Kiyoshi Ishioka

A muscle fatigue index based on the relationship between preceding background activity, and myotatic reflex response (MRR)

An index of muscular fatigue was developed using the myotatic reflex response (MRR). The MRR of masseter muscles is evoked by periodical mechanical chin tapping during clenching. The MRR waveform is composed of somewhat synchronized action potentials of muscle fibers. The authors estimate the change of the MRR waveform due to fatigue using the instantaneous frequency pattern (IFP) with the Hilbert transform. As a result, the features of IFP were different from the monotonic changes that have been observed by the conventional fatigue indices. That is, a plateau IFP was observed ahead of considerable fatigue, whereas the IFP showed a monopeak pattern during the other phase of an exercise. Also, the relationship between the preceding background mean power frequency and the instantaneous frequency around the first part of the MRR waveform was nonlinear during the whole process of fatigue. These features may allow the authors to estimate the degree of fatigue at each time instant.<<ETX>>

An Automated Measuring System for EMG Silent Period

A small, economical, and accurate system for measuring the silent period duration as well as the latency has been designed. In nine normal subjects electromyographic silent periods in the masseter muscle were measured both manually and by the system. With the comparison of those data, it is concluded that this measuring system is suitable for clinical use.

A system for measuring jaw movements in 6 degrees of freedom using high-resolution linear CCD camera

This paper describes a system for measuring jaw movements, using one of the current methods with light emitting diodes and photoelectronic cameras. The measurement accuracy thereof was considerably improved, by employing both a highresolution linear CCD camera and a new computation method.

Analysis of EMG signals during dynamic movements: parametric analysis based on the simulation

In electromyogram (EMG) analysis during dynamic movements, parametric analysis seems to be more effective than power-spectrum analysis. The authors have proposed the use of time-varying parameters (called k-parameters) of the autoregressive model, computed by a locally quasi-stationary approach. The k-parameters of a masticatory EMG showed remarkable changes during a tapping movement. The changes were studied by a simulation model based on anatomical and physiological considerations. The simulation showed that only one type of motor unit (MU) was sufficient to synthesize the surface EMG around the onsets of movement. However, the recruitment of the other type of MU was important in heavy contraction.<<ETX>>

Construction of the Data-Base for Analysis and Diagnosis of Jaw Function usnig Computer Network. Evaluation of the Expert System.

The methods for the examination, diagnosis and treatment of craniomandibular disorders are varied among medical institutions. It is intensely hoped that the standardized methods will be established as soon as possible.Therefore, a patients database and an expert system for diagnosis have been constructed and continued in cooperation with 13 universities. The universities participating in this project were connected through a computer network.The expert system was developed by using a commercially available construction tool “EXSYS”. The rules of the system were originally obtained from a dentist specializing in craniomandibular disorders.The purpose of this study was to apply this expert system to patient cases, and to discuss some problems of the system. The result was that the rates of diagnosis agreement between the expert system and 11 doctors were 60.1% in the 28 patient cases.

A study on Changes of Mandibular Movements by Aging. Part 2. Analysis of Lateral Excursions.

Mandibular movements as a whole have not been sufficiently investigated, due to the great difficulty of recording them. In order to clarify those features in three-dimensions, we measured 62 cases whose ages ranged from 20 to 79, and whose dentitions were either complete or nearly so, and whose intercuspal positions were firm. Part 1 of this study revealed the differrent types of sagittal movements seen among various age groups. We then investigated lateral excursions, gaining the following results: 1) no statistical difference could be found in the movement direction at incisor, canine or first molar either on the working or non-working sides, among any of the age groups studied; 2) the inclination of the condylar path tended to lessen with advancing age; 3) the sagittal inclination of the second molar path on the non-working side tended to be gentler in subjects 60 years and older than in younger subjects, which would reflect the previous result, and 4) there was no statistical difference in path-length of the working-side condyle among the various age groups. These results showed that the posterior guidance on the non-working side tended to change with age, even in subjects with nearly-complete dentition, probably due to the morphological changes of the temporomandibular joint.

The Inclination of Protrusive Occlusal Facets of Complete Dentures with Full Balanced Occlusion. A Comparison between its Theoretical and Experimental Values.

In the full balanced occlusion, the inclination of protrusive occlusal facets must theoretically coincide with the direction of their protrusive movements. Actual complete dentures, however, do not always satisfy this requirement, due principally to a variety of fabrication errors. Wetherefore investigated how closely actual inclination is related to the theoretical value calculated fromthe movement.We made 5 complete dentures with the identical compensating curve and 5 others without it, forpurposes of comparison. Before the automatic milling-in process was undertaken, we measured themedial cusp angle on the second premolar and both molars. We then measured the inclination ofprotrusive facets on the same tooth. Results were as follows: 1) a significant difference in the cuspangle was noted between the two groups ; 2) the inclination of the facets nearly coincided with theirtheoretical values; 3) there was no significant difference in the inclination of the facets between thetwo groups.These results proved that the inclination theorized was valid, and that the compensating curvehad little effect on the inclination of protrusive facets obtained by the milling-in process.

A case report of the prosthetic treatment of the patient with quick calculus formation.

This paper describes the prosthodontic treatment of a 24-year-old female patient who forms substantial amount of calculus quite quickly within two weeks. The bacterial composition and the saliva pH of the patient were analyzed.Veillonellawas found tobe predominant and may contribute to keep the saliva pH rather neutral, resulting in stimulationof calculus formation.A metal material for the treatment should allow lesser amount of bacterial adhesion in order to reduce calculus formation, and the alloy for porcelain-fused-to-metal was selected among 5 dental alloys by a bacterial adhesion test to make a removable type bridge ((4)(3) 2 1 (1)(2)(3)). The bacterial deposits or early calculus formed on the bridge have been removed by daily brushing or acid treatment with 1% HCl solution once a week.