Bond Strength of Resin to Acid-etched Dentin Studied by 13C NMR: Interaction between N-methacryloyl-ω-Amino Acid Primer and Dentinal Collagen

Abstract

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-ω-amino acid (NMwA) primers enhance the bonding of the resin to acid-etched dentin. The interaction between the NMwA primers and dentinal collagen was studied by the 13C NMR technique, including the observation of spin-lattice relaxation times, T1. When the dentinal collagen was dispersed into the NMwA solution, the T1 values of the two carbonyl carbons attributed to the amide and the carboxylic acid in the NMwA molecule decreased dramatically. This result was due to the interaction between the amide group and the carboxylic acid group in the NMwA molecule and the dentinal collagen molecule. The T1 values of these carbonyl carbons decreased when the number of methylene groups in the NMωA molecule increased. The interaction became stronger as the number of methylene groups in the NMwA molecule was increased. Further, the bond strength of the resin to the acid-etched dentin primed with NMwA increased with a decrease in the T1 value of the amide carbonyl carbon. The strength of the interaction of the NMwA primer to the dentinal collagen molecule, determined by the 13C NMR technique, showed a direct correlation with the bond strength of the resin to acid-etched dentin that was treated with the NMwA primer.