Synthesis and evaluation of new phosphonic, bisphosphonic and difluoromethylphosphonic acid monomers for dental application

New acid monomers 1– 3 were successfully prepared for dental applications. The capacity of these monomers to adhere to hydroxyapatite was investigated. Photopolymerization behaviors with N, N′-diethyl-1,3-bis(acrylamido)propane were studied. Bisphosphonic acid 2 exhibited the higher reactivity among the tested monomers. The adhesive properties of monomers 1– 3 were evaluated. Primers based on these new monomers were able to generate a strong bond between the tooth substance and a composite. Bisphosphonic acid 2 and difluoromethylphosphonic acid 3 gave the most promising results. Syntheses of novel 5-(methacryloyloxy)pentylphosphonic acid 1, 5-(methacryloyloxy)pentylidenebisphosphonic acid 2 and 1,1-difluoro-5-(methacryloyloxy)pentylphosphonic acid 3 are described. The ability of these monomers to adhere to hydroxyapatite was demonstrated using 31P CP-MAS NMR spectroscopy. Their copolymerization with N, N′-diethyl-1,3-bis(acrylamido)propane (DEBAAP) was investigated with photo differential scanning calorimetry. These mixtures exhibit a significantly higher reactivity than DEBAAP alone. Bisphosphonic acid 2 was shown to be significantly more reactive than monomers 1 and 3. Adhesive properties of these monomers were also studied. Adhesives based on bisphosphonic acid 2 and difluoromethylphosphonic acid 3 provide significantly higher dentin shear bond strength than the one based on phosphonic acid 1.