Biomechanical and histological behavior of Zr₇₀Ni₁₆Cu₆Al₈ bulk glassy alloy miniscrew implant in rat tibia

Objectives: Recently, a new composition Zr-based bulk metallic glasses have been developed for use as biomaterials. The purpose of this study is to clarify a hypothesis that Zr₇₀Ni₁₆Cu₆Al₈ bulk glassy alloy miniscrew implants may have significant effects on bone surrounding the miniscrew implants in comparison with pure titanium miniscrew implants by animal experiment.
Methods: Thirty-six 12-week-old male Wistar rats were used. Pure titanium and Zr₇₀Ni₁₆Cu₆Al₈ bulk glassy alloy miniscrew implants were inserted in the rat tibia. The experiments were performed measurement of the mobility of the miniscrew implants using Periotest, placement and removal torque test, and histological observation using Villanueva bone stain. From the specimens of each group, Bone-to-Implant Contact (BIC) and Bone Area (BA) were measured. Furthermore, the effect of immediate loading on the bone surrounding a miniscrew implant was evaluated. The significance of differences among mean values for groups was tested by ANOVA and Tukey’s multiple-comparison tests.
Results: At 7 days and 28 days after insertion, the periotest value of the Zr₇₀Ni₁₆Cu₆Al₈ bulk glassy alloy miniscrew implants decreased remarkably in comparison with the pure Ti miniscrew implants. The removal torque value of the Zr₇₀Ni₁₆Cu₆Al₈ bulk glassy alloy miniscrew implants were significantly higher than that of the pure Ti miniscrew implants. In histomorphometric evaluation, remarkable new bone formation could be confirmed for the group with the Zr₇₀Ni₁₆Cu₆Al₈ bulk glassy alloy miniscrew implants. BIC and BA value of the Zr₇₀Ni₁₆Cu₆Al₈ bulk glassy alloy miniscrew implants were significantly higher than that of the pure Ti miniscrew implants. Furthermore, these values for loaded with 10 g were significantly higher than for the unloaded group.
Conclusions: These results suggested that Zr₇₀Ni₁₆Cu₆Al₈ bulk glassy alloy miniscrew implants significantly enhanced osseointegration and immediate load was effective for the stability of miniscrew implants.