The use of botulinum toxin for the treatment of temporomandibular disorder.
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Adult↗
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Effect of parafunctional clenching on TMD pain.
Parafunctional activities are assumed to play an important role in temporomandibular disorders (TMD), but experimental data in support of this hypothesis are lacking. This study examined the role of parafunctional clenching on various measures of TMD pain. Five subjects participated in daily 17-minute electromyogram biofeedback training sessions structured in three phases. Subjects were instructed to maintain temporalis and masseter muscle activity below 2 microV in the first (decrease) phase of training (10 sessions), above 10 microV in the second (increase) phase (1 to 8 sessions), and below 2 microV in the third (decrease) phase (10 to 15 sessions). Preliminary screening examinations showed that none of the subjects had TMD. Two subjects reported intolerable pain during increase training, and both were diagnosed with a TMD during this phase. No subject was diagnosed with TMD pain during either decrease training phase. The authors conclude that chronic, low-level parafunctional clenching may be a factor in the cause of TMD pain.
Adult↗
Bruxing patterns in children compared to intercuspal clenching and chewing as assessed with dental models, electromyography, and incisor jaw tracing: preliminary study.
The purpose of the present study was to compare bruxing patterns in children with chewing and maximum intercuspal clenching as defined in a clinical and laboratory environment. Six non-bruxing controls and six children who actively bruxed according to parent reports were evaluated. Both control and experimental subjects were assessed by an initial questionnaire, intraoral examination, extraoral examination, dental study models, incisor mandibular tracking, and bilateral surface electromyographic recordings (e.g., EMG). Bruxing was defined as grinding, clenching, or both in combination. The clinical examination consisted of an intraoral examination of the dentition, number of occlusal contacts, and wear facets. Dental study models were used to substantiate the intraoral findings for occlusal contact and wear facets. The mandibular incisors position was tracked during opening, closing, laterotrusion, protrusion, and chewing and compared to the bruxing movements in the experimental subjects. Bilateral surface EMG signals from the temporalis and masseter muscles were recorded in three maximum intercuspal clenches, ten chewing cycles on sugarless gum, and during simulated bruxing. The dental contacts were equal in number bilaterally in both control and bruxing subjects. Both groups demonstrated wear facets, but the bruxing subjects had more facets. The wear facets indicated lateral excursions but not clenching. Only the incisor jaw tracking and bilateral EMG differentiated the bruxing patterns. In those subjects (n = 4) who clenched during bruxing, the EMG pattern was not similar to that of intercuspal clenching and demonstrated its own unique muscle recruitment for the temporalis and masseter muscles. In the subjects who exhibited lateral excursions for bruxing (n = 2), the pattern of muscle recruitment of the two-closing muscles in terms of amplitude was similar for both the bruxing and chewing gum. Our findings support a concept that bruxing may depend upon factors that modify coactivation of muscle recruitment and do not depend upon occlusal contacts.
Analysis of Variance↗
Effect of contractile activity on skeletal muscle glucose uptake. Analysis of temporal responses.
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Animals↗
Biphasic response to gut manipulation and temporal correlation of cellular infiltrates and muscle dysfunction in rat.
BACKGROUND: Surgical manipulation of the intestine results in the massive movement of leukocytes into the intestinal muscularis at 24 hours. This is associated with muscle inhibition. The aim of this study was to temporally associate leukocyte extravasation with ileus after surgical manipulation. METHODS: Rats underwent a simple manipulation of the small bowel and were killed at various times (0, 0.25, 0.5, 1, 3, 6, 12, and 24 hours) postoperatively. Jejunal circular-muscle contractile activity was assessed in a standard organ bath. Both extravasating and resident leukocytes were immunohistochemically stained in muscularis whole mounts. RESULTS: Contractile activity was significantly reduced immediately after surgery, but rapidly returned to control levels at 3 hours. After recovery, muscle function decreased at 12 and 24 hours (41% and 81%, respectively). The resident muscularis macrophage network demonstrated cellular activation 1 hour postoperatively. The number of leukocytes increased over time (neutrophils, 67.5-fold; monocytes, 98.2-fold; and mast cells, 47-fold at 24 hours). CONCLUSIONS: The functional results demonstrate a biphasic response in the suppression of muscle activity after surgical manipulation. Regression analysis (r2 = 0.998) of the temporal development of leukocyte infiltration and the protracted phase of muscle inhibition provides evidence for a correlation between cellular inflammation and postoperative dysmotility.
Animals↗
Recurrent odontogenic keratocyst within the temporalis muscle.
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Epithelium↗
Effect of canine guidance of maxillary occlusal splint on level of activation of masticatory muscles.
