This study evaluated the expression of matrix metalloproteinase-2 (MMP-2) in primary cultures of human pulp fibroblasts (HPFs) when exposed to extracts from dentin-bonding systems.Polymerized resin disks of the bonding agent of a 2-step self-etch adhesive (TechBond, Isasan, Rovello Porro, Italy) or of the primer/bonding agent a 2-step etch-and-rinse adhesive (Optibond Solo; Sybron-Kerr, Orange, CA) were immersed in HPF culture medium for 24 or 96 hours. HPFs were incubated in the adhesive-conditioned or control (untreated) culture medium for 24 hours. Western blot and immunofluorescence analyses were performed to assay MMP-2 expression.MMP-2 expression levels in HPFs cultured for 24 hours in culture medium were similar in both the control and experimental media groups showing a faint band at 67 kDa. Conversely, the HPFs incubated in the medium that contain polymerized resin disks for 96 hours showed increased MMP-2 expression compared with the untreated medium. The self-etch adhesive displayed the most pronounced induction of MMP-2 expression. These findings were confirmed by immunofluorescence analysis.HPFs display increased MMP-2 expression after 96 hours of conditioning of the HPF culture medium with polymerized disks of dentin bonding systems. This MMP-2 expression/activation may represent a defence mechanism exhibited by HPFs towards monomers eluted from the dentin bonding systems.
