Release of ICTP and CTX telopeptides from demineralized dentin matrices: Effect of time, mass and surface area

Objective: The present study evaluated the influence of time, mass and surface area of demineralized dentin collagen matrices on telopeptides release. The hypotheses tested were that the rates of ICTP and CTX release by matrix bound endogenous proteases are 1) not time-dependent, 2) unrelated to specimen mass, 3) unrelated to specimen surface area. Methods: Non-carious human molars (N = 24) were collected and randomly assigned to three groups. Dentin slabs with three different thicknesses: 0.37 mm, 0.75 mm, and 1.50 mm were completely demineralized and stored in artificial saliva for one week. Collagen degradation was evaluated by sampling storage media for ICTP and CTX telopeptidases. Activity of MMPs in the aging medium was evaluated using fluorometric activity assay kit. Results: A statistically significant (p < 0.05) decrease in the release of both ICTP and CTX fragments over time was observed irrespective of the specimen thickness. When data were normalized by the specimen mass, no significant differences were observed. Releases of ICTP and CTX were significantly related to the aging time as a function of surface area for the first 12 h. Total MMP activity, mainly related to MMP-2 and -9, decreased with time (p < 0.05). Significance: Because the release of collagen fragments was influenced by specimen storage time and surface area, it is likely that cleaved collagen fragments closer to the specimen surface diffuse into the incubation medium; those further away from the exposed surface are still entrapped within the demineralized dentin matrix. Bound MMPs can only degrade the substrate within the limited zone of their molecular mobility.