Age-Related Alterations in SIBLING Proteins and Dentin Micro-Architecture: Morphological and Molecular Associations

Background: Aging is associated with progressive structural and functional changes in dentin, reducing its mechanical integrity and increasing vulnerability to damage. Among the most important regulators of dentin physiology are extracellular matrix proteins from the SIBLING family, including Dentin Matrix Protein 1 (DMP-1), Dentin Sialophosphoprotein (DSPP), and Osteopontin (OPN). These proteins are essential for dentin mineralization, collagen organization, and tissue remodeling. Despite their critical role, knowledge about their age-related distribution and correlation with dentin structure and morphology remains limited. Aim: To examine age-dependent changes in the expression of SIBLING proteins (DMP-1, DSPP, OPN) in human dentin and to evaluate their relationship with collagen structure and ultramorphology using polarized light microscopy (PLM), immunohistochemistry (IHC), and scanning electron microscopy (SEM). Materials and Methods: Ninety extracted human teeth were categorized into young (≤17 years), mature (18-50 years), and old (>51 years) groups. IHC was applied to detect protein distribution, PLM to assess collagen organization, and SEM to evaluate dentinal morphology. Results and Conclusions: Aging was associated with increased expression of DMP-1 and OPN and a reduction in DSPP, which is particularly evident in peritubular dentin. Older samples showed collagen disorganization, reduced birefringence, and extensive intratubular mineralization. These findings suggest that age-related alterations in SIBLING proteins contribute to structural changes in dentin, providing new insights relevant to dental care in elderly patients.