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A case is presented of a 10-year-old girl who had a benign osseous tumor of the temporalis muscle. The tumor appeared to be a variant of the so-called pseudomalignant osseous tumor of the soft tissues and could readily be distinguished from both osteogenic sarcoma and myositis ossificans.
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PURPOSE: Little is known about the effects of orthodontic treatment on oral motor function. The objective of this report is to evaluate changes in mandibular motion and maximum bite force that occur between the initiation of presurgical orthodontics and its completion before surgery. PATIENTS AND METHODS: Fifteen patients (9 women, 6 men) with a variety of dentofacial deformities were examined before and after presurgical orthodontics. Mechanical advantage of the muscles and bite points, mandibular range of motion, maximum isometric bite force, and levels of electromyographic (EMG) activity in the anterior and posterior temporalis and masseter muscles during isometric bites were recorded on all subjects over time. Data obtained before and after completion of presurgical orthodontics were statistically compared. RESULTS: Presurgical orthodontics reduced mandibular mobility somewhat, but the amount was not significant. Statistically significant reductions in bite force were noted after orthodontics for incisor, canine, premolar, and molar bite positions. No significant difference in the EMG/bite force slopes was obtained, nor was there any difference in the moment arms of the bite points or the muscles of mastication from orthodontics. CONCLUSIONS: This study showed significant changes in measures of oral motor function resulting from orthodontic treatment. A larger study is needed to confirm that these results will be similar in all orthodontic patients. There is no indication that these changes are the result of physiologic alterations of the muscles of mastication. The best current explanation is that these changes result from the pain and discomfort of the orthodontic appliances and the induced malocclusion.
The organization of neuronal clusters in the rat mesencephalic trigeminal nucleus (Mes V) was analysed using fluorescent tracing techniques. Simultaneous injections of fluorescent compounds (True blue and Diamidino yellow) were made unilaterally in the masseter and temporalis muscle, or in the masseteric and temporalis nerve. Examination of labeled neurons in frozen brainstem sections showed that (1) the arrangement of temporalis and masseteric primary afferent neurons in the mesencephalic trigeminal nucleus is not somatotopic; (2) primary afferent neurons of both muscles are located at all rostrocaudal levels; and (3) clustering of temporalis, of temporalis and masseteric, and of masseretic afferent neurons occurs at all levels throughout the nucleus.
STATEMENT OF PROBLEM: Craniomandibular disorders, unilateral mastication, and asymmetry of masticatory muscles appear to be related to each other. Thus, it is of interest to investigate masticatory muscle activity during unilateral mastication in healthy subjects. PURPOSE: This study monitored contractile activity of the right and left masticatory muscles during right- and left-side gum chewing. MATERIAL AND METHODS: Electromyographic techniques were used to determine chewing cycle duration and duration of contractile activity of the masticatory muscles (right and left masseter and anterior temporalis muscles) during unilateral chewing in 40 subjects without orofacial pain. The time-course of activation of the 4 muscles was also investigated. RESULTS: Electromyographic traces showed extensive interindividual variation. In both right- and left-side chewing tests, and regardless of whether the masseter or the temporalis muscles were considered, mean duration of the contraction phase did not differ significantly between the working and nonworking sides. The working side temporalis contracted first, whether alone or at the same time as the other muscles. CONCLUSIONS: In healthy subjects, no significant differences in masticatory muscle activity should be expected between either the right and left or the working and nonworking sides.
Nine patients with contracted avascular sockets who were unable to wear prostheses, and whose prospects for maintaining viable autogenous dermis-fat grafts were diminished, underwent temporalis muscle transfer into the orbit through a window in the lateral orbital wall. The temporalis transposition was used as a vascular bed for dermis-fat orbital implantation. Postoperatively, seven of nine patients were able to wear satisfactory prostheses and four of nine patients had amelioration of their superior sulcus deformities.
