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

OBJECTIVETo investigate the effect of the biofeedback in regulating the myoelectric activities of the masseter muscles.

METHODSTwenty orthodontic patients aged from 10 to 14 years with Angle Class II malocclusion, retrusive mandible, and an ANB angle > 6° were enrolled in this study. The muscular activities of the anterior temporal muscle and the masseter muscle were evaluated before, during, and after biofeedback treatment by assessing the average integrated electromyogram and temporal/masseter (T/M) ratio in the clenching status.

RESULTSThe patients' myoelectric activities of the anterior temporal muscle was significantly increased after biofeedback treatment (P<0.05). The patients' T/M ratio in the clenching status was increased after the treatment (1.76 ± 1.46 before treatment, 4.71 ± 4.03 immediately after treatment, and 2.57 ± 2.07 at 1 day after treatment; t=4.86, P<0.05).

CONCLUSIONBiofeedback treatment can regulate the activities of the anterior temporal and masseter muscles and increase the T/M ratio in the clenching status.

Adolescent ; Biofeedback, Psychology ; Child ; Electromyography ; Humans ; Malocclusion, Angle Class II ; Mandible ; Masseter Muscle ; physiology ; Temporal Muscle ; physiology

OBJECTIVE: To evaluate the influence of inferior vestibular and part of mandibular branch of trigeminal neurotomy on sound-induced masseter reflex potentials. METHOD: Twenty guinea pigs were randomly divided into four groups, including 5 normal control guinea pigs, 5 received unilateral inferior vestibular neurotomy, 5 received unilateral inferior alveolar nerve neurotomy, and 5 received auriculotemporal nerve neurotomy. Click sound-induced masseter reflex potentials were recorded in four groups, respectively. RESULT: The thresholds of negative peak (NP) of click sound-induced masseter reflex potentials in normal control group were (90.00 +/- 8.16) dBnHL. The response rates of the NP of the masseter reflex potentials using 100, 90, 80 and 70 dBnHL monaural acoustic stimulation with unilateral recording were 100%, 70%, 40% and 0, respectively. The mean latencies of the NP were (6.55 +/- 0.25) ms, (6.61 +/- 0.16) ms and (6.70 +/- 0.13) ms, when elicited by 100,90 and 80 dBnHL acoustic stimulation respectively. There was no significant difference between the stimulus intensity and the mean latency of the NP (P > 0.05). Negative peak of click sound-induced masseter reflex potentials was not observed in the inferior vestibular neurotomy group. The NP was preserved in the inferior alveolar nerve and auriculotemporal nerve neurotomy groups. There were no significant difference of the mean thresholds and latencies of NP between normal control group and inferior alveolar nerve and auriculotemporal nerve neurotomy group (P > 0.05). CONCLUSION Click sound-induced masseter reflex potentials originates from vestibular afferents. Afferent of inferior alveolar nerve and auriculotemporal nerve can not influence the vestibular evoked masseter reflex potentials.
Afferent Pathways ; surgery ; Animals ; Guinea Pigs ; Masseter Muscle ; physiology ; Reflex, Acoustic ; Trigeminal Nerve ; surgery ; Vestibular Nerve ; surgery

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 study the changes of masseter muscle after reducing the mandibular by measuring some relative index after ostectomy of the mandibular angle along arch line.

METHODSLeft mandibular angle ostectomy was performed on New Zealand female rabbits aged three months. The right was not operated as control groups. Five rabbits were examined at the following intervals: 2, 4, 8, 12 and 24 weeks.

RESULTSThere were remarkable decreases in the experimented masseter muscle masses and the same type muscle fiber areas compared with the control group (P < 0.05). As for the fiber types, a decrease in type I fibers and an increase in type II fibers were noticed on operative side masseters (P <0.05). Sarcomere lengths in the operative side muscles were significantly reduced and showed statistical significance during first 4 weeks (P < 0.05), but there was no difference between the operative group and the control group after 8 weeks (P > 0.05).

CONCLUSIONSThe changes of masseter fibres show reconstruction of masseter muscle after mandibular angle ostectomy.

Animals ; Female ; Mandible ; physiopathology ; surgery ; Masseter Muscle ; physiology ; Oral Surgical Procedures ; Postoperative Period ; Rabbits

OBJECTIVEThe aim of this study was to investigate the expression of collagen in the process of masseter muscle reattachment to the cortical and cancellous bones of mandible.

METHODSA total of nine adult goats were used in the study. One was the control. The other eight were treated with bilateral detachment of the masseter muscles. The biopsies of bone and muscle were taken at 2, 4, 8 and 12 weeks after the operation. The characteristics of the healing muscle-bone interfaces were examined using immunohistochemical techniques.

RESULTSImmunohistochemical analysis illustrated that the locations of collagen type I, II and III were different during the healing process, but similar in the cortical and cancellous bones.

CONCLUSIONThis study demonstrates that the distribution of the three types of collagens at the muscle-bone interfaces is associated with time, but not related with their locations.

Animals ; Collagen ; biosynthesis ; genetics ; Collagen Type I ; biosynthesis ; genetics ; Collagen Type II ; biosynthesis ; genetics ; Collagen Type III ; biosynthesis ; genetics ; Female ; Goats ; Male ; Mandible ; metabolism ; pathology ; surgery ; Masseter Muscle ; metabolism ; pathology ; surgery ; Wound Healing ; physiology

OBJECTIVEThe aim of this study was to establish the average of superfacial masseter muscle of young females with normal occlusion, and further supply a clue for dentists to evaluate the muscle function of patients with malocclusion.

METHODSTotally 31 young females were investigated in this study, whose mean age was 21 years and 4 months old. Ultrasound technique was applied to obtain the ultrasound parameters of images, including area, width, mean thickness, maximal thickness of the cross-section and the length of the vertical-section of the masseter muscle under relaxing, maximal clenching and maximal protruding condition. The data were analyzed using ANOVA analysis.

RESULTSThe mean value and standard deviation of every parameter were figured out and it was found that there was a significant difference between relaxing and maximal clenching as well as maximal protruding.

CONCLUSIONThe result indicates that ultrasonic technique is an effective method for describing superfacial masseter muscle morphology and diagnosing its function.

Adult ; Dental Occlusion ; Female ; Humans ; Mandible ; physiology ; Masseter Muscle ; anatomy & histology ; diagnostic imaging ; Muscle Contraction ; Muscle Relaxation ; Ultrasonography