Mesial orthodontic movement of rat molars after extraction of the adjacent first molar and

本研究旨在开发一种可移动的超弹性镍钛（NiTi）合金封闭螺旋弹簧的新型正畸器械。采用雄性SD大鼠（5周龄）。上颌门牙被钉住并用作封闭线圈矫治器的锚固。同时拔除上颌第一磨牙。创面愈合间隔5天后，将激活闭合线圈矫治器置于固定门牙与第二磨牙之间。采用三种制备的镍钛封闭螺旋弹簧，在一定范围内产生10-40gf的力。我们首先通过将镍钛线圈弹簧放置在该位置4天至14天的不同时期来评估设备的保留性和耐用性。结果表明，在整个观察期间，大多数被调查的镍钛线圈弹簧在位置上保持激活状态，从而支持了该装置的实际用途。结合微焦x射线断层扫描（μCT）和3d重建技术对动物标本进行检查，证实第二和第三磨牙发生近中漂移，并伴有切颌前骨缝合处的力致变形。与此相关的是，在牙齿移位过程中，膈区牙槽骨的形成有了明显的进展，而体牙漂移并没有伴随任何明显的牙周韧带压迫或强直。我们还开发了实验模型，使用Alzet渗透泵在牙齿运动时全身输注双膦酸盐。组织学检查显示药物依赖性破骨细胞行为在其全身递送期间的局部变化。目前的正畸牙齿运动模型将有助于广泛研究牙齿位移在大小/时间特征下的动力学，例如，连续与间歇施加力。

The present study aimed to develop a new orthodontic apparatus integrating a removable super-elastic nickel-titanium (NiTi) alloy closed coil springs. Male SD rats (5 weeks old) were used. Maxillary incisors were pinned and utilized as anchorage for a closed-coil appliance. At the same time, upper first molars were extracted. After 5 days interval for wound healing, the activated closed-coil appliance was placed between the fixed incisor and the second molar. Three types of fabricated NiTi closed coil springs were used to generate certain ranges of force 10-40gf. We first assessed the retainability and durability of the apparatus by placing NiTi coil springs at the position for various periods ranging from 4 days to 14 days. The results supported the practical usefulness of the apparatus by showing that most of the NiTi coil springs under investigation remained activated at position throughout the observation periods. Examination of animal specimens in conjunction with microfocus x-ray tomography (μCT) and 3D-reconstruction technology validated that the second and third molars executed mesial drifts, accompanying the force-induced deformation at the incisal-premaxillary bony suture. It is pertinent that alveolar bone modeling in the intraseptal region progressed markedly during tooth displacement, whereas the bodily tooth drift did not accompany any marked compression of periodontal ligament or ankylosis. We also developed experimental models using an Alzet osmotic pump for systemic-infusion of bisphosphonate during tooth movement. Histologic examination revealed the local variation in agent-dependent osteoclastic cell behavior during its systemic delivery period. The present orthodontic tooth movement model will be useful in a wide range of investigation of the kinetics of tooth displacement under magnitude/temporal characteristics, e.g., continuous versus intermittent force application.