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Head Immobilization can Impair Jaw Function

¹ Department of Odontology, Clinical Oral Physiology, Umeå University, S-901 87, Umeå, Sweden, and Centre for Musculoskeletal Research, Gävle University, Sweden; and
² Clinical Neurophysiology, Department of Clinical Neurosciences, Umeå University, Sweden

View larger version (12K): [in a new window]   Figure 1. The basic set-up for the simultaneous recording of 3-D movements of the mandible and the head by means of a wireless optoelectronic recording system (MacReflex®). Two charge-couple device (CCD) video cameras connected to a sampling computer via a video processor recorded head movements by means of a marker tripod, attached to the bridge of the nose, and mandibular movements by means of a single marker at the center of the chin.

View larger version (17K): [in a new window]   Figure 2. Amplitudes and cycle time with/without head fixation. (a) Head and mandibular movements for one male participant during self-paced continuous maximal jaw-opening/-closing movements recorded in the 2 different test conditions: free, unrestrained movements (grey); and with head fixation (black). Head (b) and mandibular (c) movement amplitudes and cycle duration (d) for the group (n = 12) without (unfilled) and with (hatched) head fixation for the different tasks; continuous maximal jaw-opening/-closing movements at self-paced rate (Cont), at a rate of 50 cycles per min (Cont 50), and during chewing (Chew).

View larger version (38K): [in a new window]   Figure 3. Head and mandibular movements for one male participant (no. 2) recorded during self-paced continuous maximal jaw-opening/-closing in different test conditions: (a) free, unrestrained head; and (b) with head-neck fixation. Raw surface EMG recorded from anterior digastric (Dig), masseter (Mass), sternocleidomastoid (SCM), and trapezius (Trap) muscles.

View larger version (22K): [in a new window]   Figure 4. Percentage (%) of cycles with muscle activity for each participant (n = 4) and task. Activity for jaw-opening phase without (a) and with (b) head-neck fixation for muscles sternocleidomastoideus (SCM) and trapezius (Trap) for the different tasks: continuous maximal jaw-opening/-closing movements at self-paced rate (Cont), at a rate of 50 cycles per min (Cont 50), and during chewing (Chew). Activity for jaw-closing (SCM) during chewing without (c) and with (d) head-neck fixation. Numbers on x-axis denote the participants.