Background: Bruxism is a common parafunctional activity that causes destructive effects on the teeth, periodontal tissue, and temporomandibular joint, leading to hypertrophy and myositis of the masseter muscle. This study aimed to evaluate the sonography findings of masseter muscle among women with bruxism and compare them with those among healthy females.Methods: The statistical population of this study consisted of 45 female volunteers, including 23 patients with bruxism and 22 healthy subjects, referring to the Prosthodontics Department. Masseter muscles were evaluated by sonography in each group bilaterally, at rest and maximum contraction positions, and in longitudinal and transverse planes in terms of thickness. It was also examined in terms of the pattern (type I, II, and III), echogenicity (hypo, intermediate, and hyper), internal structure (homogeneous and heterogeneous), and muscle fiber limits (well-defined, poorly-defined, and ill-defined).Results: In the study of three variables of echogenicity, internal structure, and boundaries of muscle in patients with bruxism, less echogenicity (P ≤ 0.011), heterogeneous structure (P ≤ 0.003), and indeterminate boundaries (P = 0.000) were predominant, and there was a significant relationship between the two groups. Moreover, the examination of the difference in muscle thickness between the two groups showed that only the thickness of the left masseter muscle in the longitudinal plane and at rest position was significant between the healthy and bruxism groups (P = 0.040).Conclusion: There were marked sonographic changes in the masseter muscle in women with bruxism, indicating that the bruxism may affect the masseter muscle.

Masseter muscle rigidity is a known complication of drugs such as succinylcholine and volatile agents. However, muscle rigidity is an uncommon complication of propofol. We report the case of a 56-year-old ASA-PS class I woman refereeing for colonoscopy due to chronic constipation under deep intravenous sedation. She suffered masseter spasm after the injection of propofol. Masseter spasm should not be considered limited to special drug groups. In any case of difficult mouth opening, masseter spasm should be kept in mind and deepening of anesthesia or complete blockade of neuromuscular junction should be considered by the use of non-depolarizing muscle relaxants.

Background and Aim: Ultrasonography can be used as an imaging technique to study the texture and structure of a muscle (thickness, surface area, fiber length, etc.). Muscle size is an important factor in the diagnosis of muscle health or disease. Masseter is one of the masticatory muscles. Determining the thickness of the masseter muscle with regard to its function on the temporomandibular joint has an important role in the diagnosis of temporomandibular joint disorders. The aim of the present study was to determine the average thickness of the masseter muscle in healthy young people.Method and Materials: A total of 50 volunteers (25 men and 25 women) in the age range of 18-30 years participated in the current study. Sonography of the masseter muscle was carried out while participants were in supine position and a 12 MHZ linear probe was on the mandible ramus in alignment with the auricle on the muscle belly.Results: The statistical results showed high reliability of ultrasonic thickness of the masseter muscle in the rest position (ICC=0.8). Muscle thickness in young healthy participants in the rest position was 1.4±1.4 mm. A relationship was observed between gender and thickness of the masseter muscle (P=0.038).Conclusion: Sonography is a high reliable method in measuring the thickness of the masseter muscle. The masseter muscle thickness was greater in males than in females.

Objective (s): Occlusal trauma is one of the most common forms of oral biting dysfunction. Long‐term occlusal trauma could weaken the stomatognathic system; especially damage one’s masticatory muscle. Through using the rat model, this study investigated the trophic effect of ciliary neurotrophic factor (CNTF) on injured masseter muscle.Materials and Methods: Male Wistar rats (n=36) were randomly divided into five experimental groups and one control group (6 rats per group). Animals in the experimental group were cemented modified crowns on their mandibular first molars to artificially induce occlusal trauma in 1, 3, 7, 14, and 28 days. Control group was sham‐treated with forced mouth‐opening for about 5 min, while no crowns were placed. After 28 days of treatment, all rats were euthanized and their masseter muscle was collected. Through immunofluorescence and real‐time quantitative PCR, the expression of desmin, CNTF, and CNTFRa was investigated in rat masseter muscle. The microstructure of masseter muscle was observed by transmission electron microscope.Results: The expression of desmin showed a time‐dependent decrease on traumatic and non‐traumatic sides masseter, until reached the nadir at the 14th day, then restored to its normal level at the 28th day; however, the expression of CNTF and CNTFRa on the traumatic and non‐traumatic sides increased from day 7, reached the peak at the 14th day, and returned to normal level on the 28th day.Conclusion: CNTF, as an important neurotrophic factor, was tightly associated to the restoring of rat injured masseter muscle, which provides new target and treatment method for clinical application.

