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

OBJECTIVE: To investigate the correlation between the clinical diagnostic criteria of sleep bruxism and the frequency of mandibular movements during sleep. METHODS: Video polysomnography was used to record 20 healthy adults with at least one of the following clinical symptoms and signs: 1) report of frequent tooth grinding; 2) tooth wear and dentin exposure with at least three occlusal surfaces; 3) masticatory muscle symptoms in the morning; 4) masseter muscle hypertrophy. The rhythmic masticatory muscle activity (RMMA) and isolated tonic activity were scored to compare the correlations with clinical symptoms and signs. Finally, the incidence of temporomandibular disorders (TMD) was investigated in patients with isolated tonic and RMMA subjects. RESULTS: Among the 20 subjects, RMMA events were observed (5.8±3.1) times·h⁻¹ and isolated tonic episodes were observed (2.1±0.9) times·h⁻¹. The frequency of RMMA events was significantly greater in the patients with acoustic molars than in those without (P<0.05). Similarly, the frequency of RMMA events was significantly greater in the patients with tooth attrition than in those without (P<0.05). However, no difference was observed between the occurrence of RMMA and the symptoms of masticatory muscles or masseter hypertrophy in the morning. The incidence of TMD was significantly higher in the patients with RMMA than in the isolated tonic patients. CONCLUSIONS The clinical symptoms and signs often used to diagnose sleep bruxism are different clinical and physiological mandibular movements during sleep. RMMA during sleep can reflect the occurrence of tooth attrition and the high risk of TMD.
Adult ; Electromyography ; Humans ; Masticatory Muscles ; Polysomnography ; Sleep ; Sleep Bruxism ; Tooth Attrition

OBJECTIVE: This study aims to investigate the occlusal and myoelectric characteristics of implant-supported fixed denture in the mandibular region and provide reference for the design of fixed restoration. METHODS: Sixty edentulous patients with implant-supported fixed denture were selected and divided into three groups: group A, 20 cases with implant-supported fixed restoration in the maxillary region; group B, 20 cases with natural dentition, and group C, 20 cases with removable partial denture. The T-scan 8.0 digital occlusion analysis system was used to evaluate the occlusal characteristics of patients in the three groups at intercuspal, protrusion, and left and right lateral positions. Electromyography was used to analyze the myoelectric amplitude and bilateral asymmetry index of the anterior temporalis and masseter of the three groups in different states such as resting and clenching. The relationship between occlusion and myoelectricity was also investigated. RESULTS: In the occlusion analysis by T-scan, the occlusion time, the balance of left and right bite force, the left and right asymmetry of the occlusion center, the trajectory of central occlusion force, and the disclusion time were higher in group C than in groups A and B (P<0.05). No significant differences were observed in the anterior and posterior asymmetry of the occlusion center and percentage of bite force at anterior region among the three groups. In the analysis of myoelectricity, the myoelectric amplitude at resting state and the asymmetry index of masticatory muscles in group C were higher than those in groups A and B (P<0.05). The myoelectric amplitude during clenching in groups A and B groups was higher than that in group C (P<0.05). CONCLUSIONS In implant-supported fixed restoration at edentulous mandibular, when maxillary includes the removable partial denture, degree of occlusal instability and left and right asymmetry of occlusion center are greater than those with the natural dentition and implant-supported fixed denture at maxillary. The myoelectricity is closely related to occlusion. The removable partial denture can increase the myoelectric activity and reduce the potential of the masticatory muscle. The asymmetry of bilateral myoelectricity is related to the occlusion imbalance.
Bite Force ; Dental Implants ; Dental Prosthesis, Implant-Supported ; Humans ; Mandible ; Masticatory Muscles

Pseudoaneurysm of internal maxillary artery (IMA) after trauma is rare, and most cases reported are caused by maxilla-facial blunt trauma. Pseudoaneurysm is discontinuity in the vascular wall leading to an extravascular hematoma that freely communicates with the intravascular space producing pulsatile hematoma rapidly. A 44-years-old woman presented with a pulsatile swelling and pain in the left parotid region. She underwent the masticatory muscle reduction using needle injection in dentistry 1 month ago. The left facial pulsatile swelling developed after the procedure immediately and uncontrolled bleeding occurred on the day of visit to our institution. We performed emergency angiography and diagnosed pseudoaneurysm of left IMA. We treated by embolization with Histoacryl Glue through left IMA. IMA total occlusion was confirmed and symptoms improved. Pseudoaneurysm following blunt trauma of the face have been reported but are few. Furthermore, there is no report of IMA pseudoaneurysm due to direct injury by needle. Recently, many cosmetic surgery procedures using injection techniques have been performed, and it is necessary to pay attention to the direct vessel injury by the needle. And endovascular therapies can give early recovery with minimal morbidity and avoids injury to the facial nerve and its branches.
Adhesives ; Aneurysm, False ; Angiography ; Dentistry ; Emergencies ; Enbucrilate ; Facial Nerve ; Female ; Hematoma ; Hemorrhage ; Humans ; Masticatory Muscles ; Maxillary Artery ; Needles ; Parotid Region ; Surgery, Plastic

