Development of integrated jaw-neck motor function in children at 6, 10 and 13 years of age compared to adults: A kinematic longitudinal study.

BACKGROUND: The functional integration of the jaw and neck motor systems, of great importance to everyday oral activities, is established in early childhood. Detailed characterisation of this developmental progress is largely unknown. OBJECTIVE: To establish developmental changes in jaw-neck motor function in children over the ages 6-13 years compared to adults. METHODS: Jaw and head movement kinematics during jaw opening-closing and chewing were longitudinally recorded in 20 Swedish children (8 girls) at 6 (6.3 ± 0.4), 10 (10.3 ± 0.3) and 13 (13.5 ± 0.7) years of age and 20 adults (9 women, 28.2 ± 6.7). Movement amplitudes, jaw movement cycle time (CT), coefficient of variation (CV) and head/jaw ratio for amplitudes were analysed. Linear mixed effect analysis and Welch's t-test were used. RESULTS: Children showed pronounced movement variability and longer CT at 6 and 10 years old during opening and chewing (p < .001). Compared to adults, 6-year-olds showed higher head/jaw ratios (p < .02) and longer CT (p < .001) during opening and chewing, and higher CV-head (p < .001) during chewing. Whereas 10-year-olds showed larger jaw and head amplitudes (p < .02) and longer CT (p < .001) during opening, and longer CT (p < .001) and higher CV-head (p < .001) during chewing. For 13-year-olds, longer CT (p < .001) during chewing was found. CONCLUSION: Children showed pronounced movement variability and longer movement cycle time at 6-10 years and developmental progress in jaw-neck integration from 6 to 13 years, with 13-year-olds displaying adult-like movements. These results add new detailed understanding to the typical development of integrated jaw-neck motor function.