Cutaneous laser stimulation activates predominantly the A-delta and C mechano-heat nociceptors. Applied to the perioral region, low intensity CO(2)-laser pulses evoke reproducible trigeminal cortical evoked potentials (LEPs). High intensity CO(2)-laser stimuli induce a reflex response in the contracted jaw-closing muscle, the so-called laser silent period (LSP). Both LEPs and LSP provide a useful tool to study the physiology of the trigeminal nociceptive system. In ten healthy subjects we recorded the subjective ratings of the perioral laser stimulation and the trigeminal LEPs and LSP before, during and after homotopic experimental tonic muscle (infusion of hypertonic saline into the masseter muscle) and tonic skin pain (topical application of capsaicin to the cheek). LEPs were recorded from the vertex at two stimulus intensities: low (1.1 x pain threshold, PTh) and high (1.5 x PTh). LSP from masseter and temporalis muscles were recorded bilaterally through surface electromyographic (EMG) electrodes. CO(2)-laser pulses were applied to the perioral region (V2/V3) on the painful and non-painful side. The amplitude of LEPs increased with higher stimulus intensities (P<0.0001), but were suppressed by 42.3+/-5.3% during experimental muscle pain (P<0.0001) and by 41.6+/-3.2% during skin pain (P<0.0001). No pain-related effects were observed for the N and P latency of the LEPs (P> 0.20). The LSP in the masseter and temporalis muscles had similar onset-latency (80+/-5 ms), offset-latency (111+/-5 ms) and duration (31+/-4 ms). Experimental pain had no effect on the onset- and offset-latency (P>0.05). Experimental pain, whether from muscle or from skin, reduced the degree of suppression (P<0.01) and the area under the EMG curve (P< 0.005) of the LSP. The LSP was still suppressed during the post-pain recordings when the skin pain had disappeared (P<0.05). In all experiments experimental tonic pain decreased the subjective ratings of the perioral laser stimulation (P< 0.001). Experimental tonic pain, either from muscle or from skin, induced bilateral inhibitory effects on the trigeminal laser evoked potentials and brainstem reflex responses and on the subjective ratings of the laser pulses. These effects could be mediated through the activation of segmental and suprasegmental inhibitory systems that may function interdependently.
Many studies show a consistent individual chewing pattern; chewing being governed by a pattern generator and regulated by sensory feedback. The aim of this study was to determine the variation in chewing between sessions, replicates and subjects using elastic model foods. Fifteen young male subjects were selected to chew four food products differing in hardness. Four sessions were performed at 1-wk intervals for each subject and, within each session, the four model foods were presented 3 times each. Jaw movement was recorded simultaneously with masseter and anterior temporalis electromyographic activities. Several chewing characteristics increased progressively from one session to the next; the largest increase occurred from the 1st to the 2nd session, with little difference between the last two sessions. No differences were observed between the samples of the same food product within a session. As mastication progressed, the amplitude and speed of the cycles and the muscular work decreased progressively. The first cycle appeared to be very different from the subsequent for all parameters except for occlusal duration. Thus, under our experimental conditions, the origin and amount of variation in chewing patterns were identified and provide information to improve the accuracy and comparability of results in studies of mastication.
The aim of this study was to compare the effects of hard and soft splints on the activity of the anterior temporalis and masseter muscles. Surface EMG recordings were made from these muscles during clenching at 10% of maximum, 50% of maximum and at maximum clench, both before and after insertion of a hard splint. This sequence was then repeated with a soft splint. The relative level of activity in the anterior temporalis and masseter muscles at all three activity levels was quantified by means of an Activity Index, which provides a measure of the balance of activity in the masseter relative to the activity in the anterior temporalis muscle. It was found that hard splints led to a decrease in EMG activity in relation to activity with no splint in both muscles at maximum clench and particularly the anterior temporalis. Soft splints produced a slight increase in activity of both muscles, but particularly the masseter muscle. The Activity Index indicated a shift in the balance of activity away from the anterior temporalis muscles with both splints, particularly at 10% of the maximum clenching level. It is possible that the decrease in activity of the temporalis muscles relative to the masseter muscles may be a factor in the therapeutic effect of both a hard and a soft splint, although the decrease is clearly greater with the hard splint.
