Chx-Containing Adhesive Inhibits Dentin MMPs: a Zymographic Assay

Objective: Matrix metalloproteases (MMPs) are a family of enzymes involved in several developmental and disease-associated processes including degradation of resin-dentin matrices. The use of chlorhexidine a potent MMP inhibitor as additional primer during bonding procedures has been reported to be effective in the preservation of the hybrid layer over time. Thus, the purpose of this study was to identify the effectiveness of a CHX-containing Adper Scotchbond 1XT (SB1XT, 3M ESPE) on MMPs activity assayed using gelatine zymography. Methods: Dentin powder was pulverized from freshly extracted human molars. Four lots of dentin powder were obtained and treated as follow: (1) untreated mineralized dentin (control); (2) demineralized with 1% H3PO4 for 10 min; demineralized with 1% H3PO4 for 10 min then treated (3) with SB1XT or (4) with 0.2% CHX-containing SB1XT. Extracts obtained from the treated dentin powder were then electrophoresed by gelatin zymography, for detection of MMPs enzyme activity. Results: No enzymatic activity was found in proteins extracted from mineralized dentin. Zymograms of demineralized dentin extracts showed MMP-2 and -9 active forms (66 and 86-kDa isoforms, respectively). Zymograms of SB1XT-treated dentin showed MMP-2 proform (72-KDa) and active form, and a slight activity MMP-9 active form, while zymograms of CHX-containing SB1XT showed complete inhibition of MMPs activity. Conclusions: Human dentin matrices exhibit collagenolytic and gelatinolytic activity when mixed with SB1XT, while the incorporation of 0.2% CHX within SB1XT formulation resulted in complete inhibition of MMP-2 and -9 activity. Future in vitro and in vivo studies should clarify the benefits of incorporation of MMPs inhibitors within the adhesive formulation for the preservation of the hybrid layer over time.