Objectives : Degradation of hybrid layers (HL) within resin-infiltrated dentin has shown to result from multiple degradation factors, including the collagenolytic activity of specific matrix metalloproteinases (MMPs). Inhibition of host-derived MMPs may, therefore, slow the degradation of HL. To examine the effect of bonding procedures on the presence and activity of MMP-2, the null hypothesis tested is that MMP-2 presence is irrespective from the use of an adhesive system, and from the chlorhexidine pre-treatment.
Materials and methods : Powdered dentin prepared from extracted human teeth was divided into 4 groups: (G1) mineralized powder (control group); (G2) dentin powder treated with 1% H 3 PO 4 for 1 min; (G3) 1% H 3 PO 4 acid-etched dentin treated with Adper Scotchbond 1 XT (SB1XT; 3M ESPE); (G4): 1% H3PO4 acid-etched dentin treated with 0.2% chlorhexidine digluconate solution for 1 min followed by SB1XT application. The presence of MMP-2 in the untreated and treated dentin powder was assayed a colorimetric assay system that allows direct measuring of MMP-2 levels (Quantisir™, Epigentek, USA. All experiments were run in triplicate ( N = 3) and repeated three times.