This study investigated mandibular displacements during clenching in the lateral mandibular position in relation to lateral occlusal relationships. Twelve healthy human subjects (mean=26.7 years) volunteered for this study. Acrylic occlusal devices were fabricated for the lower working-side canine, working-side second molar and balancing-side second molar in order to simulate a dominant canine guidance, working-side interference (WI), balancing-side interference (BI) and bilateral balanced occlusion (BO). Vertical displacements of the mandible were recorded by linear variable differential transformers during submaximal clenching in the right lateral position. The four experimental occlusal conditions were revealed to have a significant effect on mandibular displacement patterns (ANOVA, P < 0.001). A dominant canine raiser caused a mandibular elevation with the smallest displacement at the working-side premolar and the largest displacement at the balancing-side second molar. Clenching on a WI or BI caused a mandibular elevation with the smallest displacement at the working- or balancing-side second molar, respectively. A BO resulted in the smallest upward displacement among the four experimental conditions. These results suggest that the nature of reaction forces at the temporomandibular (TM) joints caused by the elevation of the mandible varies in a predictable manner depending upon lateral occlusal relationships.
In cases of facial asymmetry with denervation atrophy of the masticatory muscles associated with head and neck tumors involving the trigeminal nerve, facial contour depression occurs selectively over the temple and masseteric area, separated by an uninvolved area over the zygomatic arch. The authors developed a new thoracodorsal artery perforator flap with two separate adiposal paddles based on their own perforators from the same mother vessel, the thoracodorsal vessel. Nearly normal temporo-masseteric contour was achieved in two patients. By freely positioning two adiposal paddles supplied by independent perforators based on the same vessel, separate non-contiguous regions of the face could be reconstructed correctly with one microvascular anastomosis in a single-stage operation, without the need for a secondary procedure to reduce the bulk over the zygomatic arch.
OBJECTIVE: The purpose of this study was to determine if mandibular motion measurements could be used to distinguish between common temporomandibular disorder (TMD) subgroups that were established on the basis of only clinical signs and symptoms. STUDY DESIGN: Patients were 41 consecutive TMD clinic patients (31 women and 10 men). These patients were divided into 6 typical TMD subgroups. The subgroups were patients with (1) arthromyalgia, (2) arthromyalgia with disk condyle incoordination, (3) disk condyle incoordination only, (4) osteoarthritis, (5) suspected disk displacement without reduction, or (6) other diagnoses. RESULTS: There were no subjects in the other-diagnosis subgroup and only 1 subject with suspected disk displacement without reduction who was dropped without further consideration. The data for mean age showed that the osteoarthritis subgroup (n = 12) was statistically older (17 years) than the disk-condyle-incoordination-only subgroup (n = 11). The mean age of the other 2 groups, arthromyalgia (n = 11) and arthromyalgia with disk condyle incoordination (n = 6), was between the osteoarthritis and the disk-condyle-incoordination-only subgroups. For the 4 TMD subgroups whose data were analyzed, the mean differences between similar jaw opening measurements ranged from 6 to 8 mm with a standard deviation of approximately 8 to 10 mm. The mean left lateral motions were 0.5 to 1.3 mm larger than observed on the right. The widest mean jaw opening (56 mm) occurred in the disk-condyle-incoordination-only group. These differences were not found to be statistically significant. CONCLUSION: Analysis of opening, lateral and protrusive jaw motion data showed these measurements could not reliably differentiate between patients with osteoarthritis, arthromyalgia, arthromyalgia with disk condyle incoordination and disk condyle incoordination only.
In 13 healthy subjects (eight men and five women, mean age, 22 years), an aluminum intercuspal interference (height, 0.25 mm) was placed on the maxillary right first premolar to study its effect on the contractile symmetry of the right and left masseter and anterior temporalis muscles when measured through a Percentage Overlapping Coefficient (POC), derived from surface electromyographic recordings of maximum voluntary teeth clenching. Additionally, and to estimate the potential of the experimental intercuspal interference to induce lateral displacement of the mandible, a Torque Coefficient (TC) was derived from surface electromyographic recordings. The conclusion was that the experimental occlusal interference gave rise to asymmetric contractile activity in the studied mandibular elevator muscles as well as a potential to displace the mandible in a lateral direction.
