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Biomedical subjects

C S Shi

Publications and source records attributed to C S Shi.

15 recordsLinked to original sources
PubMed1992

Correlations between an autoregressive model coefficient of the electromyogram of human jaw-closing muscles and maximum clenching time at the intercuspal position.

During maximum clenching in the intercuspal position, surface electromyograms of both masseters and both anterior temporales in seven healthy subjects with intact natural dentitions were sampled to generate a four-order, autoregressive model of the myoelectrical signal. The correlation coefficients and the linear regression between the model coefficients and the clenching time were calculated. The first-order autoregressive coefficient had the greatest negative correlation on average. In this model the first-order coefficient relates to muscular fatigue and the slope of the regressive equation relates to the length of time the isometric contraction can be maintained.

Adult↗
PubMed1992

Discrimination of clenches at varied jaw positions using autoregressive model coefficients of myoelectrical activities of anterior temporal and masseter muscles.

During 10% maximum clenching at intercuspal, protruded, retruded contact and lateral positions, the surface electromyograms (EMG) of bilateral anterior temporal and masseter muscles of 20 normal subjects with intact natural dentitions were recorded. The autoregressive (AR) model of the sampled EMG was then built and the obtained coefficients of the AR model were accepted as featured parameters of the EMG. Finally Bayes' stepwise discriminant analysis was used for establishing discriminant functions of estimating low level clenches at varied jaw positions. It was found that total conformation rates of internal and external sample substitution (15 and 5 subjects) were 82.67% and 78% respectively; the discriminant effect between intercuspal and retruded contact position was not up to predicted standard. The results indicate that AR model coefficients may describe the characteristics of surface EMG of masticatory muscles and easily be used in multiple statistical analysis, from which the classification and diagnosis may be taken.

Adult↗
PubMed1992

Relationship between autoregressive model coefficients of EMG and its potentials of jaw closing muscles at rest position and clenching.

At rest position and varied clenching levels at intercuspal position, autoregressive (AR) models of myoelectrical activities of both masseter and anterior temporal muscles of 11 healthy subjects with intact natural dentitions were established. The relationship between the AR model coefficients of surface EMGs and their potentials was analyzed by multiple linear regression. It was found that the fourth order coefficient of AR had the greatest effect on the EMG potential levels and their relationship was positive in all recorded muscles. The results indicate the AR coefficients may become a characteristic parameter to describe myoelectrical activity of jaw closing muscles.

Action Potentials↗
PubMed1992

Observation of proportionality of myoelectrical activity of anterior temporalis to masseter muscle during clenching at varied jaw positions.

Twelve healthy subjects with an intact permanent dentition and normal occlusion were selected for sampling of myoelectrical activity of their left and right anterior temporal and masseter muscles during habitual clenching level in varied positions. The proportionality of normalized myoelectrical potentials of anterior temporal muscle to masseter muscle at ICP and RCP was greater than one, while the proportionality at PP was less than one. In the lateral position, the proportionality on the working side was approximately equal to that at RCP, while the proportionality on the non-working side was similar to that at PP. These results suggest that temporal muscle contraction can bring the mandible upward and backward whilst the masseter muscle can elevate the mandible upward and forward.

Action Potentials↗
PubMed1992

Frequency analysis of electromyographic signals in mandibular elevators at maximum clench level.

Power spectral analysis of electromyogram (ENG) was used to investigate the relationship between mean power frequency (MPF) and sustained contraction time. Surface EMG activity was recorded from masseter and anterior temporal muscles on both sides for seven healthy subjects while clenching at intercuspal position in maximum potential level of these muscles. A visual sense feedback of EMG potential was used to control clenching level. According to linear regression analysis, there was a negative correlation between MPF of EMG and sustained contraction time. The results indicate that the slope of MPF versus contraction time may be used for detecting muscular fatigue in the stomatognathic system.

Adult↗
PubMed1991

Power spectral analysis of electromyographic signal of masticatory muscles at rest position and habitual clench.

Thirteen normal subjects were selected for this investigation. At the vertical dimension of rest position and habitual clench, their myoelectric activities of the masseter, anterior and posterior temporal, and digastric muscles on the left and right sides were simultaneously sampled and processed by computer, and the mean power frequency (MPF) and the mean amplitude (MA) of the myoelectric signal were calculated. At rest position, the temporal muscles were major muscles and the MPF differences of various masticatory muscles were not significant. At habitual clench, with the increase in MA, the MPF of various muscles increased. The results show that MPF may have application in describing a central tendency of myoelectrical signal frequency distribution and in evaluating recruitment of motor units. MPF and MA are the quantitative indices reflecting masticatory muscle function.

Adult↗
PubMed1991

A comparative study of mastication between complete denture wearers and dentate subjects.

A computer system was used for simultaneously collecting and processing mandibular movements and the myoelectric activities of the masticatory muscles of 15 dentate subjects and 11 complete denture wearers. The displacement, velocity, cycle of mandibular movements, and the muscular mean potentials were indices in observing mastication. A good complete denture should perform with physiologic characteristics, and restore masticatory function and oral health. The kinetic energy from the velocities of lateral and vertical directions can serve for the chewing and comminution of food, but lateral comminution may affect denture retention. The mean myoelectrical potentials of the mandibular elevator muscles of complete denture wearers tend to increase at the opening phase; however, the potentials decrease at the closing phase.

Adult↗
PubMed1991

A microcomputer system for collecting and processing physiological information about the masticatory system.

