Search

It is important to have an objective method for recording jaw muscle capacity such as EMG before, during and after treatment of muscle dysfunction and also for oral rehabilitation with dentures, implants or other types of restorations. Because measurements of motor unit potentials (MUPs) are needed in several areas of EMG analysis, algorithms have been developed in our laboratory for use in a small computer-aided system for semi-automatic detection and pattern recognition of MUPs. Based upon the test recordings it is suggested that a characteristic 'maximal voltage increase per microsecond during the spike-phase' can be used as a supplement to the more generally used parameter 'rise-time'. Examples are given of how the programs can be useful in the study of the functional anatomy of jaw muscles by recording normative values for MUPs and their recruitment patterns.

The neuromuscular mechanisms of the electromyographic silent period are poorly understood but clinically significant. Our purpose was to isolate the contribution of cutaneous afferents from the chin to the latency and the duration of the EMG silent period. Under the conditions of our experiment, the afferents of the mental nerve have no observable influence on the latency or the duration of the silent period educed by a menton tap.

The purpose of this research was to compare, in the subjects, the duration of the EMG silent period with jaw motion error. The results indicate that both jaw motion error and silent period duration are large in patients with TMJ-muscle-pain dysfunction, both are small in normal subjects, and both are small in successfully treated patients. There is a statistically significant correlation (r=0.91; P less than 0.01) between the two diagnostic parameters of TMJ-muscle-pain dysfunction.

An electromyographic study of the masseter and anterior part of the temporalis muscles was performed on ten patients presenting temporomandibular joint dysfunction symptoms. The EMG silent periods (SP) produced in the open-close-clench cycle and jaw-jerk reflex were compared for duration before and after treatment with an occlusal bite splint. Following use of the splint, there was a shortening of SP indicating the possible use of the duration of SP as a diagnostic measurement, and also as an indication of treatment effectiveness.

EMG study of subjects wearing immediate complete upper and lower dentures revealed marked alterations in activity of the jaw closing muscles during the biting actions recorded. This finding suggests that changes in jaw and occlusal relationships due to resorption of residual ridges and settling of the dentures also affects jaw muscle activity. The relations between EMG and morphologic findings will be analyzed further in a separate article.

Jaw muscle silent periods in response to chin taps were recorded from immediate complete denture patients before extraction of a residual anterior dentition, after insertion of the dentures, and three and six months after insertion. After three months' use of the dentures, the mean EMG silent period duration was significantly increased compared to the pre-extraction stage.

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.

During voluntary jaw clenching, a sharp tap to the menton of the mandible resulted in a transitory silent period (pause) in the electromyographic activity of the masseter and anterior temporalis muscles. Factors that could influence the duration of the silent period were studied, including direction and magnitude of the stimulus applied by the operator, the amount of muscular effort exerted by the subjects, and varying occlusal vertical dimensions. Decreased isometric muscle force resulted in statistically significant increases in silent period durations.

Abnormalities associated with the chewing contraction of the masseteric and anterior temporal muscles were evaluated in patients who sensed pain in the area of the temporomandibular joint during mandibular movement. The patients were instructed in the use of an electronic switch to mark any event of discomfort/pain during natural chewing. Individual stimulus to response reaction-times were determined. The electromyographic pattern of the jaw elevators was quantified by root mean square (r.m.s.) peak voltage and contraction time. The statistical analysis of group data showed significantly prolonged contraction times and greater r.m.s. amplitudes for chewing cycles with, compared to cycles without, indication of pain. Also, individual data showed statistically significant differences between painful and non-painful cycles in some cases. It is concluded, that the conscious perception of nociception during the closing phase of chewing is associated with an excitatory response of jaw elevators. [ABSTRACT FROM AUTHOR]

Electromyographic silent periods in response to chin taps during clench were recorded from the anterior temporalis and masseter muscles. Ten complete denture wearers were observed up to the 1-year stage of denture wear and eight patients up to the 2-year stage. Silent periods were also recorded from patients clenching on paper rolls in place of the dentures. Regarding the patterns of the silent periods, similar observations of double silent periods were made as in our previous study up to the half-year stage of denture wear (McCall, Tallgren & Ash, 1979). The frequency of the double silent periods was 13.8% at the 1-year stage and 7.3% at the 2-year stage. The mean duration of the silent periods did not differ significantly at the 1-year and 2-year stages. The mean silent period duration when clenching on paper rolls without dentures in the mouth was significantly shorter than when clenching with the dentures. [ABSTRACT FROM AUTHOR]

In a sample of fifteen partially edentulous subjects assigned for immediate complete denture treatment, a correlation analysis was performed between pre-extraction facial morphology determined from lateral cephalograms, and EMG activity of the anterior temporal and masseter muscles in maximal clench and tapping of teeth. Marked correlations observed between vertical and sagittal jaw relations and mean voltages of the jaw-closing muscles indicated strong biting activity in subjects with a square facial type. No significant associations were observed between biting strength and the age of the subjects. Correlations between facial morphological changes and changes in EMG biting activity after denture insertion and during 1 year of denture wear indicated that the anterior temporal muscles were extremely sensitive to sagittal changes in anterior occlusion. The masseter muscles were less sensitive, but responded in some instances to changes in vertical jaw relationship. [ABSTRACT FROM AUTHOR]