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驱动的正畸金属丝，并将这种新金属丝应用于有效的牙齿运动。正畸牙齿的运动是由牙周韧带（PDL）受压侧的骨吸收和PDL拉伸侧的骨形成耦合产生的，这是治疗性机械应力的结果。由于正畸治疗通常需要很长一段时间，因此龋齿、牙周病和延长治疗时间的风险对患者来说是负担。此外，据报道，总处理时间被证明与根吸收高度相关。因此，在正畸治疗过程中加速牙槽骨重塑，以缩短治疗成功所需的时间是非常重要的。一些研究表明，振动的机械刺激加速了牙齿运动的速度。另一方面，形状记忆合金独特的形状记忆和超弹性特性使其成为非常有用的生物材料。超弹性是一种应力值在钢丝变形的某一点之前保持相当恒定的现象。同时，当变形丝反弹时，应力值保持相当恒定，这一特性对正畸牙齿的运动非常有利，SMA丝因此在正畸治疗中得到了广泛的应用。本研究开发了一种具有生物相容性的钛-铌-铝（Ti-24Nb-3Al） SMA丝，并将其与钴基铁磁性SMA结合。因此，我们研制了一种磁驱动正畸丝，并使用这种磁驱动正畸丝对Wistar-strain大鼠（6周龄）上颌第一磨牙进行正畸腭部运动。每天通过无线改变磁场施加十分钟的振动。结果表明，振动加速了正畸牙的运动。

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.