Functional Integration Between the Jaw-Neck Motor Systems in Children

Objectives: To investigate the functional integration between the jaw and neck motor systems during jaw function in children by evaluating differences in jaw and head movement patterns between children and adults.
Methods: Lower jaw and head movements were recorded with an optoelectronic 3D recording system in 25 healthy 6-year olds (12 girls, 13 boys) and 24 healthy adults (12 women, 12 men, mean age 26.4 years, SD 5.04). The participants performed two jaw motor tasks: paced continuous jaw opening-closing and self-paced chewing on chewing gum. The movement variables were: i) the head and jaw movement amplitudes (mm), ii) the ratio between head and jaw movement amplitudes (%), iii) the intra-individual variation in movement cycles for both jaw and head movements expressed as a coefficient of variation (CV) and iv) the movement cycle time (sec).
Results: Head movements were present during jaw activities in both children and adults. Compared to adults, children showed significantly higher head-neck movement amplitude (1.9 mm vs. 1.2 mm; P=0.0077) during chewing and higher ratios between the head and jaw movement amplitudes for both jaw opening-closing (29% vs. 20%; P=0.0258) and chewing (15% vs. 9%; P=0.0034). Children also had larger intra-individual variation in movement cycles for both jaw and head movements. Thus, during jaw opening-closing, children showed higher variability in movement amplitudes compared to adults for the head (CV=0.70 vs. 0.50; P=0.0390) and during chewing, for both the jaw (CV=0.30 vs. 0.18; P=0.0077) and the head (CV=1.20 vs. 0.90; P=0.0005)
Conclusions: The results show similarities in jaw-neck motor behaviour between children and adults indicating that a functional integration between the jaw and neck motor systems is established early in life. The results also indicate some differences, with more variability in the movement patterns for children, which may be interpreted as immature programming of jaw-neck motor behaviour in children.