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At least 1,531 records · Page 85Linked to original sources
PubMed1982

Delayed onset of masseter muscle pain in experimental tooth clenching.

At 100% and about 50% of maximum voluntary isometric contraction strength of the masseter muscle, six healthy human subjects exercised tooth clenching until there was onset of muscle pain in 42 and 146 sec, respectively. Onset of pain, at maximum contraction strength, might have been due to the cumulative amount of activity in relatively large motor units. The delayed onset of pain might have been associated with a decline in the quantity and quality of contracting large motor units. The Clinical implications of this study suggest that an increase of the vertical dimension of the face will delay the onset of muscle pain in patients suffering from tooth clenching.

Adult↗
PubMed1983

The masseter muscle: the silent period and its clinical implications.

Standardized solenoid chin taps were delivered downward and upward as parallel as possible to the fibers of the superficial part of the masseter muscle and backward at a right angle to this direction. Each one of the 10 healthy subjects received 10 taps in each direction during isometric masseter muscle activity (clenching the teeth). Taps in all three directions evoked the classic jaw jerk response, M1, a short latency (mean, 8.3 msec) excitation followed by an SP (mean latency, 15.9 msec; mean duration, 42.6 msec). The SP duration varied considerably not only between subjects but also within individuals. Forty-nine percent of the SPs were divided into two parts by an EMG peak, M2, with mean latency 42 msec and mean amplitude 78 microV. Sometimes this peak marked the end of the SP. The SP duration has been claimed to be of diagnostic significance because it is longer in patients with mandibular dysfunction. It is concluded that the large variations of the parameter found in this as well as in other studies make it impossible to establish criteria for a healthy or pathologic SP duration. A carefully obtained history and thorough clinical examination are probably more reliable means to establish a correct diagnosis.

Adult↗
PubMed1984

Nocturnal muscle activity in the edentulous patient with and without dentures.

Nocturnal oral activity was evaluated in four complete denture wearers by means of masseter muscle EMG measurements. Patients who had worn dentures that were judged satisfactory for at least a 1-year period were selected. EMG levels were compared when subjects slept with and without the dentures in the mouth. All subjects showed a decrease in the integrated muscle activity while wearing the dentures. Additional studies need to be directed at understanding the mechanism of the effect of denture wearing on nocturnal muscle activity.

Denture, Complete↗
PubMed1985

Influence of vertical dimension on masseter muscle electromyographic activity in patients with mandibular dysfunction.

Occlusal splints were adjusted to different vertical heights and used to single out the influence of vertical dimension of occlusion in increments on BT-EMG activity of the masseter muscle in patients with mandibular dysfunction. The vertical dimension of least EMG activity was determined for each of 60 patients, who were randomly divided into three groups according to the vertical dimension at which the occlusal splint was adjusted: group No. 1, 1 mm from occlusal vertical dimension; group No. 2, mean vertical dimension, 4.25 mm; group No. 3, mean vertical dimension, 8.25 mm. Results showed a significant reduction of masseter BT-EMG activity (series A and B) at the end of the 3-week treatment period for patients in group Nos. 2 and 3 in comparison with group No. 1. Furthermore, the short-term use of occlusal splints with a vertical height that exceeded the so-called physiologic interocclusal distance did not result in an increase in masseter BT-EMG activity. This study suggests that an increase of vertical dimension of occlusion to or near the vertical dimension of least EMG activity by means of occlusal splints can be an effective way to obtain a reduction in masseteric muscle activity.

Adolescent↗
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↗
PubMed1986

Discomfort and bite force in painful masseter muscles after intramuscular injections of local anesthetic and saline solution.

Thirty women with a history of daily pain in the masseter muscles were injected with either lidocaine or saline. The participants were told that they were being given an anesthetic injection to reduce their muscular discomfort. The dentist performing the injections did not know which fluid was used. The discomfort in the masseter muscle was assessed by using Borg's new rating scale before and 10 minutes after injection. The evaluation was followed up on day 1, day 3, and day 7. Bite force was registered between the first molars on the injection side. When scale values were compared individually within groups before and after injection, a significant decrease in discomfort was found in both groups, with the exception of day 1 for the lidocaine group and days 1 and 3 in the saline group. The total lidocaine and saline groups assessed the discomfort similarly except on day 3 when the lidocaine group showed significantly less discomfort. The intraindividual force values increased significantly after injection in the saline group. This effect was not found in the lidocaine group. Despite the minor tendencies for lidocaine to have a better effect, the placebo effect was considered to be high and important.

Adolescent↗
PubMed1986

Nocturnal electromyographic evaluation of masseter muscle activity in the complete denture patient.

Nocturnal oral activity was evaluated in 12 complete denture wearers by means of EMG measurements of the masseter muscle. Patients who had worn dentures for at least 6 months were selected. EMG levels were compared when subjects slept with and without the dentures in the mouth. Three subjects appeared to have reduced EMG values when sleeping with the dentures. However, no overall group trends or significant differences were obtained. High variability in nightly EMG values could not be explained by a post hoc analysis of patient oral symptoms or denture characteristics. Efforts should be directed at improved methodology to study the specific mechanism of the effect of denture wearing on nocturnal muscle activity levels. Additional knowledge is needed on the occurrence and effects of parafunctional habits in the edentulous patients.

