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.

Electromyographic silent periods and jaw motion parameters: quantitative measures of temporomandibular joint dysfunction.

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.

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.

Duration of the electromyographic silent period following the jaw-jerk reflex in human subjects.

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.

Effect of topical application of phenylephrine hydrochloride on hyperplastic gingivitis.

A double blind study was conducted to evaluate the effectiveness of Phenodent Type A (brand of phenylephrine hydrochloride) on decongesting hyperplastic gingivitis. Three solutions were used: a 0.5% a placebo, and a 0.25% concentration of phenylephrine hydrochloride. The periodontal disease index was used to score variables which might have an effect on gingival response to local irritants. Impressions were taken and casts were made on 45 subjects at 0, 1, 3, and 6-week intervals. An instrument with accuracy of 0.001 inch was constructed to measure the changes in the interdental papillae of the stone casts. No significant reduction of gingival volume was established for any of the three solutions.

Significance of occlusion in the etiology and treatment of early, moderate, and advanced periodontitis.

Elimination of lesions diagnostic of trauma from occlusion is an essential part of complete periodontal therapy and restoration of health in the masticatory system for such patients. This can be achieved by orthodontic treatment, temporary splinting, bite-planes, occlusal adjustment and permanent splinting of teeth. Occlusal therapy may be required during periodontal treatment for trauma from occlusion and to enhance occlusal stability at any stage of periodontitis, but is most often needed in advanced periodontitis. Splinting of hypermobility of self-limiting trauma from occlusion is not indicated. Splinting may be required in addition to occlusal adjustment in moderate to severe periodontitis when trauma from occlusion is progressive.

A comparison of biofeedback and occlusal adjustment on bruxism.

Within the limits of this study and with the reported assumption that the recorded EMG activity is related to bruxism, the results of this investigation suggest that the effect of biofeedback in reducing EMG activity is more consistent than an occlusal adjustment, possibly due to differences in the cause of the initial heightened EMG activity in the group of subjects studied.

The effectiveness of subgingival scaling and root planing in calculus removal.

The study presents an evaluation of the effectiveness of subgingival scaling and root planing related to depth of pocket and type of teeth. A total of 199 teeth in 25 patients were selected; 62 were scaled and 57 were used as controls. All teeth were initially scored using the calculus index of the P.D.I. (Ramfjord). Six surface locations were probed to determine pocket depth. The levels of the gingival margin were marked on the teeth to locate supra and subgingival calculus after extraction. The experimental teeth then were scaled. Both scaled and unscaled teeth were extracted immediately after the experimental procedures. The teeth were washed with water and stained with methylene blue. They were viewed under a stereomicroscope which had a tenth grid on its eyepiece. Percent of surface covered by calculus was assessed on both scaled and unscaled teeth. The results demonstrated a high correlation between percent of residual calculus and pocket depth. It was shown that pockets less than 3 mm were the easiest sites for scaling and root planing. Pocket depths between 3 to 5 mm were more difficult to scale and pockets deeper than 5 mm were the most difficult. Tooth type did not influence the results.

An electromyographic study of jaw opening and closing reflexes in man.

The electromyographic activity of the right masseter and digastric muscles was recorded in 10 subjects. A jaw-opening reflex was observed shortly after a mechanical stimulation in subjects performing clenching and active jaw-opening exercises. The latency of this reflex activity was about 28 ms, coinciding with the termination of the silent period of the masseter muscle. The experiments show that this opening reflex can occur without masseter spindle-unloading and may respond to low-threshold afferents.

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.

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.

Philosophy of occlusion: past and present.

Controversy in a field usually stimulates research to find answers and to promote clinical excellence. Thus, differing ideas about occlusion relative to centrics, gnathology, TMD, occlusal adjustment, and periodontal therapy have led to a controversial body of literature; however, I think also it has led to better treatment for patients, regardless of whether, for example, the concept of point centric or freedom-in-centric is advocated. No one can practice dentistry without some concept of occlusion whether it is applied to one or two teeth or to complete mouth restoration. Although the work of committees to clarify terminology is quite appropriate, common usage, semantics, avoidance of confusion in the literature, and the ideological nature of the bias in science must be carefully considered. At times we learn from history that all ideologies need constant revisions; too often the need leads to changes by fiat rather than by virtue of research on problems that may actually exist in communication.

Reflections on the Michigan splint and other intraocclusal devices.

It seems obvious in retrospect that the treatment of disorders by interocclusal devices followed two paths: stabilization splints and functional orthopedic appliances. The dividing line between them is not always clear. Both have some function related to the position of the mandible. They may not differ significantly in their control of occlusal stability (e.g., telescoping devices anchored to stabilization splints). The stabilization splint, as well as other conservative measures, will play an increasing role in accepted therapy for TMD. The use of anterior repositioning devices for TMD, including MPD syndrome, will decrease. Research may provide answers that allow them to be used more specifically and predictably. Perhaps there will be but little change in their use where there is an association of TMD and Class II malocclusion. There will be an increase in the use of interocclusal devices for the treatment of snoring and obstructive apnea. Some additional directions seem to have emerged in the late 1980s and early 1990s: In the absence of pain and significant debilitation, treatment for TMD, if any, is to be reversible. Prevention or aggravation of TMD should be practiced to the extent possible during dental procedures. One long-term, well-designed, prospective study indicated that the incidence and severity of TMD could be reduced by appropriate occlusal adjustment. There is a small, but nevertheless important minority of patients with TMD who progress to persistent pain and/or dysfunction. Initial management of the vast majority of patents with TMD should be use of noninvasive reversible therapies. Surgery is indicated in only a relatively small percentage of cases of TMD. Research on interocclusal devices should not terminate simply because they are in part dental devices (i.e., biomechanical forms of treatment). The diagnosis and treatment of TMD has been called a dilemma, especially for those patients with chronic pain for whom no treatment has been effective. However, it would be ill-advised to abandon what treatment is already known to be effective by allowing those few but psychosocially important patients with chronic pain to determine what should be done for the vast majority of patients with TMD: reversible forms of treatment, including physiotherapy, pharmacologicals, and the stabilization occlusal bite plane splint.