Background: There is no general consensus in restorative dentistry about which lateral guidance should be established. Some studies have shown that canine guidance decreases the tension of masticatory muscles. Others have reported that group function might achieve a better physiologic distribution of occlusal forces. Also, some reports have shown that both guidances are equally acceptable. Despite all discussions, clinical evidence of one guidance being superior to another is limited. Thus, this study aimed to analyze the electromyographic (EMG) activity of masseter muscles in individuals with group function and canine guidance. Methods: Twenty volunteers of both genders, aged 20-25, were divided into two groups: GF (group function guidance, n = 10) and CA (canine guidance, n = 10). EMG activity of masseters was captured using surface electrodes during habitual maximum intercuspation (HMI) and right and left lateral jaw movements and recorded using EMG amplitude values (RMS –,root means square). Student’, s t-test was used to compare mean RMS values between the groups and lateral movements in each group. Results: During HMI, there was no difference in masseter EMG activity between the groups. Both masseters showed higher activity in group GF only on the right side during lateral movements, while the left masseter exhibited higher activity on the nonworking side in both groups. The activity of both masseters distributed by tooth was higher in group CA. Conclusion: During tooth restorative procedures, any guidance is acceptable considering HMI. However, group function guidance is more favorable during lateral movements due to greater dissipation of occlusal pressures.

BACKGROUND AND OBJECTIVE: Evaluating the thickness of the masseter muscle is an important determinant of the health or illness of the muscle. Investigating changes in masseter muscle thickness due to its function on the temporomandibular joint plays a significant role in detecting the cause of many disorders in this joint. The present study aims to compare the ultrasonic thickness of masseter muscle between patients with bruxism and healthy people.METHODS: This case-control study was conducted among 44 subjects in two groups (22 subjects in each group of, including 11 women and 11 men) in the age range of 18 – 30 years old in patients with bruxism and healthy people. The subjects had normal BMI, had no inflammatory disease or strike to the temporomandibular joint, and had no history of maxillofacial surgery. Ultrasound evaluation of masseter muscle was performed in a supine position, with 12 MHz linear probe along the auricle and perpendicular to mandibular ramus on muscle ventricle and the thickness of the muscle was obtained in millimeters.FINDINGS: The masseter muscle thickness was more in patients with bruxism (11.97±0.85 mm) than healthy subjects (10.76±2.2 mm) (p<0.01). The masseter muscle thickness in men (12.54±0.4 mm and 11.44±0.25 mm, respectively) was more than that of women (11.4±0.79 mm and 10.08±3.05 mm, respectively) (p=0.038).CONCLUSION: The results of this study showed that the masseter muscle thickness in people with bruxism is more than healthy people and is more in men.

Background and Objectives: Impacted third molars surgeries are common in maxillofacial surgery clinics. Post operation complications like pain, swelling, trismus are common. Most of the patients avoid surgery because of post operative discomfort. Reducing these factors is one of the necessities in dental treatments. Several studies have been conducted in case control methods. In most of these studies, interventional factors have not been controlled properly, so there are differences among results. In order to obtain an exact response in application of corticoesteroids, this study was carried out through a cross over method after controlling interventional factors.Methods and materials: A clinical trial was conducted as cross over and double blinded method. Thirty eight patients were included in the study. In every patient two third molar teeth from mandible were selected, one as a control tooth. For case group 40 mg methylprednisolone was injected in masseter muscle. All of operations were carried out by one oral surgeon. When the interval of both operations of case and control tooth was more than seven minutes, the patient was excluded from the study. In specification, systemic conditions and required information were prepared, and pain, swelling, trismus were evaluated after 48 hours and also after first week of operation by examination and completing questionnaire by participant assistant of the investigation. The interval of both operations was at least one month. The data were statistically analyzed by SPSS and Wilcoxson test.Results: There is a meaningful difference between pain, swelling and trismus scales after 48 and one week post operation in both case and control groups:(P<0.05).Conclusion: Methylprednisolone affects properly on impacted third molar surgery and post operation morbidity.

The experiments were carried out on the muscle spindle (MS) that located onto the soleus muscle (SM) in the anaesthetized rats. After applying a mechanical slow stretch (SS) on the SM, the MS wasn't influenced by this stimulant and it was in a slack status. On the other hand, the MS has showed a dysfunction. The slack status of MS, it means, without electro-mechanical activity for MS that was observed in isolating MS. And this slack status of MS also was occurred by insufficient of γ-motor stimulation. With using the passive stimulating vibration on the MS-SM, again, the slack status of MS was observed. Of course, in this experiment, before that the MS was made up with passive vibration, firstly, the activation of MS was clearly observed by gs-activity. On contrary of the positive effect of  gs into MS, there wasn't a positive effect with gd-activity into MS. But, it's stated that, there was the resting discharge (RD) in the MS during slack status and the RD scale has been significantly acceptable. The MS-RD was created with both of the SS and especially by γs stimulation, though not with gd stimulation.However, it was concluded that, the changing of MS-activity could be caused with the changing length of SK.M. In this process, the MS respond was pertinent to gs-activity. Meanwhile, the activation of γs was followed by activity of MS- chain- afferent. It's seemed that, in this loop of nervo-muscular wasn't any place for activating of MS-bag fiber.