Adult↗
PubMed1986

Concerns of patients seeking treatment for TMJ dysfunction.

One hundred fifty-seven patients, 126 women and 24 men, 10 to 75 years of age, completed a self-administered questionnaire. The questionnaire contained questions asking about the patients' chief complaint, treatment received before coming to the clinic, the patients' view of their problem, and who informed them of the possible end result of an untreated "TMJ problem." The results revealed that pain was the most commonly reported complaint (54%), discomfort and headache came second and third (52.2% and 46.5%, respectively). A significant correlation was found between inability to chew and pain, discomfort, tightness in the masticatory muscles, and locking and clicking of the joint. Most patients had received three or more types of treatment before coming to the University of Michigan, TMJ and Oral Facial pain Clinic. A significant correlation was found between an increased number of reported symptoms and an increase in the number of treatments. The most frequently used treatment methods were pain medication, mouth guard (appliances), and occlusal adjustment. Most patients (84.1%) were referred to the TMJ and Oral Facial Pain Clinic by dentists because of clicking, locking, and limitation of movement, with or without pain.

Adolescent↗
PubMed1987

Influence of group function and canine guidance on electromyographic activity of elevator muscles.

A comparative EMG study was done between two types of occlusal guidances: group function and canine guidance. The purpose was to determine which of the two occlusal schemes causes a greater reduction in muscle activity and thereby a decrease in muscle tension in eccentric mandibular positions. Full-coverage occlusal splints were made for six test subjects with normal function of the stomatognathic system. Left- and right-side integrated EMG recordings were made of the masseter and temporal muscles during static (clenching) and dynamic (lateral excursion and clenching) maximal contractions. The results showed an EMG activity reduction of the elevator muscles with group function relative to their activity in centric occlusion. A more marked reduction was observed on the mediotrusive side, mainly in the temporal muscle. With canine guidance, the reduction in elevator muscle activity is much greater, more significant, and mainly in the temporal muscle of the mediotrusive side. The clinical implications of this study suggest the use of canine guidance in laterotrusion for therapy with full-coverage occlusal splints.

Adolescent↗
PubMed1987

Determination of vertical dimension of rest. A comparative study.

The present study was undertaken to compare the VDR determined by conventional methods and EMG with biofeedback. Twenty dentulous and 20 edentulous subjects were included in the study. The VDR was determined by conventional methods using phonetic and swallowing methods. The masseter and anterior belly of the digastric muscles were used to determine the VDR by EMG with biofeedback. VDR was determined by dentulous and edentulous subjects by conventional and electromyographic methods. In edentulous subjects the VDR relation was determined by both methods with and without dentures in the mouth. All results were subjected to statistical analysis. The following conclusions are drawn from the study: The VDR as determined by both methods was similar in dentulous subjects. In edentulous subjects the difference in the VDR with and without dentures in the mouth was not statistically significant in both methods. In edentulous subjects the VDR increased in most subjects with the insertion of dentures and decreased in the remaining few subjects by either method. The difference between the VDR determined by conventional and electromyographic methods in edentulous subjects with dentures was not significant, but without dentures the difference was statistically significant. The comparison between the two methods of determining the VDR in dentulous and edentulous subjects with or without dentures in the mouth showed that VDR determined with dentures was closer to that of dentulous subjects than without dentures. It was concluded by the authors that the determination of VDR by either conventional or electromyographic methods with dentures was more accurate than determining the VDR without dentures.

Adult↗
PubMed1988

Can electrical stimulation be used to establish a physiologic occlusal position?

An electromyographic study was undertaken to discover the mechanism by which the Myo-monitor instrument causes muscle contraction. Our data, which strongly suggest that the distal axons of the motoneurons are directly stimulated, lend support to previous studies showing that the stimulus does not cause reflex activation of the jaw closing muscles. Inasmuch as the stimulus acts only in the periphery without the participation of the central nervous system, the ability of the instrument to produce a reflexly controlled occlusal position is highly questionable. Furthermore, we believe that there is no evidence that reflex jaw closure could ever be used to establish a physiologic occlusal position.

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↗
PubMed1989

Influence of balanced occlusion and canine guidance on electromyographic activity of elevator muscles in complete denture wearers.

Electromyographic recordings were made from the anterior temporal and masseter muscles during maximal voluntary clenching with complete dentures in the intercuspal position and in the laterotrusive jaw position with balanced occlusion and canine guidance. The different pattern of activity of the two muscles in the laterotrusive occlusal schemes studied suggests that their motoneuron pools receive different inputs. The lower activity in both muscles with canine guidance suggests that canine guidance may be a significant factor for preventing parafunctional activity in edentulous patients.

Aged↗