Variability of the masticatory process during chewing of elastic model foods

Many studies show a consistent individual chewing pattern; chewing being go verned by a pattern generator and regulated by sensory feedback. The aim of this study was to determine the variation in chewing between sessions, rep licates and subjects using elastic model foods. Fifteen young male subjects were selected to chew four food products differing in hardness. Four sessi ons were performed at l-wk intervals for each subject and, within each sess ion, the four model foods were presented 3 times each. Jaw movement was rec orded simultaneously with masseter and anterior temporalis electromyographi c activities. Several chewing characteristics increased progressively from one session to the next; the largest increase occurred from the Ist to the 2nd session, with little difference between the last two sessions. No diffe rences were observed between the samples of the same food product within a session. As mastication progressed, the amplitude and speed of the cycles a nd the muscular work decreased progressively. The first cycle appeared to b e very different from the subsequent for all parameters except for occlusal duration. Thus, under our experimental conditions, the origin and amount o f variation in chewing patterns were identified and provide information to improve the accuracy and comparability of results in studies of mastication .