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ABSTRACT: The purpose of this study was to investigate the stress-bearing ability of mucosa in complete denture-wearers.
The maximum bite force (MBF) was obtained in 31 voluntary complete denture-wearers with a miniature bite force instrument and a set of central bearing devices. The projective stress-bearing area in the mandible (PAM) was measured through the impression surface of the mandibular complete denture. The authors evaluated the stress-bearing ability (SBA) of mucosa in complete denture-wearers by the formula MBF/PAM.
The results showed that there was a significant positive correlation between the MBF (the mean was 15.13 kg in men and 11.39 kg in women) and the PAM (the mean was 17.15 cm2 in men and 14.46 cm2 in women) and that there was no significant difference between the mean of the SBA in men (0.89 kg/cm2) and the mean of the SBA in women (0.79 kg/cm2). The mean value of the maximum pressure borne by the mandibular edentulous region was 82 kPa (0.84 kg/cm2).
The SBA may become a valuable parameter for the design of both occlusion and reinforcement in the denture construction and for the selection of the maximum load in mechanical tests of complete dentures.
The Chinese journal of dental research: the official journal of the Scientific Section of the Chinese Stomatological Association (CSA) 10/1998; 1(2):41-5.
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ABSTRACT: Motor unit action potentials (MUAPs) propagate bidirectionally from the myoneural junction along the muscle fibre. The propagation of excitation within single motor units can be detected during sustained isometric contraction using a surface electrode array. Electromyographic (EMG) signals from an adjacent pair of contacts along the muscle fibres show a very similar wave form with a time shift. In the present study, EMG signals of the masseter and the temporal muscles were obtained from two male adults during clenching in the intercuspal position using the multichannel surface electrode with 17 x 11 contacts. The two-dimensional location of the myoneural junction for each column from the source of the propagation was estimated. Each of the myoneural junctions was located in the lower portion of the masseter muscle and in the upper portion of the temporal muscle. However, the junction was distributed within 10 mm along the muscle fibres at different contraction levels in each muscle. This noninvasive technique of multiple surface electrodes enabled us to add to knowledge of the anatomical structure of the masticatory muscles examined.
Journal of Oral Rehabilitation 06/1998; 25(5):329-34. · 1.53 Impact Factor
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ABSTRACT: We observed vertical motion of the tongue during mastication in ultrasonographic images of 6 males with an average age of 28.7 years. All subjects had complete dentition and no evidence of neurological disorders. We used a 7 MHz mechanical convex scanning transducer to obtain a continuous, real-time ultrasonic image of the tongue, and carried out real-time B-mode ultrasonic observation at the median sagittal plane of the mandible. We recorded vertical motion of the tongue in the M-mode on a line connecting the mandibular first molars. The transducer produced good quality images of the dorsal surface during mastication of peanuts, rice, crackers, boiled fish paste, pickled radishes, pudding and bananas. The transducer, which was small and light, permitted capture of the images on videotape without manual placement of the scanner. Continuous images showed that the tongue turned the food, mixed it with saliva, sorted out unsuitable particles and aided in bolus formation. Vertical motion of the tongue had two phases, sorting and bolus formation.
Journal of Osaka Dental University 11/1995; 29(2):61-9.
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ABSTRACT: Surface electromyography (EMG) has been widely used in clinical dentistry, although interpretation of the raw data is difficult owing to its low reproducibility. Linear EMG envelopes, also known as EMG profiles, which are normalized with respect to raw EMG amplitudes and stride, have been developed to analyze the time course of gait stride. Normalized EMG contraction patterns can be used for comparing individuals or recording sessions on the same individual made at different times. We made EMG profiles during unilateral gum chewing for the masticatory muscles of five asymptomatic volunteers. EMG signals were recorded from the anterior temporal (Ta), masseter (M) and anterior belly of the digastric (Da) muscles on the subject's preferred chewing side. The mandibular kinesiograph was used for tracking incisal point movement during chewing. EMGs and kinesiometric data were simultaneously recorded for 90 seconds. Ensemble averages of EMG profiles were made from 10 stable strokes after 60 seconds of initiation of chewing. Phasic characteristics of the EMG profiles were evaluated by product-moment correlation and intraclass correlation coefficients. Although the EMG profiles for Ta and M were very similar, those for Da were different from the elevator muscles.
