Effects on G Tolerance While Biting Down on a Mandibular Orthopedic Repositioning Appliance (MORA) Levels.

Biting down against a Mandibular Orthopedic Repositioning Appliance MORA that properly aligns the temporo mandibular joint TMJ requires voluntary contraction of the masseter and temporals muscles. The purpose of this study was to evaluate the effects of mouthpieces by a dentist qualified in TMJ alignment. Non-invasive PB, ECG, and facial EMG were -recorded at 1 G during isometric straining in 2 sessions of 2 strains with biting and 2 strains without biting. Using no anti-G suit, subjects were then exposed to sessions of 0.5 Gz increasing 20 second G plateaus on the WPAFB Dynamic Environment Simulator Human centrifuge until loss of peripheral vision. Seven physiological variables were recorded including facial EMG, ear pulse, and transcranial doppler signals of cerebral artery flow. G tolerance was recorded for 3 exposures using the MORA and 3 without. The resulting EMG and RMS EMG recordings indicated that subjects were not maximally contracting the involved muscles during biting and that muscle fatigue did not occur. Using the MORA resulted in a 0.3 Gz mean increase in tolerance compared with not using the MORA p0.0345.