Department of Orthodontics, University Clinic of Düsseldorf, Germany.
Department of Oral Surgery, University Clinic of Düsseldorf, Germany.
Eur J Orthod. 2021 Dec 1;43(6):708-717. doi: 10.1093/ejo/cjab065.
Orthodontic implant migration has been clinically observed in presence of continuous loading forces. Recent studies indicate that osteocytes play a crucial role in this phenomenon.
Aim of this study was to investigate local osteocytic gene expression, protein expression, and bone micro-structure in peri-implant regions of pressure and tension.
The present work reports a complementary analysis to a previous micro-computed tomography study. Two customized mini-implants were placed in one caudal rat vertebra and connected by a nickel-titanium contraction spring generating different forces (i.e. 0, 0.5, 1.0, and 1.5 N). Either at 2 or 8 weeks, the vertebrae were harvested and utilized for 1. osteocytic gene expression using laser capture micro-dissection on frozen sections coupled with qPCR, 2. haematoxylin-eosin staining for qualitative and quantitative analyses, 3. immunofluorescence staining and analysis, and 4. bone-to-implant contact on undecalcified samples.
At the two time points for all the performed analyses no significant differences were observed with respect to the applied force magnitudes and cell harvesting localization. However, descriptive histological analysis revealed remarkable bone remodelling at 2 weeks of loading. At 8 weeks the implants were osseointegrated and, especially in 1.0 and 1.5 N groups, newly formed bone presented a characteristic load bearing architecture with trabecula oriented in the direction of the loading.
The present study confirmed that stress-induced bone remodelling is the biological mechanism of orthodontic implant migration. Bone apposition was found at 'tension' and 'pressure' sites thus limiting implant migration over time.
在持续加载力的作用下，临床上已经观察到正畸种植体迁移。最近的研究表明，骨细胞在这一现象中起着至关重要的作用。
本研究旨在探讨压力和张力种植体周围区域骨细胞的基因表达、蛋白表达和骨微结构。
本工作报道了对以前的微 CT 研究的补充分析。两个定制的微型植入物被放置在一个尾骨的大鼠椎骨中，并通过镍钛收缩弹簧连接，产生不同的力（即 0、0.5、1.0 和 1.5 N）。在 2 或 8 周时，收获椎骨并用于 1. 利用冷冻切片上的激光捕获微切割进行骨细胞基因表达的 qPCR，2. 进行苏木精-伊红染色进行定性和定量分析，3. 免疫荧光染色和分析，4. 对未脱钙样本进行骨-种植体接触分析。
在所有进行的分析中，在两个时间点上，对于施加的力大小和细胞采集定位，都没有观察到显著差异。然而，描述性组织学分析显示，在加载 2 周时出现了显著的骨重塑。在 8 周时，植入物已骨整合，特别是在 1.0 和 1.5 N 组中，新形成的骨呈现出具有在加载方向上定向的小梁的特征性承重结构。
本研究证实，应力诱导的骨重塑是正畸种植体迁移的生物学机制。在“张力”和“压力”部位发现了骨沉积，从而限制了植入物随时间的迁移。