The effect of canine guidance of a full-arch maxillary flat occlusal splint on the level of activation of the anterior and posterior, temporal, masseter and suprahyoid muscles during maximal clenching, were studied in 14 subjects without craniomandibular disorders. The results revealed that, the level of electromyographic activity of anterior and posterior temporal and suprahyoid muscles during maximal clenching on the occlusal splint in habitual closure was unchanged, as compared to biting in the intercuspal position (ICP), while the activity in the masseter muscle, on average, was increased slightly (13 percent). In contrast, the level of activation of the jaw elevator muscles decreased significantly during maximal clenching on the cuspid ramp of the splint, as compared to the biting in ICP or clenching on the splint. However, the degree of reduction of activity was not symmetrical, and was most pronounced in the masseter muscle of the biting side and in the anterior and posterior temporal muscles of the non-biting side. No significant difference was observed in the activity of the suprahyoid muscles.
Adult↗
Scaling of the mandible in squirrels.
We compared the shape of the mandible among New World tree squirrels and selected outgroup taxa using linear measurements and areas defined by the median axis and conventional anatomical landmarks. We modified the median axis technique to define novel measurements, which proved complementary to those obtained from conventional landmarks. Allometric analyses showed that the scaling of the mandible among the New World tree squirrels is generally isometric (as has been observed in other groups of mammals), but diverges from isometry in a tendency in smaller animals for the masseteric ridge to be displaced anteriorly, the condylar process and posterior portion of the ascending ramus to be relatively elongated, and the coronoid process to be shortened. Allometric analyses also revealed the ways and extent that outgrowth taxa deviated from the scaling pattern observed for the New World tree squirrels. A flying squirrel (subfamily Pteromyinae), a moderate-sized callosciurine squirrel, and three species of pygmy tree squirrels from Asia and Africa show mandibular proportions very similar to those predicted for New World tree squirrels of corresponding size. Ground squirrels (tribe Marmotini) and successively more distant relatives such as Aplodontia, two myomorph rodents, and a rabbit show greater differences from the New World tree squirrels in their mandibular proportions. Combining the use of median-axis and conventional measurements makes it possible to examine changing relationships between locations of anatomically homologous landmarks and the geometry of the form.
Animals↗
Jaw muscle function and wishboning of the mandible during mastication in macaques and baboons.
An analysis of in vivo bone strain indicates that the mandibular symphysis of macaques experiences lateral transverse bending or "wishboning" during the power stroke of mastication, and this loading regime results in relatively intense concentrations of stress along the lingual aspect of the symphysis (Hylander 1984, 1985). It has been hypothesized that peak wishboning of the macaque mandible, which probably occurs at the very end of the power stroke, that is, after the initial occurrence of maximum intercuspation, is associated with the late peak activity of the balancing-side deep masseter muscle coupled with the rapid decline in the activity of the balancing-side medial pterygoid and superficial masseter muscles (Hylander et al., 1987). The main purpose of this study is to do a detailed analysis of the electromyographic (EMG) activity of the deep and superficial masseter and medial pterygoid muscles so as to provide a better understanding of the external forces associated with wishboning. This was done by recording and analyzing EMG activity from the superficial masseter, deep masseter, and medial pterygoid muscles in macaques and baboons. EMG activity was recorded from bipolar fine-wire electrodes, and the data were quantified and analyzed using digital techniques. The EMG data clearly support our original observation that the balancing-side posterior deep masseter exhibits peak EMG activity relatively late in the power stroke at a time when activity is rapidly decreasing in the balancing-side medial pterygoid and superficial masseter muscles. Moreover, peak activity of the balancing-side deep masseter occurs at a time when the activity of the working-side deep and superficial masseter and medial pterygoid muscles are also decreasing. Thus, these data are consistent with the hypothesis that wishboning of the mandible is influenced significantly by the late occurrence of force from the balancing-side deep masseter. The EMG data also indicate that residual force from the relaxing superficial masseter may contribute significantly to wishboning. Finally, patterns of wishboning are not fully accounted for by our EMG analysis of the deep and superficial masseter and medial pterygoid muscles. This is probably because the lateral ptergyoids, which can either counter increased wishboning or actually cause reverse wishboning, were not included in our EMG analysis. The EMG data demonstrate that jaw-closing muscle recruitment patterns for macaques and baboons differ from those of humans. Nevertheless, in spite of these differences, it appears, based on previously published EMG data, that the human symphysis may also experience wishboning.(ABSTRACT TRUNCATED AT 400 WORDS)
Animals↗
Smothering dystonia in a patient with oromandibular dystonia.
A case report is presented of a patient with pathologically confirmed striatonigral degeneration who experienced episodic syncope as a result of oromandibular dystonia obstructing inhalation through her mouth and nose.
