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The stoic tooth root: how the mineral and extracellular matrix counterbalance to keep aged dentin stable
Journal article   Open access   Peer reviewed

The stoic tooth root: how the mineral and extracellular matrix counterbalance to keep aged dentin stable

Mariana Reis, Yvette Alania, Ariene Leme-Kraus, Robert Free, Derk Joester, Weikang Ma, Thomas Irving and Ana K. Bedran-Russo
Acta biomaterialia, Vol.138(C), pp.351-360
01/15/2022
DOI: 10.1016/j.actbio.2021.10.051
PMCID: PMC8815755
PMID: 34740855
url
https://doi.org/10.1016/j.actbio.2021.10.051View
Published (Version of record) Open Access

Abstract

Aging is a physiological process with profound impact on the biology and function of biosystems, including the human dentition. While resilient, human teeth undergo wear and disease, affecting overall physical, psychological, and social human health. However, the underlying mechanisms of tooth aging remain largely unknown. Root dentin is integral to tooth function in that it anchors and dissipates mechanical load stresses of the tooth-bone system. Here, we assess the viscoelastic behavior, composition, and ultrastructure of young and old root dentin using nano-dynamic mechanical analysis, micro-Raman spectroscopy, small angle X-ray scattering, atomic force and transmission electron microscopies. We find that the root dentin overall stiffness increases with age. Unlike other mineralized tissues and even coronal dentin, however, the ability of root dentin to dissipate energy during deformation does not decay with age. Using a deconstruction method to dissect the contribution of mineral and organic matrix, we find that the damping factor of the organic matrix does deteriorate. Compositional and ultrastructural analyses revealed higher mineral-to-matrix ratio, altered enzymatic and non-enzymatic collagen cross linking, increased collagen d-spacing and fibril diameter, and decreased abundance of proteoglycans and sulfation pattern of glycosaminoglycans . Therefore, even in the absence of remodeling, the extracellular matrix of root dentin shares traits of aging with other tissues. To explain this discrepancy, we propose that altered matrix-mineral interactions, possibly mediated by carbonate ions sequestered at the mineral interface and/or altered glycosaminoglycans counteract the deleterious effects of aging on the structural components of the extracellular matrix. Statement of significance Globally, a quarter of the population will be over 65 years old by 2050. Because many will retain their dentition, it will become increasingly important to understand and manage how aging affects teeth. Dentin is integral to the protective, biomechanical, and regenerative features of teeth. Here, we demonstrate that older root dentin not only has altered mechanical properties, but shows characteristic shifts in mineralization, composition, and post-translational modifications of the matrix. This strongly suggests that there is a mechanistic link between mineral and matrix components to the biomechanical performance of aging dentin with implications for efforts to slow or even reverse the aging process. (c) 2021 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
 Engineering Engineering, Biomedical Materials Science Materials Science, Biomaterials Science & Technology Technology

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