Tohru Tokunaga

Influence of Bite-raising on Muscle Fiber Conduction Velocity and EMG Frequency Components in Human Masseter Muscle.

The relationship between the muscle fiber conduction velocity (MFCV), EMG frequency parameters and the occlusal vertical dimension was studied in the human masseter muscle in three normal subjects (24-27yr.). Occlusal vertical dimension was changed from the intercuspal position (ICP) to the maximum bite-raising position (12.8mm) using five different occlusal splints on the habitual opening-closing movement path. Each subject was instructed to clench on each vertical dimension at 10, 30 and 50% maximum voluntary contraction. EMG signals were detected with a surface linear electrode array with 13 contacts placed along the muscle fibers. The MFCV was calculated from the time delay between adjacent EMG signals. The frequency parameters were 10, 25, 50 and 75% cumulative power functions and mean power frequency.The results obtained were as follows:1. The MFCV was increased with the contraction level and decreased with the occlusal vertical dimension.2. The EMG power spectra were slightly shifted to lower frequencies with the occlusal vertical dimension.3. The MFCV showed a large change in the vicinity of ICP with a slight change of muscle length. It was suggested that the MFCV in ICP was an important index for occlusal reconstruction.

EMG Profiles of Masticatory Muscles during Gum Chewing.

The surface electromyographic (EMG) profiles were proposed for identifying normal muscle activity pattern by Winter et al (1987).The purpose of this study was to investigate EMG profiles of masticatory muscles during deliberate unilateral gum chewing.The EMG signals from bilateral masseter (Mm), anterior temporal (Ta) and anterior belly of digastric (Da) muscles of 5 healthy adults were recorded from for 90 seconds. The muscle activity was evaluated by the root mean-square (RMS) rectified EMG. Time averaging of each EMG over each chewing stroke was accomplished by normalizing each stroke period to 100% and then averaging each stroke at each interval over the chewing cycle to 0.3%. Normalization was achieved by setting the mean value of each subjects EMG over the chewing cycle to 100%.The resuls were summarized as follows:1. EMG profiles of masticatory muscles during deliberate unilateral gum chewing were made, which reduced inter-and intra-subject variability.2. Each muscle showed a stable pattern of muscle activity at 60-75 seconds from the beginning of mastication.3. EMG profiles in Mm of the working side were different from those of the non-working side, however, the profiles of Ta and Da were similar for both working and non-working sides.

Multiple regression analysis between gum texture and chewing movement of mandible

Iは じ め に 咀 嚼 運 動 に 影 響 を 与 え る 食 品 側 の 因 子 と して, 大 き さ,吸 水 性,味 の 強 さな どが あ る が,わ れ わ れ は 特 に テ ク ス チ ャ ー に 注 目 して き た1~3)。 これ ま で に,テ ク ス チ ャー の ひ とつ で あ る硬 さ が 咀 嚼 運 動 に 及 ぼ す 影 響 に 関 して,被 験 食 品 の 種 類 を 変 え た り,あ る い は 硬 さが ほ ぼ 一 定 で 変 化 し な い 特 殊 な ガ ム を 利 用 した 研 究 が あ る4,5)。 しか しな が ら,市 販 ガ ム で は,硬 さ,凝 集 性 お よ び 粘 着 性 な ど の テ ク ス チ ャ ー や 重 量 が チ ュ ー イ ン グ に よ っ て 経 時 的 に 変 化 す る 。 そ こで,市 販 ガ ム に お い て テ ク ス チ ャー や 重 量 の 変 化 を 経 時 的 に,定 量 的 に と らえ,あ わ せ て そ の 時 点 で の 咀 嚼 運 動 へ の 影 響 を 検 討 す る こ と を

Relationship between food texture and masticatory pain in patients with craniomandibular disorders.

This study was made to measure the food texture, caused the masticatory pain inpatients with craniomandibular disorders.The questionnaire was conducted on 40 patients about 33 kinds of food, whether these foods caused masticatory pain or not. The food texture was measured by Texturometer.The results obtained were as follows:1. The food which caused the masticatory pain in more than half patients were French bread (24 patients) and grilled dried squid (22 patients). On the other hand, foods which caused no masticatory pain were bean curd, jelly and marshmallow.2. Food texture mostly related to the masticatory pain was not only hardness but also gumminess, expressed the required force which grind food to the extent of ones swallowable condition.