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At least 19 recordsLinked to original sources
PubMed1976

[Neuromechanisms of reciprocal interrelation between jaw-opening and jaw-closing muscles in the cat (author's transl)].

Neural controlling mechanisms between the digastric (jaw-opening) and masseter (jaw-closing) muscles were studied in the cat. High threshold afferent impulses from the anterior belly of the digastric muscle to masseteric montoneurons in the trigeminal motor nucleus induced an EPSP-IPSP sequence of potentials with long latency, and high threshold afferent impulses from the masseter muscle also exerted a similar effect on digastric motoneurons in the same nucleus innervating the anterior belly of the digastric muscle. These results suggest that reciprocal inhibition via Ia interneurons as observed between the flexor and extensor muscles in the spinal cord does not exist between the digastric and masseter muscles in the cat. However, the respective motoneurons innervating the masseter and digastric muscles receive inputs of early excitation-late inhibition via high threshold afferent nerve fibers from each antagonistic muscle. As such, since EPSPs preceding IPSPs are recognized, these high threshold afferent impulses may exert not only a reciprocal inhibitory effect, but also a synchronous excitatory or inhibitory effect on the antagonistic motoneurons.

Action Potentials↗
PubMed1977

Biologic laws governing functions of muscles that move the mandible. Part IV. Degree of jaw separation and potential for maximum jaw separation.

Accurate diagnosis and treatment of the gnathostomatic system require an understanding of both its biomechanics and its physiology. Clinically, the treatment consists of modifying the existing occlusal program to relieve stress from distressed tissues. The objective of treatment is to effect a neuromuscular release of the mandible. This may be accomplished by (1) equilibration of the natural occlusion, (2) orthodontics, (3) restorative procedures, or (4) surgery. Most frequently, however, the treatment entails some combination of these procedures. The criteria for success of treatment are not determined by the method or technique employed but by the neuromuscular response that the treatment produces. The purpose of this article is not to suggest which occlusal scheme produces the most favorable muscle response in the gnathostomatic tissues. Neither is an objective of this article to teach the mandible-manipulation techniques that are needed to identify occlusal irritants, perform occlusal equilibrations, or obtain accurate centric relation recores. The objective of this article is to emphasize that there are definite principles by which the muscles respond to occlusal contacts. Occlusal contacts can excite bruxism and the sequelae to bruxism. Knowledge of the laws which govern functions of the muscles that move the mandible enables the dentist to acquire the mandibular-manipulation skills that are necessary for the effective diagnosis and treatment of occlusal conditions.

Biology↗
PubMed1976

TVR and vibration-induced timing of motor impulses in the human jaw elevator muscles.

In order to investigate myotatic reflex involvement in jaw muscle control, an analysis was made of the motor responses induced by mechanical vibration (120-160 Hz) of the jaw elevator muscles in healthy subjects. As seen in torque measurements and mean-voltage electromyographic (EMG) recordings, the vibration caused involuntary reciprocal changes in jaw muscle tone, the contraction force increasing in jaw elevators and decreasing in antagonistic jaw opening muscles. This tonic vibration reflex (TVR) elicited from the jaw elevators exhibited many characteristics similar to those previously described for limb muscle tonic vibration reflexes: it varied in strength from one subject to the next independently of the briskness of the jaw elevator tendon jerks; it had a gradual onset with successive recruitment of jaw elevator motor units firing largely out of phase with one another and at rates much lower than the vibration frequency; it was susceptible to voluntary control--when allowed visual feed-back from the torque meter all subjects were able to suppress the TVR and keep mean contraction force constant. The results indicate that with respect to the tonic motor response to sustained inflow in the Ia afferent nerve fibres, the jaw elevators do not differ markedly from other skeletal muscles. Independently of whether a TVR was present or not, the vibration caused a timing of the motor unit discharges in the jaw elevators that could not be controlled voluntarily and that showed up in gross EMG recordings as a marked grouping of discharges synchronous with each wave of vibration. A similar but less distinct grouping of the gross EMG pattern was seen in limb muscles exposed to vibration, the dispersion increasing with the peripheral conduction distances of the reflex arcs. It is suggested that contrary to the TVR, which depends on the sustained mean level of the Ia afferent input, the timing phenomenon depends, like the tendon jerk, on the degree of synchrony in the afferent Ia volleys. Monosynaptic projections may well be involved in the dynamic timing of motor discharges during tonic firing, but this does not imply that the TVR or the tonic stretch reflex is dependent upon such projections.

Action Potentials↗
PubMed1979

Effects of x-rays on nerve-dependent (limb) and nerve-independent (jaw) regeneration in the adult newt, Notophthalmus viridescens.

