title: Assessment by nano-indentation of the hardness and elasticity of the resin-dentin bonding area.
abstract: The hardness and Young's modulus of the successive layers across a resin-dentin bonding area were determined by nano-indentation for four commercially-available dentin adhesive systems, of which two were also applied with a different conditioning agent. With a computer-controlled nano-indentation technique, minute triangular indentations were made within a small area of a few micrometers' diameter at a load of a few milli-Newtons. The load and displacement of the indenter were continuously monitored during the loading-unloading sequence, so hardness and Young's modulus could be computed as a function of the indenter geometry and the applied load. The hardness of the resin-dentin interdiffusion zone was significantly lower than that of unaltered dentin. A gradient of moduli of elasticity was observed from the rather stiff dentin over a more elastic resin-dentin interdiffusion zone and adhesive resin layer to the restorative composite. That gradient was more substantial in those systems that produced relatively thick adhesive resin layers or supplementally provided a filled low-viscosity resin as an intermediate layer between the adhesive resin and the bulk restorative composite. Such an elastic bonding area might have a strain capacity sufficient to relieve stresses between the shrinking composite restoration and the rigid dentin substrate, thereby improving the conservation of the dentin bond and, as a consequence, the marginal integrity and retention of the restoration.
authors.affiliation: Department of Operative Dentistry and Dental Materials, Katholieke Universiteit te Leuven, Belgium.
authors.forename: B
authors.initials: B
authors.lastname: Van Meerbeek
authors.forename: G
authors.initials: G
authors.lastname: Willems
authors.forename: J P
authors.initials: JP
authors.lastname: Celis
authors.forename: J R
authors.initials: JR
authors.lastname: Roos
authors.forename: M
authors.initials: M
authors.lastname: Braem
authors.forename: P
authors.initials: P
authors.lastname: Lambrechts
authors.forename: G
authors.initials: G
authors.lastname: Vanherle
mesh_terms: D003188:Composite Resins / Q000737:chemistry; D003799:Dental Stress Analysis / Q000295:instrumentation; D003804:Dentin / Q000502:physiology / Q000648:ultrastructure*; D017220:Dentin-Bonding Agents / Q000737:chemistry*; D004548:Elasticity; D006244:Hardness; D006801:Humans; D008689:Methacrylates / Q000737:chemistry; D019279:Resin Cements; D013314:Stress, Mechanical; D013499:Surface Properties
chemical_list: C074864:All-Bond system; C029849:Clearfil Bonding Agent; D003188:Composite Resins; D017220:Dentin-Bonding Agents; D008689:Methacrylates; C070605:Mirage-Bond; D019279:Resin Cements; C041330:Scotchbond