Novel Coatings to Prevention Ion Loss From Stainless Steel Alloys

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Children with extensive decay, large lesions or multi-surface lesions in primary molars are routinely treated with stainless steel crowns because of their cost-effectiveness, ease of placement, and longevity.  Despite these advantages, patient and parental objections concerning their appearance and their potential in nickel ion release sensitization are commonly raised. Nickel allergic contact dermatitis is the most prevalent allergy in North America today.

Objective: This project tested the ability of a novel coating method which improves esthetics, to also reduce metal ion release from stainless steel alloy (SS) immersed in a corrosive media.

Methods: Discs of SS (15.25mm diameter) were cleaned ultrasonically in ethanol.  Representative discs were coated using a novel Atomic Layer Deposition (ALD) coating process with a 100nm thick layer of SiO₂.  This extremely thin coating process renders the surface tooth-colored.  Samples (n=3 per time point) of the coated discs were placed in a lactic acid corrosive test solution according to ISO Standard 10271:2001.  Uncoated discs served as control samples.  Test solutions were added to obtain 1 ml of solution per cm² of sample surface area.  Samples were maintained at 37°C for test periods of 1, 10, and 100 hours. Test solutions were analyzed by Inductively Coupled Plasma Mass Spectrometry (ICP-MS) to detect the presence of Ni, FE and Cr ions in solution. Three replicate measurements were made for each sample and the average values were compared using a t-test with alpha=0.05.

Results: Ion release values are shown in the figure.  At all time points, the coated discs released significantly fewer ions than the uncoated discs.

Conclusions:  When esthetic ALD coatings are used on SS crowns, they result in significant reduction or even elimination of ion loss from the metal into the oral cavity.