Hybrid formation and improvement for bonding to tooth hard tissue

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Improvements in adhesives based on adherent surface treatment and functional macromolecules have permitted the use of adhesive dentistry technique in a wide field, from caries prevention through prosthetic rehabilitation. However, the adhesion within the severe intra-oral conditions presents problems in marginal sealing, adhesive strength and durability. The main reasons may be the formation, structure and mechanical properties of the interfacial layer between the tooth structure and the adhesive (resin). Aiming to obtain a sound interfacial layer formation, in this study we developed and analyzed the properties of a primer with strong interaction between the structural elements of the interfacial layer, which are apatite and collagen.1) The primer was prepared by synthesis of aminoacid methacrylates (NMGly, NMBu, NAAsp, NMVa, NMCa, etc) and dissolution in distilled water in a series of concentrations. 2) The interaction between primer and dentinal collagen was obtained by measurement … More of the relaxation time (T1) with NMR.3) For bond strength measurements, human and bovine dentin ground with silicon carbide paper (600-grit) were treated with the experimental primers, followed by application of a commercially available ester-phosphate based bonding agent and filling with composite resin. 4) The SEM and TEM were used for structural analysis of the adhesive interfaces and adherent surfaces.The interaction between collagen and primers based on amino-acid methacrylate solutions varied depending on the type of aminoacid. The sequence of strong combinations was as follows : Va>Bu>Ca>Ala>Gly. The bond strength of bonding agents after treatment to dentin with 40% phosphoric acid and each type of primer was from 9 to 16 Mpa, showing correlation with the results for collagen and primer interactions. A hybrid layer of collagen and polymerized resin 4 to 6 μm wide was formed in the dentin side of the adhesive interface. The results of this study show that a primer with strong interaction to the adherent substrate is indispensable for adhesion. Less