In 32 Caucasian adult males serial MRI scans of the jaw muscles were taken approximately perpendicular to the mean fibre direction of the jaw muscles to determine their cross-sectional areas. These areas are proportional to the maximal isometric strength of a muscle. To describe facial skeletal variation, nine angular and 21 linear cephalometric measurements were recorded, and statistically reduced by means of multiple regression and principal component analysis. Six components were extracted, rotated, and subsequently correlated with the maximal cross-sectional areas of the jaw elevators and anterior digastric muscle. Positive significant correlations were found between a linear combination of several transversal skull dimensions on the one hand, and the maximal temporalis and masseter cross-sections on the other. A negative significant correlation was found between the flexure of the cranial base and the temporalis cross-section. Surprisingly, no significant correlations were found between either anterior facial height or posterior facial height and any of the jaw muscles cross-sections. It was concluded that, in adult males with normal skull shape, relationships exist to a limited extent between craniofacial morphology and the cross-sectional areas of the jaw muscles.
An objective parameter for the electromyographic evaluation of the masticatory function of edentulous patients was studied. The normal ranges of the parameters for such subjects were also established. This study focused on the time parameter of electromyography, which is one of the most reproducible parameters. The variation coefficient of the time parameters (interval and duration) were revealed to be reliable and reproducible for the evaluation of masticatory functions.
As induced by an occlusal splint over a period of 1 week, this study monitored surface electromyographic changes in the postural contractile activities of jaw elevator and depressor muscles in six healthy adults. The immediate effect of the occlusal splint was to increase the postural contractile activities of the suprahyoid muscles. All postural muscle activities showed wide-ranging biological variation, but the activities induced by the splint tended to stabilize within 1 week, with decreased postural activities in the masseter and anterior temporalis muscles, and increased postural activities in the suprahyoid muscles.
The purpose of this study was to make observations of electromyographic (EMG) signal levels from a group of individuals to describe different mandibular tasks and use them as predictors of these activities. The sample consisted of 22 volunteer subjects (12 women and 10 men) with mean values for age, weight and height of 29.3 years, 69 kg and 168 cm respectively. Three separate recording sessions were performed for each subject. During each session the subjects were asked to perform different voluntary mandibular tasks. The EMG activity for each task was recorded from the anterior temporalis (T(a)) and masseter muscles (M(m)) bilaterally. The EMG recordings were related to task, session, task-session interaction, gender, age, weight and height using SAS version 6.12. The EMG data from the four muscles were considered as covariates to classify tasks. Overall, 78% of the group tasks were correctly classified. When the masticatory activities were classified as high and low EMG signal level group, the overall classification rate improved with an accuracy of 88%, sensitivity of 86%, specificity of 88%, positive predictive value of 76% and negative predictive value of 94%. The tasks, sessions, task-session interactions, gender, age, weight and height did not have any significant effect on the EMG recordings. It can be concluded that distinguishing among different mandibular tasks of a subject can be achieved when the individual EMG signal levels were compared with the EMG signal levels of subjects that were used to describe different mandibular activities.
The aim of this study was to investigate the effects of an original orthodontic functional appliance [function generating bite for deep bite correction (FGB-D)] on masticatory muscle activity in subjects suffering from muscle-related temporomandibular disorders (TMD). Electromyographic (EMG) analysis was performed on 33 young adults (nine men, 24 women) to evaluate the contractile symmetry of the right and left masseter and anterior temporalis muscles. The subjects were divided into three groups: a muscle-related TMD group requiring orthodontic treatment for deep bite correction (three men, eight women) and treated with FGB-D; a muscle-related TMD group not requiring orthodontic treatment (three men, eight women) and treated with a Michigan occlusal splint; and a TMD-free group (three men, eight women) as a control group. Records were made by surface EMG of maximum voluntary teeth clenching, with and without the functional appliance or occlusal splint in place, before and after 12 months of therapy. A torque index was derived from the surface EMG recordings to estimate lateral displacement of the mandible. The results show that the FGB-D corrects the torque index and thus the lateral displacement of the mandible.