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

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.

Graphical abstractNew 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.Figure optionsDownload full-size imageDownload as PowerPoint slide