Gu G, Lemery S A, King G J
Department of Orthodontics, School of Dentistry, University of Washington, Seattle 98195-7446, USA.
Angle Orthod. 1999 Dec;69(6):515-22. doi: 10.1043/0003-3219(1999)069<0515:EOARAD>2.3.CO;2.
Clinical orthodontists frequently reactivate appliances following decay. Studies of tooth movement and tissue responses following reactivations indicate that linear tooth movement and rapid recruitment of osteoclasts can be achieved if reactivation is timed to coincide with the latter part of the bone remodeling cycle initiated by the first activation. Both can be delayed if reactivations are timed for the early part of the previous cycle. The objective of this study was to examine tooth movement, root resorption, and osteoclast recruitment following appliance reactivation after the first activation had decayed. Bilateral orthodontic appliances were activated with 40 cN in 144 rats to mesially tip the maxillary molars. After 16 days, rats were randomized into two groups of 72. In group 1, appliances were reactivated in precisely the same manner as the first activation. In group 2, appliances were sham-reactivated. Rats were sacrificed at 1, 3, 5, 7, 10, and 14 days. Orthodontic movement was measured cephalometrically; changes in osteoclasts and root resorption were assessed at both compression and tension sites histomorphometrically; tartrate-resistant acid phosphatase (TRAP) was measured in alveolar bone and serum biochemically. Orthodontic tooth movement was linear in group 1, but osteoclasts required 3 to 5 days to appear. There were no group- or time-related differences in root resorption. Bone TRAP levels were elevated in both groups but dropped significantly (p<0.01) in group 2 at day 7. Appliance reactivations that followed decay of the first activation produced efficient tooth movement without increased risk of root resorption, but these changes were not accompanied by rapid osteoclast recruitment at compression sites. Timing appliance reactivations for the latter portion of the previous bone remodeling cycle could have significant clinical advantages because the delay period seen in tooth movement following a single activation or short-term reactivation can be avoided.
临床正畸医生经常在牙齿龋坏后重新激活矫治器。对重新激活后牙齿移动和组织反应的研究表明，如果重新激活的时间与首次激活引发的骨重塑周期的后半部分相吻合，就可以实现线性牙齿移动和破骨细胞的快速募集。如果重新激活的时间定在前一个周期的早期，这两者都会延迟。本研究的目的是检查首次激活后矫治器龋坏时重新激活后的牙齿移动、牙根吸收和破骨细胞募集情况。在144只大鼠中，用40 cN激活双侧正畸矫治器，使上颌磨牙向近中倾斜。16天后，将大鼠随机分为两组，每组72只。在第1组中，矫治器以与首次激活完全相同的方式重新激活。在第2组中，矫治器进行假重新激活。在第1、3、5、7、10和14天处死大鼠。通过头影测量法测量正畸移动；通过组织形态计量学评估压缩和拉伸部位破骨细胞和牙根吸收的变化；通过生化方法测量牙槽骨和血清中的抗酒石酸酸性磷酸酶（TRAP）。第1组的正畸牙齿移动是线性的，但破骨细胞需要3至5天才能出现。牙根吸收在组间或时间上没有差异。两组的骨TRAP水平均升高，但第2组在第7天显著下降（p<0.01）。首次激活龋坏后重新激活矫治器可产生有效的牙齿移动，而不会增加牙根吸收的风险，但这些变化并未伴随着压缩部位破骨细胞的快速募集。将矫治器重新激活的时间定在前一个骨重塑周期的后半部分可能具有显著的临床优势，因为可以避免单次激活或短期重新激活后牙齿移动中出现的延迟期。
