Effect of self-etching primers containing N-acryloyl aspartic acid on dentin adhesion

The purpose of this study was to evaluate the feasibility of aspartic acid derivative, N-acryloyl aspartic acid (N-AAsp) when used as a self-etching p rimer prior to the application of a commercial bonding agent containing 10- methacryloxydecyl dihydrogen phosphate. N-AAsp was synthesized by the react ion of DL-aspartic acid and acryloyl chloride. N-AAsp can be dissolved in w ater up to 25 wt % and can adequately remove the smear layer. When 20 wt % N-AAsp was applied as a self-etching primer, the tensile bonding strength o f resin composite to dentin doubled to 16.0 MPa compared with that of the n onetching group or the 40 wt % H3PO4 etching/water rinse group. Scanning el ectron microscopic observations revealed that the formation of the hybrid l ayer at the interface between the resin composite and dentin and the thickn ess of the hybrid layer increased with N-AAsp concentration. The hybrid lay er in the specimens treated with 20 wt % N-AAsp aqueous solution presented a uniform structure, whereas those treated with 5 wt % N-AAsp solution show ed a porous structure. We conclude that 20 wt % N-AAsp aqueous solution has good potential value as a self-etching primer. (C) 2000 John Wiley & Sons, Inc.