Mechanical properties and biocompatibility of a novel miniscrew made of Zr(70)Ni(16)Cu(6)Al(8) bulk metallic glass for orthodontic anchorage

The purpose of the present study was to fabricate a miniscrew possible for clinical application using Zr(70)Ni(16)Cu(6)Al(8) bulk metallic glass (BMG), which has high mechanical strength, low elastic modulus, and high biocompatibility. First, the elastic moduli of Zr-based metallic glass rods made of Zr(55)Ni(5)Cu(30)Al(10), Zr(60)Ni(10)Cu(20)Al(10), Zr(65)Ni(10)Cu(17.5)Al(7.5), Zr(68)Ni(12)Cu(12)Al(8), and Zr(70)Ni(16)Cu(6)Al(8) were measured. Zr(70)Ni(16)Cu(6)Al(8) had the lowest elastic modulus among them. Then, we fabricated Zr(70)Ni(16)Cu(6)Al(8) BMG miniscrews with diameters from 0.9 to 1.3 mm, conducted a torsion test, and implanted them into the alveolar bone of beagle dogs to compare insertion torque, removal torque, Periotest, new bone formation around the miniscrew, and failure rate compared with 1.3 mm diameter Ti-6Al-4 V miniscrew. The Zr(70)Ni(16)Cu(6)Al(8) BMG miniscrew exhibited a high torsion torque even if the miniscrew had a small diameter. Zr(70)Ni(16)Cu(6)Al(8) BMG miniscrews with a diameter of 1.1 mm or less had higher stability and lower failure rate than 1.3 mm diameter Ti-6Al-4 V miniscrews. Furthermore, the smaller diameter Zr(70)Ni(16)Cu(6)Al(8) BMG miniscrew was shown, for the first time, to have a higher success rate and to form more new bone around the miniscrew. These findings suggested the usefulness of our novel small miniscrew made of Zr(70)Ni(16)Cu(6)Al(8) BMG for orthodontic anchorage.