Jaw clenching modulates sensory perception in high- but not in low-hypnotizable subjects.
OBJECTIVE
To investigate the effect of jaw clenching on the sensations evoked at segmental and nonsegmental levels by painful and nonpainful stimuli and in relation to hypnotic susceptibility.


METHODS
The effect of jaw clenching on painful and nonpainful sensations on the face and leg was studied in high-hypnotizable (HH) and low-hypnotizable (LH) subjects. Sixteen healthy subjects were selected and assigned to either the HH group (n = 8) or the LH group (n = 8). Painful and nonpainful electrical stimuli were delivered in random order to the face and leg. The subjects rated the intensity of the evoked sensation on a visual analog scale (VAS) while clenching or not clenching their jaw.


RESULTS
Jaw clenching significantly attenuated the VAS sensory ratings of all the subjects under various conditions (F(1-31) = 6.15, P < .02). When the HH and LH subjects were analyzed separately, jaw clenching was found to be effective in reducing sensations only in the HH subjects (F(1-15) = 8.30, P = .01), only those evoked in the face (segmental level), and only those evoked by nonpainful stimuli (tied Z = 2.52, tied P < .02).


CONCLUSIONS
Sensory modulation produced by jaw clenching may be related to hypnotic susceptibility. On the whole, jaw clenching had a weak, local effect in modulating sensation, in contrast to its known widespread effect on motor behavior.
Tal
Michael
M
Department of Anatomy and Cell Biology, School of Dental Medicine, Hebrew University, Jerusalem, Israel. talm@cc.huji.ac.il
Sharav
Yair
Y
D000328:Adult; D000704:Analysis of Variance; D001732:Bite Force; D004558:Electric Stimulation; D005145:Face; D005260:Female; D006801:Humans; D006990:Hypnosis; D007866:Leg; D008297:Male; D008410:Masticatory Muscles / Q000502:physiology*; D009119:Muscle Contraction / Q000502:physiology; D010147:Pain Measurement; D012677:Sensation / Q000502:physiology*; D018709:Statistics, Nonparametric