Characterization of as-received, retrieved, and recycled stainless steel brackets.

AIM

The purpose of the present study was to investigate the composition and to assess the microhardness and structure of as received, retrieved, and recycled stainless steel brackets.

MATERIALS AND METHODS

New, used, and recycled brand-, slot size-, and prescription-matched appliances were subjected to scanning electron microscopy (SEM), energy dispersive (EDS) electron probe microanalysis, metallographic analysis, and Vickers microhardness testing. Elemental analysis was performed on randomly selected bulk material base and wing areas. Basic metal content and microhardness results were statistically analyzed using a two-way ANOVA and the Tukey test, with treatment (as received, retrieved, and recycled) and bracket region (base, wing) serving as discriminating variables (alpha = 0.05).

RESULTS

The results showed that there was no alteration in the bulk composition of the brackets among the three conditions. In contrast, differences were noted between bracket base and wing with respect to elemental composition among all groups, implying that the base and wings were manufactured from different alloys. The metallographic etching identified no difference in grain structure between the bracket base and wing components for all groups, regardless of treatment. Vickers microhardness demonstrated significant differences in hardness between base and wing for all groups and between recycled and retrieved states for the wing component.