The periodontal ligament (PDL) is a highly heterogeneous fibrous connective tissue and plays a critical role in distributing occlusal forces and regulating tissue remodeling. Its mechanical properties are largely determined by the extracellular matrix, comprising a collagenous fiber network interacting with the capillary system as well as interstitial fluid containing proteoglycans. While the phase-contrast micro-CT technique has portrayed the 3D microscopic heterogeneity of PDL, the topological parameters of its network, which is crucial to understanding the multiscale constitutive behavior of this tissue, has not been characterized quantitatively. This study aimed to provide new understanding of such microscopic heterogeneity of the PDL with quantifications at both tissue and collagen network levels in a spatial manner, by combining phase-contrast micro-CT imaging and a purpose-built image processing algorithm for fiber analysis. Both variations within a PDL and among the PDL with different shapes, i.e. round-shaped and kidney-shaped PDLs, are described in terms of tissue thickness, fiber distribution, local fiber densities, and fiber orientation (namely azimuthal and elevation angles). Furthermore, the tissue and collagen fiber network responses to mechanical loading were evaluated in a similar manner. A 3D helical alignment pattern was observed in the fiber network, which appears to regulate and adapt a screw-like tooth motion under occlusion. The microstructural heterogeneity quantified here allows development of sample-specific constitutive models to characterize the PDL’s functional and pathological loading responses, thereby providing a new multiscale framework for advancing our knowledge of this complex limited mobility soft-hard tissue interface.

牙周韧带 (PDL) 是一种高度异质的纤维结缔组织，在分配咬合力和调节组织重塑方面发挥着关键作用。其机械性能主要由细胞外基质决定，包括与毛细血管系统相互作用的胶原纤维网络以及含有蛋白聚糖的间质液。虽然相衬显微 CT 技术描绘了 PDL 的 3D 微观异质性，但其网络的拓扑参数对于理解该组织的多尺度本构行为至关重要，但尚未定量表征。本研究旨在通过以空间方式在组织和胶原网络水平上进行量化，提供对 PDL 的这种微观异质性的新理解，通过将相衬显微 CT 成像和用于纤维分析的专用图像处理算法相结合。在组织厚度、纤维分布、局部纤维密度和纤维取向（即方位角和仰角）方面描述了 PDL 内和具有不同形状的 PDL 之间的两种变化，即圆形和肾形 PDL。此外，以类似的方式评估了组织和胶原纤维网络对机械负荷的反应。在纤维网络中观察到 3D 螺旋对齐模式，这似乎可以调节和适应咬合下的螺旋状牙齿运动。此处量化的微观结构异质性允许开发特定于样本的本构模型来表征 PDL 的功能和病理负荷反应，