Effects of N-methacryloyl-ω-amino acid primer pretreatment on the bond strength of the resin to acid-etched dentin

Abstract

To ascertain the adhesion mechanism of resins to etched dentin treated with hydrophilic primers such as N-methacryloyl-ω-amino acids (NMωA), the effect of the application of NMωA primers on the bond strength of the resin and also the characteristics of the 'hybrid layer' were investigated. Here, the concept of 'hybrid layer' has been proposed previously by Nakabayashi et al. When the demineralized dentin was treated with the NMωA solution, the bond strength increased remarkably, thus indicating the formation of a hybrid layer. It can be construed that NMωA primers allowed for diffusion of the bonding agent to the dentinal collageous layer that was exposed by acid etching, and thereby the creation of a hybrid layer. To obtain an understanding of how NMωA primers improved bond strength at the interface between the resin and dentinal collagen, the 13C-NMR spectra of NMαA wore observed in the absence and presence of demineralized dentin. The 13C peak intensifies of all of the carbons of the NMαA species were dramatically reduced in the presence of the dentin. Specifically, the reduction of the carbon peak intensity of carboxylic acid in the NMαA species was reduced by 30%. This indicated that the unionized carobxylic acid in the NMαA primer interacted with the dentinal collagen. Thus, the composite resin can be considered to adhere to the dentinal collagen through the unionized NMαA that interacts with the dentinal collagen.