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Background: Everyday jaw functions such as jaw opening, chewing, and eating are highly important for oral and general health. In adults, these actions involve coordinated activity between the jaw and neck, with jaw opening typically accompanied by neck extension and jaw closing with neck flexion. This reflects an elaborate and synchronized integration between trigeminal and cervical sensorimotor function. However, there is a notable lack of studies investigating the presence of this integration in children, how it develops throughout childhood, and how it manifests during early adolescence. The primary aim of this thesis was to explore the integrated jaw-neck motor function in children and adolescents compared to adults. This was achieved through a detailed description and objective quantification of jaw-neck movement patterns using kinematic analysis.

Methods: The thesis is based on four studies conducted at the Motion Laboratory, Department of Odontology, Umeå University, Sweden. Study I assessed the accuracy of a 3D kinematic method and test-retest reliability of functional jaw range of motion observed in 17 pain-free adult participants. Study II explored jaw-neck movement integration during jaw motor tasks in 25 healthy 6-year-olds and 24 adults. Study III followed 20 of these 25 children at ages of 10 and 13 to evaluate developmental changes in jaw-neck motor function compared to adults. Study IV characterized initial jaw and head movement adjustments during jaw function in 20 healthy young adolescents and 20 adults. All participants underwent clinical examination of the jaw and neck system, followed by motion capture of jaw and head movements during jaw opening-closing and chewing tasks.

Results: The 3D kinematic method displayed high accuracy. Jaw movements in the horizontal plane showed higher variability, likely due to biomechanical complexity. Compared to adults, 6-year-olds exhibited integrated jaw-neck motor function, though their movement patterns remained immature, characterized by smaller magnitudes, increased variability in jaw-neck coordination, and greater relative contribution of head movements and longer cycle durations during jaw motor tasks. Between the ages of 6, 10 and 13, motor development progressed during functional jaw movements. At ages 6 and 10, movement variability and cycle durations were more pronounced than in adults. By age of 13, movement patterns more closely resembled those of adults; however, initial movement characteristics still differ between adolescents and adults.

Conclusions: This thesis mapped typical developmental changes in the jaw-neck motor function from childhood to early adolescence. The kinematic method used provides reliable measurements for capturing these changes. Significant differences in spatial and temporal movement parameters were observed between children, adolescents and adults. Between the ages of 6, 10 and 13, the movement pattern becomes more coordinated and increasingly resembles that observed in adults. However, a distinction between adolescents and adults persists during the initiation of a motor task, suggesting that jaw-head movement coordination continues to refine from early adolescence into adulthood. Normative values based on key jaw-neck movement events during typical development may be of great importance for identifying atypical development and may be valuable when assessing children and adolescents with pain and motor disabilities in the jaw-neck system.