RESUMEN
Objective:To investigate the biomechanical effect of magn et ic expansion by a new electronic speckle pattern interferometry. Methods :One fresh human skull of 12 years old with intact suture tissues and pe riodontal membrane was adopted. Magnetic expansion was loaded on the maxilla for 1,5,15,30 and 60 min respectively by magnetic force (NdFeB).Relative informa tion on the maxillary complex was acquired by electronic speckle pattern interfe rometry(ESPI). The deforming fringes was processed by the microcomputer image s ystem and the corresponding out-of plane displacement of the maxillary complex was analyzed. Results:Fringes of the maxillary complex were obs erved on monitor screen when magnetic force was loaded. From 1 min to 30 min-lo ading the fringe density was increasing, but decreased 1 h after loading. There was no fringe in the suture of the skull. Greate deformity was found on the lowe r part of maxilla. Conclusion:Magnetic force of expansion is con centrated in the deep structure of the maxillary complex.
RESUMEN
Objective: To test the mechanical properties o f N48 NdFeB magnet.Methods:Samples of N48 NdFeB magnet in the size of 2 mm?3 mm?4 mm were prepared, the residual flux density,coercive force and maximum energy product of the samples were measured, the magnetic density aroun d the magnets,the attractive and repulsive force between two magnets in 0~10 mm air gap were investegated.Results:The residual flux density of t he N48 NdFeB magnet was 1.373 T, coercive force 1 037 A/m and maximum energ y product 368 kJ/m 3.The magnetic density at magnet surface was 0.338 T,it decr eased to 0 at the point that leave magnet surface 20 mm away. The highest attrac tive force was 4.47 N between two magnets, the attractive force was 4.47~0.39 N in 0~5 mm air gap.The highest repulsive force was 2.82 N and the repulsive force was 2.82~0.39 N in 0~5 mm air gap.Conclusion:The magnetic and m echanical properties of the N48 NdFeB magnet can meet the standard of the orthod ontic force.