A mastication test was needed with a material that forms a bolus and is soft enough to be chewed by persons with compromised oral function, in particular patients confronted with oral cancer. We therefore developed a wax-mixing ability test and compared it with a comminution test using Optocal as test food. We hypothesized that the mixing ability test would be better at differentiating between groups of persons with compromised masticatory performance than the comminution test. Sixty healthy subjects were recruited in three groups of 20, matched for age and gender: a group with natural dentition; a group with full dentures; and a group with maxillary denture and implant-supported mandibular overdenture. The mixing ability test was found to discriminate better between the two full-denture groups than the comminution test.

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Maximum voluntary bite force has often been studied as an indicator of the functional state of the masticatory system. Bilateral, as well as unilateral, methods have been used to determine bite force. Only a few studies have compared the outcomes of both methods. The aim of this study was to measure bite force and jaw-muscle activity during bilateral as well as unilateral maximum clenching in a large number of healthy subjects, so that the results could be compared. In a group of 81 dentate subjects we observed an average bilateral bite force of 569 N. The average unilateral bite force was significantly lower, being 430 N (right) and 429 N (left). Masseter and anterior temporal muscle activities were also significantly lower during unilateral clenching as compared with bilateral clenching. The masseter muscles showed no difference in activity between the ipsilateral side and the contralateral side during unilateral clenching. In contrast, the activity of the anterior temporal muscle on the ipsilateral side was significantly higher than on the contralateral side. Thus, the change in the forces acting on the jaw during unilateral clenching compared with bilateral clenching leads to a different response in the temporal muscles than in the masseter muscles.

1. During chewing, little muscle activity is required to make open-close movements with the mandible, and much additional muscle activity (AMA) of the closing muscles is needed to overcome the resistance of food. The neuromuscular control of the AMA was investigated. 2. Subjects made rhythmic open-close movements at their natural chewing frequency controlled by a metronome. Food resistance was simulated by an external force, acting on the jaw in a downward direction during part of the closing movement. Sequences of cycles with a force were unexpectedly alternated with sequences of cycles without a force. Jaw movement, and surface electromyograph (EMG) of the masseter, temporalis, and digastric muscles on both sides were recorded during cycles before and after the transition from force to no force (Disappear experiment) and vice versa (Appear experiment). 3. The movement trajectory of the second and following cycles after the transition from force to no force or vice versa were similar. Thus adaptation to the changed circumstances occurred in both types of experiments within two open-close cycles. 4. In the first cycle with force in the Appear experiments, the AMA started, on average, 129 ms after the onset of the force. In all other cycles with force, the AMA started, on average, 70 ms before the onset of the force at a low level and steeply increased 23 ms after the onset of the force. 5. In the first cycle without force in the Disappear experiments, the AMA started, on average, 69 ms before the moment at which the force would have started. However, the large contribution to the AMA had disappeared.(ABSTRACT TRUNCATED AT 250 WORDS)