Does inhibition of proteolytic activity improve adhesive luting?

Endogenous enzymes may be involved in the biodegradation of adhesive restorationtooth interfaces. Inhibitors of matrix metalloproteinases (MMPs) have been suggested to retard the bond-degradation process. Limited data are available on whether composite cements may also benefit from MMP inhibitors. Therefore, the aim of this study was to determine the effect of two MMP inhibitors chlorhexidine digluconate (CHX) and galardin on the microtensile bond strength (TBS) of two self-adhesive composite cements to dentin. Ceramic specimens were cemented to bur-cut dentin surfaces using the self-adhesive composite cements RelyX Unicem 2 (3M ESPE) or Clearfil SA (Kuraray), or the etch-and-rinse composite cement Nexus 3 (Kerr) that served as the control. The surfaces were left untreated or were pretreated with MMP inhibitors (2% CHX or 0.2mM galardin). The TBS was determined immediately' and upon ageing (water storage for 6months). Statistical analysis revealed a significant effect of the factors composite cement' and storage', as well as all interactions, but no effect of the MMP inhibitors. After 6months of ageing, the TBS decreased for all cements, except for the multistep etch-and-rinse luting composite when it was applied without MMP inhibitors. The MMP inhibitors could not prevent the decrease in TBS upon ageing and therefore do not improve the luting durability of the composite cements tested.