석회화 순환처리와 flute 형성이 Ti-6Al-4V 합금제 교정용 미니스크류의 생체활성도에 미치는 영향

다국어 초록 (Multilingual Abstract)

Objectives: The purpose of this study is to evaluate the effect of structural change and implementation of bioactivity to the surface of Ti-6Al-4V alloy orthodontic miniscrews through anodization and pre-calcification treatment.
Materials & Methods: Ti-6Al-4V ELI alloy rods were CNC-machined to fabricate orthodontic miniscrews with diameter of 1.4㎜ × 3.3㎜ in length. A spiral flute was designed to change the structure of the miniscrews. To create a large surface area for the macroscopic and microscopic attachment of bioactive materials, the surface of the orthodontic miniscrews were immersed in an aqueous electrolyte solution by adding 20wt% H2O and 1.5wt% NH4F to glycerol. Voltage of 20V with current density of 20 ㎃/㎠ was applied for 1 hour to form a nanotube TiO2 layer. Afterwards, to improve the bioactivity, miniscrews were immersed in 0.5 vol% silica aqueous solution at 37ºC for 5 minutes, and then cyclic pre-calcification treatment with 0.03M NH4H2PO4 and 0.01M Ca(OH)2 solution at 90 ºC was repeated for 20 times. And to evaluate the effect of the change in concentration of NH4H2PO4 solution on bioactivity, these processes were also repeated with 0.06M NH4H2PO4 solution. X-ray diffraction analysis was performed to investigate the crystalized precipitated material, and cytotoxicity test was performed to evaluate the biocompatibility of treated surface. In order to investigate the bioactivity, the presence or absence of hydroxyapatite precipitation was investigated in vitro. Also, to evaluate the effect of this bioactive surface treatment on retention of miniscrews in vivo, miniscrews with and without treatment or with and without spiral flute were implanted into rabbit’s tibia. Removal torque was measured after 4-week installation. The surface of removed miniscrews were examined with optical microscope and confocal laser scanning microscope.
Results: There were TiO2 nanotubes completely self-aligned and formed in a dense structure on the surface of the anodized miniscrew. A fine granular cluster layer of hydroxyapatite and octacalcium phosphate were formed on the surface of miniscrew subjected to pre-calcification treatment, and it was confirmed that the bioactivity was improved. The bioactivity was enhanced with higher NH4H2PO4 concentration. Removal torque and bone density in surface treated groups and groups with spiral flute increased when compared with the untreated group and groups without flute, resulting in improved initial stability. However, there was no significant change depending on the concentration of NH4H2PO4. According to the results of confocal laser scanning microscopic observation, new bone formed from the basal bone towards the surface of the miniscrew in untreated groups. However, in surface treated group, new bones formed from the surface of the miniscrew towards the basal bone, showing a directionality.
Conclusions: With spiral flute and cyclic pre-calcification treatment, bone adhesion to Ti-6Al-4V alloy orthodontic miniscrew surface and removal torque increased which will be advantageous in enhancing the stability of orthodontic miniscrews in orthodontic treatment.

목차 (Table of Contents)

• 그림목차 2
• 표목차 4
• 초록 5
• I. 서론 9
• II. 재료 및 방법 12
• III. 결과 20
• IV. 고찰 28
• V. 결론 36
• VI. 참고문헌 53