title: Microhardness evaluations of resin-dentin bonding areas by nano-indentation.
abstract: The purpose of this experiment was to determine the hardness values of the hybrid layer and its surroundings through the continuous use of a microhardness measuring device. Black's Class V cavities were prepared in nine dog teeth. The cavities were divided into four groups according to the dentin adhesive system applied. The adhesive systems were: "Bond One System", "Liner Bond II sigma System", "One Step System", and "Single Bond System". The treated teeth were observed at seven days post-application. Specimens were cross-sectioned perpendicularly or horizontally to the resin-dentin interface and embedded in epoxy resin. Their surfaces were polished. The microhardness of the resin-dentin bonding area was measured with a nano-indentation tester. The hardness values at a point of 10 microns distant from the interface in the direction of the dentin differed between systems. It appeared that this was influenced by the presence of the decalcified dentin not impregnated by resin, differences in the chemistry forming the hybrid layer, and the composition of the bonding resin. The hardness of the dentin-bonding interface and its surroundings was determined, and these areas were observed using SEM. Three layers were confirmed the healthy dentin layer, the composite resin layer, and the hybrid layer, (in which decalcified dentin impregnated by resin and that not impregnated by resin are considered to be mix). In the hybrid layer, no impression was found by SEM although the hardness in the bonding interface was significantly different. These layers appear to be more elastic and softer than the healthy dentin.
authors.affiliation: Third Department of Conservative Dentistry, Tokyo Dental College, Chiba, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Nakazawa
authors.forename: E
authors.initials: E
authors.lastname: Seino
authors.forename: T
authors.initials: T
authors.lastname: Ushiki
authors.forename: T
authors.initials: T
authors.lastname: Ogata
authors.forename: Y
authors.initials: Y
authors.lastname: Hirai
authors.forename: E
authors.initials: E
authors.lastname: Kawada
authors.forename: Y
authors.initials: Y
authors.lastname: Oda
mesh_terms: D000818:Animals; D017438:Bisphenol A-Glycidyl Methacrylate; D001840:Dental Bonding; D003804:Dentin / Q000648:ultrastructure; D017220:Dentin-Bonding Agents; D004285:Dogs; D006168:Guinea Pigs; D006244:Hardness; D008422:Materials Testing; D008689:Methacrylates; D019279:Resin Cements
chemical_list: C115611:BOND-1 adhesive; C103506:Bis-GMA, BPDM, HEMA dental-bonding resin; C084544:Clearfil Linerbond System; D017220:Dentin-Bonding Agents; D008689:Methacrylates; D019279:Resin Cements; C115612:single bond; D017438:Bisphenol A-Glycidyl Methacrylate