The silent period in the masseter and anterior temporalis muscles in young adult subjects unaware of mandibular dysfunction symptoms

In fourteen individuals unaware of mandibular dysfunction symptoms, latency and duration of the silent period in the masseter and anterior temporalis muscles at tooth tapping and jaw jerk were reasonably reproducible after 5 weeks and 5 months. Although the subjects felt no discomfort in the stomatognathic system, in some of them mild to moderate muscle tenderness, TMJ sound and occlusal disharmony were found at clinical examination. The relationship between these symptoms and the silent period was analysed. Muscle tenderness was the only factor to affect the silent period. The subjects with muscle soreness had a shorter duration of the silent period than the subjects without such symptoms.     

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.     

The influence of stimulus type and stimulus strength on the silent period in human masticatory muscles

The silent period in the jaw-closing muscles of nine healthy subjects was investigated. The stimulus types used were the open–close–clench movement (OCC), the mechanical chin tap and electrical skin stimulation. Irrespective of the jaw-closing speed for the OCC movements only the unmeasurable and single type silent periods were observed. Increasing the chin tap strength resulted in a decreasing percentage of single type silent periods and an increasing number of depressed, double and merged silent periods. The duration of the short and combined silent period was shorter for the OCC movements than for the chin taps. For the chin taps an increasing stimulus strength resulted in longer silent periods. Only the transition from hard to painful chin tap showed a slight, but significant decrease in short silent period duration. The beginning of the late inhibitory period, which could sometimes be evoked by electrical skin stimulation, coincided with the beginning of the second inhibitory phase of the chin-tap evoked double silent period. The long silent period as shown by one of the subjects cast doubt on the validity of the relationship between silent period duration and TMJ dysfunction.     

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.     

The silent period in the masseter and the anterior temporalis muscles in adult patients with mild or moderate mandibular dysfunction symptoms

The electromyographical silent period in the masseter and the anterior temporalis muscles during tooth tapping and jaw jerk were studied in patients with fairly mild temporomandibular joint dysfunction symptoms. The length of the silent periods in the patient group did not differ generally from that in a control group. During tooth tapping, however, patients with distinct muscular disorders had shorter silent period duration (7.7 ms) than patients with other symptoms or when compared with control subjects (10.5 and 11.3 ms, respectively). The duration returned to normal after correction of the muscular disorders. This finding suggests that the duration of the silent period is affected by the muscle condition. Patients with obvious muscular disorders of mild to moderate magnitude, thus, may show a shorter silent period duration during tooth tapping.     

The variability of EMG silent periods in TMJ patients

The variability of the EMG silent period in jaw closing muscles of TMJ dysfunction patients was examined. Considerable within-subject variability was found in the duration of the silent period. This variability increased with symptom severity. The authors recommend that multiple measurements be averaged to obtain a more accurate estimate of the silent period duration.     

Analysis of the effects of treatment on some reflexes of human jaw elevator muscles.

Electromyographic analysis was carried out prior to occlusal equilibration for patients who had some form of TMJ dysfunction and again after treatment. The results were compared with similar analyses for patients without any symptoms of dysfunction (controls) and for patients who had been wearing some kind of occlusal appliance as treatment for dysfunction. The parameters measured were the period of minimal activity (inactive phase of jaw elevators sometimes referred to as the inactive phase), the duration of muscle contraction before tooth contact (DMC), the period of muscle activity after tooth contact (latency), the inhibitory response, and the duration of the clench phase of the temporal and masseter muscles. In general the pathological series had longer cycles, longer DMC, longer clench phases and less significant correlation coefficients than the controls. The results indicated a dominance of the closing muscles in the pathological groups over the other parameters of the cycle during metronome monitoring. Also, the controls and the POST equilibration group yielded readily to cortical command. The parameters of the cycle in the POST-equilibration group were facilitated as compared to the other groups.     

