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Biomedical subjects

W D McCall

Publications and source records attributed to W D McCall.

At least 19 recordsLinked to original sources
PubMed1991

Electronic technology for clinical prosthodontics.

A review of the literature on electrodiagnostic devices indicates that current studies have not substantiated claims regarding the utility of these devices in clinical dentistry. Research design problems, such as inadequate control subjects and use of inappropriate statistical tests, limit the conclusions that can be drawn from the results of these studies. Further research, including measurements of sensitivity and specificity, is needed in order to indicate the diagnostic utility of jaw tracking or electromyography in clinical dentistry.

Diagnosis, Oral↗
PubMed1990

Effects of chewing frequency and bolus hardness on human incisor trajectory and masseter muscle activity.

Nine adults with no orofacial dysfunctions were instructed to chew a standardized piece of soft or hard gum on the right side in time with a metronome set at 46, 100 or 160 beats/min. Jaw movements were recorded with a Myotronics kinesiograph and masseter electromyograms were detected with surface electrodes. The chewing patterns on either gum were not significantly different in any of their spatial or temporal aspects, in mean or peak opening or closing velocities, or in the timing or level of activity in either masseter at any of the three chewing frequencies. These findings suggest that during metronome-paced chewing the change in sensory feedback resulting from a change in gum hardness exerts little or no effect on either the spatial or temporal aspects of masticatory motor output.

Electromyography↗
PubMed1990

Devices for the diagnosis and treatment of temporomandibular disorders. Part I: Introduction, scientific evidence, and jaw tracking.

This three-part series of articles summarizes the uses of several devices or groups of devices intended for the diagnosis or treatment of temporomandibular disorders (TMD) and compares their claimed clinical usefulness with the present scientific evidence. Part I of this review defines TMD; discusses the principal criteria for evaluating published scientific clinical evidence such as reliability, validity, sensitivity, and specificity; gives a rationale for the clinical "gold standard" against which diagnostic and therapeutic devices must be compared; and evaluates the status of jaw tracking for the diagnosis of TMD. This review and evaluation led to the conclusion that, at the present time, the claim that jaw-tracking devices have a diagnostic value for TMD is not well supported by the scientific evidence.

Evaluation Studies as Topic↗
PubMed1990

Devices for the diagnosis and treatment of temporomandibular disorders. Part II: Electromyography and sonography.

This second article in the three-part series on temporomandibular disorder (TMD) devices compares the claimed diagnostic usefulness of electromyography and sonography with the present scientific evidence. This review concludes that there is no evidence to support the use of either surface electromyography or silent period duration for the evaluation or diagnosis of TMD. Furthermore, in view of the available evidence, sonography and Doppler ultrasound have no particular advantage over a conventional stethoscope or direct auscultation.

Auscultation↗
PubMed1989

The effect of L-tryptophan supplementation and dietary instruction on chronic myofascial pain.

Effects of L-tryptophan supplementation and dietary manipulation were tested on patients with chronic myofascial pain around the temporomandibular joints. In this study, however, reduction of chronic pain reported in previous similar studies was not duplicated. No significant reduction in pain was noted in the groups receiving tryptophan and dietary manipulation compared with control groups.

Dietary Carbohydrates↗
PubMed1989

Interrater reliability in masticatory muscle palpation.

Muscle palpation is an important procedure in screening for TM disorders and assessing results of treatment outcome studies, but interpretation of response may be subjective and vulnerable to examiner bias. Masticatory muscle palpation scoring was evaluated with respect to interrater agreement on 31 myofascial pain-dysfunction patients participating in a medication study. Two clinicians independently palpated the temporomandibular joints, muscles of mastication, and related head and neck musculature on three different occasions over the 6-week period of the study. Standardization of palpation technique and initial protocol for interpretation of subject response were discussed prior to the first examination. Further clarification and reinforcement of examination methodology and scoring were carried out prior to the second examination, 1 week later. Another 5 weeks passed, with no further standardization, before the third and last examination. A behaviorally anchored scoring system (0 to 3) was used to rate response to palpation. Results indicate that two investigators can achieve a fair degree of reliability when carefully standardized, further interrater standardization can result in higher reliability, and reliability can be maintained over at least a 5-week period of time.

Humans↗
PubMed1988

Comparison of automatic and voluntary chewing patterns and performance.

Chewing, like respiration, is ordinarily performed as an automatic motor act, yet both can be voluntarily controlled. No in-depth analyses of voluntary chewing exist. Therefore, we have analyzed on a cycle-by-cycle basis voluntarily controlled chewing, and compared it with automatic chewing. We assessed the performance during voluntarily controlled chewing by obtaining constant error and variable error scores. Nine healthy adults with full dentition were subjects (Ss). Their three-dimensional jaw movements and movement times were derived from Kinesiograph recordings obtained while chewing a standard piece of gum on the right side of the mouth. Burst durations and onset latencies of masseter activity were obtained from surface-recorded EMGs. Frequency during automatic chewing was obtained from data recorded while the subject viewed a film. Next, the subject chewed in time with a metronome set at this "automatic" rate. Intrasubject variability among 30 consecutive chewing cycles during voluntary was less than during automatic chewing. In every S gape and ipsilateral jaw excursions and the variability of burst durations of masseter activity were less during voluntary than during automatic chewing, showing that both the spatial and temporal aspects of the two types of chewing differ significantly. Ss varied in ability to follow the metronome. A S's constant error might be small, yet his variable error might be large, as if feed-back-based corrections influenced cycle-to-cycle variability. Fast chewers had smaller constant and variable error scores than did slow chewers, suggesting a speed-accuracy relationship. In summary, both temporal and spatial aspects of voluntary chewing were modified compared with those of automatic chewing. During voluntarily controlled chewing, cycle-to-cycle variability was less compared with automatic chewing due to reductions in variability of occlusal phase and the masseter's burst durations, and total jaw excursions were less because gapes and ipsilateral deviations during closing were reduced.

