Abstract
Purpose : The purpose of this study was to examine the change in spinal cord excitability in a leg muscle during maximal voluntary clenching on a stabilization appliance.
Materials and Methods : The H reflex of the soleus muscle was elicited in five healthy male volunteers by electrical stimulation of the tibial nerve under the following five dental occlusal conditions : mandibular rest position (RP : control), maximum voluntary clenching in the intercuspal position (IP), maximum voluntary clenching on a hard acrylic stabilization appliance (H-SA), maximum voluntary clenching on a soft stabilization appliance (S-SA) and maximum voluntary clenching on a very soft stabilization appliance (VS-SA).
Results : The soleus H reflex modulations in the IP, H-SA, S-SA and VS-SA conditions were 117.6%, 119.5%, 126.2% and 133.6%, respectively. There was a significant difference between IP and S-SA, and IP and VS-SA (p=0.0001-0.0226) ; however, there was no significant difference between IP and H-SA (p=0.3412-0.9940). Significant positive correlations between the magnitude of the soleus H reflex and the masseter electromyogram activity were found in each subject (r=0.670-0.862, p<0.05).
Conclusion : This study demonstrated that the spinal cord excitability in the motor pathway of a leg muscle was considerably raised during clenching on a soft stabilization appliance compared to a hard stabilization appliance, suggesting that a powerful biting action on a resilient intraoral appliance strongly influences the motor system in humans.
