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Biomedical subjects

M M Ash

Publications and source records attributed to M M Ash.

At least 37 records · Page 2Linked to original sources
PubMed1986

Current concepts in the aetiology, diagnosis and treatment of TMJ and muscle dysfunction.

The complexity of managing TMJ and muscle dysfunction is reflected in the variety of treatment modalities that are continually being advocated. The multidimensional nature of the problem is readily appreciated in a TMJ Oral-Facial Pain Clinic where most of the referred patients represent a broad spectrum of treatments that have failed. Where such a clinic has been present for several decades the introduction of new ideas, or the reintroduction of old forms of treatment, are readily seen as well as the quantity and quality of treatment successes and failures. A major shift in ideas concerning the natural history of TMJ/muscle dysfunction, and an explosion of treatment problems and failures related to mandibular repositioning appliances and surgery suggest the need to reconsider various approaches to the diagnosis and treatment of TMJ and muscle dysfunction. Guidelines for diagnosis and treatment of these disorders are discussed.

Analgesics↗
PubMed1985

Non-linear amplification of electromyographic signals with particular application to human chewing.

A method is described for logarithmically-amplifying electromyographic signals so that the most commonly-occurring events within them are enhanced selectively before digital conversion. There is a need to resolve low and intermediate levels of activity during chewing, while preserving the occasional high-level responses. Besides achieving a higher resolution in subsequent digital sampling, this signal-processing technique increased the representation of low and intermediate activities in polygraphic displays. It further ensured that signals were presented to the A/D converter within the code width of the instrument.

Amplifiers, Electronic↗
PubMed1985

Short and long latency jaw-opening reflex responses elicited by mechanical stimulation in man.

Jaw-opening reflex responses elicited by tapping the chin during maximum clenching in incisal edge-to-edge contact position were studied in 10 healthy subjects. Stimuli were also delivered during weak clenching on a rubber stamp, separating the incisors by approx. 10 mm and protruding the mandible to the edge-to-edge incisor relationship. All four central incisors were stimulated simultaneously. With weak stimuli, there was a short-latency (9.5 ms) digastric response which may have had a disynaptic pathway. Taps of moderate strength produced long-latency (20 ms) responses, and sometimes a short-latency (9.5 ms) component as well. Strong (non-painful) taps produced an even longer-latency digastric response, 30 ms or more following the stimulus with less synchronization than earlier responses. Jaw-jerk reflexes occurred 8.5 ms following the tap, independently of the magnitude of the stimulus. Local anaesthesia of the upper and lower incisors abolished the digastric muscle response. Thus large periodontal afferents may be responsible for the early digastric reflex activity and smaller fibres for later effects. Temporal summation of the reflex response probably occurred when all incisors were stimulated simultaneously.

Adult↗
PubMed1985

The anatomy and electrical activity of the platysma muscle.

Dissection of seven cadavers showed that the platysma muscle may cover large parts of the masseter muscle. The platysma may thus be a significant source of artefact activity when recording the masseteric activity with surface electrodes. This is illustrated by a patient-case. The electrical activity of the platysma muscle was studied during jaw movements in normal, healthy subjects. Activity was regularly recorded during the latter half of large vertical jaw opening movements and, in five of the seven subjects, in the ipsilateral platysma muscle also during combined lateral-vertical jaw opening movements. The platysma may, therefore, in some individuals, have a functional role during the opening phase of chewing cycles when this has a marked lateral component.

Adolescent↗
PubMed1985

Demonstration of chewing motor disorder by recording peripheral correlates of mastication.

Chewing motor performance was examined in twenty-one patients. Twelve patients had TMJ dysfunction syndrome, eight had occlusal trauma, and one had CNS impairment. Surface electromyography and three-dimensional jaw movement was recorded. Discomfort was recorded by the patient during chewing of beefstick. Specific changes in mandibular movement were related to the presence of pain, discomfort and other symptoms of the TMJ dysfunction syndrome.

Adult↗
PubMed1985

The effect of acrylic bite plane splints and their vertical dimension on jaw muscle silent period in healthy young adults.

A significant question relative to treatment and disappearance of symptoms is raising the bite in combination with a maxillary bite plane splint in patients with TMJ muscle dysfunction. The objective of this research was to investigate the effect, if any, occlusal bite plane splints have on the latency and duration of the mention tap silent period and particularly whether the degree to which the bite is raised is of significance. Recordings were made in healthy young adults from both anterior temporal and masseteric muscles while subjects were clenching at their 70% maximum clenching effort. Placement of a splint significantly (P less than 0.05) prolonged the silent period duration (SPD). However, mean SPD values taken at two different vertical raised bites did not differ significantly (P greater than 0.05). The anterior temporal muscle SPD was less sensitive to a smaller change of vertical dimension than the masseteric SPD. Silent period latencies remained unchanged in all experimental conditions.

Acrylic Resins↗
PubMed1985

The refractory period of the masseteric cutaneous silent period.

Silent periods were elicited in the electromyographic activity of the masseter and temporalis muscles from six normal subjects, by electrical stimulation of the skin over the contralateral masseter during clenching. Pairs of suprathreshold square pulses with varied time intervals were delivered using surface electrodes. It was found that the silent periods, which were mostly of the long latency (about 53 ms) type, had a refractory period, during which a new silent period could be evoked only by increasing the strength of the second stimulus. This refractory period could last for up to 1.5 s. During the first 200 ms after the first stimulus a second silent period was almost impossible to evoke with the moderately painful stimuli used in the present experiments. It is suggested that the refractory period should be considered as significant for the methodology when recording the silent period duration. It is also suggested that the long latency silent period should be recorded as a separate parameter and differentiated from the short latency (10-12 ms) silent period. This may be of special importance to recognize when a short latency silent period and a long latency silent period merge.

Adolescent↗
PubMed1983

Changes in jaw relations, hyoid position, and head posture in complete denture wearers.

In a group of 18 partially edentulous patients provided with immediate complete dentures, changes in hyoid bone position and craniocervical posture were examined on cephalometric radiographs made during 1 year of denture use. The findings indicated that the changes in hyoid bone position largely followed the pattern of forward-upward rotation of the mandible due to ridge resorption. During this course the hyoid position in relation to the cervical spine showed a mean increase. The hyocervical changes, however, showed less variability than the hyomaxillary and hyomandibular changes. The posture of the head and cervical column showed no definite mean changes during the 1-year period. On the other hand, analysis of individual changes revealed that a pronounced decrease in mandibular inclination due to ridge resorption was associated with retroclination of the cervical column and decreased craniocervical angulation. These postural changes may be regarded as adaptive changes to a marked initial change in mandibular position.

Adult↗