QAMs inhibit dentin endogenous MMPs: ELISA and zymographic assay

Quaternary ammonium methacrylates (QAMs) are claimed to inhibit dentin matrix metalloproteinases (MMPs), which contribute to progressive degradation of collagen fibrils in hybrid layers. Thus, dentin treatment with QAMs-based primers has been proposed.

Objectives: This study tested the hypothesis that there are no differences in MMP-2 and -9 activity after treatment of dentin with QAMs-containing experimental adhesive blends.

Methods : Powdered dentin prepared from extracted human teeth was treated as follows: 1) untreated mineralized powder; 2) demineralized with 10% H₃PO₄; demineralized with 1% H3PO4 for 10 min then treated with 3) 2-acryloxyethyltrimethylammoniumchloride (ATA; 30vol%), 4) methacryloylcholinemethylsulphate (MCMS; 30vol%), 5) 2-(methacryloyloxy)ethyl]trimethylammoniumchloride (METMAC; 30vol%) or 6) methacryloyloxydodecylpyridinium bromide (MDPB; 5vol%). MMP-2 and -9 activity was determined using ELISA test (Biotrak™ activity assay system; GE Healthcare) and gelatin zymography. Assays were performed in triplicate.

Results : The activity of MMP-2 after the treatment with QAMs decreased in relation to the tested QAMs (inhibition was ranked in the following order MDPB>METMAC>MCMS>ATA), while all tested QAMS were able to almost completely inhibit MMP-9 activity. The zymographic assay confirmed the ELISA findings.

Conclusions : The hypothesis tested was rejected since differences in MMP-2 and -9 activities were recorded after treatment with QAMs based primers. Further studies are needed to clarify the role of QAMs on the durability of the adhesive interface if blended within adhesive systems.

Supported, in part, by grants FIRB RBAP1095CR, PRIN 2009SAN9K5 and 2009FXT3WL from MIUR, Italy, and R01DE015306 from the NIDCR to DP (PI) and grant #8126472 from the Academy of Finland to AT-M (PI).