Bond strength of resin to acid-etched dentin studied by 13C NMR:: Interaction between N-methacryloyl-ω-amino acid primer and dentinal collagen

The application of the hydrophilic methacrylate primer to acid-etched dentin increases the bond strength of the resin to the acid-etched dentin. However, the mechanism for the bonding of the resin to dentinal collagen through the primer remains to be determined. Before a more effective adhesive primer can be developed, we must understand the adsorption behavior of the primer to the dentinal collagen. The purpose of this study was to determine how 5 derivatives of N-methacryloyl-omega-amino acid (NM omega A) primers enhance the bonding of the resin to acid-etched dentin. The interaction between the NM omega A primers and dentinal collagen was studied by the C-13 NMR technique, including the observation of spin-lattice relaxation times, T-1. When the dentinal collagen was dispersed into the NM omega A solution, the T-1 values of the two carbonyl carbons attributed to the amide and the carboxylic acid in the NM omega A molecule decreased dramatically This result was due to the interaction between the amide group and the carboxylic acid group in the NM omega A molecule and the dentinal collagen molecule. The T-1 values of these carbonyl carbons decreased when the number of methylene groups in the NM omega A molecule increased. The interaction became stronger as the number of methylene groups in the NM omega A molecule was increased. Further, the bond strength of the resin to the acid-etched dentin primed with NM omega A increased with a decrease in the T-1 value of the amide carbonyl carbon. The strength of the interaction of the NM omega A primer to the dentinal collagen molecule, determined by the C-13 NMR technique, showed a direct correlation with the bond strength of the resin to acid-etched dentin that was treated with the NM omega A primer.