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Effect of pH on dentin protease inactivation by carbodiimide

A water-soluble crosslinking agent, 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC), has been used as a pretreatment of acid-etched dentin to inactivate matrix-bound endogenous dentin proteases. The aim of this study was to evaluate the effect of pH on the inactivation capacity of EDC. Demineralized dentin beams (1 × 2 × 6 mm) were divided into six groups (n = 8 per group). Then, EDC (0.3 M) was solubilized in distilled water with pH of 2, 4, 6, 7, 9, or 11. Control EDC was solubilized in 0.1 M 2-(N-morpholino) ethanesulfonic acid (MES) buffer and its pH was adjusted to 6. The dentin beams were pretreated for 1 min with EDC at each pH or with EDC in MES buffer at pH 6.0 and then incubated in 1 ml of simulated body fluid (pH 7.2) for 1, 3, 7, or 14 d. Untreated beams served as controls. At each study time-point, the dry mass of dentin beams was assessed and the incubation media were analyzed for carboxyterminal telopeptide of type-I collagen (ICTP) and C-terminal telopeptide of type I collagen (CTX) using specific ELISAs. Data were subjected to repeat-measures anova. The results of the study indicated that specimens pretreated with EDC in MES buffer showed the lowest collagen degradation in terms of mass loss and release of telopeptides, while specimens pretreated in alkaline media showed the highest collagen degradation. This study indicates that the pH of the EDC solution plays an important role in the stability of dentin protease inactivation.