Effect of dentin etching and chlorhexidine application on metalloproteinase-mediated collagen degradation

Abstract

Dentin matrix metalloproteinases (MMPs) are involved in the degradation of collagen in resin-dentin interfaces. This study evaluated whether collagen degradation can be prevented by chlorhexidine digluconate (CHX) after different dentin demineralization procedures. The demineralization of human dentin was performed with phosphoric acid (PA), EDTA or acidic monomers (Clearfil SE Bond and Xeno V). Specimens were stored (for 24 h, or for 1 or 3 wk) in the presence or absence of CHX. In half of the groups, active MMP-2 was incorporated into the storage solution. At the end of each storage period, the C-terminal telopeptide (ICTP) concentration (which indicates the amount of collagen degradation) was measured in the storage solution. Collagen degradation was higher in PA- and EDTA-demineralized dentin. Chlorhexidine digluconate reduced collagen degradation in these groups only for 24 h. When dentin was demineralized with Clearfil SE Bond or Xeno V, collagen degradation was reduced by up to 30%, but the addition of exogenous MMP-2 significantly increased collagen degradation. In self-etchant-treated dentin, the inhibitory effect of CHX on MMPs lasted for up to 3 wk. Treating dentin with EDTA, PA or self-etching agents produces enough demineralization to permit cleavage of the exposed collagen. Monomer infiltration may exert protection on demineralized collagen, probably through immobilization of MMPs. The partial inhibitory action of CHX on MMP activity produced by self-etching adhesives was prolonged compared with the short-acting PA- or EDTA-treated dentin.

Figure 1

Mean and SD of collagen degradation (%) of mineralized and treated human dentin explants after different storage times. Without (left), and with (right) addition of active MMP-2. 1a and 1b after 24 h; 1c and 1d after 1 wk; 1e and 1f after 3 wk. AS: artificial saliva; MMP2: active metalloproteinase 2; CHX: digluconate chlorhexidine; MIN: mineralized dentin; PA: phosphoric acid demineralized dentin; EDTA: EDTA-demineralized dentin; SE: Clearfil SE Bond-treated dentin; XE: Xeno V-treated dentin. The amount of ICTP liberated from the PA-demineralized dentin in the absence of chlorhexidine, and in the presence of active MMP-2 after 3 weeks was set to 100%, and the collagen degradation in the rest of the groups was calculated in each single experiment as a percent of this value.