Signs of temporomandibular disorders in tinnitus patients and in a population-based group of volunteers: results of the Study of Health in Pomerania

The literature has documented a controversial discussion on the possible relationship of otogenous symptoms and craniomandibular dysfunction since the 1920s. Therefore, an investigation was conducted which consisted of two parts: a case study with population-based controls and a cross-sectional study. The aim of the first study was to screen a group of patients suffering from acute or chronic tinnitus for temporomandibular disorders (TMD) in comparison with a population-based group of volunteers without tinnitus. To this end, 30 patients (13 females and 17 males, age 18-71 years) suffering from acute hearing loss associated with tinnitus, isolated acute tinnitus, and chronically transient tinnitus were examined for symptoms of craniomandibular dysfunction. The results were compared with those of clinical functional analysis from 1907 subjects selected representatively and according to age distribution from the epidemiological 'Study of Health in Pomerania' (SHIP); the occurrence of tinnitus was ruled out in these control subjects. Statistical analysis was performed with Chi-square and Mann-Whitney U-tests. Sixty per cent of the tinnitus patients and 36.5% of the control subjects exhibited more than two symptoms of TMD (P = 0.004). Tinnitus patients had significantly more muscle palpation pain (P < 0.001), temporomandibular joint (TMJ) palpation pain (P < 0.001), and pain upon mouth opening (P < 0.001) than the general population group. No statistical differences were found in TMJ sounds, limitation of mandibular movement, or hypermobility of the TMJ. Furthermore, 4228 subjects of the population group examined in the epidemiological study were screened for co-factors of tinnitus with the help of a multivariate logistic regression model which was adjusted for gender, age, and a variety of anamnestic and examined data. Increased odds ratios (OR) were found for tenderness of the masticatory muscles (OR = 1.6 for one to three painful muscles and OR = 2.53 for four or more painful muscles), TMJ tenderness to dorsal cranial compression (OR = 2.99), listlessness (OR = 2.0) and frequent headache (OR = 1.84) A relationship between tinnitus and TMD was established in both examinations. Tinnitus patients seem to suffer especially from myofascial and TMJ pain. A screening for TMD should be included in the diagnostic survey for tinnitus patients.     

Reflex activity in the masseter muscle of young individuals

The monosynaptic myotatic (jaw jerk) potential (MSP) evoked in the relaxed masseter by a tap on the chin and recorded electromyographically in this muscle (latency 6-3 ms, duration 5-9 ms) was similar in subjects with, or without TMJ clicking. The latency of the myotatic potential was significantly shorter (5.8 ms) when evoked during isometric contraction. The duration was 5-2 ms. A potential with similar characteristics as the MSP was evoked by TMJ clicking, as we believe by excitation of muscle spindles from tissue transmitted vibrations (latency 5-5 ms, duration 5-6 ms). The TMJ click evoked MSP could in the contracting massester be followed by silent periods (SPs) both of the early (latency about 10 ms) and the late type (latency about 50 ms). A tap on the chin during isometric contraction of the jaw elevators, was followed by an SP of the early type (latency 12-2 ms, duration 17-5 ms) and sometimes by an SP of the late type (latency 58 ms, duration 18 ms). The late SP occurred significantly more often in patients with TMJ-dysfunction. The period of lower activity following an MSP can be divided into two phases: a first phase with a complete electrical silence, denoted SP, and a second phase during which the activity is slowly increasing to reach the control level. This latter phase will be called "depressed activity" (DA) and is introduced as a new parameter. The SP with tooth tapping (latency 10-5 ms, duration 9-4 ms) was similar in groups with or without TMJ clicking. The superimposed MSP (SMSP) preceding the SP at tooth tapping is supposed to be a manifestation of the "load-compensation reflex".     

The silent period duration of the masticatory muscles

This study was conducted to determine whether the reflex activity of the masticatory muscles is altered in prostheses wearers. The electromyographic silent period was measured on an oscilloscope screen. Thirty subjects were examined. Five subjects had natural dentitions. Twenty-five partially edentulous subjects wore removable prostheses. The silent period duration reached 18 to 21 ms on the masseter muscles and 20 to 22 ms on the temporal muscles. These values were not significantly different for subjects with and without teeth and in the control group. The duration of the silent period was the same for patients wearing prostheses and for subjects with natural teeth. This finding suggests that wearing a prosthesis does not change the normal activity of the masticatory muscles.     