Airway Obstruction↗
Electromyographic signal changes during exercise in human chronic jaw-muscle pain.
Twelve individuals (2 males, 10 females) with chronic masticatory muscle pain and 11 individuals (2 males, 9 females) without, had their bite force and surface electromyography from the right and left superficial masseter and anterior temporalis muscles recorded before, during and after a 30-s sustained submaximal clenching task. This task was performed at 50% of the force level of each subject's maximum voluntary contraction (MVC) for 30 s. Brief (3 s) 50% MVC efforts were recorded at 15-s intervals, three times before and six times after the sustained clench. Each subject performed this pattern of activities three times with a 15-min rest between each trial. The centre frequency (CF) of the electromyographic power spectrum was calculated by fast Fourier transformations. The mean CF at the end of the 30-s clench and the rate of change at the CF during the clenching task were analysed between groups, sides and muscles. The data indicated that the masseter CF decreased at a significantly faster rate for the first clenching trial in the muscle-pain group. Conversely, the rate of change of the temporalis CF did not significantly differ for the two groups during the three clenching trials. By the third trial the CF of the exercised masseter in the non-pain group exhibited a similar rate of change to that in the pain group. This suggests that both repeated exercise and the presence of chronic inflammation increase the rate of change of the electromyographic signal of the contracting masseter. The mechanism underlying this increased change is unknown.
Adult↗
Vectorial analysis of the static equilibrium of forces generated in the mandible in centric occlusion, group function, and balanced occlusion relationships.
Mechanical analyses supporting various and prevailing stomatognathic concepts of occlusal function are sparse. This study, using a mechanical model, simulates a system in function and provides a vectorial analysis based on a static equilibrium of forces generated in a mandible at 10 different positions. The positions analyzed were one in centric occlusion and nine in eccentric positions. Four eccentric positions were in a balanced occlusal relationship and five were in group function. Among other conclusions that were drawn, the most relevant seems to be the finding that cusp inclines and condylar path inclination have a profound influence on the forces acting within the joints and dentition.
Bite Force↗
Clinical, radiographic, and electromyographic study of patients with internal derangement of the temporomandibular joint.
Fifteen patients with internal derangement of the temporomandibular joint (TMJ) were examined clinically, radiographically, and electromyographically. Electromyographic recordings were also obtained from 11 subjects without signs or symptoms associated with their TMJs or masticatory musculature. All the patients with internal derangement demonstrated interferences on the ipsilateral side. This was interpreted as the result of disc displacement producing a reduced joint space and, consequently, a decreased vertical dimension on the symptomatic side. Slow opening and closing mandibular movements without clenching could be performed by healthy persons without noticeable EMG activity in the temporalis and masseter muscles. In association with disc displacement, electromyographic activity of the temporalis and masseter muscles occurred when the condyle slid over the posterior band of the disc and could be interpreted as an arthrokinetic reflex caused by distraction. Continuous muscle activity could be provoked by TMJ disc displacement and ceased when the disc position was normalized on mouth opening, only to occur again every time the disc became displaced on mouth closure. Anterior disc displacement without reduction (closed lock) could cause spastic activity in the temporalis muscle on the affected side. Spastic activity of the masseter and temporalis muscles occurring on the same side as a joint with anterior disc displacement hinders or inhibits the condylar movement necessary to achieve reduction.
Action Potentials↗
Chewing behaviour and bolus formation during mastication of meat with different textures.
During chewing, meat is mashed under compression and shear bite forces whilst saliva is incorporated. The resulting mixture is shaped into a cohesive bolus by agglomeration of small particles, and triggers a swallow. This study aimed to investigate the relationship between chewing behaviour and bolus formation of meat with different textures. Twenty-five consenting young adults participated in this study. Electromyographic activity was recorded from surface electrodes on the elevator muscles (masseter and temporalis) during mastication of cold beef. Two different textures (T(1): tough and dry; T(2): tender and juicy) were studied, and subjects were asked to chew the beef and then spit out the bolus either: (1) after a constant chewing period of 7s or (2) when the bolus was ready to be swallowed. Meat samples were weighed before and after chewing to determine weight changes due to saliva incorporation and the release of meat juice. Cutting tests were applied to measure the maximum shear force. The mechanical shear force was maximal for meat before chewing (T(1)=124 N/cm(2); T(2)=83 N/cm(2)) and decreased with increased chewing duration. Texture differences analysed from mechanical measurements remained significant even when the boli were ready for swallowing (T(1)=39 N/cm(2); T(2)=32 N/cm(2)); the toughest meat gave the toughest bolus. Muscular activity adapted to the texture of the meat as soon as chewing began, and remained constant over the observed chewing period. Mean muscular activity was higher during the chewing of tough meat than during the chewing of tender meat. As a consequence, by the time a bolus was ready to be swallowed, more saliva had been incorporated into the tough meat samples (mean weight increase: 36%) than the tender meat samples (mean weight increase: 30%).
