title: Marginal adaptation of posterior resins: effect of dentin-bonding agent and hygroscopic expansion.
abstract: The wall-to-wall polymerization contraction of three composite resins, provisionally accepted by the American Dental Association for use in posterior teeth, was investigated in dentin cavities prepared in extracted human teeth. The marginal adaptation was measured in a light microscope 10 min after polymerization or after 28 days of water absorption. The three composites were tested with and without previous application of two dentin-bonding agents. Used as the control was a microfilled resin intended for use in anterior teeth. None of the two dentin-bonding agents could prevent the formation of a contraction gap of any of the four resins, but the results obtained with the anterior material were significantly better than those obtained with the posterior resins. The reason for the low efficacy of the dentin-bonding agents, when used with the posterior resins, is assumed to be the high viscosity of these restoratives, caused by both the high quantity of fillers and the composition of the organic components. As to the hygroscopic expansion, the contraction gaps of the anterior resin were closed within 28 days, while the posterior materials all had a residual gap. The reason for the smaller hygroscopic expansion of the posterior resins is assumed to be related to the reduced quantity of organic material in these composites.
authors.forename: E K
authors.initials: EK
authors.lastname: Hansen
authors.forename: E
authors.initials: E
authors.lastname: Asmussen
mesh_terms: D000042:Absorption; D001641:Bicuspid; D003188:Composite Resins; D001840:Dental Bonding; D003804:Dentin; D006801:Humans; D008963:Molar; D013499:Surface Properties
chemical_list: D003188:Composite Resins