骨陶瓷修复牙槽嵴缺损对正畸牙槽骨改建和牙根吸收机制的动态实验研究

Alveolar ridge defect is an inevitable phenomenon after tooth extraction. After removal of tooth, alveolar bone continues to resorb and reduce its width and height at the extraction site and eventually becomes a dense region primarily consisting of cortical bone. In patients who need orthodontic treatment, moving teeth in this alveolar defect often causes orthodontically induced root resorption (OIRR) , gingival recessions and traumatic injuries.For patients with cleft lip and palate, this alveolar ridge defect also impedes tooth eruption, delays orthodontic tooth movement, and prolongs treatment time.. Therefore, how to prevent alveolar ridge resorption and move the tooth safely becomes more and more popular in the esthetic dentistry..Nowadays, the main technique of alveolar ridge preservation is to place the bone graft or bone substitute into the extraction site. The bone graft includes autogenous bone, alloplast, biomembrane, etc, which all have their own disadvantages in the clinical use, and are not completely satisfied by the doctors. Hydroxyapatite/ Beta-tricalcium phosphate(Bone ceramic) is one of the lately developed alloplast with the characteristic of biocompatible, bioactive and bioguided. However, whether it has the potential of bone-guide and the tooth moves in the alveolar ridge augmented with Bone ceramic are still unknown.. Histology are the conventional approaches to investigate the morphology of alveolar bone, but these are invasive approaches which can not observe the real-time 3D trabecular structure properties. Now it is resolved by high-resolution Micro-CT. With its high resolution and non-invasion, Micro-CT is preferred by more and more researchers to observe 3D trabecular structure. However, there are few studies to investigate the tooth root surface and alveolar trabecular bone structure during tooth movement.. Bone strength is not only affected by bone structure such as bone microstructure, bone turnover rate, microdamage and mineralization, etc, but also the biomechanical properties of the bone. Most researches focused on bone density and structure on the bone strength, however, fewer people investigated biomechanical properties of the bone. Nanoindentation testing has become a popular technique for mechanical testing of mineralized biological tissues. Due to the small volume of material sampled for each indentation test, the technique is well suited to examination of local mechanical properties in inhomogeneous biological tissues such as alveolar bone. However, fewer studies investigated the nanoindentation on the changes of the alveolar bone biomechanical properties during tooth movement.. The aim of this research is to evaluate tooth movement rate, the changes of bone structure and mechanical properties and root resorption after placing Bone ceramic and deproteinized bovine bone mineral into the alveolar ridge defect.

新型生物材料骨陶瓷修复牙槽嵴缺损后，牙齿在其中的移动速率，牙槽骨微结构性能变化，牙根吸收的发生机制还不明确。在完成了大鼠正畸牙齿移动和牙根吸收发生机制的Micro-CT动态观察研究基础上，本研究拟在5周龄SD大鼠上颌骨制造牙槽嵴缺损，应用骨陶瓷填埋修复缺损30天后，在邻近骨缺损的第二磨牙加载10g力近中移动。使用活体Micro-CT分别于加力后第0,7,14,21,28天扫描上颌骨，动态测量牙齿移动速率，骨小梁结构参数，牙根吸收体积。同时，牙槽嵴缺损处做纳米压痕测试、三维有限元分析和免疫组化观察。目的是发现骨陶瓷修复牙槽嵴缺后，牙齿移动，牙槽骨微结构性能变化和牙根吸收的机制，为今后应用新型生物材料骨陶瓷修复牙槽嵴缺损和正畸治疗打下实验基础。

研究背景：新型骨充填材料骨陶瓷修复牙槽嵴缺损后，牙齿在骨充填材料中的移动方式，牙槽骨微结构和生物力学性能变化，牙根吸收的发生机制还不明确。.主要研究内容：本研究在5周龄SD大鼠上颌骨制造牙槽嵴缺损，应用骨陶瓷和Bio-Oss骨粉填埋修复缺损30天后，在邻近骨缺损的第二磨牙加载10g力近中移动。使用活体Micro-CT分别于加力不同时间点扫描上颌骨，动态测量牙齿移动方式，骨小梁结构参数，牙根吸收体积。利用三维有限元建模分析牙根表面，牙根周围骨松质，骨密质受力状况，同时，在牙槽嵴缺损处进行纳米压痕测试，H&E和免疫组化观察。.重要结果：研究结果发现，1、牙齿移动距离中骨陶瓷组最小；2、牙齿倾斜度对照组最大（8.13±2.7），Bio-Oss组居中（6.31±2.2），骨陶瓷组最小（5.12±2.1）；3、骨陶瓷组磨牙近中根近中面骨密度和骨硬度最高；4、所有磨牙牙根在正畸加力过程中都发生了牙根吸收，H&E染色发现骨陶瓷组牙根吸收主要位于远中根的远中面，牙根吸收陷窝较小而表浅，TRAP染色未发现破骨细胞出现；5、三维有限元分析发现骨陶瓷组牙根近远中面受力均匀，未见明显应力集中区。.科学意义：本课题揭示了牙齿在骨充填材料中移动的基本规律，牙槽骨动态改建特点和牙根吸收的发生机制。研究结果表明，骨陶瓷作为一种新型的骨修复材料，修复局部骨缺损后，不会阻挡正畸牙齿移动，牙齿移动速度虽然减慢，但移动方式倾向于整体水平移动，牙根吸收尚不明显，骨陶瓷可作为牙槽骨缺损后较理想的骨修复材料，牙齿移动安全，有效。