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PubMed1999

Changes in masticatory patterns after bilateral fracture of the mandibular condylar process.

PURPOSE: Because the morphology of the temporomandibular joint is thought to control movements of the mandible during mastication, bilateral fractures of the condylar process should disrupt masticatory patterns. The purposes of this study were 1) to document changes in masticatory patterns after such fractures, and 2) to determine whether and when normal masticatory patterns are recovered. PATIENTS AND METHODS: Twenty-two patients (15 men and 7 women) were examined at 6 weeks, 6 months, 1 year, 2 years, and 3 years after bilateral condylar process fractures. Patients were age and sex matched to a control sample. Incisor movements in three dimensions, along with muscle activity from the anterior temporalis, posterior temporalis, and superficial masseter, were recorded at 500 Hz during mastication of a gummy candy. RESULTS: Although the patients showed no reduction of interincisal opening during mastication, the opening was achieved with reduction of anterior translation of the condyles. Patients had significantly narrower chewing cycles, with significantly lower adductor muscular effort during the closing phases of mastication. Differences from controls were no longer detectable 1 year after the fractures. CONCLUSION: The amount of opening during mastication may appear clinically normal in patients with bilateral condylar process fractures. However, disruption of controlling structures and lateral pterygoid function appears to reduce the amount of anterior translation and lateral excursion during the chewing cycle. Reduced adductor muscle activity during the closing phases may reduce loads on the fractured condylar processes. In general, these patients recover normal masticatory cycles within 1 year.

Adolescent↗
PubMed1981

The temporalis muscle flap in oral reconstruction. A cadaveric, animal and clinical study.

The possibility of rotating the temporalis muscle down into the mouth, after division of the zygomatic arch and base of the coronoid, was studied in cadaver material and in the rhesus monkey. Six human subjects are described in whom this muscle flap was employed successfully in oral reconstruction after either hemimandibulectomy or hemimaxillectomy. The flap remained viable in all subjects, and in six experimental monkeys. It proved useful in contour restoration, repair of the palate and of the floor of mouth. Further work is being undertaken on combination with skin grafts and myocutaneous flaps.

Aged↗
PubMed1995

Prevention of mandibular fractures by using constructional design principles. I. Computer simulation of human mandibular strength after segmental resections.

A study was carried out on mechanical stress at the resection site in mandibles undergoing segmental resections. A computer simulation model was used to study particularly the effect of various radii of the posterior resection corners and the effect of elimination of muscle action. It was found that an enlarged radius of the resection corner in conjunction with coronoid process resection on the ipsilateral side offers the best condition to prevent fracture of the mandible.

Biomechanical Phenomena↗
PubMed2001

Changes in masticatory function after orthognathic treatment in patients with mandibular prognathism.

Changes in masticatory function were measured in 27 patients in whom mandibular prognathism was corrected surgically. The mean value of masticatory efficiency before treatment was 46% of that of control subjects with normal occlusion. It improved, but remained at 60% of the control value postoperatively. Similar changes were seen in the number and area of occlusal contacts and the integrated muscle activities of the masseter and temporalis on the chewing side, but the postoperative improvement in masticatory efficiency was mainly the result of improvement in masseter activity. The mean values of masticatory cycle variables in the patient group did not differ significantly from those of the controls. Their preoperative mean coefficients of variation, which were significantly higher than those of the controls, decreased significantly postoperatively. These results suggest that the stability of masticatory rhythm was improved by orthognathic surgery.

Adolescent↗
PubMed1990

Degenerative changes in masseter and temporalis muscles in limited mouth opening and TMJ ankylosis.

The masseter and temporalis muscles were studied ultrastructurally in eight cases suffering from restricted mouth opening and TMJ ankylosis. The changes varied from slight degeneration of muscle fibers, such as accumulation of lipid or lipofuscin deposits, Z-band streaming and derangement of myofilaments, in one case to moderate or severe changes of muscle atrophy and necrosis in the remaining seven cases. Nemaline bodies were also observed in one of these seven cases. In addition to these muscle changes neural degeneration especially of myelinated nerves were found in three of the cases studied. The present findings showed that in spite of the diversity of the underlying factors affecting the joint, there was many similarities in the changes observed within the muscle. It is postulated that these degenerative muscle changes probably play an important role in restricted mouth opening and TMJ ankylosis, and that some of these muscle pathology may be the result of neural involvement.

