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.
Results : Means of MMP-2 quantification are listed in table:
| Group | MMP-2 |
|---|---|
| Group 1: mineralized dentin | 0.892 ± 0.048 a |
| Group 2: 1% H3PO4 demineralized dentin | 0.505 ± 0.014 b |
| Group 3: SB1XT | 1.412 ± 0.016 c |
| Group 4: 0.2% CHX + SB1XT | 1.028 ± 0.032 d |
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