title: Effect of storage times and mechanical load cycling on dentin bond strength of conventional and self-adhesive resin luting cements.
abstract: BACKGROUND
  The lack of long-term bond stability between resin cements and dentin may compromise the success of indirect restorations.
  
  
  OBJECTIVE
  The purpose of this study was to evaluate the effects of long-term storage in artificial saliva and mechanical load cycling on the microtensile bond strength of conventional and self-adhesive resin cements to dentin.
  
  
  METHODS
  The occlusal dentin surfaces of 128 human molars were exposed and flattened. The teeth were assigned to 16 groups (n=8) according to resin cement and in vitro aging strategy. Two self-adhesive resin cements (RelyX Unicem and Clearfil SA Cement) and 2 conventional cementing systems (RelyX ARC and Clearfil Esthetic Cement) were used. Resin cements were applied to prepolymerized indirect resin disks, which were bonded to the dentin surfaces and light polymerized. The control groups were represented by immediate microtensile bond strength (24 hours) and aging methods were performed with mechanical load cycling or storage in artificial saliva (1 year and 2 years). Bonded beams were tested in tension until failure. Data (MPa) were analyzed by Proc Mixed for repeated measures and the Tukey-Kramer test (α=.05).
  
  
  RESULTS
  The self-adhesive resin cements exhibited higher microtensile bond strength than conventional cementing systems for all conditions studied. The microtensile bond strength of RelyX ARC and self-adhesive resin cements did not decrease after storage in artificial saliva and mechanical load cycling. The Clearfil Esthetic Cement showed the lowest microtensile bond strength and a significant reduction after 2 years of storage in artificial saliva.
  
  
  CONCLUSIONS
  The storage times and mechanical load cycling did not affect the microtensile bond strength of self-adhesives and RelyX ARC resin cements. The highest microtensile bond strength was obtained for self-adhesive resin cements, with no significant difference between them.
authors.affiliation: Department of Restorative Dentistry, Piracicaba Dental School, State University of Campinas, Piracicaba, SP, Brazil.
authors.forename: Thaiane R
authors.initials: TR
authors.lastname: Aguiar
authors.affiliation: Doctoral student, Department of Restorative Dentistry, Piracicaba Dental School, State University of Campinas, Piracicaba, SP, Brazil.
authors.forename: Carolina B
authors.initials: CB
authors.lastname: André
authors.affiliation: Professor, Department of Restorative Dentistry, Dental Materials Division, Piracicaba Dental School, State University of Campinas, Piracicaba, SP, Brazil.
authors.forename: Lourenço
authors.initials: L
authors.lastname: Correr-Sobrinho
authors.affiliation: Assistent Professor, Department of Operative Dentistry, School of Dentistry, Ponta Grossa State University, Ponta Grossa, PR, Brazil.
authors.forename: César A G
authors.initials: CA
authors.lastname: Arrais
authors.affiliation: Associate Professor, Department of Social Dentistry, Piracicaba Dental School, State University of Campinas, Piracicaba, SP, Brazil.
authors.forename: Gláucia M B
authors.initials: GM
authors.lastname: Ambrosano
authors.affiliation: Associate Professor, Department of Restorative Dentistry, Piracicaba Dental School, State University of Campinas, Piracicaba, SP, Brazil. Electronic address: giannini@fop.unicamp.br.
authors.forename: Marcelo
authors.initials: M
authors.lastname: Giannini
mesh_terms: D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry; D001840:Dental Bonding; D003799:Dental Stress Analysis / Q000295:instrumentation; D003804:Dentin / Q000648:ultrastructure*; D006801:Humans; D055115:Light-Curing of Dental Adhesives; D008422:Materials Testing; D011092:Polyethylene Glycols / Q000737:chemistry; D058105:Polymerization; D011109:Polymethacrylic Acids / Q000737:chemistry; D019279:Resin Cements / Q000737:chemistry*; D012464:Saliva, Artificial / Q000737:chemistry; D013314:Stress, Mechanical; D013718:Tensile Strength; D013997:Time Factors
chemical_list: C581302:Clearfil SA; D003188:Composite Resins; D011109:Polymethacrylic Acids; C483701:Rely X Unicem; C462240:RelyX ARC; D019279:Resin Cements; D012464:Saliva, Artificial; C477352:Sinfony composite resin; C530542:clearfil esthetic cement; D011092:Polyethylene Glycols; D017438:Bisphenol A-Glycidyl Methacrylate