Journal
BIOMATERIALS
Volume 28, Issue 35, Pages 5238-5245Publisher
ELSEVIER SCI LTD
DOI: 10.1016/j.biomaterials.2007.08.031
Keywords
atomic force microscopy (AFM); interface; collagen fibers; periodontium; nanoindentation
Funding
- NIDCR NIH HHS [P01DE09859, P01 DE009859, T32 DE007306, K99 DE018212-01A1, T32DE07306, K99 DE018212, P01 DE009859-15, T32 DE007306-12, K99DE018212-01A1] Funding Source: Medline
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In this study, a comparison between structure, chemical composition and mechanical properties of collagen fibers at three regions within a human periodontium, has enabled us to define a novel tooth attachment mechanism. The three regions include, (1) the enthesis region: insertion site of periodontal ligament (PDL) fibers (collagen fibers) into cementum at the root surface, (2) bulk cementum, and (3) the cementum-dentin junction (CDJ). Structurally, continuity in collagen fibers was observed from the enthesis, through bulk cementum and CDJ. At the CDJ the collagen fibers split into individual collagen fibrils and intermingled with the extracellular matrix of mantle dentin. Under wet conditions, the collagen fibers at the three regions exhibited significant swelling suggesting a composition rich in polyanionic molecules such as glycosaminoglycans. Additionally, site-specific indentation illustrated a comparable elastic modulus between collagen fibers at the enthesis (1-3 GPa) and the CDJ (2-4 GPa). However, the elastic modulus of collagen fibers within bulk cementum was higher (4-7 GPa) suggesting presence of extrafibrillar mineral. It is known that the tooth forms a fibrous joint with the alveolar bone, which is termed a gomphosis. Although narrower in width than the PDL space, the hygroscopic CDJ can also be termed as a gomphosis; a fibrous joint between cementum and root dentin capable of accommodating functional loads similar to that between cementum and alveolar bone. From an engineering perspective, it is proposed that a tooth contains two fibrous joints that accommodate the masticatory cyclic loads. These joints are defined by the attachment of dissimilar materials via graded stiffness interfaces, such as: (1) alveolar bone attached to cementum with the PDL; and (2) cementum to root dentin with the CDJ. Thus, through variations in concentrations of basic constituents, distinct regions with characteristic structures and graded properties allow for attachment and the load bearing characteristics of a tooth. Published by Elsevier Ltd.
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