一側の歯牙の破折による両側咬筋活動の変化
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概要
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The purpose of the present study was to examine changes in EMG activities of the left and right masseter muscles during feeding after fracture of the tooth in the rat. Male Wister rats weighing over 320g were fixed with a pedestal for connecting with wires from recording electrodes by dental cement on the center of the cranial bone under anesthesia. Thin Teflon coated wires connected to the pedestal led under the skin to the left and right masseter muscles and cut ends of these wires were sewed on the masseter muscles and employed as recording electrodes. In recording EMG, the wire of the pedestal and the input box of amplifier were connected by other thin wires. The rat could move and eat freely in the cage. The control EMG was recorded after a week from setting the pedestal and the crown of lower first molar (or 3 molar) was fractured thereafter. The postoperative EMG was recorded about 5 days after fracture of the crown of a molar (or 3 molar) and subsequent EMG recording was carried on at an interval of about a week. The amplitude and integrated value of EMG in the left and right masseter muscles were compared. The main findings were summarized as follows. 1. In intact rats, several small amplitude discharges were generated at the beginning and followed by series of discharges with large amplitude and brief duration generated at regular intervals during feeding. The first small discharges generated when rat bite off food pellets with incisors and following series of discharges with large amplitude were elicited when rat masticated with molar teeth. 2. After the fracture of the crown of the tooth, these discharges became small and irregular ; therefore, the two types of discharges became undistinguishable. 3. The amplitude of discharges in the fracture side become smaller than that of control in all the cases. This decrease of amplitude in the fracture side continued for a long term. The amplitude of discharges in the fracture side was smaller than that of intact side in all the cases. This decrease in the fructure side continued for a long term, too. 4. The integrated value of discharges in the fracture side become smaller than that of control in all the cases. This decrease of integrated value of the fracture side continued for a long term. The integrated value of discharges in the fracture side was smaller than that of intact side in all the cases. This decrease in the fracture side continued for a long term, too.
- 九州歯科学会の論文
- 1993-02-25