Craniomandibular stiffness toward maximum mouth opening in healthy subjects: a clinical and experimental investigation.

A new technique for measuring craniomandibular stiffness during mouth opening to the border position was tested. A small force transducer and a jaw tracking device were used to calculate the stiffness in a healthy group of male and female students. Simultaneous EMG recordings were taken from the masticatory muscles to observe the EMG activity during the experimental tests. The craniomandibular stiffness curves of the male group exhibited a stiffer behavior than those of the female group (P less than 0.05). The clinically obtained "endfeel" distance exhibited a significant correlation with different stiffness sections in the stiffness curves (P less than 0.05). Enhanced muscular involvement during mouth opening to the border position was shown as an increase in the clinical endfeel distance.