Dentine bonding agents
Bonding agents are often methacrylates with some volatile carrier and solvent like acetone. They also contain some diluent monomers, most typically HEMA and TEGDMA, but occasionally UDMA. For proper bonding of resin composite restorations, dentin should be conditioned with polyacrylic acids to remove a smear layer, created during mechanical treatment with dental bore, and expose some of the collagen network or organic matrix of dentin. Dentine should NEVER be etched with a phosphoric acid etching agent, as it will cause hyposensitivity and dehydrate dentine tubules- which effects the retention of GIC base products. Adhesive resin should create the so-called hybrid layer (consisting of a collagen network exposed by etching and embedded in adhesive resin). This layer is an interface between dentin and adhesive resin and the final quality of dental restoration depends greatly on its properties. Modern dental bonding systems come as a “three-step system”, where the etchant, primer, and adhesive are applied sequentially; as a “two-step system”, where the etchant and the primer are combined for simultaneous application; and as a “one-step system”, where all the components should be premixed and applied in a single application (so-called seventh generation of bonding agents).
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