Surface characteristics and mechanical behavior of retrieved orthodontic microimplants

Abstract

Objectives

To observe the surface characteristics and mechanical behavior of retrieved microimplants under clinically simulating experimental conditions and to investigate the feasibility of reuse of microimplants.

Materials and methods

The microimplants, inserted at different angles, were retrieved from the patients (RMIP) and the artificial bone (RMIA). Surface characteristics, including morphologic changes of tips and thread edges, length reduction, and surface compositional variation, were evaluated using a field emission scanning electron microscope, a stereoscopic microscope, and energy-dispersive X-ray spectroscopy, respectively. Mechanical behavior comprising maximum insertion torque (MIT) and insertion time was tested with the artificial bone under clinically simulating conditions.

Results

The tips and thread edges were worn out to various degrees in retrieved microimplants and thin deposits were observed on the surface in the RMIP group. Traces of foreign elements, such as iron, sulphur, and calcium, were detected on the surface of RMIP. Both MIT and insertion time of retrieved microimplants were increased compared to their initial use, and were much greater in RMIP. The increases of MIT were seen in all groups inserted at the insertion angle of 45° compared with 90°, although the differences were not statistically significant.

Conclusions

Retrieved microimplants exhibited different degrees of changes on surface characteristics and mechanical behavior, with more changes in RMIP. The reuse of microimplants for immediate relocation in the same patient may be acceptable; however, postponed relocation and allogeneic reuse of microimplants are not recommended in clinical practice.

中文概要

目的

在临床模拟试验条件下,观察正畸微小种植体临 床用后的表面特征与力学性能,探讨正畸微小种 植体再使用的可行性。

创新点

比较了两种回收来源的正畸微小种植体(临床用 后回收和植入人工骨后回收)的表面特征与力学 性能,同时还考虑了不同植入角度的影响。

方法

将符合纳入条件的临床用后正畸微小种植体回 收,另将新正畸种植体以不同角度植入临床模拟 条件下的人工骨并取出回收,分别比较了不同来 源正畸微小种植体的表面特征以及力学性能。使 用场发射扫描电镜、立体显微镜以及X 射线能谱 仪评估了正畸微小种植体尖端及螺纹的形态和 长度变化,以及表面元素变化等表面特征;并在 临床模拟试验条件下测试了最大植入扭矩和植 入时间等力学性能(图1)。

结论

不同回收来源的正畸微小种植体表现出表面特征 以及力学性能的不同变化。临床用后回收的正畸 微小种植体尖端及螺纹表现出更多的磨损,其表 面附着有一薄层沉积物,最大植入扭矩以及植入 时间增大明显。建议正畸微小种植体再使用时, 针对同一患者在某些临床条件下可考虑植入后 立即取出并以一定角度再植入,但是临床使用过 一段时间的正畸种植体尤其是微小种植体不建 议再次植入;针对不同患者,临床操作中不建议 微小种植体的再次使用。