Effects of remote facilitation on ankle joint movement: Focusing on occlusal strength and balance.

Abstract

Remote facilitation refers to teeth occlusion-activated spinal cord activity resulting in increased trunk and limb muscle strength. Facilitation depends on dentition-related pressure during occlusion and masticatory muscle contraction strength. This study aimed to clarify the neurophysiological phenomenon and mechanisms by which occlusal strength and balance affect leg muscle activity and smooth joint movement execution. To examine occlusal strength, three conditions were set: no contact between teeth and Moderate- and Maximum-strength occlusion (No-bite, Moderate, and Max conditions, respectively). To assess occlusal balance, we measured occlusal forces and calculated the left-right force ratio. We designated the sides with higher and lower occlusal pressure as hypertonic and hypotonic, respectively. We assessed ankle dorsiflexion movements with joint movement and isometric tasks. The rate of joint development and peak ankle dorsiflexion torque were significantly higher under occlusion (moderate and max compared to No-bite conditions), and the joint movement performance time was significantly shorter under Moderate compared to No-bite conditions. The joint movement execution time change rate from No-bite to Moderate condition was significantly lower on the Hypertonic side. Joint movement function was most improved under Moderate conditions. While remote facilitation improves with higher occlusal strength, leading to increased muscle strength, there is optimal occlusion intensity in joint movement. Moreover, an occlusal balance-dependent imbalance exists in remote facilitation between the Hyper- and Hypotonic sides. Thus, low-intensity occlusion is optimal for smooth joint movement, and unbalanced occlusion results in asymmetrical motor function facilitation.