title: Early hardness of self-adhesive resin cements cured under indirect resin composite restorations.
abstract: OBJECTIVE
  To determine the influence of curing mode on the surface hardness of seven resin cements used to lute indirect composite restorations.
  
  
  METHODS
  Seven commercial dual-curing resin cements were tested: two were total-etch (RelyX ARC [3M ESPE, St. Paul, MN, USA] and Variolink II [Ivoclar Vivadent, Schaan, Liechtenstein]); one was self-etch (Multilink Automix [Ivoclar Vivadent]), and four were self-adhesive (RelyX Unicem [3M ESPE], Maxcem Elite [Kerr Corp., Orange, CA, USA], SmartCem2 [Dentsply, Detrey, GmbH, Konstanz, Germany], and G-Cem [GC CORPORATION, Itabashi-Ku, Tokyo, Japan]). Three specimens (0.5 × 6.5mm) of each material were prepared for each of three experimental groups: Group 1 (cements allowed to self cure); Group 2 (cements light-cured for 40 seconds); and Group 3 (cements light-cured for 80 seconds). All specimens were cured through a 4-mm-thick composite cylinder (Filtek Z250-A3). Surface microhardness numbers were determined at 20 min after preparation. Results were analyzed by two-way analysis of variance and Student-Newman-Keuls tests (p<0.05).
  
  
  RESULTS
  Superficial hardness was significantly influenced by the resin cement tested (p<0.0001), the curing mode (p<0.0001), and their interaction (p<0.0001). RelyX ARC exhibited the highest mean microhardness values regardless of the curing mode. Light-curing significantly increased the microhardness of all resin cements studied, and these values increased even further with a doubling of irradiation time. Self-adhesive cements exhibited different behavior according to the curing mode. RelyX Unicem was highly sensitive to light irradiation, showing the lowest mean values in the self-curing mode. After light irradiation for 40 or 80 seconds, Maxcem Elite exhibited the lowest mean hardness values of all the resin cements tested.
  
  
  CONCLUSIONS
  The microhardness of resin cements is highly dependent on the brand. Dual-curing resin cements should always be light irradiated for longer periods than that recommended by manufacturers.
  
  
  CONCLUSIONS
  Dual-curing resin cements should always be light-cured for longer irradiation times, as light irradiation for 80 seconds yields the highest microhardness values in comparison with self-curing or light irradiation for 40 seconds. However, some self-adhesive resin cements exhibit low microhardness values when used to cement 4-mm-thick indirect composite restorations regardless of the curing mode applied.
authors.affiliation: Department of Health Sciences III, Rey Juan Carlos University, Avda. de Atenas s/n, 28922 Alcorcón, Madrid, Spain.
authors.forename: Isabel
authors.initials: I
authors.lastname: Giráldez
authors.forename: Laura
authors.initials: L
authors.lastname: Ceballos
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Garrido
authors.forename: Jesús
authors.initials: J
authors.lastname: Rodríguez
mesh_terms: D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry*; D003764:Dental Materials / Q000737:chemistry*; D003793:Dental Restoration, Permanent; D006244:Hardness; D006801:Humans; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry; D011092:Polyethylene Glycols / Q000737:chemistry; D058105:Polymerization; D011109:Polymethacrylic Acids / Q000737:chemistry; D011140:Polyurethanes / Q000737:chemistry; D019279:Resin Cements / Q000737:chemistry*; D055116:Self-Curing of Dental Resins / Q000379:methods*; D013499:Surface Properties; D013997:Time Factors
chemical_list: D003188:Composite Resins; D003764:Dental Materials; C528107:G-Cem resin cement; C515955:Maxcem; D008689:Methacrylates; D011109:Polymethacrylic Acids; D011140:Polyurethanes; C483701:Rely X Unicem; C462240:RelyX ARC; D019279:Resin Cements; C533204:filtek Z350; C502351:multilink adhesive system; C029824:urethane dimethacrylate luting resin; C103502:Variolink; D011092:Polyethylene Glycols; D017438:Bisphenol A-Glycidyl Methacrylate