Reduced functional loads alter the physical characteristics of the bone-periodontal ligament-cementum complex
Reduced functional loads alter the physical characteristics of the bone-periodontal ligament-cementum complex
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DOI：
10.1111/j.1600-0765.2011.01396.x
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发表时间：
2011-12-01
影响因子：
3.5
通讯作者：
Ho, S. P.
中科院分区：
文献类型：
--
作者：
Niver, E. L.;Leong, N.;Ho, S. P.
背景与目的：利用小型动物模型，如啮齿动物，通过改变功能负荷的大小来确定骨-牙周韧带-牙齿复合物的适应性特性。据报道，由于较软的饮食而导致的较低负荷的适应性反应包括肌肉发育减少，头盖骨结构-功能关系改变，牙周韧带间隙变窄，皮质骨和牙槽颌骨的矿物质水平以及牙槽骨的糖胺聚糖水平发生变化。然而，到目前为止，动态骨-牙周韧带-骨质复合体对长时间减少负荷的适应性作用尚未得到充分解释，特别是关于骨、牙周韧带和骨质的同时适应。因此，本研究采用大鼠模型，研究了减少功能负荷对骨-牙周韧带-牙骨质复合体的形态、力学性能和矿物特征等物理特性的时间影响。材料与方法：两组6周龄雄性Sprague-Dawley大鼠分别饲喂硬度范围为127 ~ 158 N/mm的硬颗粒和0.3 ~ 0.5 N/mm的软粉状的营养相同的食物。通过以下变化来确定骨-牙周韧带-骨质复合体的时空适应性：(i)牙周韧带胶原取向和双折射（偏振光显微镜），骨和骨质适应（组织化学），骨和骨质形态（微x射线计算机断层扫描）；（ii）牙周韧带-牙骨质和牙周韧带-骨界面的x射线衰减矿物剖面；（iii）在6、8、12和15周时通过微压痕测定标本的骨和骨质显微硬度。结果：随着时间的延长，功能负荷的减少导致以下适应：(1)牙周韧带取向改变，牙周韧带胶原双折射降低，表明牙周韧带更新率降低，牙根骨质吸收减少；（ii）由于矿物质的差异，牙周韧带-骨和牙周韧带-牙骨质界面的x射线衰减逐渐增加，两组之间的梯度没有显著差异；（iii）与高负荷组相比，15周时牙槽骨（0.93 +/- 0.16 GPa）和牙骨质（0.803 +/- 0.13 GPa）的显微硬度显著（p < 0.05）降低（分别为1.10 +/- 0.17和0.940 +/- 0.15 GPa），表明负荷对骨和牙骨质局部矿化的时间效应。结论：长期减少功能负荷对骨-牙周韧带-牙骨质复合体局部承载部位的形态、力学性能和矿物变化有不同的影响。这些观察到的局部变化反过来可以帮助解释牙骨关节的整体生物力学功能和适应性。从临床翻译的角度来看，我们的研究提供了对牙周病和/或正畸和修复治疗期间改善牙齿功能的负载调节的见解。
Background and Objective: Adaptive properties of the bone-periodontal ligament-tooth complex have been identified by changing the magnitude of functional loads using small-scale animal models, such as rodents. Reported adaptive responses as a result of lower loads due to softer diet include decreased muscle development, change in structure-function relationship of the cranium, narrowed periodontal ligament space, and changes in the mineral level of the cortical bone and alveolar jaw bone and in the glycosaminoglycans of the alveolar bone. However, the adaptive role of the dynamic bone-periodontal ligament-cementum complex to prolonged reduced loads has not been fully explained to date, especially with regard to concurrent adaptations of bone, periodontal ligament and cementum. Therefore, in the present study, using a rat model, the temporal effect of reduced functional loads on physical characteristics, such as morphology and mechanical properties and the mineral profiles of the bone-periodontal ligament-cementum complex was investigated.Material and Methods: Two groups of 6-wk-old male Sprague-Dawley rats were fed nutritionally identical food with a stiffness range of 127-158 N/mm for hard pellet or 0.3-0.5 N/mm for soft powder forms. Spatio-temporal adaptation of the bone-periodontal ligament-cementum complex was identified by mapping changes in the following: (i) periodontal ligament collagen orientation and birefringence using polarized light microscopy, bone and cementum adaptation using histochemistry, and bone and cementum morphology using micro-X-ray computed tomography; (ii) mineral profiles of the periodontal ligament-cementum and periodontal ligament-bone interfaces by X-ray attenuation; and (iii) microhardness of bone and cementum by microindentation of specimens at ages 6, 8, 12 and 15 wk.Results: Reduced functional loads over prolonged time resulted in the following adaptations: (i) altered periodontal ligament orientation and decreased periodontal ligament collagen birefringence, indicating decreased periodontal ligament turnover rate and decreased apical cementum resorption; (ii) a gradual increase in X-ray attenuation, owing to mineral differences, at the periodontal ligament-bone and periodontal ligament-cementum interfaces, without significant differences in the gradients for either group; (iii) significantly (p < 0.05) lower microhardness of alveolar bone (0.93 +/- 0.16 GPa) and secondary cementum (0.803 +/- 0.13 GPa) compared with the higher load group insert bone - (1.10 +/- 0.17 and cementum = 0.940 +/- 0.15 GPa, respectively) at 15 wk, indicating a temporal effect of loads on the local mineralization of bone and cementum.Conclusion: Based on the results from this study, the effect of reduced functional loads for a prolonged time could differentially affect morphology, mechanical properties and mineral variations of the local load-bearing sites in the bone-periodontal ligament-cementum complex. These observed local changes in turn could help to explain the overall biomechanical function and adaptations of the tooth-bone joint. From a clinical translation perspective, our study provides an insight into modulation of load on the complex for improved tooth function during periodontal disease and/or orthodontic and prosthodontic treatments.