New Bioactive Glass Coating Process for Orthodontic Stainless Steel

Objectives: In this study, bioactive glass (BG) were deposited onto orthodontic stainless steel disks by an electrophoretic deposition (EPD) process, and the BG coating was characterized esthetically, morphologically, and compositionally. Additionally, the effects of the BG coating on the remineralization ability of etched dental enamel was investigated.

Methods: Mechanically polished stainless steel disk specimens were coated with BG particles using EPD process. Non-coated specimens served as the control. The BG coatings were characterized by spectrophotometry (UV-2600, Shimadzu) and scanning electron microscopy with energy dispersive X-ray spectrometry (SSX-550, Shimadzu). Embedded human enamel blocks were etched with phosphoric acid, fixed on a specimen stage with BG-coated specimens and then immersed in artificial saliva for 3 months. Nanoindentation testing of the enamel surfaces was conducted before and after etching and during the immersion (ENT-1100a, ELIONIX). Mean values for hardness and elastic modulus were compared using ANOVA and Tukey’s test, with P set at < 0.05 for statistical significance.

Results: The EPD process using alternating current produced higher values in both reflectance and lightness. Additionally, the BG coating was thinner than that prepared using direct current. All of the BG coatings displayed good interfacial adhesion, and Si and O were the major components. The hardness and elastic modulus of etched enamel specimens immersed with most BG-coated specimens recovered significantly with increasing immersion time compared with the non-coated specimen, and significant acid-neutralization was observed for the BG-coated specimens.

Conclusions: The surface modification technique using EPD and BG coating on orthodontic stainless steel may assist the development of new non-cytotoxic orthodontic metallic appliances having satisfactory appearance and remineralization ability.