Syntheses of O-Methacryloyl-N-Acyl Tyrosines and Their Adhesiveness to Un-etched Human Dentin

O-Methacryloyl-N-acyl tyrosines (MAATY) having acyl groups with the various chain length were synthesized and the strength of bonding agents, consisting of MAATY as an adhesive monomer, to unetched human dentin was studied to elucidate the relationship between the molecular structure of MAATY and its adhesive characteristics. Increasing the flexibility of the carboxyl group of tyrosine favors the interaction with the tooth substrate, causing strict bonding. Also, the properties of the neighboring carboxyl group, i. e., steric hindrance and hydrophobicity, hydrophobic-hydrophilic balance in the monomer, and shrinkage of the monomer at copolymerization, are considered important. Especially, steric hindrance of the substituted group neighboring the carboxyl group of tyrosine would play an extremely important role in the adhesion of O-methacryloyl-N-octanoyl tyrosine. The maximum tensile bond strength was obtained with a bonding agent consisting of O-methacryloyl-N-hexanoyl tyrosine (15 mol%) and hydroxyethyl methacrylate (85 mol %), and the strength (4.75 MPa) was the maximum in all methacrylates with phenylalanine as a bone structure.