Adult↗
PubMed1988

The effect of prior jaw motion on the plot of electromyographic amplitude versus jaw position.

Fabrication of interocclusal splint at a thickness determined by the vertical dimension at which the jaw muscle EMG amplitude is minimum has been recommended. However, the effect of prior jaw motion and the effect of the recording site on the EMG amplitudes and on the vertical dimension of minimum EMG activity have not been documented. IEMG amplitudes at various static jaw positions achieved during opening and during closing were analyzed in nine subjects. Surface IEMGs were recorded over the left anterior temporal muscle, left masseter and left suprahyoids muscles, and by nonspecific EMG recording as described by Rugh and Drago. The jaw position was recorded in 5 mm increments by a kinesiograph. After 30 seconds of relaxation, 10 successive IEMG reading at 4-second integration times were obtained at each recording site. These 10 recordings at each requested jaw position were averaged and analyzed. The IEMG activity changed with different jaw position. As the jaw opened from centric occlusion, the IEMG from jaw closing muscles decreased to a minimum and then increased with further opening. Moreover, the IEMG for a particular jaw position differed depending on the history of the jaw movement, that is, whether the position was achieved after an opening step or after a closing step. Two factors, the amount of jaw opening and the history of jaw movement to reach that position, seemed to influence the IEMG differently in each of the recorded muscles.

Adult↗
PubMed1987

Follow-up study of silent periods in complete denture wearers.

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.

Adult↗
PubMed1986

A numerical model of temporomandibular joint loading.

A numerical model of the mandible, its articulating surfaces, and the forces exerted by the primary masticatory muscles has been developed for the purpose of investigating loading of the temporomandibular joint. Evidence is presented which shows that the temporomandibular joint. Evidence is presented which shows that the temporomandibular joint is a load-bearing joint over the normal functional range of bite-force positions and angles. In this investigation, temporomandibular joint loads were found to vary from a maximum appositional force of 60% of the bite force (when bite forces were applied to the incisors) to a distracting force of about 5% of the bite force (when applied to the distal surfaces of the third molars). TMJ loads tended to reach a minimum as a result of vertically directed bite forces positioned at the second molars. A range of conditions in which bite forces were directed parallel to or within approximately 20 degrees of the mid-sagittal plane was found to be conducive to stability of the temporomandibular joint. This stability included symmetry in the direction and in the magnitude of condylar loads as well as the presence of small forces tending to oppose the condyle and articular eminence. TMJ loads tended to reach a maximum in response to mediolaterally directed bite forces. This result is consistent with the fact that no muscle of mastication exhibits a spatial orientation in which the muscle fibers are predominantly mediolateral in direction.

Bite Force↗
PubMed1985

Measurement of silent period durations by hand and by commercial device.

Silent period durations obtained from the masseter muscle in response to taps to the chin during a clench were measured by the commercially available MDM device and by hand measurement from polygraph tracings. Of the 160 pairs of silent periods, 15 were measurable by polygraph but not by MDM, 20 were not measurable by polygraph but were measured by MDM, and 125 were measured by both. Of the 125 silent periods, the MDM gave a shorter reading in 112. Within-subject correlation coefficients between the two measurement methods ranged from -0.038 to + 0.95; the average (0.75) was significantly different from zero. The among-subject correlation coefficient was + 0.26 and was not significant. These data raise questions about the reliability and validity of silent period durations measured by the MDM device.

Electromyography↗
PubMed1979

Jaw muscle silent periods before and after rapid palatal expansion.

1. The electromyographic silent period was observed in jaw-closing muscles during a maximal clench following a tap to the mandibular symphysis in eight subjects before and after rapid palatal expansion. 2. No differences in mean silent period duration were observed among the three jaw-closing muscles examined. 3. A large (r = 0.96) and statistically significant (p less than 0.01) correlation coefficient between two sets of silent period durations at one session indicates that these measurements are repeatable and reliable. 4. The mean silent period duration for the eight patients with malocclusions was 33.5 msec. prior to rapid palatal expansion and 51.2 msec. after the completion of palatal expansion. The difference was statistically significant (p less than 0.01) and represents a 61 percent increase. 5. Patients with symptoms of TMJ dysfunction are not the only group showing a prolonged silent period duration.

Adolescent↗
PubMed1979

The role of cutaneous receptors in the menton tap silent period.

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.

Adult↗
PubMed1979

EMG silent periods in immediate complete denture patients: a longitudinal study.

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.

Adult↗
PubMed1978

Functional occlusal forces: an investigation by telemetry.

In normal chewing the forces exerted on the occlusal surface seldom exceeded 10 to 15 pounds, as recorded by an eight-channel force transmitter in a removable fixed partial denture. Ninety-five percent of forces were less than 3.5 pounds for subject A, 2.0 pounds for subject B, and 10.0 pounds for subject C. The chewing frequency and the places of maximal force on the occlusal surface were relatively constant. The electromyographic chewing patterns could be considered normal in all circumstances. There was a remarkable statistically significant day-to-day variation in force values. The forces also changed for different kinds of food. The differences between maximum and minimum force values were highest in voluntary, nonfunctional movements.

Arachis↗