The role of acrylophosphonic acid monomers in the formation of hybrid layers based on self-etch adhesives

The role of acrylophosphonic acid monomers in the formation of hybrid layers based on self-etch adhesives. Objectives Our plan was to define the reaction products formed when an acrylophosphonic acid reacts with tooth hard tissue. Our aim was to describe the incorporation of the reaction products in the hybrid layer formed. Methods Potentiometric methods were used to measure acid dissociation constants and investigate calcium complex formation. Infrared spectroscopy and NMR were used to follow water contents and show transformation of phosphorous containing compounds. Results The acrylophosphonic acid contained in AdheSE (Ivoclar Vivadent, Schaan, Liechtenstein) is characterized by two acidities with pKa1 = 2.4 and pKa2 = 7.0, and interacts with calcium ions in a purely ionic fashion. When hydroxyapatite crystals are dissociated by the presence of AdheSE, brushite is formed together with a calcium cross-linked network of the phosphonate containing copolymer. Conclusion The results give a new image of the hybrid layer where the adhesive behaves like an ionomer resin incorporating collagen but also minerals and salt bridges.