Adult↗
Technique evolution for facial paralysis reconstruction using functioning free muscle transplantation--experience of Chang Gung Memorial Hospital.
The author performed facial reanimation by using functioning free muscle transplantation in 116 cases from 1986 to 2000. Three consecutive five-year periods are presented in relation to each stage of the author's technical improvement. The first five years bulkiness and asymmetrical smiling with weak gum exposure were encountered and required correction. The second five years was a period of technical improvement, but with residual deformities. The third five-year period was one of technique refinement. The author extended the utility of the gracilis for different and more challenged problems, such as the use of a muscle plus skin two-unit composite flap connected by the septoperforator nutrients, not only for facial reanimation but also for intra-oral contracture release or extra-oral facial soft tissue and skin deficits replacement.
Facial Paralysis↗
Adaptation of craniofacial muscles in subjects with craniomandibular disorders.
The purpose of this study was to examine muscle function in subjects with muscle pain. Forty-three subjects with pain in the craniomandibular muscles, clinically determined by manual palpation, were studied for alteration in recruitment of temporalis, masseter, and suprahyoid muscles during a series of phasic movements. Seventeen normal subjects were used as controls. The subjects with muscle pain were divided into three subgroups: (1) those with pain in both mandibular and neck muscles; (2) those with pain in these two muscle groups with joint degeneration; and (3) those subjects with pain only in mandibular muscles. Surface electromyographic (EMG) recordings were taken as each subject performed 16 different responses in which mandibular incisor movement was tracked simultaneously. The results show that the subjects with muscle pain use their anterior temporalis muscles with less frequency (i.e., probability) and with less intensity in several responses than normal subjects. These responses include rapid vertical closing movements, retrusion, ipsilateral laterotrusion, and natural as well as contralateral mastication. The masseter muscle is impaired much less in its function, and the recruitment of the suprahyoid muscles is not affected in the patients with muscle pain. Comparison of the bilateral activity in the anterior temporalis muscles during intercuspal clenching shows that the subjects with muscle pain often demonstrate a more severe asymmetrical recruitment of these muscles than the more symmetrical recruitment seen in normal subjects. Similar observations were made for the masseter muscle. These studies demonstrate that subjects with muscle pain in craniomandibular muscles alter the recruitment of their jaw muscles, thus supporting the concept that the neuromuscular system is altered in patients with craniomandibular disorders.
Adult↗
The temporalis osteomuscular flap versus the free calvarial bone graft. An experimental study in the growing rabbit.
The authors have conducted an experimental study on the evolution of temporalis osteomuscular flaps compared with calvarial free bone grafts in young rabbits. The evaluation of the results has been performed with macroscopic, radiological and histological investigations in an early and late postoperative phase. This study has confirmed that the bone flaps remain viable and are characterized by a normal evolution. There is no evidence of anomaly of craniofacial growth nor asymmetry when compared with the contralateral side. On the other hand, the free bone grafts show the typical signs of necrosis and resorption. Some asymmetries are produced in comparison with the contralateral side, these being particularly evident in the two-months samples, while the overall craniofacial growth is not seriously impaired. This experimental study confirms the reliability of the temporalis osteomuscular flap in facial reconstruction.
Animals↗
Comparison of electromyographic pattern of sensory experts and untrained subjects during chewing of Mahon cheese.
Use of electromyography (EMG) to monitor mastication is a relatively new concept in assessing food physical and sensory properties. Although expert assessment of cheese characteristics is widely used, the effect of training in sensory analysis on mastication patterns, as assessed using EMG is not well known. Nine samples of the same Mahon cheese (60 days ripening) were given to 24 subjects (8 experts, 16 untrained) and EMG recorded for each chewing sequence. Three samples were tested in a single session by each subject, and three sessions carried out on different days. EMG was recorded from four masticatory muscles for each subject. From EMG records the following was extracted: number of chews, chewing time, mean and maximum voltage of EMG bursts (i.e. chews) across chewing sequence, chewing work and chewing rate. No gender bias was found for the EMG parameters considered, therefore, as regards gender, each group was considered to be homogeneous. Variability within-subjects across samples was greater for experts than untrained subjects. Significant differences in chewing time, chewing work and chewing rate were found between the expert and untrained groups. Data analysis of the three sessions showed an influence of cognitive constructs, mediating states, on the chewing process. The experts were found to be goal driven as to their mastication process. Experts showed no significant differences between sessions, untrained subjects were found to vary their EMG output in successive sessions for number of chews, chewing time, mean voltage, and chewing work.
Adult↗