BACKGROUND: Botulinum toxin injection on the masticatory muscle induces the osteopenic condition on the ipsilateral condyle. Bisphosphonate suppresses bone resorption and is used to treat osteopenic or osteoporotic condition. This study aimed to evaluate the effect of bisphosphonate administration on prevention of condylar resorption and botulinum toxin A-induced disuse osteopenia in rats. RESULTS: The volume of the condyle and bone volume/tissue volume (BV/TV, %) showed a strong tendency towards statistical significance (p = 0.052 and 0.058). Trabecular thickness (Tb.Th, mm) and trabecular number (Tb.N, 1/mm) were significantly smaller in the Botox group than in the other groups (p < 0.05). The volume of the condyle and BV/TV in the bisphosphonate 100 and bisphosphonate 200 groups showed similar values when compared with the control group. CONCLUSION: Bisphosphonate administration after botulinum toxin A injection in the masticatory muscles appears to prevent condyle resorption and botulinum toxin-induced disuse osteopenia in rats.
Animals ; Bone Diseases, Metabolic ; Bone Resorption ; Botulinum Toxins ; Mandibular Condyle ; Masticatory Muscles ; Rats ; Temporomandibular Joint

Patients with masticatory muscle tendon-aponeurosis hyperplasia (MMTAH) experience limited mouth opening due to restricted muscle extension. Hyperplastic aponeurosis and tendons lead to the restriction of muscle extension. The criteria for the diagnosis of MMTAH are limited mouth opening that progresses very slowly from adolescence, intraoral palpation reveals a hard cord-like structure along the overhang of the anterior border of the masseter muscle on maximum mouth opening, and a square mandible. Conservative treatment, including pharmacotherapy, occlusal splint and physical therapy are ineffective. The standard therapy is surgical treatment, such as anterior partial aponeurectomy of the masseter muscle and coronoidectomy. The long-term results are very satisfying.
Adolescent ; Diagnosis ; Drug Therapy ; Humans ; Hyperplasia ; Mandible ; Masseter Muscle ; Masticatory Muscles ; Mouth ; Occlusal Splints ; Palpation ; Tendons

OBJECTIVE: To study the clinical characteristics of mandibular movement and masticatory muscle function in preoperative and postoperative patients with unilateral mandibular tumors in the region of mandibular body and ramus by combining digital mandibular movement records with electromyography, and to preliminarily explore the relationship and mechanism between movement and masticatory muscle function. METHODS: Six preoperative patients with tumor in unilateral body and ramus of mandible were included, and three postoperative patients with unilateral segmental resection and reconstruction of mandibular bone were included. The mandibular movement recording system and surface electromyography system were used to collect the movement trajectory of the patients' mandibular marginal movement and chewing movement, and the surface electromyography of bilateral masseter and temporalis was recorded concurrently. The surface electromyography of bilateral masseter and temporalis was collected when the patients were at relaxation and at maximal voluntary clenching (MVC). The motion trajectory was observed on the digital virtual model, and the motion amplitude and direction of mandibular marginal movements were analyzed. The characteristics of masticatory electromyogram (EMG) activity in affected and unaffected sides at relaxation, MVC and bilateral mastication were analyzed, and the asymmetry indexes and activity indexes were calculated. RESULTS: The preoperative mean maximum opening of the patients was (35.20±6.87) mm. Three patients had mild mouth opening limitation, and all the patients' mouth opening trajectory was skewed to the affected side. During lateral movements, the mean range of motion of the affected side [(10.34±1.27) mm] and that of the healthy side [(6.94±2.41) mm] were significantly different. The maximum opening of the postoperative patients was (30.65±17.32) mm, and the mandibular marginal movement characteristics were consistent with those of the patients before surgery. During MVC in the preoperative patients, the median EMG activities of the masseter muscle [44.20 (5.70, 197.90) μV] and the temporalis muscle [42.15 (22.90, 155.00) μV] on the affected side were slightly lower than those of the masseter [45.60 (7.50, 235.40) μV] and the temporalis muscle [63.30 (44.10, 126.70) μV] on the healthy side. In the postoperative patients, individualized changes occurred. Some patients suffered from weakened electromyographic activity on the affected side, while some other ones showed hyperelectromyographic activity on the affected side. CONCLUSION Both benign and malignant tumors as well as their surgery can cause abnormal mandibular movements and change of electromyographic activity of bilateral masseter and temporalis muscles.
Electromyography ; Humans ; Mandible ; Mandibular Neoplasms ; Masseter Muscle ; Mastication ; Masticatory Muscles ; Movement ; Temporal Muscle

