Comparison of chin and jaw movements during gum chewing

Statement of problem. Knowledge of mastication is based on studies that use jaw tracking equipment in nonroutine settings. Ethologists would argue tha t such data probably does not reflect routine masticatory function. If jaw movements could be tracked noninvasively, then the hypothesis that jaw trac king equipment and nonroutine settings alter mastication could be investiga ted. Purpose. This study quantitatively evaluated the relationship between chin and jaw movements during a gum-chewing task. Material and methods. Masticatory chin and jaw movements of 50 subjects wer e tracked in the x-, y-, and z-axes for 15 seconds, which resulted in appro ximately 15 chewing cycles obtained per subject. For each chewing cycle, ma gnitude and timing of displacement, velocity and acceleration extrema in ea ch axis were computed for both jaw and chin movement data. Extrema means we re calculated for each 15-second trial. The respective means representing c hin versus jaw movements were compared with linear regression and correlati on analyses. Results. All mean extrema were significantly correlated (r range 0.30-0.99; P<.05). Magnitude correlations were larger than timing correlations for ac celeration extrema. In contrast, magnitude correlations were smaller than t iming correlations for displacement extrema. The highest correlation occurr ed for chewing rate. Conclusions. Chin and jaw movements were correlated during chewing; however , only chewing rate was highly predictable from chin movement data.