中文摘要：

目的：研究持续或间断应力加载对正畸微种植体稳定性的影响。方法：将144枚微种植体植入36只Beagle犬两侧上颌骨第一磨牙和第二前磨牙根间区域,持续组（n=12）连续加载应力,间断A组（n=12）和B组（n=12）分别以12和24h为周期间断加载应力。术后1、3、5、7周处死,作显微CT和力学拉拔测试。结果：3组显微CT指标均随时间延长逐渐上升,而Fmax在第5周达峰值,第7周略有下降。在所有时间点,持续组的所有指标均低于两个间断组,且间断组A的各项指标均高于间断组B。结论：间断相比持续应力加载更有利于微种植体稳定性的获得,且12h的加载周期比24h更能促进骨-微种植体结合。

英文摘要：

Objective：To evaluate the influence of continuous or intermittent force on stability of titanium microscrews.Methods：144microscrews were inserted bilaterally in intraradicular zones of maxillary first molar and second premolar in 36 beagles.Loads were delivered consecutively in continuous group（n=12）,in cycles of 12on/paused for 12 hin intermittent group A（n=12）,and in cycles of 24on/paused for 24 hin intermittent group B（n=12）.The on/off cycles were repeated for 1,3,5or 7weeks,after which the animals were sacrificed,and microscopic computerized tomography（μCT）and pullout test were applied.Results：TheμCT parameters of microscrews in all three groups increased gradually with loading time.Fmax increased and reached a peak at week 5but dropped slightly at week 7.In continuous group,all measurements were lower than those in intermittent groups at all time points.All values in intermittent group A were higher than those in intermittent group B.Conclusion：An intermittent loading regimen appears to be more favorable for obtaining stability than continuous loading,and a 12h/12 h on/off loading cycle is superior to a 24h/24hon/off protocol in promoting bone-implant contact.