Effect of a one-step self-etch adhesive on endogenous dentin matrix metalloproteinases.

Degradation of the hybrid layer created in dentin by dentin adhesives is caused by enzyme activities present within the dentin matrix that destroy unprotected collagen fibrils. The aim of the present study was to evaluate the effect of a one-step self-etch adhesive system on dentinal matrix metalloproteinases 2 and 4 (MMP-2 and MMP-9, respectively) using in situ zymography and an enzymatic activity assay. The null hypothesis tested was that there are no differences in the activities of dentinal MMPs before and after treatment with a one-step adhesive system. The MMP-2 and MMP-9 activities in dentin treated with the one-step adhesive, Adper Easy Bond, were quantified using an enzymatic activity assay system. The MMP activities within the hybrid layer created by the one-step adhesive tested were also evaluated using in situ zymography. The enzymatic assay revealed an increase in MMP-2 and MMP-9 activities after treatment with adhesive. In situ zymography indicated that gelatinolytic activity is present within the hybrid layer created with the one-step self-etch adhesive. The host-derived gelatinases were localized within the hybrid layer and remained active after the bonding procedure. It is concluded that the one-step self-etch adhesive investigated activates endogenous MMP-2 and MMP-9 with the dentin matrix, which may cause collagen degradation over time.

Effect of carbodiimide (EDC) on the bond stability of etch-and-rinse adhesive systems.

OBJECTIVE: Recent studies supported the use of protein cross-linking agents during bonding procedures to inactivate endogenous dentin proteases, preventing dentin collagen degradation thus improving bond durability. The aim of this study was to evaluate the effect of a 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC)-containing conditioner on the stability of the adhesive interface created by two etch-and-rinse adhesives. METHODS: Human dentin was etched with 35% phosphoric acid, treated with 0.3M EDC-containing conditioner followed by a three-step or a two-step etch-and-rinse adhesive. Adhesives were applied to control specimens without EDC pre-treatment. Specimens were subjected to microtensile bond strength test and pulled to failure after 24h or 1 year of storage and interfacial nanoleakage expression was evaluated and quantified by light microscopy. Additionally, to investigate endogenous dentin matrix metalloproteinase activity a zymographic assay was performed on protein extracts obtained from phosphoric-acid-etched dentin powder with or without EDC treatment. RESULTS: The use of the EDC-containing conditioner did not affect immediate bond strength to dentin but contributed to preserve the bond strength after 1 year (p<0.05) for both tested adhesives. No difference was found in the interfacial nanoleakage expression that increased after aging irrespective from the treatment. EDC pre-treatment inhibited dentin endogenous MMPs as assayed with the zymography. SIGNIFICANCE: In conclusion, the results of the study provide proof that EDC can produce long-term inactivation of MMPs in acid-etched dentin matrices contributing to bond strength preservation over time. Future studies are needed to support the use of EDC in vivo.