Actin Cytoskeleton↗
PubMed1990

Fusimotor control of muscle spindle sensitivity during respiration in the cat.

1. The two types of fusimotor neurones, dynamic and static, can be differentiated by their effects on muscle spindle afferents. We have recorded the activity of muscle spindle primary afferents from the intercostal nerves of anaesthetized or decerebrate cats. A 4 Hz sinusoidal stretch was applied to the muscle containing the spindles of interest before and after crushing the nerve proximal to the recording site to eliminate fusimotor effects. The relative activity of the dynamic and static fusimotor neurones was inferred from the change in the spindle afferents' response. 2. Some areas of intercostal muscle normally showed phasic activity linked to respiration, where as other areas of intercostal muscle showed no EMG activity under our experimental conditions. In areas of intercostal muscle lacking EMG activity, the afferents' mean rate was higher and the modulation around the mean was lower at all phases of the breathing cycle when the efferent supply was intact. This result suggests the muscle spindles were receiving a steady level of static fusimotor activity. 3. Spindle primary afferents from regions of intercostal muscle that were typically recruited during respiration had an additional increase in mean rate and modulation around the mean rate in phase with the EMG activity. This is suggestive of phasic activation of dynamic fusimotor neurones in addition to static fusimotor discharge. 4. Thus, the two types of fusimotor neurones can be activated separately by the CNS to control the sensitivity of muscle spindles. The regional differences in the recruitment patterns of fusimotor neurones parallels the functional specializations of different areas of the intercostal muscles. The temporal modifications of fusimotor activity during each respiratory cycle means that the segmental reflex gain will vary in those intercostal muscles that are active during respiration. 5. These findings regarding the CNS recruitment of the two types of fusimotor neurones during respiration are similar to those reported for the hindlimb extensors during locomotion, but differ from those reported for jaw muscles during chewing. This may reflect differing control strategies being used by the CNS to meet the unique demands of the various rhythmical movements.

Action Potentials↗
PubMed1985

Arrangement of supramandibular and suprahyoid motoneurons in the rat; a fluorescent tracer study.

The arrangement of the motoneurons innervating the supramandibular and suprahyoid muscles was studied in Wistar albino rats using two fluorescent tracers: nuclear yellow and true blue. All supramandibular motoneurons were found within the trigeminal motor nucleus; they appeared to be somatotopically arranged. The suprahyoid motoneurons were located in an accessory trigeminal-facial motor complex. No overlap of the motoneuron pools of the supramandibular and suprahyoid muscle group was observed. Only motoneurons ipsilateral to the treated muscles were labeled. It was shown that a one-to-one relationship always exists between motoneuron and muscle.

Animals↗
PubMed2006

Occlusion, sternocleidomastoid muscle activity, and body sway: a pilot study in male astronauts.

