Ahmad Khalid A, Drummond James L, Graber Thomas, BeGole Ellen
Department of Orthodontics, College of Dentistry, University of Illinois at Chicago, IL 60612-7212, USA.
Am J Orthod Dentofacial Orthop. 2006 Sep;130(3):275.e11-5. doi: 10.1016/j.ajodo.2006.01.024.
Rare earth magnets have been used in orthodontics, but their corrosion tendency in the oral cavity limits long-term clinical application. The aim of this project was to evaluate several; magnet coatings and their effects on magnetic flux density.
A total of 60 neodymium-iron-boron magnets divided into 6 equal groups--polytetrafluoroethylene-coated (PTFE), parylene-coated, and noncoated--were subjected to 4 weeks of aging in saline solution, ball milling, and corrosion testing.
A significant decrease in magnet flux density was recorded after applying a protective layer of parylene, whereas a slight decrease was found after applying a protective layer of PTFE. After 4 weeks of aging, the coated magnets were superior to the noncoated magnets in retaining magnetism. The corrosion-behavior test showed no significant difference between the 2 types of coated magnets, and considerable amounts of iron-leached ions were seen in all groups.
Throughout the processes of coating, soaking, ball milling, and corrosion testing, PTFE was a better coating material than parylene for preserving magnet flux density. However, corrosion testing showed significant metal leaching in all groups.
稀土磁体已应用于正畸领域，但其在口腔中的腐蚀倾向限制了其长期临床应用。本项目的目的是评估几种磁体涂层及其对磁通密度的影响。
将总共60块钕铁硼磁体分为6组，每组数量相等，分别为聚四氟乙烯涂层（PTFE）、聚对二甲苯涂层和未涂层，在盐溶液中进行4周老化、球磨和腐蚀测试。
涂覆聚对二甲苯保护层后，磁体磁通密度显著降低，而涂覆PTFE保护层后磁通密度略有下降。老化4周后，涂层磁体在保持磁性方面优于未涂层磁体。腐蚀行为测试表明，两种涂层磁体之间没有显著差异，且所有组中均观察到大量铁浸出离子。
在整个涂层、浸泡、球磨和腐蚀测试过程中，PTFE在保持磁通密度方面是比聚对二甲苯更好的涂层材料。然而，腐蚀测试表明所有组中均有显著的金属浸出。
