Evaluation of Force Changes in Triple-Magnet Setup for orthodontic Tooth Movements

Introduction : A major challenge in orthodontic treatment with magnets is the severe distance-related force decay, which is a direct consequence of the inverse square law and prevents the delivery of a continuous force. Achieving light and continuous force is crucial for optimal orthodontic tooth movement. Methods : This is a basic and experimental study. A custom-made Magnet Holding Structure (MHS) was designed and 3D-printed to position three magnets. MHS maintained magnets in desired position to simulate canine, first premolar and first molar spatial relationship. It had two separate main part and had mounted on universal testing machine. The moving part of MHS mounted on upper mobile part of testing machine and had one cubic hole (2*5*8mm). The stationary part of MHS had two cubic holes(2*5*8mm) with 22mm distance and mounted on lower immobile part of testing machine. Neodymium magnet sizes was 2*5*10. Upper and Lower magnet mounted into the stationary part of MHS. All three magnets were parallel to each other on flat side and perpendicular to the moving line. The middle magnet mounted into mobile part with 7mm distance to lower magnet and 15mm to upper one (Point 1). It repulsed with lower magnet and attracted with upper one. Mobile part of testing machine moved in rate of 1mm/second up to 7 millimeters (Point 8). Forces in each millimeter were recorded. This was also done for 2*5*5mm and 4*5*5mm magnet. Sample size was 20 in each setup. The data were analyzed using ANOVA and Bonferroni post-hoc tests. Results : The data, which followed a normal distribution, showed that the mean forces in setups using 2*5*10mm and 2*5*5mm magnets were not statistically different across various distances, confirming the hypothesis that the Triple-Magnet Setup (TMS) can provide a stable force. In contrast, the 4*5*5mm magnet setup exhibited a statistically significant difference in force at the final measurement point. Furthermore, a comparison with the traditional Double-Magnet Setup (DMS) revealed that the TMS significantly reduced the percentage of force decay over distance for all magnet sizes tested. Conclusion : Triple-Magnet Setup (TMS) can deliver almost linear force magnitudes and provide constant and continuous force system. TMS comparing with single/double magnet setups can deliver larger forces with same magnet sizes and distances, so, optimum orthodontic forces can be provided with smaller size of magnets.