The biomechanical characteristics of the bone-periodontal ligament-cementum complex

Abstract

The relative motion between the tooth and alveolar bone is facilitated by the soft-hard tissue interfaces which include periodontal ligament-bone (PDL-bone) and periodontal ligamentcementum (PDL-cementum). The soft-hard tissue interfaces are responsible for attachment and are critical to the overall biomechanical efficiency of the bone-tooth complex. In this study, the PDLbone and PDL-cementum attachment sites in human molars were investigated to identify the structural orientation and integration of the PDL with bone and cementum. These attachment sites were characterized from a combined materials and mechanics perspective and were related to macro-scale function.High resolution complimentary imaging techniques including atomic force microscopy, scanning electron microscopy and micro-scale X-ray computed tomography (Micro XCT™) illustrated two distinct orientations of PDL; circumferential-PDL (cir-PDL) and radial-PDL (rad-PDL). Within the PDL-space, the primary orientation of the ligament was radial (rad-PDL) as is well known. Interestingly, circumferential orientation of PDL continuous with rad-PDL was observed adjacent to alveolar bone and cementum. The integration of the cir-PDL was identified by 1 to 2 μm diameter PDL-inserts or Sharpey's fibers in alveolar bone and cementum. Chemically and biochemically the cir-PDL adjacent to bone and cementum was identified by relatively higher carbon and lower calcium including the localization of small leucine rich proteins responsible for maintaining soft-hard tissue cohesion, stiffness and hygroscopic nature of PDL-bone and PDLcementum attachment sites. The combined structural and chemical properties provided graded stiffness characteristics of PDL-bone (E r range for PDL: 10 -50 MPa; bone: 0.2 -9.6 GPa) and PDL-cementum (E r range for cementum: 1.1 -8.3 GPa), which was related to the macro-scale function of the bone-tooth complex.

Image-Based, Fiber Guiding Scaffolds: A Platform for Regenerating Tissue Interfaces

“…There are limited studies for multiple tissue regeneration and interfacial tissue integration for functional constructs of neogenic complexes such as ligament bone or cartilage bone. 5,6,25,44 In recent studies, multi-phasic scaffolds or physical gradient constructs have been investigated as vehicles for facilitating multiple tissue formation within a single system, 7,8 as well as bioactive molecule-induced tissue morphogenesis. 9 Various in vitro approaches emphasize the strong potential of geometric control for tissue regeneration and morphogenesis with diverse types of cells.…”

“…[10][11][12] A limited number of research studies report on the geometric influences on in vivo spatiotemporal tissue regeneration and orchestration, and, more specifically, functional recovery due to unpredictable and uncontrollable reorganization and rearrangement of regenerated tissues. 13,44 One of the most important requirements for a functional periodontal complex is the alignment of type-I collagen bundles/PDL fibers perpendicular to the tooth root surface. We previously developed an image-based, fiber-guiding scaffolding system, 36,37 which facilitated the formation of ligamentous tissue with a perpendicular/oblique orientation, compartmentalized bone, and ligament regeneration with functional tissue integration.…”

Fibromodulin and Biglycan Modulate Periodontium through TGFβ/BMP Signaling

“…PDL cells promote formation of an extracellular matrix (ECM), composed mainly of collagen fibrils (primarily type I) that insert into the surrounding hard tissues to suspend the tooth. The softer PDL absorbs functional loads by acting as a cushion between the 2 mineralized tissues, alveolar bone and tooth cementum (Ho et al, 2010;Marchesan et al, 2011). When mechanically loaded, the PDL behaves as a viscoelastic gel, orchestrated by a meshwork of cell-cell and cell-matrix interactions involving locally secreted growth factors.…”

Spatiotemporally Controlled Microchannels of Periodontal Mimic Scaffolds

“…However, it remains challenging to determine geometric influences and develop optimal microenvironments for (1) multitissue neogenesis, (2) tissue interface compartmentalization, and (3) polarization of connective tissue fibers at structural interfaces (Ho et al, 2010;Park et al, 2012;Vaquette et al, 2012;Jeon et al, 2014). Fiber-guiding scaffolds previously emphasized a topologic design of the PDL interface influences of the ligament orientation for bone-ligament complex regeneration compared to salt-leached, amorphous architectures, which facilitated limited multiple tissue regeneration without refunctionalizing (Park et al, 2012).…”