Clarifying Optimal Occlusion to Improve Athletic Performance Focusing on Brain and Spinal Function

Abstract

Teeth clenching greatly impacts athletic performance, but the optimal occlusal force and balance between the left and right sides remain unclear. Therefore, the present study aimed to investigate the effect of imbalanced occlusal pressure on remote facilitation, focusing on spinal function and locus coeruleus activation. Fourteen healthy adults with normal occlusion were enrolled; those with malocclusion were excluded from the analyses. Occlusal pressure measurements included maximum occlusal force and balance of occlusal pressure between the left and right sides. The sides with higher and lower occlusal pressures were referred to as the Hyper and Hypo sides, respectively. Electromyography electrodes were attached to the bilateral masseter, anterior temporal, and soleus muscles. The occlusion conditions were as follows: no-bite condition（no contact of the dental arches）， contact condition（contact of the dental arches without clenching）， and conditions of 12.5%, 25%, and 50% of the maximum voluntary contraction（MVC） of the right masseter muscle, as well as a max condition. Spinal excitability was evaluated using the H-re?ex, which was measured by electrically stimulating the tibial nerve in both lower limbs, with the stimulus intensity set so that the soleus H-wave amplitude was 20% of the maximum M-wave amplitude. Additionally, the pupil diameter on both sides was measured as an indicator of locus coeruleus activity. We analyzed the muscle activity of each muscle under each occlusion condition, H-wave amplitude values on both sides, and pupil diameter on both sides. Statistical processing included two-way repeated measures analysis of variance, and post hoc tests involved t-tests between conditions. The signi?cance level was set at 5%. The masseter and anterior temporal muscle activities were signi?cantly higher on the hyper side than on the hypo side in the 12.5%, 25%, 50% MVC, and max conditions （p< 0.05）．Spinal excitability and pupil diameter were significantly higher in the 12.5%, 25%, 50% MVC, and max conditions than in the no-bite condition（p < 0.05）． Furthermore, spinal excitability was signi?cantly higher on the hyper side than on the hypo side in the max condition（p < 0.05）．Pupil diameter was signi?cantly higher on the hyper side than on the hypo side in the 12.5%, 25%, 50% MVC, and max conditions （p< 0.05）． Our results suggest that imbalanced occlusal pressure leads to imbalances in locus coeruleus and spinal excitability activities. Given that such imbalances in the locus coeruleus and spinal excitability negatively affect cognitive and motor functions, the correction of occlusal pressure balance may be important.