanism of changes compared to the controls.

METHODSTwelve chronic MMP patients and 12 matched controls participated in this study. TSEPs of bilateral masseter regions and inferior alveolar nerves were measured and compared between patient and control groups. The collected waves were concluded and those with appearance rate over 75% - 100% were selected. The latencies of waves were analyzed by use of the paired t test and independent-samples t test.

RESULTSFive stable-appearing waves were obtained and named P1, N1, P2, N2, P3. The latency of P1 was significant reduced in patients (P < 0.05). The latencies of other waves were prolonged, but only P2 and N2 in left were significantly changed (P < 0.05).

CONCLUSIONSTSEP latencies of chronic MMP patients changed in certain regular pattern and TSEP could be used as a parameter to disclose the trigeminal system abnormalities of the patients. The reduced latency of P1 might indicate the increasing conductivity of trigeminal nerves under level of ganglion Gasseri and the prolongation of latency of P2 was possibly related to inhibitory effects of the brain stem.

Adult ; Case-Control Studies ; Chronic Disease ; Evoked Potentials, Somatosensory ; physiology ; Female ; Humans ; Male ; Masticatory Muscles ; physiopathology ; Middle Aged ; Neuralgia ; diagnosis ; physiopathology ; Trigeminal Nerve ; physiopathology ; Young Adult

This study was conducted to establish a functional mandibular biomechanical model for use in the follow-up biomechanical study of the integrated and fractured mandible. The integrated and dry human mandible was used, and the corresponding maxilla and cranial base was duplicated by resin and plaster. 2-mm silicon rubber was used for simulation of the temporomandibular joint (TMJ) disc. A simulated TMJ and physiological mandibular model was developed by four pairs of muscular loadings (Masseter= 180 N, Temporalis = 190 N, Medial Pterygoideus = 120 N, Lateral Pterygoideus = 40 N) in each muscular center, and the functional loading corresponding with physiological condition was reflected and simulated more realistically when compared with that of the previously reported mandibular models which were developed by occlusion loading or by only one pair of muscles loading. In summary, we have established a functional mandibular model which can be used to analyze the biomechanical behavior in various functional conditions.
Biomechanical Phenomena ; Humans ; Mandible ; physiology ; Masseter Muscle ; anatomy & histology ; physiology ; Masticatory Muscles ; physiology ; Models, Biological ; Pterygoid Muscles ; anatomy & histology ; physiology ; Stress, Mechanical ; Temporal Muscle ; anatomy & histology ; physiology ; Temporomandibular Joint ; physiology

OBJECTIVETo establish an experimental model which was the masticatory myocyte culture and force stimulation in vitro and study the proliferation changes of cultured masticatory myocytes caused by mechanical compression in young rat.

METHODSFlow cytometry (FCM) was used to examine the changes of cellular DNA content and cell cycles of cultured masticatory myocytes.

RESULTSThe DNA content in experimental groups was higher than that in control. After the compressive force was applied for 2 hours, the proliferation index (PI) in experimental group became higher than that in control. Under a continuous pressure for 4 hours, the PI in 2,000 mu strain group reached the maximum (48.9%) but the PI in 4,000 mu strain group reached the minimum (39.0%).

CONCLUSIONThe proliferation of masticatory myocytes from young rat increased under certain force and certain period of time, but decreased if the force applied was overloaded.

Animals ; Cell Division ; Cells, Cultured ; DNA ; analysis ; Dental Stress Analysis ; Flow Cytometry ; Masticatory Muscles ; cytology ; physiology ; Muscle Cells ; cytology ; physiology ; Rats ; Rats, Sprague-Dawley ; Stress, Mechanical

15 male Wistar rats of 8 weeks old were used in this experment. After deeply anesthesia, the masseter muscles, digastric muscles, lateral pterygoid muscles were stimulated in the apartment that was made by us. The curves that express the relations of force-electronic stimulates were recorded and the constitutive equations of these muscles were given. When a single electronic signal stimulates the muscle, the respondence of the muscles can be expressed as F = A(e-alpha t - e-beta t) and the constant A, alpha, beta were determined. When the frequency of the electronic stimulation was higher than 3 Hz, the respondence was expressed as F = Ce-gamma/t + Dsin omega t and the constants C, D and gamma were determined. When the frequency of the electronic stimulation was thirty or higher, the tetanic convulsion occurred.
Animals ; Electric Stimulation ; Jaw ; physiology ; Male ; Masticatory Muscles ; physiology ; Muscle Contraction ; physiology ; Myography ; Rats ; Rats, Wistar ; Time Factors