Activation of Gelatinolytic/Collagenolytic Activity in Dentin by Self-Etching Adhesives

Objective: Acids are known to activate dentin MMPs.  All self-etching all-in-one dental adhesives are acidic (pH 1.5-2.7) and may activate dentin MMPs.  Purpose: The purpose of this study was to compare the ability of several all-in-one adhesives to activate gelatinolytic/collagenolytic activity in mineralized dentin.  Methods: Powdered dentin was made from extracted human teeth and was mixed with one of three all-in-one adhesives (Clearfil Tri-S Bond, G-Bond, Adper Prompt L-Pop) or a self-etching primer (Clearfil SE Bond primer) for varying times and then the reaction was stopped by extracting the acidic adhesives from the powder using acetone.  The gelatinolytic/collagenolytic activity of the dentin powder was assayed using commercially available fluorescein-labeled substrates using EnzChek kits (Molecular Probes, Eugene, OR) using appropriate controls and blanks.  Results:

Values are mean ± SD (n=5 plates or 25 wells per group).  Groups identified by different superscript letters are significantly different (p<0.05).  LC=light curing.

Conclusion: There was a significant direct correlation between gelatinolytic activity and pH (R²=0.85, p<0.025) with Tri-S giving the highest activity.  Strong acids expose enzymes but denature them.  Weaker acids expose enzymes without denaturing them as much.  Coating dentin powder with Tri-S resin prevented fluorescein-labeled gelatin or collagen from gaining access to the enzyme even though it activated the enzyme.  Self-etch adhesives may activate latent MMP activity to near maximum levels and contribute to degradation of resin-dentin bonds over time.  Supported, in part, by R01 DE 014911 from the NIDCR (P.I. D.Pashley).