Thermal degradation of EDC-cross-linked dentinal collagen

Purpose: 1-Ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) has been shown to cross-link type I collagen, in dentin. The aim of this preliminary study was to detect the cross-linking reaction promoted by EDC in different aqueous solutions by measuring the thermal degradation temperature (TDT) of human dentin collagen over time. The null hypothesis tested was that no differences would have been found among the untreated dentin collagen and the EDC-treated specimens. Methods and materials: 3 dentin slabs (1 mm thick, 6 mm diameter) were completely demineralized in 10% H3PO4 solution and washed in MilliQ water in agitation for at least 24 h. A Fourier transform infrared (FTIR) spectroscopy analysis of each slab confirmed the absence of mineral. Each demineralized slab was radially sectioned in 7 specimens 1 mm 7 1 mm 7 1 mm and dried in anhydrous atmosphere with SiO2. For each slab 1 specimen was analyzed with a differential scanning calorimeter (DSC, Q10 TA Instruments) to obtain the TDT of dehydrated collagen. The other 6 specimens of each slab were immersed in the assigned EDC aqueous solution (0.1 M, 0.5 M or 1 M) for 10, 20, 30, 40, 50 or 60 min (T10, T20, T30, T40, T50, T60 respectively), rinsed for 15 min in demineralized water under agitation, dehydrated and analyzed with the DSC to obtain the TDT of EDC-treated collagen. All data were statistically analyzed (Kruskal\u2013Wallis test, Mann\u2013Whitney test). Results: The thermal degradation temperatures of untreated and EDC-treated dehydrated dentin collagen are shown in the table below. No statistical differences were found. Conclusion: EDC-treated dentin collagen did not show a higher TDT than the untreated control irrespective from concentration and time of application, thus the null hypothesis was confirmed. An improved TDT is an indirect indicator of a more resistant and highly cross-linked collagen network. More data are needed to confirm these preliminary results and further studies are necessary to define the role of EDC in collagen reinforcement strategies. This study was supported by FIRB RBAP1095CR, PRIN 2009SAN9K5 and 2009FXT3WL of MIUR and by R01 DE015306 from the NIDCR to DHP (PI)