背景:牙槽骨牙骨质和牙槽骨之间的功能相互作用通过牙槽骨关节(DAJ)中独特定位的70-80µm宽的纤维和光滑韧带进行调节。在这项研究中,DAJ的结构和生物力学特性,牙周膜间隙(PDL空间也称为关节空间),牙槽骨,在空间和时间上都绘制了控制脂多糖(LPS)影响的DAJ生物力学的牙根牙骨质。
方法:20只大鼠的半上颌(6周龄时4只对照,4个对照和4个12周龄时受到LPS的影响,使用混合技术研究了4个对照和4个LPS在16周龄时受到影响);微X射线计算机断层扫描(5µm分辨率)与原位生物力学测试相结合。评估了骨和牙骨质体积分数的时间变化。另外六只SpragueDawley大鼠的矿物质并置率(MAR)趋势(3只对照,3LPS影响)通过将空间荧光染料信号转换为骨骼的功能生长速率(线性因子-RW)来揭示,牙本质,和牙骨质对来自100µm半上颌骨切片的荧光染料信号进行快速傅立叶变换。
结果:受LPS影响的DAJ生物力学的总体变化(6周时牙齿位移增加2.5-4.5倍,牙齿旋转增加2倍,在12周时,位移没有增加,旋转增加了7倍;相对于对照,骨有效应变在6周时增加了27%,在12周时增加了11%)与DAJ冠状区域的结构变化有关(从0到6周,PDL空间增加了15%,而从6到12周,与对照相比,PDL空间增加了5%)。观察到结扎的和年龄匹配的对照之间的PDL空间的显著增加(p<0.05)。在12周时结扎的骨分数明显低于其年龄匹配的对照组,6周时组间无显著性差异(p>0.05)。与对照组相比,根尖区域的牙骨质生长更快,但呈非线性增长(6周和12周时牙骨质分数(CF)分别增加11%和20%)。牙槽骨显示出特定部位的非线性生长,与牙本质相比,MAR总体增加(LPS治疗后108.5µm/周,至126.7µm/周)(对照与对照相比,28.3µm/周受LPS影响的26.1µm/周)和牙骨质(对照中的126.5µm/周与受LPS影响的119.9µm/周)。在6周龄时观察到结扎样本中CF的显著增加(p<0.05)。
结论:牙骨质和骨骼对机械化学刺激的解剖学特异性反应,通过改变牙齿移动,它们对观察到的PDL空间变化的集体时间贡献得以延续。数据通过牙骨质的非线性生长响应的优势突出了DAJ函数的“弹性”,PDL空间的变化,骨骼结构。尽管骨和牙骨质结构存在显著差异,数据提供了有关牙骨质作为重建DAJ功能能力的内置补偿机制的反动作用的见解。牙槽骨和牙骨质结构的空间变化,因此韧带空间,强调距离侮辱地点更远的适应,这也是这项研究的另一个新颖见解。这些适应在关节功能(生物力学)的背景下相关时表明,尽管是病态的,但它们确实是维持DAJ功能所必需的。
BACKGROUND: The functional interplay between cementum of the root and alveolar bone of the socket is tuned by a uniquely positioned 70-80 µm wide fibrous and lubricious ligament in a dentoalveolar joint (DAJ). In this study, structural and biomechanical properties of the DAJ, periodontal ligament space (PDL-space also known as the joint space), alveolar bone of the socket, and cementum of the tooth root that govern the biomechanics of a lipopolysaccharide (LPS)-affected DAJ were mapped both in space and time.
METHODS: The hemi-maxillae from 20 rats (4 control at 6 weeks of age, 4 control and 4 LPS-affected at 12 weeks of age, 4 control and 4 LPS-affected at 16 weeks of age) were investigated using a hybrid technique; micro-X-ray computed tomography (5 µm resolution) in combination with biomechanical testing in situ. Temporal variations in bone and cementum volume fractions were evaluated. Trends in mineral apposition rates (MAR) in additional six Sprague Dawley rats (3 controls, 3 LPS-affected) were revealed by transforming spatial fluorochrome signals to functional growth rates (linearity factor - RW) of bone, dentin, and cementum using a fast Fourier transform on fluorochrome signals from 100-µm hemi-maxillae sections.
RESULTS: An overall change in LPS-affected DAJ biomechanics (a 2.5-4.5X increase in tooth displacement and 2X tooth rotation at 6 weeks, no increase in displacement and a 7X increase in rotation at 12 weeks; 27% increase in bone effective strain at 6 weeks and 11% at 12 weeks relative to control) was associated with structural changes in the coronal regions of the DAJ (15% increase in PDL-space from 0 to 6 weeks but only 5% from 6 to 12 weeks compared to control). A significant increase (p < 0.05) in PDL-space between ligated and age-matched control was observed. The bone fraction of ligated at 12 weeks was significantly lower than its age-matched control, and no significant differences (p > 0.05) between groups were observed at 6 weeks. Cementum in the apical regions grew faster but nonlinearly (11% and 20% increase in cementum fraction (CF) at 6 and 12 weeks) compared to control. Alveolar bone revealed site-specific nonlinear growth with an overall increase in MAR (108.5 µm/week to 126.7 µm/week after LPS treatment) compared to dentin (28.3 µm/week in control vs. 26.1 µm/week in LPS-affected) and cementum (126.5 µm/week in control vs. 119.9 µm/week in LPS-affected). A significant increase in CF (p < 0.05) in ligated specimens was observed at 6 weeks of age.
CONCLUSIONS: Anatomy-specific responses of cementum and bone to the mechano-chemo stimuli, and their collective temporal contribution to observed changes in PDL-space were perpetuated by altered tooth movement. Data highlight the \"resilience\" of DAJ function through the predominance of nonlinear growth response of cementum, changes in PDL-space, and bone architecture. Despite the significant differences in bone and cementum architectures, data provided insights into the reactionary effects of cementum as a built-in compensatory mechanism to reestablish functional competence of the DAJ. The spatial shifts in architectures of alveolar bone and cementum, and consequently ligament space, highlight adaptations farther away from the site of insult, which also is another novel insight from this study. These adaptations when correlated within the context of joint function (biomechanics) illustrate that they are indeed necessary to sustain DAJ function albeit being pathological.