The modifications induced by microgravity on the coordinated patterns of movement of the head, trunk, and limbs are reported on extensively. However, apparently there is little data on the masticatory muscles. In normal gravitational conditions, information from the neck and stomatognathic apparatus play a role in maintaining the body's balance and equilibrium. The current pilot study used normal gravity conditions to investigate the hypothesis of a functional coupling between occlusion and neck muscles and body postural oscillations. The immediate effect of modified occlusal surfaces on the contraction pattern of the sternocleidomastoid muscles during maximum voluntary clenching and on the oscillation of the center of foot pressure was analyzed in 11 male astronauts (aged 31-54 yrs). All subjects were healthy and free from pathologies of the neck and stomatognathic apparatus. Occlusal splints were prepared using impressions of their dental arches. The splints were modeled on the mandibular arch, had only posterior contacts, and were modified to obtain a more symmetric, standardized contraction of the masseter and temporalis muscles during teeth clenching. Surface EMG activity of the sternocleidomastoid muscles was recorded during a maximal voluntary clench with and without the splint. Sternocleidomastoid potentials were standardized as percent of the mean potentials recorded during a maximum contralateral rotation of the head, and the symmetry of the EMG waves of left- and right-side muscles was measured. Body sway was assessed with and without the splint, either with eyes open or closed. The variations of the center of foot pressure were analyzed through bivariate analysis, and the area of the 90% standard ellipse was computed. Within each visual condition (eyes open or closed), the difference between the areas of oscillation measured with and without the splint was computed. Muscular activity was more symmetric with the splint. The area of oscillation of the center of foot pressure was larger without the splint than with the splint, both with eyes open and eyes closed. The modifications, induced by the occlusal splint in the sternocleidomastoid muscles' symmetry, and center of foot pressure differential area with closed eyes, were significantly related (p < 0.05): the larger the increment in muscular symmetry, the smaller the area of oscillation with the splint as compared to without the splint. A functionally more symmetric maxillo-mandibular position resulted in a more symmetric sternocleidomastoid muscle contraction pattern and less body sway. Modifications in the contraction of the masticatory muscles may therefore affect the whole body.

Adult↗
PubMed1994

Reanimation of the face after facial nerve palsy resulting from resection of a cerebellopontine angle tumour.

Twenty-three patients with facial nerve paralysis following surgery for a cerebellopontine angle tumour had a facial-hypoglossal anastomosis and simultaneous anastomosis of the cervical ansa with the distal stump of the hypoglossal nerve. In 18 patients, simultaneously with the neural anastomoses, additional transpositions of the temporalis and masseter muscles were performed. At follow-up examination 3-87 months after reconstructive surgery, eight patients had House grade II, ten grade III and five grade IV outcome. The EMG evidence of reinnervation was observed 5-11 months after anastomosis. Combination of the facial-hypoglossal anastomosis with simultaneous myoplasty and with anastomosis of the distal hypoglossal nerve stump to the ansa cervicalis provides the advantage of immediate protection against ophthalmic complications, prevents hemiatrophy of the tongue and gives good functional results when reinnervation of the facial muscles takes place.

Adult↗
PubMedDate not supplied

Masticatory function and patient satisfaction with implant-supported mandibular overdentures: a prospective 5-year study.

PURPOSE: The aim of this study was to assess the outcome of treatment with implant-supported mandibular overdentures in terms of biting and chewing, in entirely satisfied and not fully satisfied patients. MATERIALS AND METHODS: Twelve edentulous patients who had worn dentures for at least 5 years participated. They were in good health but had retention problems with their mandibular dentures. First, all patients received new dentures. After 3 months, two Astra Tech implants were placed in the anterior part of the mandible, and 6 months later the abutments were connected. Patient assessment (questionnaire) and functional recordings (chewing ability, bite force, electromyographic activity) were performed with the new dentures, and again 3 months, 1 year, and 5 years after overdenture treatment. RESULTS: After treatment, all patients were able to comminute hard and tough food, the maximum bite force and the chewing activity increased in parallel, and the duration of the chewing cycle was reduced. Every patient felt improved function and reduction of chewing pain. However, the seven patients not fully satisfied with the function of the implant-supported mandibular overdentures were characterized by lower muscle activity, even before implant placement, than the entirely satisfied patients. CONCLUSION: Implant-supported mandibular overdenture treatment permits better biting and chewing function than conventional complete dentures.

Acrylic Resins↗
PubMed2004

Reduction of clinical temporomandibular joint pain is associated with a reduction of the jaw-stretch reflex.

