Site comparisons of dentine collagen cross-links from extracted human teeth

Covalent intermolecular cross-links in collagen provide the dentine matrix with stability and tensile strength. The density of collagen cross-links varies depending on the site within the same tissue. This variation is probably due to factors such as the different amounts of stress and different turnover rates at the respective sites. The aim was to quantify the collagen cross-links in different tooth groups as an adaptation to functional requirements. For this purpose, the types and content of major cross-links in dentine collagen of human teeth from three different sites were measured and compared: incisors, premolar-canines and molars. After removal of cementum and pulp, 23 extracted teeth at different ages (27-69 yr) were individually pulverized and demineralized with EDTA. Collagen was reduced with standardized NaB3H4, hydrolysed, and subjected to amino acid and cross-link analyses. Each cross-link was quantified on the basis of mole per mole of collagen. The results indicated: (1) all teeth contained labile, reducible (dehydro-dihydroxylysinonorleucine and dehydro-hydroxylysinonorleucine) and stable, non-reducible (pyridinoline and its lysyl analogue) cross-links, and (2) the content of both reducible and non-reducible cross-links was least in incisors and greatest in molars. This suggests that dentine collagen matrix maybe functionally adaptive.