ABSTRACT
OBJECTIVES: Acrylophosphonic acid (H(2)L) was reacted with biological apatite originating from dental enamel powder in order to identify and study the reaction products formed during the use of self-etch monomers. Nuclear magnetic resonance spectroscopy (NMR) showed the formation of brushite and a calcium salt of acrylophosphonic acid. This Ca salt was further synthesized and characterized by NMR, Fourier transform-infrared (FT-IR) and chromatography coupled with potentiometric analysis. The results reveal that calcium ions form a compound with two mono-deprotonated acrylophosphonate anions at physiological pH values. Thus, dissolution of the biological apatite by the acid-etch releases phosphate and calcium ions that combine to form brushite. The remaining dissolved Ca neutralize the acrylophosphonic acid to form an ionic salt of formula Ca(HL)(2). SIGNIFICANCE: The stoichiometry of this calcium salt allows us to conclude that, following a self-etch procedure, dissolved Ca ions participate in the formation of crosslinks in the complex photopolymerized copolymer composite network of the hybrid layer.
Subject(s)
Acid Etching, Dental , Acrylic Resins/chemistry , Dentin-Bonding Agents/chemistry , Hydroxyapatites/chemistry , Organophosphonates/chemistry , Resin Cements/chemistry , Calcium/chemistry , Calcium Phosphates/chemical synthesis , Diphosphonates/chemical synthesis , Humans , Magnetic Resonance Spectroscopy , Molar, Third , Phase Transition , Spectroscopy, Fourier Transform InfraredABSTRACT
UNLABELLED: 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 pK(a1)=2.4 and pK(a2)=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.
