Diverse jaw-neck motor behaviour in individuals with dento-skeletal deformities

Objectives: Recent studies showing that head-neck movements are an integral part of jaw function imply that jaw activities require a healthy state of both the jaw and the neck motor systems. This is supported by our previous findings of disturbed integrative jaw-neck behaviour in Whiplash Associated Disorders. The present aim was to examine integrative jaw-neck behaviour in dento-skeletal deformities. Methods: Seven females and five males (mean age 25 years; SD 5) with dento-skeletal deformities (DSD) participated in the study. They were consecutive patients referred to the Dept of Oral and Maxillofacial Surgery, Umeå University for orthognathic surgery. A wireless optoelectronic technique for three-dimensional (3D) movement recording was used to simultaneously record movements of the mandible and the head-neck during maximal jaw opening-closing tasks, at fast and slow speed, Subjects were seated in an upright position, with back support up to the mid-scapular level without headrest. Each task was repeated for 5 times. The results were compared with our previous data in healthy of same age group. Results: Compared with healthy, (a) the DSD group showed similar 3D mandibular amplitude but 50 % smaller 3D head extension amplitude (p = 0.015); (b) longer duration of the fast jaw opening-closing cycle (1.36 s; SD 0.42) (p= 0.04); and (c) a delayed head movement at start of jaw opening (p ≤ 0.04). Conclusion: The results suggest that dento-skeletal deformities are associated with a diverse integrative jaw-neck function. The data will be a basis for further analyses of adaptive jaw-neck motor behaviour following surgical correction.