Structure and Properties of Murine and Human Dentin
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Structure and Properties of Murine and Human Dentin Stefan Habelitz, Shabnam Zartoshtimanesh, Mehdi Balooch, Sally J. Marshall, Grayson W. Marshall, and *Pamela K. DenBesten, Department of Preventive and Restorative Dental Sciences, *Department of Orofacial Sciences, University of California, 707 Parnassus Ave., San Francisco, CA 94143-0758, USA ABSTRACT Mice are commonly considered the model mammal for many biomedical studies. In this work, mouse and human dentin were compared to specify structural and mechanical differences to establish a baseline for comparison of dental tissues between these species. Atomic force microscopy revealed tubules of about 1.0 to 1.6 µm in diameter as the main structural feature in dentin of both species. Nanoindentation yielded the elastic modulus about 15% lower in murine intertubular dentin while the hardness was almost equal. Dynamic stiffness mapping confirmed the lower elastic properties and also revealed that the peritubular region of increased mineralization around tubules is drastically reduced or maybe absent in murine dentin of this age. This study suggests that structural and mechanical differences need to be considered when murine dentin is used as a model system. INTRODUCTION Advances in biotechnology facilitated the design of mice with transgenic or deleted genes with the goal to elucidate the functions of various genes in the development, biology, pathology, structure, composition of various tissues and organs[1]. Research on mineralized tissues relies heavily on the use of mouse-models. An important issue for decades has been the assessment of the quality of bone, in particular with respect to osteoporosis and other bone diseases that affect the strength of the mineralized tissues[2-4]. Recent studies suggest that bone strength is not only a function of mass, but also related to local properties and concentrations of its component, like matrix proteins and apatite mineral as well as to the hierarchical structural design with these components as building blocks[5, 6]. Therefore, research on mineralized tissue requires a detailed analysis of microstructure and properties to give a more complete picture of the effect of a defective or altered gene or other factors studied through the mouse model. Mice teeth are of particular interest, since at least the incisors erupt continuously and therefore provide easy access to all stages of dental development in a single tooth, while molars provide insight into a mineralized tissue that remains unaltered after its development and does not undergo remodelling. Research on mice teeth has contributed significant knowledge in gene expression and function in amelogenesis and towards the etiology and pathology of genetic defects[7-9]. While these studies primarily focused on the biology, biochemistry and morphology of dental tissues, recent studies have pointed out the importance of a broader spectrum of criteria including micro- and nanostructure and nanomechanics to quantitatively distinguish between phenotypes[10, 11]. The ai
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