Masticatory Side-switch and Mixing Ability.

Masticatory mixing ability will be calculated from the mixing capacity for each type of test (free, right, left and guided). Chewing gum will flattened between two rigid surfaces to a thickness of 1.5 mm. The two sides of the chewing gum will then be scanned at a resolution of 300 dpi. The images will be processed with "ImageJ" with the "Color-Histogram" plugin. Before mixing, the green and red color of the chewing gum are represented in the histogram of the red channel as two separate peaks: one in low intensity and one in high intensity, representing the green and red color of chewing gum, respectively. After mixing, the colors are mixed and so the two peaks merge into one peak. The standard deviation of the intensity distribution is taken as a measure of the mixture of the two colors in the chewing gum. The standard deviation at an early stage of mixing is relatively high, and decreases as the colors are mixed; thus, a high value of the mixing index means a high mixing capacity.

The number of side switches during the 40 masticatory cycles for each assay will be determined using slow playback of the video recordings of the freestyle mastication test. In the case that this switch is a change of side from left to right or right to left, we will assign a value of "1". If this switch consists of a change from the right or left to central or vice versa, we will assign a value of "0.5". If there is no change of side, the value assigned to this chewing cycle will be "0". To determine the Side-switch Index, the number of side changes will be divided by the maximum number of changes possible during these 5 assays (78).

Masticatory frequency will be assessed as the ratio of masticatory cycle number to masticatory time (in cycles per minute).

The degree of muscular fatigue while chewed the gum was assessed by asking the question "How much muscular fatigue do you think this masticatory test caused you?" using a 0-10 point scale (considering 0= Not at all to 10= very much). Participants will rate the masticatory test after each assay.

The degree of salivary secretion while chewed the gum was assessed by asking the question "How much saliva secretion do you think this masticatory test caused you?" using a 0-10 point scale (considering 0= Not at all to 10= very much). Participants will rate the masticatory test after each assay.

The degree of taste perception while chewed the gum was assessed by asking the question "To what degree do you think this masticatory test facilitates taste perception?" using a 0-10 point scale (considering 0= Not at all to 10= very much). Participants will rate the masticatory test after each assay.