Structure, chemical composition and mechanical properties of human and rat cementum and its interface with root dentin

Abstract

This work seeks to establish comparisons of the physical properties of rat and human cementum, root dentin and their interface, including the cementum-dentin junction (CDJ), as a basis for future studies of the entire periodontal complex using rats as animal models. In this study the structure, sitespecific chemical composition and mechanical properties of cementum and its interface with root dentin taken from 9-to 12-month-old rats were compared to the physiologically equivalent 40-to 55-year-old human age group using qualitative and quantitative characterization techniques, including histology, atomic force microscopy (AFM), micro-X-ray computed tomography, Raman microspectroscopy and AFM-based nanoindentation. Based on results from this study, cementum taken from the apical third of the respective species can be represented as a woven fabric with radially and circumferentially oriented collagen fibers. In both species the attachment of cementum to root dentin is defined by a stiffness-graded interface (CDJ/cementum-dentin interface). However, it was concluded that cementum and the cementum-dentin interface from a 9-to 12-month-old rat could be more mineralized, resulting in noticeably decreased collagen fiber hydration and significantly higher modulus values under wet conditions for cementum and CDJ (E rat-cementum = 12.7 ± 2.62 GPa; E rat-CDJ = 11.6 ± 3.20 GPa) compared to a 40-to 55-year-old human (E human-cementum = 3.73 ± 1.81 GPa; E human-CDJ = 1.5 ± 0.71 GPa). The resulting data illustrated that the extensions of observations made from animal models to humans should be justified with substantial and equivalent comparison of data across age ranges (life spans) of mammalian species.

Calcium orthophosphates (CaPO 4 ): Occurrence and properties

“…The same 117 homogenized biopsy samples were analyzed by wavelength-dispersive X-ray fluorescence to quantify the carbonate substitution in biological apatite as a function of age. Although the changes observed in carbonate substitution were relatively slight (at most 10 %), there was a general increase from 0 to 90 years that is distinct from the absence of a change in crystallinity after age 30 in these samples (Boskey and Coleman 2010 Gaft et al 1996;Huang et al 2007;Yin et al 2013;Ho et al 2009a). Both the crystal sizes and carbonate content were found to increase during aging in rats and cows (LeGeros et al 1987;Rey et al 1995b).…”

“…Unlike bones, teeth consist of at least two different CaPO 4 materials: enamel, which is a rigid, inert and acellular outer layer, and dentine, which is a bone-like Mg-rich hard tissue that forms the bulk of vertebrate teeth. In addition, there is cementum, which is a thin layer of a bone-like calcified tissue that covers dentine at the roots of teeth and anchors them to the jaw (Ho et al 2009a, b;Bosshardt and Selvig 2000;Yamamoto et al 2010). Finally, there is the core called pulp (commonly called ''the nerve'')-it is a remnant of the embryologic organ for tooth development and contains nerves and blood vessels necessary for tooth function.…”

“…Reprinted from Ref. (Lowenstam and Weiner 1989) with permission Prog Biomater (2016) 5:9-70 37 enamel but is greater than that of bone or cementum (Ho et al 2009a). When pulp of the tooth dies or is removed by a dentist, the properties of dentine change: it becomes brittle, liable to fracture and looses a reparative capability.…”

Tooth Organ Engineering: Biological Constraints Specifying Experimental Approaches

“…Similar challenges exist when trying to restore dentin/enamel, dentin/cementum, or cementum/periodontal fibers interfaces and maintain their specific mechanical properties. During tooth development, tissues interfaces usually show multi-step formation where extensive matrix remodeling takes place (Bosshardt et al, 2005;Ho et al, 2009;Imbeni et al, 2005). In all these interfaces, there is a tight structure-function relationship.…”

Tissue Engineering for Tissue and Organ Regeneration

“…Similar challenges exist when trying to restore dentin/enamel, dentin/cementum, or cementum/periodontal fibers interfaces and maintain their specific mechanical properties. During tooth development, tissues interfaces usually show multi-step formation where extensive matrix remodeling takes place (Bosshardt et al, 2005;Ho et al, 2009;Imbeni et al, 2005). In all these interfaces, there is a tight structure-function relationship.…”