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Right Masseter Muscle (right + masseter_muscle)
Selected AbstractsAntero-posterior activity changes in the superficial masseter muscle after exposure to experimental painEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 2 2002Jens C. Türp The aim of this randomized, controlled, double-blind study was to examine how the activation pattern of the masseter muscle changes during natural function when experimental pain is induced in a discrete anterior area of the muscle. In 20 subjects, three bipolar surface electrodes and three intramuscular fine-wire electrodes (antero-posterior mapping) were simultaneously attached above and in the right masseter muscle to record the electromyographic (EMG) activity during unilateral chewing before and after infusion of a 0.9% isotonic and 5% hypertonic saline bolus in the anterior area of the muscle. The activity of the contralateral masseter muscle was registered by surface electrodes. In addition, the development of pain intensity was quantitatively measured with a numerical rating scale (NRS). While both saline concentrations caused pain, the hypertonic solution evoked stronger pain. The experiments also provided evidence of a significant although differential activity reduction of the ipsilateral masseter muscle in the antero-posterior direction. The activity reduction decreased with increasing distance from the location of the infusion. The results support the idea that the strategy of differential activation protects the injured muscle while simultaneously maintaining optimal function. [source] The effect of oral splint devices on sleep bruxism: a 6-week observation with an ambulatory electromyographic recording deviceJOURNAL OF ORAL REHABILITATION, Issue 7 2006T. HARADA summary, This study investigated the effect of stabilization splint (SS) and palatal splint (PS), which had the same design as SS except for the elimination of the occlusal coverage, on sleep bruxism (SB) using a portable electromyographic (EMG) recording system. Sixteen bruxers participated in this study. The EMG activities of the right masseter muscle during sleep were recorded for three nights each in the following five recording periods: before, immediately after, and 2, 4 and 6 weeks after the insertion of the splint. The crossover design, in which each splint was applied to each subject for 6 weeks with an interval of 2 months for a washout period, was employed in this randomized-controlled study. The number of SB events, duration and total activities of SB were analysed. The number of SB events before the insertion of splints (baseline) was 2·98 ± 1·61 times h,1. Both splints significantly reduced SB immediately after the insertion of devices (P < 0·05, one-way repeated-measures anova followed by Dunnett); however, no reduction was observed in 2, 4 or 6 weeks (P > 0·05). There was no statistical difference in the effect on SB between the SS and PS (P > 0·05, two-way repeated-measures anova). Both splints reduced the masseter EMG activities associated with SB; however, the effect was transient. [source] Differential activity patterns in the masseter muscle under simulated clenching and grinding forcesJOURNAL OF ORAL REHABILITATION, Issue 8 2005H. J. SCHINDLER summary, The aim of this study was to investigate (i) whether the masseter muscle shows differential activation under experimental conditions which simulate force generation during clenching and grinding activities; and (ii) whether there are (a) preferentially active muscle regions or (b) force directions which show enhanced muscle activation. To answer these questions, the electromyographic (EMG) activity of the right masseter muscle was recorded with five intramuscular electrodes placed in two deep muscle areas and in three surface regions. Intraoral force transfer and force measurement were achieved by a central bearing pin device equipped with three strain gauges (SG). The activity distribution in the muscle was recorded in four different mandibular positions (central, left, right, anterior). In each position, maximum voluntary contraction (MVC) was exerted in vertical, posterior, anterior, medial and lateral directions. The investigated muscle regions showed different amount of EMG activity. The relative intensity of the activation, with respect to other regions, changed depending on the task. In other words, the muscle regions demonstrated heterogeneous changes of the EMG pattern for the various motor tasks. The resultant force vectors demonstrated similar amounts in all horizontal bite directions. Protrusive force directions revealed the highest relative activation of the masseter muscle. The posterior deep muscle region seemed to be the most active compartment during the different motor tasks. The results indicate a heterogeneous activation of the masseter muscle under test conditions simulating force generation during clenching and grinding. Protrusively directed bite forces were accompanied by the highest activation in the muscle, with the posterior deep region as the most active area. [source] Validation of diagnostic criteria for sleep bruxismJOURNAL OF ORAL REHABILITATION, Issue 9 2002K. BABA Several diagnostic criteria for bruxism can be taken from the literature; however, most of them have never been validated. This study examined whether predictor variables taken from physical examinations and questionnaires were related to the actual bruxism levels. Fifty dental students agreed to participate in this study and eight examination variables and seven questionnaire variables were collected from them. The subjects measured their nocturnal EMG activity from the right masseter muscle for six consecutive nights in their home by means of a portable EMG device. Off-line analysis was performed on data from second to sixth nights. By using a custom made software, all EMG activity elevations above a minimum threshold of 50% of each subject's individually established maximum voluntary contraction (MVC) level were quantified with regard to the duration and number of elevations and then three outcome variables, which were event number per hour (number/h), event duration per hour (duration h,1), and duration per event (duration/event), were calculated. A multiple stepwise regression (MSR) analysis was conducted to assess the 15 predictor variables and the three outcome variables. These MSR analyses revealed that the joint sound score remained in the regression equation as a predictor (n=50, P < 0·05) of the likelihood that a subject would exhibit longer bruxism events (duration h,1and number h,1). It must be noted that the self-awareness and tooth attrition status were found not to be strong predictors and even for the above variable where significant association was found, the likelihood ratio between the variable and predicted outcomes was not robust. [source] | ||||||||||