Value of EMG analysis of mandibular elevators in open-close-clench cycle to diagnosing TMJ disturbance syndrome

The EMGs of the temporal and masseter muscle, in sixty patients with temporomandibular joint disturbance syndrome (TMJDS) and thirty normal controls, were recorded during rhythmical open-close-clench cycle movement and before and after occlusal splint therapy. The duration of the muscle contraction before initial tooth contact (DMC), the latent period (LP) and the silent period (SP) of the myoelectrical activity were used as indices for exploring their diagnostic value. In contrast with the controls, DMC, LP and SP lengthened in the patients. The DMC was prolonged in those patients where there were TMJ sounds, the inter-cuspated position did not coincide with the muscular contact position and there was deviated mandibular movement. An increase of the SP was related to tooth contact on the balancing side. After treatment, the DMC and SP in the patients returned to the level of the controls. It was found that the internal correction rate of Fisher's linear discriminate function established for the DMC and SP of the temporal and masseter muscles was 80.9% and 85.1% respectively. The results show that the DMC and SP of the temporal and masseter muscles have some value in diagnosing muscular dysfunction and discriminating therapeutic effectiveness.     

Electromyographic screening of myogenous and arthrogenous TMJ dysfunction patients

Sixty patients, clinically examined for TMJ dysfunction, were also electromyographically screened. The TMJ dysfunction pain in forty patients was evaluated to be mainly of a myogenous origin and in fourteen patients of a mainly arthrogenous origin. Due to lack of findings in the clinical examination six patients were not to be classified into either of the two groups. They were excluded from the EMG study. For the EMG examination the patients were asked to clench for 30 s in the intercuspal position at 50% of the maximum EMG activity of the masseter muscles. Surface electromyograms of the right and the left masseter and anterior part of the temporalis muscles were monitored. The amplitude of the EMG signal, the duration of the silent period and the changes in the frequency composition of the signal during the 30 s contraction were analysed. Statistically significant differences between the two patient groups were found in EMG amplitude and in silent period duration. However, the difference in silent period duration was due to the dependency of the silent period on the activation level of the muscle. No statistically significant difference in silent period was found when this dependency was corrected for in the data. The EMG parameters related to muscular fatigue phenomena did not show any difference between the two groups. The difference in EMG amplitude and consequently the difference in silent period duration support the clinically made distinction into mainly a myogenous or mainly an arthrogenous origin of TMJ dysfunction pain.     

A four-year follow-up, by means of a questionnaire, of patients with functional disturbances of the masticatory system

From a group of consecutive patients referred for diagnosis and treatment of functional disturbances of the masticatory system, two groups, a young group (16-30 years, 113 subjects) and an older group (55-80 years, sixty-three subjects) were selected for a follow-up study. A self-administered questionnaire was mailed to them 4 years after the start of treatment. They had answered a similar questionnaire at the first visit. Of the selected patients, 148 (84%) participated. If explainable losses are excluded, the response rate was 89%. Most of the pain and dysfunction symptoms had diminished significantly in frequency while 'peripheral' symptoms such as tinnitus, vertigo, tongue pain and swallowing difficulties had the same prevalence on both occasions. Two-thirds of the patients reported a positive effect of treatment, without any significant difference between the younger and the older group. The remaining symptoms differed, however. The older group reported pain in the face and jaws, vertigo, tinnitus, tongue pain and TMJ crepitation more often than the younger group, while the opposite was found for TMJ clicking and tooth grinding. Only one variable from the original questionnaire (duration of initial symptoms), with none from the first clinical examination, was significantly correlated to the retrospective assessment of treatment outcome. This shows that it is difficult to predict the long-term outcome of treatment from data collected at the first examination of a patient with TMJ pain and dysfunction, but that a long duration of symptoms may have a negative influence on the prognosis.     

Jaw muscle silent periods by tooth tap and chin tap

Electromyographic silent periods from jaw closing muscles were elicited during a clench by tapping on the chin and on selected teeth both in asymptomatic subjects and in subjects reporting symptoms of temporomandibular joint dysfunction. The mean duration in response to a chin tap was significantly shorter in the asymptomatic group than in the dysfunction group. No significant differences in mean duration elicited by tooth taps were found between groups. Other comparisons of mean durations such as among muscles, among teeth, or between chin taps and tooth taps failed to achieve statistical significance.     

The effect of the bite plane splint on the electromyographic silent period duration

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.     