Journal of Osaka Dental University 05/1995; 29(1):1-8.
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ABSTRACT: Various amplitude normalization procedures for surface electromyographic (EMG) signals have been utilized to reduce the inter- and intrasubject variability of data collected on gait analysis. We examined two normalization methods (normalization to mean of ensemble average: NME, and normalization to peak of ensemble average: NPE) for intersubject variability and reproducibility surface EMG profiles for the masticatory muscles during unilateral gum chewing. The EMG profiles for the anterior temporal (Ta), posterior temporal (Tp), masseter (M) and anterior belly of the digastric (Da) muscles on the chewing side from five normal subjects were made at three different sessions. Coefficients of variation and intraclass correlation coefficients were used to assess variability and reproducibility. Each normalization procedure the intersubject variability of unnormalized EMG profiles for Ta, Tp and M. The NME procedure provided lower intersubject variability for Da. The reproducibility of unnormalized profiles for Ta, Tp and M was significantly improved by both procedures (p < 0.05). NME on Da was more effective in its reproducibility (p < 0.05). We found that the phasic characteristics of muscular activity influenced the outcome of amplitude normalization.
Journal of Osaka Dental University 04/1995; 29(1):19-28.
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ABSTRACT: A study was designed to measure noninvasively the deep temperature of the temporomandibular joint (TMJ) region and corresponding regions of the masticatory muscles at rest. With a transcutaneous probe, the deep thermometry of the right and left anterior (Ta) and the posterior portion (Tp) of the temporal muscles, the mid-portion of the superficial belly of the masseter muscles (Mm), and the TMJ regions were measured. In 20 normal male subjects, the deep temperature of the Ta region (mean 36.342 degrees C), the Tp region (mean 36.345 degrees C), and the TMJ region (mean 36.06 degrees C) was higher than that of the Mm region (mean 35.897 degrees C) at rest. In addition, no differences in the deep temperature were observed between the right and left Ta, Tp, Mm, and TMJ regions at rest. All of the normal subjects showed differences between the right and left TMJ region of less than 0.3 degrees C. In 10 patients with craniomandibular disorders, however, eight patients showed differences of more than 0.3 degrees C between the asymptomatic and asymptomatic TMJ region. Because of high sensitivity and specificity, the deep thermometry measurements can provide useful non-invasive information.
Journal of Prosthetic Dentistry 03/1993; 69(2):216-21. · 1.32 Impact Factor
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ABSTRACT: We recorded intercuspal occlusal contacts using silicone for 20 subjects with complete dentition maintaining their masseter muscle contraction levels at 10 and 30% of maximum EMG activity. A computer-aided video system was used to read the silicone image and translate the intensity of transmitted light to the thickness corresponding to the distance between opposing teeth. The intraocclusal distance was greater in the anterior than in the posterior teeth. The intraocclusal distance in the canines was intermediate between that in the incisors and posterior teeth. Although these tendencies were the same at the 10 and 30% EMG levels, an increase in the EMG level decreased all the distances.
Journal of Osaka Dental University 11/1991; 25(2):83-8.
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ABSTRACT: During sustained isometric contraction of the jaw muscles, the surface electromyography (EMG) power spectrum compresses into lower frequencies. This compression has been mainly attributed to the change of the conduction velocity of the action potentials along the muscle fibers. In this study, the muscle fiber conduction velocity of the masseter muscle was measured by using the surface electrode array and the cross-correlation technique. The conduction velocity of the masseter muscle varied from 6.83 to 18.01 m/s among the eight subjects, and slightly increased with the contraction level.
Frontiers of Medical & Biological Engineering 02/1991; 3(3):215-9.
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ABSTRACT: The purpose of this study was to estimate the location of the end plate in the masseter muscle, and to decide the appropriate position of surface electrodes for recording electromyograms (EMG) in humans. The subjects were 16 males who had no signs or symptoms of muscular disease. Identical electrode arrays were placed on the masseter muscles on each side. Each subject was asked to clench in the intercuspal position at various levels of maximum EMG amplitude. Eleven amplified EMGs were monitored simultaneously using a linear electrode array consisting of 12 stainless steel contacts. Various values were observed in different regions of the masseter muscle for the root mean square rectified EMG during brief isometric contraction. The superior region of the muscle had lower values than the inferior. The end-plate zone, which is in the center of the lower half of the masseter muscle, showed a lower amplitude than other regions. The propagation of motor unit action potentials was also observed. It was concluded that, aside from the end-plate zone, a position within the lower half of the muscle was most suitable for recording the surface EMG of the masseter muscle.