AIMS: To examine the jaw-stretch reflex after injection of local anesthetic (LA) into painful temporomandibular joints (TMJs), since the functional role of jaw-stretch reflexes in patients with painful temporomandibular disorders is still not well understood. METHODS: Thirteen female patients with a clinical diagnosis of disc displacement without reduction and TMJ pain participated in this open study. Reflex responses were evoked by fast stretches at 15% of the maximal voluntary contraction level before and after injection of 1 mL carbocaine into the painful TMJ. Electromyographic (EMG) activity was recorded from the left and right masseter and temporalis muscles, and the mean level of prestimulus EMG activity and peak-to-peak amplitude of the stretch reflex were measured. Visual analog scale ratings of TMJ pain and TMJ pressure pain thresholds (PPTs) were also obtained. Eleven healthy women were examined with the same protocol (except for PPT determinations) before and after injection of LA into the TMJ. RESULTS: In patients, injection of LA reduced the TMJ pain during jaw movements and maximum clenching (P < .021) and increased the PPTs in the painful TMJ (P < .01). The prestimulus EMG activity in the masseter on the painful side (feedback muscle) was unaffected by the injection of LA (P > .262). There were no significant side-to-side asymmetries of latency or amplitude measures of the stretch reflex in the patient group. Both the peak-to-peak amplitude and the normalized peak-to-peak amplitude of the stretch reflex were reduced in the masseter and temporalis muscles on the painful side and in the masseter on the nonpainful side after LA injections (P < .048). There were no effects of LA injections into the TMJ in the healthy group on any EMG or stretch parameters. CONCLUSION: These results do not support the notion of asymmetries in the jaw-stretch reflex in patients with TMJ pain, but they do suggest that the reflex sensitivity can be influenced by nociceptive activity from the TMJ area.

Adult↗
PubMed1994

Assembly of body wall muscle and muscle cell attachment structures in Caenorhabditis elegans.

C. Elegans has four muscle quadrants that are used for locomotion. Contraction is converted to locomotion because muscle cells are anchored to the cuticle (the outer covering of the worm) by a specialized basement membrane and hemidesmosome structures in the hypodermis (a cellular syncytium that covers the worm and secretes the cuticle). To study muscle assembly, we have used antibodies to determine the spatial and temporal distribution of muscle and attachment structure components in wild-type and mutant C. elegans embryos. Myofibrillar components are first observed diffusely distributed in the muscle cells, and are expressed in some dividing cells. Later, the components accumulate at the membrane adjacent to the hypodermis where the sarcomeres will form, showing that the cells have become polarized. Assembly of muscle attachment structures is spatially and temporally coordinated with muscle assembly suggesting that important developmental signals may be passed between muscle and hypodermal cells. Analysis of embryos homozygous for mutations that affect muscle assembly show that muscle components closer to the membrane than the affected protein assemble quite well, while those further from the membrane do not. Our results suggest a model where lattice assembly is initiated at the membrane and the spatial organization of the structural elements of the muscle is dictated by membrane proximal events, not by the filament components themselves.

Animals↗
PubMedDate not supplied

Acute bilateral trigeminal neuropathy associated with nervous system lymphosarcoma in a dog.

A nine-year-old dog presented with clinical signs consistent with bilateral trigeminal neuropathy. Multicentric lymphoma was diagnosed, and neoplastic lymphocytes were identified in the cerebrospinal fluid. Electromyography revealed spontaneous activity in temporal and masseter muscles. Histopathological examination demonstrated neoplastic cell invasion of temporal and masseter myofibers and of multiple peripheral nerves, including the trigeminal nerve. Central nervous system pathology consisted primarily of spinal root and leptomeningeal lymphoid cell infiltration with relative sparing of spinal cord and brain parenchyma.

Animals↗
PubMed1979

Temporal firing sequences of antagonistic muscles.

The purpose of this study was to assess the relationship between paired agonist/antagonist muscle firing times and accompanying time to peak EMG amplitudes with a 75 degree ballistic right forearm flexion task during experimental conditions of A) no external limb resistance, B) 3.1 Kg., and C) 9.8 Kg. of premovement limb resistance. In addition, total reaction time and movement time values were compared relative to the experimental conditions. Twelve male subjects practiced the flexion task for three days until criterion measures stabilized. Following five control measures on each of the next two days, 10 trials each of conditions A, B, C appearing in random order were administered. Results indicated that as external limb resistance increased (from A to B to C), movement time decreased by 30 msec., total reaction time increased by 52 msec., while biceps latency remained unchanged. There were significant (p less than0.05) increases in triceps latency, biceps and triceps time to peak EMG amplitude only with respect to the greatest external resistance (condition C). It is speculated that coordination may be defined in terms of the temporal firing sequences within an agonist/antagonist muscle group.

