Effects Of Simulating Static Magnetic Fields Of Dental Magnetic Attachments On The Electrophysiological Properties Of Ion Channels

Moderate-intensity (1mT-1T) static magnetic fields (SMF) can be produced by permanent magnets as well as electromagnets in our daily life. Dental magnetic attachments are typical examples for the application of magnets and magnetic forces in contemporary dentistry. In their course of development from early open-circuit magnet system to nowadays close-circuit magnet system, for different type of magnets, controversial opinions persist about whether their SMF have oral biosecurity. Meanwhile, the effects of SMF on other biological systems have also been discussed for decades. Previous studies revealed that SMF can alter the central nervous function, peripheral nerve conduction, neuromuscular activity and synaptic transmission. However, the mechanisms underlying such effects are not entirely clear.In this study, two sets of SMF exposure devices were manufactured to simulating the SMF of commonly used dental magnetic attachments. Then, trigeminal ganglion neurons (TRGN) were acutely dissociated and cultured from neonatal SD rats. After being identified by their neurological characteristics, TRGN were exposed to 125mT and 12.5mT SMF in the exposure devices, respectively. Transmission electron microscope was used to examine the changes of the cellular structures; laser scanning confocal microscope (LSCM) was applied to measure the intracellular free Ca²⁺ concentration; whole-cell patch clamp recordings were also carried out on TRGN to survey two main types of voltage-gated potassium channels (VGPCs) currents, I_K,A and I_K,V. Meanwhile, under the exposure of SMF, electrophysiological recordings were performed on the sciatic nerve preparations from bullfrogs and the electrophysiological behaviors of the nerves were studied. The results demonstrated that,1. In the circumstances of this study, 1h to 3h exposure of 125mT and 12.5mT SMF had no effect on the cellular structures within TRGN;2. No changes of activation kinetics of I_K,A and I_K,V were found between the 125mT exposure group and control. However, the inactivation rate and velocity of those VGPCs currents were significantly altered by 125mT SMF;3. In the circumstances of this study, the changes of intracellular free Ca²⁺ concentration within TRGN were slowed by 125mT and 12.5mT SMF. When SMF were removed, the intracellular free Ca²⁺ concentration in the TRGN of 125mT SMF group showed partial recovery, while there was a full recovery found in the 12.5mT SMF exposed group;4. 125mT and 12.5mT have no effect on the excitability as well as the conduction behaviors of bull-frog sciatic nerves in vitro.Those experimental findings suggested that moderate-intensity SMF had certain effects on the electrophysiological characteristics of ion channel on cellular level. Such effects might be intensity-dependent and were not permanent. As far as the time-course of SMF exposure carried out in this study was concerned, more evidences should be gathered to determine the long-term effects of SMF on biological systems.