BACKGROUND: The objective of this study was to evaluate the influence of masticatory muscle injection of botulinum toxin type A (BTX-A) on the growth of the mandibular bone in vivo. METHODS: Eleven Sprague-Dawley rats were used, and BTX-A (n = 6) or saline (n = 5) was injected at 13 days of age. All injections were given to the right masseter muscle, and the BTX-A dose was 0.5 units. All of the rats were euthanized at 60 days of age. The skulls of the rats were separated and fixed with 10% formalin for micro-computed tomography (micro-CT) analysis. RESULTS: The anthropometric analysis found that the ramus heights and bigonial widths of the BTX-A-injected group were significantly smaller than those of the saline-injected group (P < 0.05), and the mandibular plane angle of the BTX-A-injected group was significantly greater than in the saline-injected group (P < 0.001). In the BTX-A-injected group, the ramus heights II and III and the mandibular plane angles I and II showed significant differences between the injected and non-injected sides (P < 0.05). The BTX-A-injected side of the mandible in the masseter group showed significantly lower mandibular bone growth compared with the non-injected side. CONCLUSION: BTX-A injection into the masseter muscle influences mandibular bone growth.
Animals ; Bone Development ; Botulinum Toxins ; Botulinum Toxins, Type A ; Formaldehyde ; Mandible ; Masseter Muscle ; Masticatory Muscles ; Rats ; Rats, Sprague-Dawley ; Skull

Clinical limitations following closed reduction of an intracapsular condylar fracture include a decrease in maximum mouth opening, reduced range of mandibular movements such as protrusion/lateral excursion, and reduced occlusal stability. Anteromedial and inferior displacement of the medial condyle fragment by traction of the lateral pterygoid muscle can induce bone overgrowth due to distraction osteogenesis between the medial and lateral condylar fragments, causing structural changes in the condyle. In addition, when conventional maxillomandibular fixation (MMF) is performed, persistent interdental contact sustains masticatory muscle hyperactivity, leading to a decreased vertical dimension and premature contact of the posterior teeth. To resolve the functional problems of conventional closed reduction, we designed a novel method for closed reduction through protrusive MMF for two weeks. Two patients diagnosed with intracapsular condylar fracture had favorable occlusion after protrusive MMF without premature contact of the posterior teeth. This particular method has two main advantages. First, in the protrusive position, the lateral condylar fragment is moved in the anterior-inferior direction closer to the medial fragment, minimizing bone formation between the two fragments and preventing structural changes. Second, in the protrusive position, posterior disclusion occurs, preventing masticatory muscle hyperactivity and the subsequent gradual decrease in ramus height.
Humans ; Jaw Fixation Techniques* ; Masticatory Muscles ; Methods ; Mouth ; Osteogenesis ; Osteogenesis, Distraction ; Pterygoid Muscles ; Tooth ; Traction ; Vertical Dimension

Clinical limitations following closed reduction of an intracapsular condylar fracture include a decrease in maximum mouth opening, reduced range of mandibular movements such as protrusion/lateral excursion, and reduced occlusal stability. Anteromedial and inferior displacement of the medial condyle fragment by traction of the lateral pterygoid muscle can induce bone overgrowth due to distraction osteogenesis between the medial and lateral condylar fragments, causing structural changes in the condyle. In addition, when conventional maxillomandibular fixation (MMF) is performed, persistent interdental contact sustains masticatory muscle hyperactivity, leading to a decreased vertical dimension and premature contact of the posterior teeth. To resolve the functional problems of conventional closed reduction, we designed a novel method for closed reduction through protrusive MMF for two weeks. Two patients diagnosed with intracapsular condylar fracture had favorable occlusion after protrusive MMF without premature contact of the posterior teeth. This particular method has two main advantages. First, in the protrusive position, the lateral condylar fragment is moved in the anterior-inferior direction closer to the medial fragment, minimizing bone formation between the two fragments and preventing structural changes. Second, in the protrusive position, posterior disclusion occurs, preventing masticatory muscle hyperactivity and the subsequent gradual decrease in ramus height.
Humans ; Jaw Fixation Techniques* ; Masticatory Muscles ; Methods ; Mouth ; Osteogenesis ; Osteogenesis, Distraction ; Pterygoid Muscles ; Tooth ; Traction ; Vertical Dimension