title: Relationship between composite fracture toughness and bond strengths to enamel and dentine.
abstract: BACKGROUND
  This study aimed to evaluate the association between the fracture toughness of two nanofilled-hybrid resin composites (Clearfil Majesty Esthetic [CME], Kuraray Medical, Japan; Estelite Σ [ES], Tokuyama, Japan) and their bond strengths to enamel and dentine mediated by a self-etching primer system (Clearfil SE Bond [CSE]; Kuraray).
  
  
  METHODS
  Twenty-four permanent human molars were sectioned into enamel and dentine specimens and finished with 600-grit silicon carbide paper, bonded with CSE and either CME or ES, for μ-shear bond strength (μSBS) and μ-tensile bond strength (μTBS). The specimens were tested until failure at a cross-head speed of 1 mm/min, failure loads recorded, bond strengths calculated and results analysed using independent samples t-tests. Eight single-notched bar-shaped specimens, 30 mm × 5.2 mm × 2.2 mm, were prepared for each resin composite and fracture toughness measured using four-point bending at a cross-head speed of 0.5 mm/min. Results were analysed using independent samples t-tests.
  
  
  RESULTS
  For μSBS and μTBS, there was no significant difference between the resin composites for enamel or dentine. The fracture toughness of CME was significantly higher than that of ES.
  
  
  CONCLUSIONS
  For both enamel and dentine, resin composite fracture toughness affected neither μTBS nor μSBS to enamel or dentine.
authors.affiliation: Melbourne Dental School, The University of Melbourne, Victoria, Australia. olabisi.adebayo@utoronto.ca
authors.forename: O A
authors.initials: OA
authors.lastname: Adebayo
authors.forename: M F
authors.initials: MF
authors.lastname: Burrow
authors.forename: M J
authors.initials: MJ
authors.lastname: Tyas
mesh_terms: D000134:Acid Etching, Dental / Q000379:methods; D003188:Composite Resins / Q000737:chemistry*; D001840:Dental Bonding / Q000379:methods*; D003743:Dental Enamel / Q000737:chemistry*; D003799:Dental Stress Analysis; D003804:Dentin / Q000737:chemistry*; D017220:Dentin-Bonding Agents / Q000737:chemistry*; D006801:Humans; D008422:Materials Testing; D008689:Methacrylates; D008855:Microscopy, Electron, Scanning; D033081:Shear Strength; D013499:Surface Properties; D013718:Tensile Strength
chemical_list: D003188:Composite Resins; D017220:Dentin-Bonding Agents; D008689:Methacrylates