title: Failure Strengths of Composite Additions and Repairs.
abstract: OBJECTIVE
  When adding composite to a cured composite restoration, the intent is to achieve the same failure strength as the original restorative material. This study evaluated the failure strengths of added or repaired composite using various chemical and/or mechanical surface treatments.
  
  
  METHODS
  Failure strengths were determined using a four-point bending test. Beam-shaped specimens were fabricated by adding new composite to cured composite (Filtek Supreme Ultra). The cured composites were either fresh or aged seven days (N=10-14). The composite surfaces were left unground or were ground before treatment with various combinations of roughening, acid etching, silane, and dental adhesives (conventional Adper SingleBond Plus or new multimode Scotchbond Universal) and/or tribochemistry (CoJet system). Monolithic composite specimens were the control. Failure strengths were statistically analyzed using one-way analysis of variance and the Fisher protected least significant difference (α=0.05).
  
  
  RESULTS
  Failure strengths (mean ± standard deviation) when composite was added to unground freshly cured composites (111±25 MPa) and aged composites using a new multimode adhesive with (102±22 MPa) or without (98±22 MPa) tribochemical treatment were not significantly lower than the monolithic specimens (122±23 MPa). Grinding the surfaces of freshly cured composite significantly reduced failure strength, either with (81±30 MPa) or without (86±31 MPa) use of conventional adhesive. Failure strengths of aged composites were also significantly lower (51±21 MPa with SingleBond Plus), even after tribochemical treatment (71±29 MPa with SingleBond Plus; 73±35 MPa with Silane-Visiobond).
  
  
  CONCLUSIONS
  Using a new multimode adhesive when adding composite to freshly cured or aged composite substrates recovered the failure strength to that of the original monolithic composite.
authors.forename: D
authors.initials: D
authors.lastname: Tantbirojn
authors.forename: C
authors.initials: C
authors.lastname: Fernando
authors.forename: A
authors.initials: A
authors.lastname: Versluis
mesh_terms: D017438:Bisphenol A-Glycidyl Methacrylate; D003188:Composite Resins; D001840:Dental Bonding; D003738:Dental Cements; D019232:Dental Restoration Failure; D058250:Dental Restoration Repair / Q000379:methods*; D003799:Dental Stress Analysis; D017220:Dentin-Bonding Agents; D066298:In Vitro Techniques; D008422:Materials Testing; D019279:Resin Cements; D012821:Silanes
chemical_list: D003188:Composite Resins; D003738:Dental Cements; D017220:Dentin-Bonding Agents; C000590992:Filtek Supreme Ultra; D019279:Resin Cements; D012821:Silanes; D017438:Bisphenol A-Glycidyl Methacrylate; C081713:Visio-Bond; C041330:Scotchbond