Kim Soojin, Herring Susan, Wang I-Chung, Alcalde Rafael, Mak Victor, Fu Isaac, Huang Greg
US Army, Seoul, Korea.
Am J Orthod Dentofacial Orthop. 2008 Feb;133(2):189.e1-9. doi: 10.1016/j.ajodo.2007.07.016.
In this study, we investigated orthodontic space closure of premolar extraction sites with miniplate anchorage compared with conventional tooth-borne anchorage in 8 adult beagle dogs.
A split-mouth design with all 4 quadrants was used. Four premolars were extracted to create adequate space for premolar retraction. Retraction was performed with nickel-titanium coil springs. In the control side, the premolars were retracted against other teeth, and, in the experimental side, the premolars were retracted against miniplates. Each quadrant received 2 additional bone screws as bone markers for cephalometric superimposition. Lateral cephalograms were taken at initial activation, 6 weeks, and 12 weeks. Three parameters were measured and evaluated: linear space closure, angular tipping, and amount of anchorage slippage.
Overall, the miniplates had a high success rate of 93.8% (15 of 16) during the 12-week period of orthodontic loading. Similar amounts of space closure were observed in the control and the experimental sites. A statistically significant difference was observed for the amounts of tipping and anchorage slippage of miniplates vs tooth-borne anchorage. In the maxilla, the mean miniplate tipping was 0.1 degrees , whereas mean tipping of the anchor teeth was 9 degrees (P = .01). In the mandible, the miniplates tipped an average of 3.4 degrees , whereas the mean tipping of the anchor teeth was 13.3 degrees (P = .02). In the maxilla, the miniplates had 1% anchorage loss, whereas the tooth anchors had 37.1% anchorage loss (P = .001). In the mandible, the miniplates had a mean anchorage loss of 4.5%, whereas the tooth anchors had a mean anchorage loss of 31.1% (P = .001).
Although the total amount of space closure was similar in both the control and the experimental groups, the mechanism of space closure was different. In the control group, slippage of the anchor teeth accounted for approximately a third of the space closure. In the experimental group, the miniplates had minimal movement, and space closure was achieved almost entirely by movement of the target teeth. These results confirm that miniplates provide virtually absolute anchorage.
在本研究中，我们在8只成年比格犬身上，研究了与传统牙支抗相比，使用微型钛板支抗关闭前磨牙拔除位点正畸间隙的情况。
采用全口四个象限的分口设计。拔除四颗前磨牙以创造足够的间隙用于前磨牙后移。使用镍钛螺旋弹簧进行后移。在对照侧，前磨牙相对于其他牙齿后移；在实验侧，前磨牙相对于微型钛板后移。每个象限额外植入两颗骨螺钉作为头颅侧位片重叠测量的骨标记物。在初始加力、6周和12周时拍摄头颅侧位片。测量并评估三个参数：线性间隙关闭、角度倾斜和支抗滑动量。
总体而言，在12周的正畸加载期内，微型钛板的成功率为93.8%（16个中有15个）。在对照位点和实验位点观察到相似的间隙关闭量。微型钛板与牙支抗的倾斜量和支抗滑动量存在统计学显著差异。在上颌，微型钛板的平均倾斜度为0.1度，而作为支抗的牙齿平均倾斜度为9度（P = 0.01）。在下颌，微型钛板平均倾斜3.4度，而作为支抗的牙齿平均倾斜度为13.3度（P = 0.02）。在上颌，微型钛板的支抗丧失为1%，而牙支抗的支抗丧失为37.1%（P = 0.001）。在下颌，微型钛板的平均支抗丧失为4.5%，而牙支抗的平均支抗丧失为31.1%（P = 0.001）。
尽管对照组和实验组的间隙关闭总量相似，但间隙关闭机制不同。在对照组中，支抗牙的滑动约占间隙关闭的三分之一。在实验组中，微型钛板移动极小，间隙关闭几乎完全通过目标牙的移动实现。这些结果证实微型钛板提供了几乎绝对的支抗。
