Effect of carboidiimide on thermal denaturation temperature of dentin collagen

Objectives 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) has been shown to cross-link dentin type I collagen. Increased cross-linking usually elevates the glass transition temperature of polymers. The aim of this study was to evaluate the cross-linking reaction promoted by EDC in different aqueous concentrations by measuring the thermal denaturation temperature (Td) of human dentin collagen. Methods The Td of dehydrated collagen and of insoluble dentin matrix collagen immersed in 0.5 M or 1 M EDC aqueous solution for different treatment times was obtained using a Differential Scanning Calorimeter (DSC). Specimens were also analyzed by Energy Dispersive X-Ray Spectroscopy. Results EDC-treated dentin collagen showed a significantly higher Td than the untreated specimens when immersed in either 0.5 M EDC or 1 M EDC for 10 min or longer (p < 0.05). EDC-treated dentin collagen showed an increase of sulfur and chloride, not detectable in EDC-untreated dentin specimens. Conversely, the relative amount of carbon, nitrogen and oxygen was not modified by treatments. Significance EDC-treated dentin collagen showed a higher Td than the untreated control at all tested concentrations and immersion times. A higher Td can be considered an indirect indicator of a more resistant and highly cross-linked collagen network. More data are needed to confirm these results.