Sawicka Monika, Bedini Rossella, Wierzbicki Piotr M, Pameijer Cornelis H
Department of Orthodontics, Medical University of Gdansk, Gdansk, Poland.
Folia Histochem Cytobiol. 2014;52(4):289-96. doi: 10.5603/FHC.a2014.0037. Epub 2014 Dec 22.
Root resorption is an undesirable but very frequently occurring sequel of orthodontic treatment. The aim of this study was to compare root resorption caused by either continuous (CF) or interrupted (IF) orthodontic force.
The study was performed on human subjects on 30 first upper and lower premolars scheduled for extraction for orthodontic reasons. During four weeks before extraction 12 teeth were subjected to either CF or IF. The force was generated by a segmental titanium-molybdenum alloy cantilever spring that was activated in buccal direction. Initially a force of 60 CentiNewton was used in both CF and IF groups, the force in the former, however, was reactivated every week for 4 weeks. There was no reactivation of force in the IF group after initial application. A morphometric analysis of root resorption was performed by microcomputed tomography and the extent of tooth movement was measured on stone casts. Furthermore, a Tartarate-Resistant Acidic Phosphatase activity (TRAP), the marker enzyme of osteoclasts and cementoclasts, was determined by histochemical method. The Mann-Whitney U test was used to compare the difference in measured parameters between treatment and control tooth groups.
The number of resorption craters was significantly higher and their average volume almost twice as large in the CF compared to the IF group (p < 0.05). However, the distance of tooth displacement was similar for both groups. Cementoclasts were detected with the TRAP technique on the surface of two teeth only; both were subjected to continuous force.
The use of IF leads to less destruction of root structure as opposed to continuous force while the same tooth movement was achieved.
牙根吸收是正畸治疗中一种不良但非常常见的后遗症。本研究的目的是比较持续（CF）或间歇（IF）正畸力引起的牙根吸收情况。
本研究对30颗因正畸原因计划拔除的上下颌第一前磨牙的人类受试者进行。在拔牙前四周，12颗牙齿分别接受CF或IF处理。力由分段钛钼合金悬臂弹簧产生，该弹簧向颊侧激活。最初，CF组和IF组均使用60厘牛顿的力，然而，CF组的力每周重新激活一次，持续4周。IF组在初始施加力后不再重新激活。通过微型计算机断层扫描对牙根吸收进行形态计量分析，并在石膏模型上测量牙齿移动的程度。此外，通过组织化学方法测定抗酒石酸酸性磷酸酶活性（TRAP），这是破骨细胞和成牙骨质细胞的标记酶。采用曼-惠特尼U检验比较治疗组和对照组牙齿测量参数的差异。
与IF组相比，CF组的吸收坑数量显著更多，其平均体积几乎是IF组的两倍（p < 0.05）。然而，两组的牙齿位移距离相似。仅在两颗牙齿的表面用TRAP技术检测到了破牙骨质细胞；这两颗牙齿均受到持续力作用。
与持续力相反，使用IF在实现相同牙齿移动的同时，对牙根结构的破坏更少。
