Abstract
In this study, we measured the change of blood flow in the prefrontal cortex induced by changes in mandibular position in order to investigate the possibility of an objective method for determining the vertical dimension of occlusion. The subjects were 18 adults with individual normal occlusion. The neural activity of the prefrontal cortex was measured using functional near-infrared spectroscopy (fNIRS) when wearing bite-raising splints of different heights (0 mm as control, +2 mm, +4 mm, and +6 mm). Emotional changes were subjectively evaluated using the Visual Analog Scale (VAS). The results showed that the discomfort of the VAS scores increased significantly with the increase of the vertical dimension of occlusion.
On the other hand, the neural activity of the prefrontal cortex decreased as the vertical dimension of occlusion increased, and significantly decreased in comparison with 0 mm, +4 mm and +6 mm. In particular, a significant decrease was observed near the frontal pole. These results suggest that the blood flow of the prefrontal cortex changes according to the vertical dimension of occlusion and that the vertical dimension of occlusion can be assessed non-invasively and objectively from the brain activity.
