EFFECT OF ACUTE NASAL OBSTRUCTION ON MASTICATORY FUNCTION

Abstract

The present study was undertaken to examine how masticatory function is affected by an acute nasal obstruction. Nasal obstruction was performed by pinching the nose of each subject with a nose clip. We measured the chewing time, water content of food bolus and the volume of saliva secreted during the mastication of peanuts. In addition, the chewing cycle time, burst duration time and the interval time were also analyzed from the results obtained electromyographically. Comparisons were made between the normal and the nasal obstructed condition in the same subject. The chewing time under nasal obstructed condition was significantly prolonged compared to control condition, whereas the water content of food bolus and volume of saliva secreted during mastication was unchanged. The chewing cycle time tended to be prolonged by nasal obstruction. The interval time was significantly prolonged by nasal obstruction, while the burst discharge time was not significantly changed. These results indicate that the water content of food bolus as an important factor for the determination of the chewing time under a nasal obstructed condition as well as in a normal condition. Therefore, the prolongation of chewing time under a nasal obstructed condition is possibly attributed to a compensatory action for getting an equivalent water content of food bolus under normal condition. Key word: Acute nasal obstruction, Water content of food, EMG, Masticatory function, Introduction Numerous investigators have reported that masticatory function is affected by various factors. The chewing force, the number of chewing strokes and the time until swallowing vary according to the texture of food, such as its hardness, shape and stickiness (Shiere and Manly, 1952; Kawamura and Nobuhara, 1957; Thexton et al., 1980; Liao et al., 1990). The volume of saliva secreted during mastication depends on the water and taste substances containing food (Watanabe and Dawes, 1988; Watanabe et al., 1993a; Watanabe et al., 1998). However, most of these studies have been carried out on healthy subjects. There is little information about the effect of acute nasal obstruction on masticatory function. The conryzal type of cold easily gives rise to the acute nasal obstruction. The present study was undertaken to examine how masticatory function is affected by an acute nasal obstruction. Based on the results, we have reported the effect of acute nasal obstruction on masticatory function , especially the effect on chewing time. Materials and Methods 1. Subjects The experiments were carried out in 5 subjects with a mean age of 28.8 •} 6.5 (mean •} SD.) years. All subjects were students or teaching staff of our university. They were free 〒061-0293北 海道石狩郡 当別 町字金沢1757 北海道医療大学歯学部小児科学講座 TEL:01332-3-1211FAX:01332-3-1412 8巻1号(1998) Nasal obstruction and Mastication 67 from any clinical signs and symptoms of the stomatognathic system and had no history of nasal disease. Informed consent was obtained from each subject prior to the experiments. 2. Procedure for acute nasal obstruction The nose of each subject was pinched by a nose clip and this situation was refereed to as a nasal obstructed condition. The completeness of nasal obstruction was checked by no leakage of expired air from the nasal cavity. 3. Measurements of chewing time, water content of food bolus and volume of saliva secreted during mastication. Peanuts was used as the test food. The water content and the volume of saliva secreted during mastication were calculated by the chewing-spit method described by Richardson and Feldman (1986). That is, each subject took a 3g portion of peanuts and chewed until such time as the subject would normally swallow. Just before the occurrence of swallowing, the food bolus was spit out into a previously weighted container. The volume of saliva secreted during that time was calculated by subtracting the initial weight of food from that of the food-saliva mixture. The time required to the point before swallowing was measured as the chewing time. 4. Recording and analyzing of electromyogram Electromyograms (EMG) of the working side of the masseter muscle were recorded from a pair Ag AgCl surface disc electrodes placed on the facial skin over the middle portion of the muscle and stored on DAT tape. The data stored on DAT tape were analyzed by a personal computer. The chewing cycle time, the burst duration time and the interval time were measured by an analysis program (QP-110J, NIHON KOHDEN). The significance of the difference between values under the normal condition and those under the nasal obstructed condition in the same subject was tested by the paired t-test. Results 1. Chewing time Chewing time under the normal and the nasal obstructed condition is shown in Table 1.Under the normal condition, the chewing time was individually variable, ranging from 19.0•}3.2 (mean•}SD.) sec in subject 3 to 48.2•}4.3 sec in subject 4, while it was a narrow variation in the same subject. The chewing time in all subjects was prolonged by nasal obstruction. The maximum and the minimum values in the nasal obstructed condition was 29.3•}2.4sec in subject 3 and 79.0•}4.9sec in subject 4, respectively. The chewing time of subjects 1, 3 and 4 under the nasal obstructed condition showed a significant prolongation compared with that under the control condition (P<0.001). 2. Water content of food bolus Table 2 shows the water content of food bolus under the normal and the nasal obstructed conditions. Under the normal condition, the maximum value of water content of food bolus was 66.1•}2.0 % in subject 2 and the minimum value of that was 32.8•}5.6 % in subject 4 under the nasal obstructed condition, the maximum and the minimum values were 66.1•}2.4 % in subject 2 and 34.1•}4.9 % in subject 4, respectively. In all subjects, except for subject 1, there were no significant differences under Table 1. Chewing time for mastication of peanuts in normal and nasal obstructed conditions. Values are mean•}SD.. Number of trials in each subject is 7. * indicates significant difference from the control condition at p<0.001. 68 Mika SUGAWARA et al. 8巻1号(1998) the water content of food bolus between the normal condition and the nasal obstructed