Can laser welding stop corrosion of new generation magnetic attachment systems?

Abstract

Rare earth magnets have been used in both prosthodontics and orthodontics, but their corrosion tendency in the oral cavity limits long term clinical application. The purpose of this study was to evaluate corrosion of new generation magnetic attachments in two different pH corrosive environments and to answer the question: 'can corrosion reach the magnet in spite of laser welding?'. Forty magnetic attachment systems (Hyper slim, Hicorex slim, Dyna and Steco) were immersed in two media, 1% lactic acid solution (pH=52.3) and 0.9% sodium chloride solution (pH=57.3) for 14 days. After immersion, samarium, cobalt, neodymium and boron ions released from the magnetic attachments were analysed using inductively coupled plasma mass spectrometry. Moreover, iron ions released from the magnetic attachments were detected by atomic absorption spectroscopy. The data were statistically evaluated with Kruskal-Wallis and post hoc Tukey-Kramer multiple comparisons test (?=50.05). In all groups, Dyna, Hicorex slim, Hyper slim and Steco, there were statistically significant differences between sodium chloride and lactic acid solutions. Different amounts of neodymium, boron, iron, samarium and cobalt ions released from magnetic attachments were detected in the corrosive environments. There was a significant decrease in the corrosion of the magnets, but corrosion was not completely stopped. Laser welding zone was broken down, and corrosion reached the magnet. © W. S. Maney & Son Ltd. 2011.