The newt limb requires nerves for successful regeneration, but the jaw appears to be nerve independent. Among the current hypotheses for the regeneration-inhibitory action of X-rays is one proposing inactivation of nerves as the main cause. We decided to test this hypothesis by comparing the irradiation levels necessary for inhibition of limb and jaw regeneration. Jaws and left front limbs were exposed locally to doses of ionizing X-irradiation ranging from 250 to 2000 R at least 6 weeks prior to amputation of the jaw and both front limbs. After 90 days post-amputation all surviving animals were examined grossly for signs of regeneration. In addition, some of the controls and most of those receiving 250, 500 and 1000 R were processed for histological examination. All unirradiated limbs and jaws supported regeneration. Those exposed to 250 R also regenerated, but a third of the jaws were hypomorphic. At 500 R and above, neither jaws nor limbs regenerated. Since both systems were affected by similar doses of X-rays, it appears that nerves are not the primary X-ray target in adult newts.

Animals↗
PubMed1979

Silent period and jaw jerk reflex in patients with osseointegrated oral implant bridges.

The silent period in the masseter and in the anterior portion of the temporal muscle during tooth tapping, the rate of tooth tapping and the jaw jerk reflex evoked by a tap on the chin were compared in individuals with oral implant bridges and with natural teeth. Thirteen women with osseointegrated oral implant bridges in one or both jaws, aged 42-59 years, were compared with 10 women, aged 42-64 years, with natural teeth. There was no difference between women, aged 42-64 years, with natural teeth. There was no difference between women with implant bridges and those with natural teeth in tooth tapping rate or in the occurrence, latency or duration of the jaw jerk reflex. A silent period during tooth tapping was found in 12 of the 13 women with implant bridges. The latency of the silent period was the same as in the subjects with natural teeth but the duration tended to be somewhat longer. The jaw jerk and the silent period were the same in individuals with implants in both jaws as in the whole implant group. It is therefore concluded that periodontal or mucous membrane receptors cannot be solely responsible for the silent period.

Adult↗
PubMed1979

Tonic stretch reflexes in lip, tongue and jaw muscles.

Despite considerable speculation it remains unclear as to whether stretch reflexes perform a functional role in speech articulator muscles. Recent research, however, has shown that long loop stretch reflex mechanisms are brought into play during voluntary contraction of limb muscles and a functional role in oscillatory damping has been suggested. It was decided, therefore, to use a method and a technique of analysis similar to that used in limb muscles to search for tonic stretch reflex (TSR) responses in lip, tongue and jaw muscles during sustained voluntary contraction. The term 'action TSR' is used to differentiate stretch reflex responses measured from voluntary activity from those measured at rest. Simultaneous electromyogram (EMG) recordings were taken from the lip, tongue and jaw musculature in normal, stutterer and cerebral spastic subjects. Subjects were instructed to hold the appropriate articulator in a fixed position while the experiment applied an irregular, continuously changing, stretching force. The stretch and EMG signals were analyzed using a cross correlation and spectral analysis technique. This provided a sensitive means of detecting any EMG fluctuations which covaried with applied stretch and might therefore be classified as reflex. No suggestion of such action TSR responses could be found in lip or tongue muscles of any of the subjects tested, including the cerebral spastic subjects with dysarthric speech. It is therefore concluded that action TSR mechanisms are not operative in control of lip and tongue muscles in man. Furthermore, dysarthric speech in cerebral spasticity cannot be attributed to exaggerated tone of lip and tongue muscles resulting from hypersensitivity of TSR mechanisms. In contrast, clear action TSR responses were demonstrable in jaw closing muscles while in jaw opening muscles, small amplitude responses were detected but were not substantial in comparison with background activity. Since the action TSR is present in jaw and limb muscles, but absent in lip and tongue muscles, the suggestion of a functional role of this reflex in damping mechanical oscillations associated with inertial loads is further supported.

Adult↗
PubMed1978

Distortion of mandibular kinesthesia induced by vibration of human jaw muscles.

Kinesthetic experience accompanying vibration of human jaw muscles was investigated in 12 healthy subjects. Vibration of the masseter muscle with the jaw in a 20-mm opened position caused the subjects either to underestimate jaw closing effects or to experience jaw opening movements depending on whether the mandible was free to move or kept in a constant position. During vibration of the depressor muscles with the mandible in its rest position the subjects underestimated an opening movement, but fixation of the mandible caused no illusions of movement. All kinesthetic illusions perceived during vibration corresponded to elongation of the muscles under study beyond their actual length. Distortion of kinesthesia was independent of the amplitude and frequency of vibration and it persisted during anesthesia of the temporomandibular joints and loading of the mandible. It can be concluded that jaw muscle receptors may contribute to mandibular kinesthesia.

Humans↗
PubMed1979

Quantitative analysis of histological parameters in giant cell lesions of the jaws and long bones.