Journal of Osaka Dental University 11/1990; 24(2):135-40.
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ABSTRACT: As more dentists diagnose and treat the patient with temporomandibular disorders, muscle palpation has been recognized as a valuable diagnostic method. But this method was depended on sensibility and experience of the operator. The purpose of this study was to establish the quantification of muscle palpation by new pressure pain threshold apparatus. Pressure pain threshold (PPT) was determined by the subject when a ramp force applied to the skin changed from "pressure" to "pain". The subjects for the experiments were 90 normal males, 100 normal females and one patient with temporomandibular disorders. Total of 12 sites, anterior temporal M., posterior temporal M., superficial portion of masseter M. and deep portion of masseter M., were measured. The results obtained were as follows: 1. The females showed lower PPT than the males. 2. No difference of PPT between right and left sides was recognized in normal subject, but the significant difference in the patient. 3. PPT of the normal subjects were significantly higher in the posterior temporal M. than the other sites and lower in the superficial portion of masseter M. than the other sites.
Nihon Hotetsu Shika Gakkai Zasshi 07/1990; 34(3):573-8.
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ABSTRACT: Many methods have been clinically applied for the occlusal analysis in the intercuspal position. However, none of these methods are quantitative. This study described the new software version of the T-Scan system to record and analyze occlusal contact balance in the anterior-posterior and right-left directions. Six time moment statistics and five force moment statistics were calculated in the midsagittal and the incisal axes of the occlusal plane. In the present study, informed consent was obtained from 60 subjects with natural dentitions and from two patients with craniomandibular disorders. In normal subjects, the time moments and the force moments of occlusal contacts were symmetrical about the midsagittal axis of occlusal plane. The location of the center of effort for the antero-posterior occlusal contacts, which was measured from the incisal axis of occlusal plane, was also in the first molar region. However, any of the above mentioned statistics was abnormal in the patients with craniomandibular disorders.
Nihon Hotetsu Shika Gakkai Zasshi 05/1990; 34(2):340-9.
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ABSTRACT: This study was made to measure non-invasively the deep temperature of the temporomandibular joint [TMJ] region at rest. The transcutaneous probe making use of zero-heat-flow method was utilized for the deep thermometry. The following results were obtained. 1. In 20 normal male subjects, no differences of the deep temperature were recognized between the right and the left TMJ regions. 2. In 10 patients with temporomandibular disorders, the deep temperature of the symptomatic TMJ side was significantly higher than that of asymptomatic side.
Nihon Hotetsu Shika Gakkai Zasshi 05/1990; 34(2):359-63.
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ABSTRACT: This study was carried out to non-invasively measure the deep temperature of the temporomandibular joint (TMJ) region at rest and after 100 opening and closing movements of the mandible. Using a transcutaneous probe, we performed deep thermometry by the zero-heat-flow method. A RAM-Pack recording system was employed, and the data were processed by and stored in a microcomputer. In 20 normal male subjects, no differences were observed in the deep temperature of the right and left TMJ regions at rest and after exercise. However, in patients with temporomandibular disorders, the deep temperature of the symptomatic joint was higher than that of the asymptomatic joint. The difference, however, gradually decreased to normal with occlusal splint therapy. Thus, it is clear that the deep temperature of the TMJ region provides useful information about inflammation of the TMJ.
Journal of Osaka Dental University 05/1989; 23(1):29-38.
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Nihon Hotetsu Shika Gakkai Zasshi 01/1988; 31(6):1553-7.
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Nihon Hotetsu Shika Gakkai Zasshi 07/1987; 31(3):770-7.
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ABSTRACT: The T-Scan system was used to evaluate the distribution of time and force in occlusal balance. Sixty normal subjects demonstrated bilateral balance and an anteroposterior center of force in the first molar region. However, patients with craniomandibular disorders demonstrated marked differences from the control group. The T-Scan system was found to be clinically useful as a diagnostic screening method for occlusal stability in intercuspal position.
The International journal of prosthodontics 7(1):62-71. · 1.38 Impact Factor
