Development of a magneto-driven orthodontic wire and its application for efficient tooth movement

本研究的目的是开发一种磁力驱动的正畸钢丝，并将其应用于有效的牙齿移动。正畸牙齿的移动是由于治疗性机械应力导致的牙周膜(PDL)压缩侧的骨吸收和PDL拉伸侧的骨形成的耦合而产生的。由于正畸治疗通常需要很长的时间，因此患龋齿、牙周病和延长治疗期对患者来说是一种负担。此外，据报道，总的治疗时间与牙根吸收高度相关。在这方面，在正畸治疗过程中加速牙槽骨改建，缩短成功治疗所需的时间是很重要的。一些研究表明，振动的机械刺激加快了牙齿的移动速度，另一方面，形状记忆和超弹性的独特性质使形状记忆合金(SMA)成为非常有用的生物材料。超弹性是一种现象，在这种现象中，应力值保持相当恒定，直到钢丝变形的某个点。同时，当变形的金属丝反弹时，应力值保持不变，这一特性非常有利于正畸牙齿的移动，因此SMA丝在正畸治疗中得到了广泛的应用。本研究开发了一种被认为是生物相容性的钛-铌-铝(Ti-24Nb-3Al)SMA丝，并将其与钴基铁磁性SMA相结合。因此，我们研制了一种新型的磁控正畸钢丝，并用该钢丝对Wistar大鼠(6周龄)的上颌第一磨牙进行了正畸腭部移动。通过无线改变磁场，每天振动10分钟。结果表明，振动加速了正畸牙的移动。

The aim of this study was to develop a magneto-driven orthodontic wire and to apply this new wire for efficient tooth movement Orthodontic tooth movement is generated by the coupling of bone resorption on the compressed side of the periodontal ligament (PDL) and by bone formation on the stretched side of the PDL as a consequence of therapeutic mechanical stress. Since orthodontic treatment usually takes place over a long period of time, the risk of caries, periodontal disease, and prolonged treatment period are burdensome for the patient. Furthermore, it has been reported that total treatment duration proves to be highly correlated with root resorption. In this respect, it is important to accelerate alveolar bone remodeling during orthodontic treatment, to shorten the time required for successful therapy. Some studies revealed that mechanical stimulation by vibration accelerated the speed of tooth movement.On the other hand, the unique properties of shape memory and superelasticity have made shape memory alloys (SMAs) very useful biomaterials. Superelasticity is a phenomenon in which the stress value remains fairly constant up to a certain point of wire deformation. At the same time, when the deformed wire rebounds, the stress value remains fairly constant The property is very advantageous for orthodontic tooth movement, and the SMA wires have thus been widely used in orthodontic treatment.In this study, a titanium-niobium-aluminum (Ti-24Nb-3Al) SMA wire, which was considered to be biocompatible as a nickel free wire, was developed, and combined with a cobalt-based ferromagnetic SMA. Thus, a magneto-driven orthodontic wire was newly developed, and orthodontic palatal movement of maxillary first molars in Wistar-strain rats (age; 6 weeks) was performed with this new wire. The vibration was applied for ten minutes everyday by a wirelessly changing the magnetic field. The results suggested that the vibration accelerated orthodontic tooth movement.