Synthesis, photopolymerization and adhesive properties of new hydrolytically stable phosphonic acids for dental applications

Abstract

Novel monomers 2-(N-methylacrylamido)ethylphosphonic acid, 6-(N-methylacrylamido)hexylphosphonic acid, 10-(N-methylacrylamido) decylphosphonic acid, and 4-N-methylacrylamidomethyl)benzylphosphonic acid have been prepared in good yields for use in dental adhesives. They have been fully characterized by 1H-NMR, 13C-NMR, 31P-NMR, and by HRMS. All monomers are hydrolytically stable in aqueous solution. Free radical homopolymerizations of these monomers have been carried out in solution of ethanol/water (2.5/1:v/v), using 2,2′-azo(2-methylpropionamidine) dihydrochloride (AMPAHC) as initiator. They lead to homopolymers in moderate to excellent yields. Structure of the polymers has been confirmed by SEC/MALLS and 1H-NMR spectra. The photopolymerization behavior of the synthesized monomers with N,N′-diethyl-1,3-bis(acrylamido)propane has been investigated by DSC. New self-etch primers, based on these acrylamide monomers, have been formulated. Dentin shear bond strength measurements have shown that primers based on (N-methylacrylamido)alkylphosphonic acids assure a strong bond between the tooth substance and a dental composite. Moreover, the monomer with the longest spacer group provides the highest shear bond strength. © 2008 Wiley Periodicals, Inc.