LAUSR

OBJECTIVE This study aimed to identify the changes in the time-dependent deformation response of coronal dentin with ageing and its relationship with changes in chemical composition. BACKGROUND The structural behaviour of dentin with ageing is affected by changes in the density and diameter of its dentinal tubules (ie porosity), as well as changes in chemical composition throughout the tooth. However, little is known about the time-dependent deformation behaviour of aged dentin and the importance of its hierarchical structure and variations in chemical composition. MATERIALS AND METHODS The spherical indentation response of aged coronal dentin was analysed in the outer, middle and inner regions, and its time-dependent deformation response was modelled in terms of its microstructure and chemical composition using a model recently proposed for young dentin. RESULTS The viscous deformation behaviour of aged dentin followed a power-law response with a decrease in the stress exponent when compared to young dentin. These results can be explained by cross-linking of the collagen present in the tissue. CONCLUSION A decrease in the deformation ability of aged dentin was found. This behaviour could be a result of a dissolution process and reprecipitation of the minerals present in intertubular dentin into the dentinal tubules.