Abstract
It has known that the resin-dentin bonding created using contemporary dentin bonding systems deteriorates over time, being the optimization of bonding interface one of the most important challenges for restorative dentistry. The lack of resin protection and presence of water leave the demineralized collagen fibrils vulnerable to hydrolytic degradation. Besides, host-proteases of dentin matrix (matrix metalloproteinases and cysteine cathepsins) have shown marked involvement in degradation of collagen fibrils in both processes, dentin caries and hybrid layer durability. Thus, new and promising approaches has been studied for using remineralizing agents that replace the dentin water containing intra and interfibrillar collagen spaces with nanomeric-size apatite crystals, returning the structural integrity of demineralized dentin and developing a perfect resin/dentin bond. Actually, this strategy could inhibit the action of proteolytic enzymes, since the presence of intrafibrillar apatite crystals could "fossilize" MMPs and cathepsins, blocking their movements and their catalytic site on collagen. In the linked PhD project supported by FAPESP (PhD fellowship 2014/22899-8), we firstly adapted a protocol to develop an artificial caries-like lesion, which was achieved by the formation of S. mutans biofilm on dentin surface. We demonstrated that, in respect to proteolytic activity of dentin, the formed lesion was quite similar to natural caries. Subsequently, we treated the artificial caries-like lesion with three different remineralizing approaches previously to the bonding procedures, and observed by in situ Zymography that casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) and the self-assembling peptide P11-4 were able to decrease the proteolytic activity at hybrid layer, in addition to improve the microtensile bonding strength of caries-affected dentin. Thus, in attempt to support our findings, the purpose of this project is mainly to evaluate the action of remineralizing agents (NaF, CPP-ACP and P11-4) on the inhibition of proteolytic activity of artificial caries-affected dentin, by ICTP and CTX analysis. Moreover, we intend to verify the influence of the same remineralizing agents on the sealing of the bonding interface of caries-affected dentin, by micro-permeability assay. The results of this research project are expected to provide new knowledge of inhibitors of proteolytic activity on dentin could not only repair the mineral loss of the tissues affected by caries, but also facilitate the fossilization of enzymes, inhibiting the proteases activity for a long-term and, subsequently, increasing the durability of the adhesive restorations.
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