Adult↗
PubMed2003

Temporal arteritis associated with systemic necrotizing vasculitis.

OBJECTIVE: To evaluate the clinical and laboratory characteristics of patients with systemic vasculitis associated with temporal artery involvement. METHODS: From a cohort of 120 patients fulfilling American College of Rheumatology criteria for temporal arteritis, we retrospectively identified 7 patients with systemic necrotizing vasculitis associated with histological temporal arteritis. RESULTS: Among the 7 patients, 2 had classic polyarteritis nodosa, one had unclassified systemic vasculitis, one had Wegener's granulomatosis (WG), and 3 had microscopic polyangiitis. The mean age of the patients was 70.2 years, and cranial symptoms revealed the disease in all but one patient. Temporal arteritis was generally associated with extracephalic manifestations suggestive of systemic vasculitis. Antineutrophilic cytoplasmic antibodies were positive in 3 of the 4 patients with small vessel vasculitis. Pathologically, the main temporal artery was involved in all but one patient, with inflammatory infiltrate of vasa vasorum and adventitia associated in 5 with small tributary involvement. Fibrinoid necrosis was rare, observed in 2 specimens; 2 patients with unclassified systemic vasculitis and WG had a classic giant cell arteritis (GCA) histologic pattern. Only one patient had exclusive involvement of small vessels, surrounding the spared main temporal artery. Muscle biopsies showed histopathological evidence of vasculitis in 2 patients, skin biopsy in one, and vein biopsy in the other. CONCLUSION: Temporal artery involvement in systemic necrotizing vasculitis was generally associated with extracranial clinical features suggestive of systemic vasculitis. Temporal artery biopsy is a simple tool for diagnosis of vasculitis, but the histopathological findings do not always discriminate between necrotizing vasculitis and classic GCA.

Aged↗
PubMed1980

Corticospinal tract interaction in locomotor development and motor units formation: an hypothesis.

In rat and kitten postnatal development the Corticospinal Tract (CST) growth has a temporal relationship with the development of mature locomotion and the elimination of polyneuronal innervation, and the formation of motorunits in the hindlimb muscles. This temporal correlation suggests a possible interaction of the CST with spinal motoneurons in the formation of functional groups of motorunits. Further, evidence is also given that spinal motoneuron size is plastic in the polyneuronal period; this indicates that motoneurons adapt themselves to their motorunits in postnatal life. This hypothesis suggests a causal interaction among these three neuronal events; the relevance of this interaction to the maturation of locomotor function is discussed.

Aging↗
PubMed2003

Temporal relation between leukocyte accumulation in muscles and halted recovery 10-20 h after strength exercise.

Effects of normal strength exercise on leukocyte accumulation were examined in 10 well-trained male subjects (27.2 +/- 2.7 yr). The workout, consisting of five maximal sets of three repetitions of leg press exercise and five maximal sets of six repetitions of knee extension exercise, was performed with the dominant leg, and the other leg served as control. Repeated maximal isokinetic knee extensions at 60 degrees /s were performed to evaluate neuromuscular fatigue and recovery after the workout. Accumulation of leukocytes was assessed with 99mTc-labeled cells, and repeated images of the thighs were taken 1-24 h after the workout. Maximal force-generating capacity in the exercised leg was reduced by 17 +/- 2% (P < 0.01) after the workout. The course of recovery followed a biphasic pattern characterized by halted recovery 10-23 h after exercise. The presence of leukocytes was approximately 10% higher in the exercised than in the control thigh 10 h after exercise (P < 0.05). This difference increased to approximately 15% at 20 h after exercise (P < 0.05). The retarded recovery of maximal force-generating capacity 10-20 h after exercise, together with a significant infiltration of leukocytes in exercised muscle during the same time interval, shows a temporal relation between leukocyte infiltration and impaired recovery.

Adult↗