A software system has been written for IBM PC, XT, AT and compatible computers to be used for data collection, analysis and display. The system supports the sampling and processing of data for jaw movement tracks, myoelectrical activities of masticatory muscles, the temporomandibular joint (TMJ) and occlusal sounds and bite force, etc. The package includes the following functions: calculating displacement, velocity, curvature, and curvature center of jaw movement trace, analyzing myoelectrical signals in amplitude integration, root mean square and power spectrum, processing TMJ sounds and occlusal sounds and bite force, analysing jaw movement traces and myoelectrical activities during mastication simultaneously, determining the maxillomandibular relations, etc. The program also provides versatile formatting capability for video, printing and plotting of data, and graph creation. The most of the above programs have flexibility and adaptability to other physiological signal processes.

Bite Force↗
PubMed1991

Influence of an occlusal splint on integrated electromyography of the masseter muscles.

In order to examine the effect of an occlusal splint on the integrated electromyography (EMG) of the masticatory muscles, EMG of bilateral masseter muscles of 23 patients with temporomandibular joint disturbance syndrome (TMJDS), with and without an occlusal splint, was measured and integrated on line during maximum clenching. It was found that the integrated myoelectrical value of the masseter muscle on the involved and non-involved side was reduced with the occlusal splint. The absolute difference between integrated myoelectrical values in the left and right masseter muscles was reduced with an occlusal splint, but the relative difference remained virtually unchanged. These results indicate that the occlusal splint can decrease masseter muscle activity and thus exert a therapeutic effect.

Adult↗
PubMed1991

Power spectral analysis of occlusal sounds of natural dentition subjects.

Fifteen subjects with complete natural dentitions were selected for investigation of their occlusal sounds on the left and right sides by means of power spectral analysis. It was found that the occlusal sounds consisted of various frequency components. Their mean power frequencies (MPF) and frequencies at 10, 20, 50, 80 and 90% of cumulative power (F10, F20, F50, F80, F90) on the left and right sides were almost identical (P greater than 0.05). The correlation coefficients between MPF and F50, MPF and F50 with the others were high. The results indicate that F20, MPF or F50 and F80 may be used as indices to describe the power spectral shape, and that power spectral analysis of occlusal sounds may be used as a contribution to diagnosis of occlusal conditions.

Adult↗
PubMed1990

Masticatory efficiency determined with direct measurement of food particles masticated by subjects with natural dentitions.

The size of soya particles masticated by 10 subjects with natural teeth were directly measured by means of a graphic digitizer and a computer at a varied number of masticatory strokes. The statistical parameters were calculated by computer and a test of normality was used for estimating the frequency distribution. It was found that the frequency distribution of chewed particle size was a positive skew state; its shape was asymmetric, wide, and flat. After natural logarithm transformation the distribution tended toward normal. Increasing the number of masticatory strokes decreased the mean and median of the distribution (p less than 0.01) and did not change the coefficient of variation, skewness, and kurtosis (p greater than 0.05). The results show that the distribution of chewed particle size tends toward a normal logarithmic distribution; the distribution shapes at various numbers of strokes are the same; these parameters can be used for determining masticatory efficiency. Direct measurement of the particles is more convenient and reliable than dyeing particles or fractionating the particles in a sieve system.

Adult↗
PubMed1990

Comparison of food particle distribution masticated by subjects wearing complete dentures and with natural teeth.

The sizes of soya particles masticated by 12 complete denture wearers and 10 subjects with natural dentition were directly measured by means of a graphic digitizer and computer, following a varied number of chewing strokes. It was found that the chewed particle size frequency distributions of the two groups tended to a state of normal logarithm distribution. Compared with the dentate subjects, the mean, 20th, 50th and 80th percentile of the particle sizes chewed by complete denture wearers were increased, whilst the distribution shapes were nearly identical. The results suggest that there are no qualitative differences in the manner in which the two groups break up food. Selection and breakage functions of complete denture wearers are decreased, and this could be related to the denture conditions and the change of oral state in such individuals.

Adult↗
PubMed1989

Proportionality of mean voltage of masseter muscle to maximum bite force applied for diagnosing temporomandibular joint disturbance syndrome.

Maximum bite force in the region of the right first maxillary molar and the corresponding mean voltage of the right masseter muscle of 29 patients suffering from temporomandibular joint dysfunction and 27 healthy controls were measured. In contrast with the controls, the maximum bite force of the patients was smaller (p less than 0.01), the mean voltage was nearly equal (p greater than 0.05), and the proportionality of the mean voltage to the maximum bite force of the patients was greater (p less than 0.01). These results tend to indicate that the masticatory muscles of patients with temporomandibular joint dysfunction are in a state of hyperactivity and tension. The proportionality method suggested in this article is more convenient and easier to apply than previously proposed methods that measure the slope of voltage/tension curves. It may, therefore, have clinical value in the diagnosis of patients with temporomandibular joint disorders.

Adolescent↗
PubMed1989

Postural and maximum activity in elevators during mandible pre- and post-occlusal splint treatment of temporomandibular joint disturbance syndrome.

Electromyograms (EMGs) of the temporal and masseter muscles in sixty patients with temporomandibular joint disturbance syndrome (TMJDS) and thirty controls were recorded and integrated on-line in the postural position and during maximum clenching, before and after occlusal splint therapy. Contrasting with the controls, the myoelectrical activity of the patients was higher in the postural position and lower during maximum clenching, whilst the former in percentage terms increased when compared to the latter. After treatment, the EMG indexes in some patients returned partially, and in others completely, to a normal level. Tenderness in the mandibular elevators, deviated opening and organic change in the TMJ increased the postural myoelectrical activity, in percentage terms, against that of maximum clenching. The myoelectrical activity of the mandibular elevators in the postural position and during maximum clenching was smaller in patients with the occlusal splint than in those without. The results show that the mandibular elevators in the patients with TMJDS were hyperactive and tense, and that the occlusal splint was useful for treating such dysfunction.

Adult↗