Salmória Karine Kimak, Tanaka Orlando Motohiro, Guariza-Filho Odilon, Camargo Elisa Souza, de Souza Leandro Teixeira, Maruo Hiroshi
Graduate Dentistry Program in Orthodontics, Pontifical Catholic University of Paraná, Curitiba, Brazil.
Am J Orthod Dentofacial Orthop. 2008 Jun;133(6):790.e15-22. doi: 10.1016/j.ajodo.2007.12.020.
The objectives of this study were to evaluate insertional torque of mini-implants (MI) for orthodontic anchorage, to compare their axial pull-out strength at 0 (T0), 15 (T15), and 60 (T60) days after placement, to determine initial and peri-implant cortical bone thickness, and to analyze the correlations among these variables.
Sixty MI were placed in the mandibles of 10 dogs. Peak insertional torque values were recorded, and, after the animals were killed, specimens were prepared. The MI were aligned with a testing machine to register axial pull-out strength. Cortical bone thickness was measured after removal of the MI. Statistical analyses were conducted with ANOVA and Tukey HSD tests.
Pull-out strength and peri-implant cortical bone thickness had differences (P <0.01) at the various times. The T0 value showed the highest pull-out strength, and the smallest peri-implant cortical bone thickness was at T60. There was a regular correlation between pull-out strength and peri-implant cortical bone thickness at T0 (r = 0.44, P = 0.05). There was no correlation between insertional torque and pull-out strength, and insertional torque and initial cortical bone thickness.
Pull-out strength is greater immediately after placement of MI, cortical bone thickness decreases because of bone resorption, and insertional torque is not an efficient method for predicting the retention of MI.
本研究的目的是评估用于正畸支抗的微型种植体（MI）的植入扭矩，比较其在植入后0天（T0）、15天（T15）和60天（T60）时的轴向拔出力，确定种植体初始及种植体周围皮质骨厚度，并分析这些变量之间的相关性。
将60枚微型种植体植入10只犬的下颌骨。记录峰值植入扭矩值，在处死动物后制备标本。将微型种植体与测试机对齐以记录轴向拔出力。去除微型种植体后测量皮质骨厚度。采用方差分析和Tukey HSD检验进行统计分析。
在不同时间点，拔出力和种植体周围皮质骨厚度存在差异（P<0.01）。T0值显示拔出力最高，种植体周围皮质骨厚度最小的是在T60。在T0时，拔出力与种植体周围皮质骨厚度之间存在显著相关性（r = 0.44，P = 0.05）。植入扭矩与拔出力之间以及植入扭矩与初始皮质骨厚度之间均无相关性。
微型种植体植入后即刻拔出力更大，由于骨吸收皮质骨厚度减小，植入扭矩不是预测微型种植体固位力的有效方法。
