Effect of corrosive environments and thermocycling on the attractive force of four types of dental magnetic attachments

Background/purpose: One of the problems that has limited magnets' wide acceptance by clinicians is their low corrosion resistance. The purpose of this study was to determine the effect of corrosive environments and thermocycling on the attractive force of different types of new generation magnetic attachments. Materials and methods: We measured the attractive forces of 60 magnetic attachment systems (Hyper slim, Hicorex slim, Dyna, and Steco) with a universal test machine. We then immersed 40 of the magnetic attachment systems in two media, namely, 1% lactic acid solution (pH 2.3), and 0.9% NaCl solution (pH 7.3). The remaining magnetic attachments were put through 10,000 thermal cycles (5 degrees C/55 degrees C). We measured the attractive forces of the magnetic attachment systems again after immersion and thermocycling to compare data. The data were statistically evaluated with one-way analysis of variance, paired samples t-test, and post hoc Tukey-Kramer multiple comparison tests (alpha = 0.05). Results: We found significant differences between the mean values before and after immersion in corrosive environments (P < 0.05). In contrast to the Dyna and Steco systems (P < 0.001), the differences between the attractive forces before and after thermocycling were not statistically significant for the Hicorex slim and Hyper slim systems (P > 0.05). Conclusion: Magnetic attachments showed lower attractive force after immersion in corrosive environments compared to their initial retentive force. In addition, closed-field systems were not affected by the thermocycling procedures and were more resistant than open-field systems to thermal variations characteristic of the oral cavity. Copyright (c) 2012, Association for Dental Sciences of the Republic of China. Published by Elsevier Taiwan LLC. All rights reserved.