Synthesis and photo-polymerization of an aryl diphosphonic acid-containing dimethacrylate for dental materials

Abstract

A new dental dimethacrylate monomer containing phosphonic acid functionality, 2,5-bis(methacryloyloxy)-1,4-phenylenediphosphonic acid (1), was synthesized by silylation of 2,5-bis(diethoxyphosphoryl)-1,4-phenylene bis(2-methylacrylate) (2) with trimethylsilyl bromide (TMSBr) followed by the hydrolysis of the silyl ester. The monomer was solid and soluble in ethanol and water. The structure of this monomer was characterized by 1H-, 13C-, 31P-NMR and FT-IR spectroscopy. The aqueous solution of 1 is acidic (pH 1.65), so that it is expected to etch enamel and dentin, but is prone to hydrolysis over long storage periods. The co-polymerization behavior of this monomer with 2-hydroxyethyl methacrylate (HEMA) was investigated in water using photodifferantial scanning calorimeter at 40°C with bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (BAPO) as photoinitiator. It was observed that the addition of monomer 1 to HEMA slightly decreased both the maximum rate of polymerization and conversion. The thermal solution co-polymerization of this monomer with acrylamide (AAm) and HEMA gave cross-linked polymers, indicating its incorporation into the co-polymers. The interaction of this monomer with hydroxyapatite was observed using FT-IR spectroscopy. This monomer was found to be more suitable for dental composites than dental adhesives. © 2010 Koninklijke Brill NV, Leiden.