Stereological techniques have been used to compare histological parameters of the giant cell component in 10 giant cell tumours of long bones, 10 central giant cell granulomas of the jaws and 10 peripheral giant cell granulomas of the jaws. The giant cell parameters investigated were: mean profile diameter, mean diameter, mean profile axial ratio, volume-to-surface ratios, nuclear numerical density, profile area and cell volume. Serial sections were cut at 4 micron from routinely fixed, paraffin-embedded specimens of each case and two sections, separated by 100 micron, were stained with haematoxylin and eosin. Random fields were photographed until at least 25 giant cell profiles had been recorded from each of the two sections of each lesion. The processed film was projected for point and intersect counting, the entire procedure ensuring double-blind assessment of the cases under investigation. In general there was no significant difference for any of the parameters between the giant cells of central and peripheral jaw lesions. There was a significant difference, however, between the giant cells of central jaw lesions and long bone tumours in respect of both nuclear numerical density and mean absolute cell volume.

Adolescent↗
PubMed1977

Chondrosarcoma of the jaws and facial skeleton: a review of the Japanese literature.

From the 35 cases of chondrosarcoma, the maxilla was the most frequently affected site (35.5%) and the mandible was the next (29.4%). Painless swelling is the conspicuous symptom for chondrosarcoma of the lower jaw and nasal complications are often recorded with the lesions of the upper jaw. Several kinds of histologically malignant featurs coexisted which made diagnosis complicated. The three-year survival rate was about 50% for chondrosarcoma of the lower jaw and much lower for the upper jaw.

Adolescent↗
PubMed1977

[The atrophic jaw from the prosthodontist's point of view].

The uncritical acceptance of the functional impression and of gnathological concepts are among the greatest hindrances when attempting to build full dentures on atrophic alveolar processes. To provide the most atraumatic transfer of the vertical and horizontal chewing forces from the atrophic jaw to the denture the denture bearing mucosa has to be perfectly adapted to the bony relief by the special kind of mucostatic impression as described in this article. Utterly inadequate is the jaw relation in retruded position, in which no human with or without natural teeth ever chews. This is the reason why prosthetics on edentulous jaws must observe mastication centric with freedom to the most retruded position of the mandible. In addition prosthetics on edentulous, atrophic jaws must observe the muscle grip on polished denture surfaces, the autonomous chewing stability and an occlusal pattern conforming to the masticatory movements. To this end, the author has created and developed the Condylator articulator and the Condyloform teeth.

Aged↗
PubMedDate not supplied

Jaw cysts: diagnosis and treatment.

The classification, embryology, histopathology, clinical features, and treatment of benign jaw cysts are presented. Emphasis is placed on the differentiation of benign cysts from malignant radiolucent lesions of the jaws. Preservation of adjacent teeth and over vital structures is of paramount importance in the management of jaw cysts.

Bone Cysts↗
PubMed1975

Discharge of spindle afferents from jaw-closing muscles during chewing in alert monkeys.

The discharge of muscle spindle afferents from monkey spindle afferents from monkey jaw-closing muscles was studied during mastication of natural foods by extracellular recording from the fibers or cell bodies of the tract and mesencephalic nucleus of the fifth nerve. In all, 39 muscle afferents were studied. The spindle associated with 18 of the afferents was positively identified by the afferent's response to gentle, localized palpation of either the temporalis or masseter muscle. Discharge patterns were observed during mastication, and in the majority of cases the qualitative passive response characteristics of the spindle afferent were determined. During steady chewing spindle afferent discharge typically paused briefly during the initial rapid upward part of the chewing cycle. Firing generally began as the jaw slowed its upward movement, and firing rates during the slow grinding portion of the upward movement were within the range of 50-80 spikes/s. All spindles exhibited a brisk discharge during the opening movement, typically within the range of 100-150 spikes/s. One-third of the spindle afferents exhibited a brief, high-frequency burst of firing at the very beginning of the opening movement, presumably as a result of stretch applied to a spindle just previously subjects to fusimotor excitation. Although the results of the study make it clear that spindles in jaw-closing muscles are coactived along with the extrafusal muscle fibers, the fusimotor bias does not seem capable of sustaining discharge in the face of rapid shortening of the muscle. Furthermore, the fact that discharge rate during opening, when the jaw-closing motoneurons are quiescent, is much higher than at any part of the closing cycle, when the motoneurons are active, suggests that the muscle spindles cannot provide the primary excitatory drive to the motoneurons.

Acoustic Stimulation↗
PubMed1979

Primary tumors of the jaws in children.

Reports on primary tumors of the jaw in children are infrequent. This article reports 24 cases of primary tumors and tumor-like conditions of the jaws in children. All varieties of odontogenic and nonodontogenic tumors are seen in the jaw; fibro-osseous lesions are the most common. A possible explanation for the high incidence of mesenchymal lesions in children may be related to the shedding and eruption of teeth. The differences between childhood and adult types of ameloblastomas are highlighted.

Adolescent↗