Korean J Dent Mater.  2021 Dec;48(4):245-254. 10.14815/kjdm.2021.48.4.245.

Effect of cyclic pre-calcification treatment on bioactivity of Ti-6Al-4V alloy orthodontic miniscrew

• Park JH
• Hwang JY
• Won EK
• Kim YW
• Yang KR
• Jeon WY
• Lee MH
• Bae TS

• KMID: 2524540
• DOI: http://doi.org/10.14815/kjdm.2021.48.4.245

Abstract

This study was performed to evaluate the effect of cyclic precalcification treatment on the improvement of bioactivity of Ti-6Al-4V mini-screws. The cutted plate-shaped specimens of 10 mm × 10 mm dimensions, and a mini-screw with a diameter of 1.6 mm × 6.0 mm in length were used. Anodic oxidation treatment was carried out in a glycerol electrolyte solution containing 20 wt% H₂O and 1.5 wt% NH 4F. Voltage of 20 V with current density of 20 mA/cm² was applied for 1 hour to form a nanotube TiO₂ layer. Afterwards, to improve the bioactivity, specimens were immersed in 0.5 vol% silica aqueous solution at 37 ℃ for 5 minutes, and then cyclic precalcification treatment with 0.05 M NH ₄H₂PO₄and 0.01 M Ca(OH)₂ solution at 90 ℃ was repeated with 20 times. Based on surface treatment the experimental groups were divided into three groups, namely untreated group (UT), anodized and heat-treated group (AH), and anodized, silica-treated, cyclic precalcified and heat-treated group (ASPH). There were TiO₂ nanotubes completely self-aligned and formed in a dense structure on the surface after anodic oxidation treatment. A fine granular cluster layer of hydroxyapatite and octacalcium phosphate were formed on the surface after the cyclic precalcification treatment. As a result of immersion test in the simulated body fluid (SBF), bioactivity was confirmed to be improved by the precipitation of protrusions appearing at the initial stage of formation of hydroxyapatite.

Keyword

Orthodontic mini-screw; Anodic oxidation; Cyclic precalcification; Bioactivity