The influence of cranio-cervical posture on maximal mouth opening and pressure pain threshold in patients with myofascial temporomandibular pain disorders.

OBJECTIVE The aim of this study was to assess the influence of cranio-cervical posture on the maximal mouth opening (MMO) and pressure pain threshold (PPT) in patients with myofascial temporomandibular pain disorders. MATERIALS AND METHODS A total of 29 patients (19 females and 10 males) with myofascial temporomandibular pain disorders, aged 19 to 59 years participated in the study (mean years±SD; 34.69±10.83 y). MMO and the PPT (on the right side) of patients in neutral, retracted, and forward head postures were measured. A 1-way repeated measures analysis of variance followed by 3 pair-wise comparisons were used to determine differences. RESULTS Comparisons indicated significant differences in PPT at 3 points within the trigeminal innervated musculature [masseter (M1 and M2) and anterior temporalis (T1)] among the 3 head postures [M1 (F=117.78; P<0.001), M2 (F=129.04; P<0.001), and T1 (F=195.44; P<0.001)]. There were also significant differences in MMO among the 3 head postures (F=208.06; P<0.001). The intrarater reliability on a given day-to-day basis was good with the interclass correlation coefficient ranging from 0.89 to 0.94 and 0.92 to 0.94 for PPT and MMO, respectively, among the different head postures. CONCLUSIONS The results of this study shows that the experimental induction of different cranio-cervical postures influences the MMO and PPT values of the temporomandibular joint and muscles of mastication that receive motor and sensory innervation by the trigeminal nerve. Our results provide data that supports the biomechanical relationship between the cranio-cervical region and the dynamics of the temporomandibular joint, as well as trigeminal nociceptive processing in different cranio-cervical postures.