The periodontal ligament (PDL) plays a critical role in providing immediate response to abrupt high loads during mastication while also facilitating slow remodeling of the alveolar bone. The PDL exceptional functionality is permitted by the unique nonuniform structure of the tissue. Two distinct areas that are critical to PDL function were previously identified: the furcation and the dense collar. Despite their hypothesized functions in tooth movement and maintenance, these 2 regions have not yet been compared within the context of their native environment. Therefore, the objective of this study is to elucidate the extracellular matrix (ECM) structure, composition, and biomechanical function of the furcation and the collar regions while maintaining the 3-dimensional (3D) structure in the murine PDL. We identify significant difference between the collar and furcation regions in both structure and mechanical properties. Specifically, we observed unique longitudinal structures in the dense collar that correlate with type VI collagen and LOX, both of which are associated with increased type I collagen density and tissue stiffness and are therefore proposed to function as scaffolds for tooth stabilization. We also found that the collar region is stiffer than the furcation region and therefore suggest that the dense collar acts as a suspense structure of the tooth within the bone during physiological loading. The furcation region of the PDL contained more proteins associated with reduced stiffness and higher tissue remodeling, as well as a dual mechanical behavior, suggesting a critical function in loads transfer and remodeling of the alveolar bone. In summary, this work unravels the nonuniform nature of the PDL within the 3D structural context and establishes understanding of regional PDL function, which opens new avenues for future studies of remodeling, regeneration, and disease.

The composition and structure of bones is important to the function of the periodontal ligament (PDL) in particular and to tooth movement overall. One bone crucial to the arrangement of teeth is the alveolar process, which connects teeth to the jawbone through intramembranous bone formation housing the cementum. Comprising of both cortical bone and cancellous bone, the alveolar process is unique in function as it is able to endure tension during mastication by working with the PDL Seeing that alveolar bone can endure tension and compression forces provokes question towards how the composition and structure influences this bone. Using immunohistochemistry (IHC) staining, collagen II, IX, and XI, have all been found in the alveolar bone; these are a set of tissue specific collagens that are found at low levels in intramembranous bone. Identifying this type of collagen in the alveolar bone is unusual as it is mainly found in cartilage and the vitreous humor in the eye. These observations will provide insights into the connection between collagen in the alveolar process and basic structure‐function relations of the tooth‐PDL‐bone system, while establishing a better understanding of tooth movement reactivity and the development of treatments to periodontal diseases. Support or Funding Information Harvard School of Dental Medicine AFM project