Hiroo Kotani

Relation Between Integrated Electromyographic Activity and Biting Force During Voluntary Isometric Contraction in Human Masticatory Muscles

The relation between integrated electromyographic activity and computed biting force during voluntary isometric contraction was evaluated in the masticatory muscles of healthy subjects. The slopes of the curves relating integrated electromyographic activity to computed biting force in masseter muscles were steeper on the non-preferred chewing side than on the preferred chewing side, and they progressively became steeper during the course of continuous isometric contraction of a given biting force.

Effect of occlusal splints on the electromyographic activities of masseter muscles during maximum clenching in patients with myofascial pain-dysfunction syndrome

Integrated EMG activities of masseter muscles during maximum voluntary isometric contraction with and without full-arch maxillary stabilization splints were observed in patients with MPD syndrome having occlusal interferences and in healthy subjects having no occlusal interferences. The masseter muscle activity was more significantly reduced in patients with MPD syndrome during maximum clenching with splints than in those patients without splints. In healthy subjects, such a significant difference could not be observed with and without splints. This finding suggests that the elimination of the occlusal interferences by means of occlusal splints could reduce the degree of sensory information from the periodontal receptors during nocturnal clenching or grinding. This could result in a decrease in masseter muscle activity giving rise to muscular relaxation.

The usage period of dentures and their residual monomer contents

The quantity of residual monomer content in 24 maxillary dentures was detected by gas liquid chromatography. The residual monomer contents tended to be lower in dentures used for long periods than in those used for short periods. Decreases in the quantities of residual monomer in acrylic resin dentures as a result of aging can be expressed in a hyperbola. The fitted curve also suggests that most of the loss could be accomplished in 5 years; however, complete loss of the residual monomer content takes many years.

Integrated electromyographic activity and biting force during rapid isometric contraction of fatigued masseter muscle in man.

Abstract The slopes of the curves relating integrated electromyographic activities to biting forces during rapid isometric contractions ( voltage tension curve) were investigated before and after fatiguing contraction of the masseter muscle. The slope of the curves depended on the speed of isometric contraction in non-fatigued masseter muscle. When the muscle was fatigued, the speed became slower and the slope became steeper. This increased slope was not solely due to a decrease in the speed of isometric contraction, and it was shown that more electrical activity was associated with exertion of a tension in the fatigued state, as was evident from the voltage factor calculated in this experiment. This phenomenon could be due to fatigue in the intracellular mechanism of the muscle fibre contraction.

Quantitative electromyographic diagnosis of myofascial pain-dysfunction syndrome

The slopes of the V/T curves of masticatory muscles were determined in patients with MPD syndrome, and the changes in the slopes were observed prior to and during electrical muscle stimulation and splint therapy. The slopes of the V/T curves in patients with MPD syndrome were significantly steeper than those of the healthy subjects. In patients with MPD the slopes were decreased by electrical muscle stimulation of moderate duration and by insertion of the splint. These findings suggest that the most simple procedure for the diagnosis of MPD syndrome is to compare the slopes in MPD patients with those of healthy subjects. The observation of the changes in slopes during electrical muscle stimulation and splint therapy permits a more quantitative diagnosis of MPD syndrome. It also permits a quantitative measurement of improvement of symptoms in patients with MPD syndrome.

Denture stomatitis and ABO blood types

To determine the interrelation between ABO blood types of denture wearers, denture plaque accumulation, and denture stomatitis, 442 denture wearers were studied using a simplified culture method, which is convenient to use in the dental office. The degree of plaque accumulation and the occurrence of denture stomatitis varied depending on the blood type of the patients. Especially in blood group O compared with other types, both denture plaque accumulation and denture stomatitis were found to be higher or more severe. These results suggest that the ABO blood group is one of the etiologic factors of denture stomatitis and that denture wearers of blood group O are more susceptible to denture stomatitis.