title: Fracture toughness versus micro-tensile bond strength testing of adhesive-dentin interfaces.
abstract: OBJECTIVE
  To assess interfacial fracture toughness of different adhesive approaches and compare to a standard micro-tensile bond-strength (μTBS) test.
  
  
  METHODS
  Chevron-notched beam fracture toughness (CNB) was measured following a modified ISO 24370 standard. Composite bars with dimensions of 3.0×4.0×25 mm were prepared, with the adhesive-dentin interface in the middle. At the adhesive-dentin interface, a chevron notch was prepared using a 0.15 mm thin diamond blade mounted in a water-cooled diamond saw. Each specimen was loaded until failure in a 4-point bend test setup and the fracture toughness was calculated according to the ISO specifications. Similarly, adhesive-dentin micro-specimens (1.0×1.0×8-10 mm) were stressed in tensile until failure to determine the μTBS.
  
  
  RESULTS
  A positive correlation (r(2)=0.64) was observed between CNB and μTBS, which however was only nearly statistically significant, mainly due to the dissimilar outcome of Scotchbond Universal (3M ESPE). While few μTBS specimens failed at the adhesive-dentin interface, almost all CNB specimens failed interfacially at the notch tip. Weibull moduli for interfacial fracture toughness were much higher than for μTBS (3.8-11.5 versus 2.7-4.8, respectively), especially relevant with regard to early failures.
  
  
  CONCLUSIONS
  Although the ranking of the adhesives on their bonding effectiveness tested using CNB and μTBS corresponded well, the outcome of CNB appeared more reliable and less variable. Fracture toughness measurement is however more laborious and requires specific equipment. The μTBS nevertheless appeared to remain a valid method to assess bonding effectiveness in a versatile way.
authors.affiliation: KU Leuven-Biomat, Department of Oral Health Sciences, KU Leuven (University of Leuven), Leuven, Belgium. jan.demunck@med.kuleuven.be
authors.forename: Jan
authors.initials: J
authors.lastname: De Munck
authors.forename: Anne-Katrin
authors.initials: AK
authors.lastname: Luehrs
authors.forename: André
authors.initials: A
authors.lastname: Poitevin
authors.forename: Annelies
authors.initials: A
authors.lastname: Van Ende
authors.forename: Bart
authors.initials: B
authors.lastname: Van Meerbeek
mesh_terms: D003188:Composite Resins / Q000737:chemistry; D001840:Dental Bonding; D003764:Dental Materials / Q000737:chemistry; D003799:Dental Stress Analysis / Q000295:instrumentation; D003804:Dentin / Q000648:ultrastructure*; D017220:Dentin-Bonding Agents / Q000737:chemistry*; D055119:Elastic Modulus; D006801:Humans; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry; D008855:Microscopy, Electron, Scanning; D018583:Pliability; D019279:Resin Cements / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D013696:Temperature; D013718:Tensile Strength; D013997:Time Factors; D014867:Water / Q000737:chemistry
chemical_list: C074864:All-Bond system; C438313:Clearfil SE Bond; D003188:Composite Resins; D003764:Dental Materials; D017220:Dentin-Bonding Agents; D008689:Methacrylates; C469607:OptiBond FL; D019279:Resin Cements; C581746:vertise flow; D014867:Water; C065770:Herculite XR; C041330:Scotchbond