Method: Ninety extracted third molars were used to prepare dentin beams. After baseline measurement of the dry mass, beams were divided into 9 groups (n=10/group) and demineralized in 10% or 37% PA for 6, 12, 18, or 24 hrs. The beams that were kept mineralized served as control. After demineralization and assessment of dry weight, the beams were incubated in 1mL calcium and zinc containing artificial saliva at 37 °C for 1, 3 and 7 days. After each incubation period aliquots of the incubation media were analyzed for pyridinoline-crosslink degradation fragment of the C-terminal telopeptide of type I collagen (ICTP) for MMP-mediated degradation and deoxypyridinoline degradation fragment of the C-terminal telopeptide region of type I collagen (CTX) for cathepsin mediated degradation using ELISA immunoassay kits. Beams were dried and re-weighed to determine loss of dry weight following each incubation period. Data were analyzed using ANOVA and Tukey’s test.
Result: The overall ICTP release from dentin beams were significantly higher compared to CTX release (p<0.05). Demineralization duration and PA concentration had significant effect on the weight loss, ICTP and CTX production from dentin matrix (p<0.05). The specimens demineralized for 24 hrs released significantly higher amounts of CTX and ICTP compared to 6 hrs (p<0.05). Both CTX and ICTP release were significantly higher at 1 day compared to 3 or 7 days.
Conclusion: The prolonged demineralization duration increases both the MMP and cathepsin-mediated activity in dentin.