Threshold for Detection of Incisal Forces Is Increased by Jaw Movement

Current knowledge regarding the sensitivity of the teeth to forces is based on psychophysical experiments that measured touch detection thresholds under static jaw conditions. It is not known whether jaw movements alter the perception of forces applied to the teeth, but, based on limb movement studies, it is hypothesized that the perception of mechanoreceptor outputs will be downwardly modulated by jaw movements. We predicted that, compared with static jaw conditions, rhythmic jaw movements would be associated with significantly higher psychophysical thresholds for the detection of incisally applied forces. In eight participants, mechanical pulses were delivered to an incisor during static jaw holding or during cyclic jaw opening and closing. Analogous to findings in human limbs, the psychophysical salience of periodontal mechanoreceptor feedback was downwardly modulated by physiologically relevant movements; detection thresholds for mechanical pulses applied to a central incisor were significantly higher during jaw-closing movements than during static jaw positioning.