Relationship of electromyographic parameters in jaw dysfunction patients classified according to Helkimo's index

Forty-two jaw pain-dysfunction syndrome patients (PDS) were divided into three groups depending on the severity of their condition using the Helkimo clinical dysfunction index. For both the left and right masseter and anterior temporal muscles three parameters of their electromyographic activity were measured, the silent period (SP), the root mean square value (RMS) and the mean power frequency (MPF). During the experiments the patients were instructed to clench as hard as possible in the intercuspal position. No statistically significant differences could be found between the values for any of the muscles measured between the different Helkimo clinical dysfunction groups. However, when the affected side was compared with the unaffected side in this patient material, statistically significant longer silent period durations and greater RMS values were found in the masseter muscles of the affected side group.     

Correlations of electromyographic silent period duration and the Helkimo dysfunction index.

Fifty-eight patients seen for consultation concerning mandibular dysfunction symptoms were examined utilizing the Helkimo index of dysfunction and electromyographic silent period recordings from masticatory muscles. The data collected were analyzed for correlations between the two parameters. Several significant correlations were noted between certain variables of the dysfunction index and the duration of the silent period. The mean duration of the silent period increased with increasing dysfunction index value. However, the clinical significance of this correlation is not established as long as we do not know the validity of neither the dysfunction index nor the the EMG silent period duration.     

Evaluation of the effect of anxiety on the masseteric silent period duration

The duration of the masseteric silent period (SPD) and environmental stress are parameters which have been associated with the symptoms of masticatory dysfunction. In this study, the relationship between differing levels of anxiety and the masseteric silent period duration, for nineteen subjects reporting a history of symptoms of mandibular dysfunction, was evaluated by a stress model based on the Sta X-1 anxiety test. The results suggest that the durations of masseteric silent periods were not significantly affected by differing levels of anxiety.     

颅颌功能紊乱的耳症及治疗研究

目的 研究颅颌功能紊乱（ＣＭＤ）者耳症的发生纺、临床特征及对肌位Ｈｅ板的治疗反应。方法 将２０８例ＣＭＤ者分为耳症组与非耳症组进行研究,临床症状以Ｈｅｌｋｉｍｏ指数计算。结果 ＣＭＤ者耳症发生率２６．４％,女性明显高于男性,其中耳鸣发生率１４．９％,耳痛发生率１０．６％,耳且盘突关系异常者显著多于非耳症组,临床症状表现为ＤｉⅡ者明显遍于非耳症组,耳症出现与颞颌关系结构紊乱密切相关而与髁突器质性改变     

Functional disturbances of the masticatory system related to temporomandibular joint involvement by rheumatoid arthritis

Several theories have been proposed concerning the aetiology of dysfunction of the temporomandibular joint (TMJ). To analyse the relationship of radiographic changes to clinical signs and symptoms of TMJ dysfunction, the present study was conducted in subjects highly predisposed to TMJ involvement, i.e. in patients with rheumatoid arthritis (RA). The aim of the study was to estimate the frequency of disturbances in the masticatory system of RA patients. In addition, the relationship between TMJ abnormalities and the signs and symptoms of dysfunction was investigated. The study consisted of sixty patients with RA and forty control subjects. Asymptomatic subjects were more frequent in the RA group than in the controls. Muscle pain during palpation was recorded in 53.3%, clicking in 53.3%, crepitation in 21.7%, reduced movement capacity of the TMJ in 41.7%, and restricted mouth opening in 31.7% of the RA patients examined. In the control group the most common symptoms and signs were clicking (57.5%), muscle pain during palpation (57.5%) and restricted opening (25.0%). Normal radiographic appearance of the TMJ in RA patients was found in 31.7%. Minor changes comprised 31.7%, moderate changes 21.6%, and severe changes or total loss of the condyle 15.0%. In the control group a normal joint was detected in 87.5%, while minor changes were encountered in 7.5%, and moderate or severe changes only in 5.0%. No relationship was found between Helkimo's anamnestic, clinical or occlusal indices and the severity of the disease graded according the criteria outlined by the American Rheumatism association (ARA). In the ARA group the frequency of signs and symptoms of dysfunction increased with the destructive changes in the TMJ area. In the controls, muscle pain during palpation and clicking sounds in the TMJ were most commonly connected with normal radiographic appearance of the TMJ. In the discriminant analysis the most discriminating factors were crepitation, tenderness to palpation of muscles and movement of TMJ.