The process of dentin caries is a complex event involving demineralisation and matrix degradation. The objective of this study was to biochemically characterise
collagen, the major dentin matrix component, by
amino acid and cross-link analyses in two distinct
carious dentin regions of human primary teeth. Twenty-seven carious primary teeth were obtained from 3 to 11-year-old patients and three layers of dentin, i.e. outer, inner
carious dentin and normal dentin, were identified by a 1%
acid red solution and dissected from each tooth. The samples were pulverised, the respective layers obtained from three to five teeth were pooled and six samples per layer were analysed. Aliquots of the dried dentin
powder were hydrolysed with 6N HCl at 110 degrees C for 24h and subjected to
amino acid analyses. Other aliquots were demineralised, reduced with standardised NaB3H4, hydrolysed and subjected to quantitative
collagen cross-link analyses. The results demonstrated that in the outer carious layer the
collagen-associated
amino acids were significantly lower and the reducible cross-links were markedly diminished when compared to the other two groups. There was no significant difference in these parameters between the inner carious and the normal layers. The data indicate that while the
collagen in the outer
carious dentin is significantly altered and degraded, the one in the inner
carious dentin is relatively unaffected in primary teeth.