Improvement of osseointegration of Ti–6Al–4V ELI alloy orthodontic mini-screws through anodization, cyclic pre-calcification, and heat treatments

Abstract

Background Mini-screws are widely used as temporary anchorages in orthodontic treatment, but have the disadvantage of showing a high failure rate of about 10%. Therefore, orthodontic mini-screws should have high biocompatibility and retention. Previous studies have demonstrated that the retention of mini-screws can be improved by imparting bioactivity to the surface. The method for imparting bioactivity proposed in this paper is to sequentially perform anodization, periodic pre-calcification, and heat treatments with a Ti–6Al–4V ELI alloy mini-screw. Materials and methods A TiO2 nanotube-structured layer was formed on the surface of the Ti–6Al–4V ELI alloy mini-screw through anodization in which a voltage of 20 V was applied to a glycerol solution containing 20 wt% H2O and 1.4 wt% NH4F for 60 min. Fine granular calcium phosphate precipitates of HA and octacalcium phosphate were generated as clusters on the surface through the cyclic pre-calcification and heat treatments. The cyclic pre-calcification treatment is a process of immersion in a 0.05 M NaH2PO4 solution and a saturated Ca(OH)2 solution at 90 °C for 1 min each. Results It was confirmed that the densely structured protrusions were precipitated, and Ca and P concentrations, which bind and concentrate endogenous bone morphogenetic proteins, increased on the surface after simulated body fluid (SBF) immersion test. In addition, the removal torque of the mini-screw fixed into rabbit tibias for 4 weeks was measured to be 8.70 ± 2.60 N cm. Conclusions A noteworthy point in this paper is that the Ca and P concentrations, which provide a scaffold suitable for endogenous bone formation, further increased over time after SBF immersion of the APH group specimens. The other point is that our mini-screws have a significantly higher removal torque compared to untreated mini-screws. These results represent that the mini-screw proposed in this paper can be used as a mini-screw for orthodontics.

Surface Treatment of Dental Mini-Sized Implants and Screws: A Systematic Review with Meta-Analysis

“…In order to assess the effect of the surface treatments, follow-up times ranged from 12 h 20 to 10 [ 28 ] and 12 weeks [ 29 ]. The in vitro studies were published between 2010 [ 30 ] and 2023 [ 31 , 32 , 33 , 34 ]. Table 2 presents the characteristics and results of the in vitro studies.…”

Enhancement of bioactivity and osseointegration in Ti-6Al-4V orthodontic mini-screws coated with calcium phosphate on the TiO2 nanotube layer

“…The new bones were connected in the direction of the basal bone, confirming that osseointegration had increased. 31 Osseous tissue materials were also attached to the surface of the mini-screws after the removal torque was measured, which is considered to be the result of stronger bonding of the new bone to the surface of the mini-screws.…”

Evaluation of osseointegration of Ti-6Al-4V alloy orthodontic mini-screws with ibandronate-loaded TiO₂ nanotube layer

“…As these mini-screws made it easier to adjust the anchorage, they are widely used in the process of orthodontic treatment 5,6) . Titanium 6Aluminum 4Vanadium (Ti-6Al-4V) alloy has been widely used as a material for orthodontic miniscrews with its excellent biocompatibility, chemical stability, and mechanical properties 7,8) . However, a nonreactive rutile oxide layer is formed on the surface of a titanium implant manufactured through the process of implant processing, cleaning, and sterilization 9) .…”