INFLUENCE OF MASTICATION ON SALIVA, PLAQUE PH AND MASSETER MUSCLE-ACTIVITY IN MAN

An earlier study showed that frequent gum chewing may enhance parotid gland function and reduce the acidogenicity of dental plaque. The aim now was to determine whether these effects would be observed after a 2 -week period of diet altered to increase masticatory effort, and secon darily to assess the effects of chewing gum on masseter muscle activit y. Ten subjects took part in the first experiment. Saliva was collecte d before and after the diet change and the plaque pH response to a suc rose challenge was measured. Subjects completed 3-day diet histories a nd wore electromyographic (EMG) devices to record masseter activity. I n the second experiment, 10 subjects wore EMG devices for 3 days to re cord masseter activity on three daily regimens: baseline (no gum chewi ng), hourly gum chewing (sugar-free gum chewed for 10 min every hour) and chewing five sticks of gum each for 20 min during the day. Data we re analysed by paired t test or repeated-measures analysis of variance . For the first experiment, EMG data indicated significant increases i n chewing activity (p < 0.05), although there were no changes in saliv ary flow rates or the plaque pH response to sucrose. The second experi ment showed that total EMG activity increased significantly on both gu m-chewing regimens (p < 0.01), the magnitude of the increase being gre ater for hourly chewing. Overall, masseter EMG activity was increased 41% by diet alteration, compared to increases of 96 and 152% on the fi ve-stick and hourly gum-chewing regimens, respectively.