title: Fracture toughness of packable and conventional composite materials.
abstract: BACKGROUND
  The introduction of packable composite has expanded the choices of materials for the restoration of posterior teeth. Few independent studies are available on the fracture toughness (K(IC)) of the presently available packable composites compared with more conventional composite alternatives.
  
  
  OBJECTIVE
  This investigation evaluated the relative fracture toughness of 3 packable composites, 2 conventional composites, and 1 laboratory-processed composite.
  
  
  METHODS
  Six composite materials were tested in this study. These included: 3 packable composites (Alert, SureFil and Solitaire), 2 conventional composites (Herculite and Heliomolar), and 1 laboratory-processed composite (Belleglass). K(IC) was determined by preparing 8 mini-compact test specimens (8.2 mm diameter x 2 mm thickness) for each composite in a polytetrafluoroethylene split-mold with introduced precracks created with a razor blade. Specimens were stored in distilled water at 37 degrees +/- 2 degrees C for 7 days. Testing was performed on a universal testing machine at a displacement rate of 0.5 mm/min until fracture. Analysis of variance (P<.0001) and Ryan-Einot-Gabriel-Welsch multiple range tests (P<.05) were performed on all data.
  
  
  RESULTS
  The mean fracture toughness of Alert (1.57 Mpa x m(1/2)) was significantly greater than any of the other composites tested. Solitaire, a packable composite, exhibited a mean fracture toughness (0.67 MPa x m(1/2)) that was significantly lower than any of the other materials tested. No significant difference was noted between Belleglass (1.27 MPa x m(1/2)), SureFil (1.25 MPa x m(1/2)) and Herculite (1.16 MPa x m(1/2)).
  
  
  CONCLUSIONS
  Within the limitations of this study, the glass fiber-reinforced packable composite exhibited improved fracture toughness when compared with the other composite materials tested.
authors.affiliation: Section of Restorative Dentistry, Prosthodontics and Endodontics, College of Dentistry, The Ohio State University, Columbus, Ohio 43210, USA. knobloch.3@osu.edu
authors.forename: Lisa A
authors.initials: LA
authors.lastname: Knobloch
authors.forename: Ronald E
authors.initials: RE
authors.lastname: Kerby
authors.forename: Robert
authors.initials: R
authors.lastname: Seghi
authors.forename: Jeffrey S
authors.initials: JS
authors.lastname: Berlin
authors.forename: Nancy
authors.initials: N
authors.lastname: Clelland
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry; D000704:Analysis of Variance; D003188:Composite Resins / Q000737:chemistry*; D019232:Dental Restoration Failure; D003793:Dental Restoration, Permanent; D003799:Dental Stress Analysis; D005898:Glass; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry; D008963:Molar; D011140:Polyurethanes / Q000737:chemistry; D019279:Resin Cements / Q000737:chemistry; D018709:Statistics, Nonparametric
chemical_list: D000180:Acrylic Resins; C406265:Alert composite resin; C029012:Composite Dental Resin; D003188:Composite Resins; C513708:Heliomolar; D008689:Methacrylates; D011140:Polyurethanes; D019279:Resin Cements; C113049:Solitaire composite resin; C403464:SureFil packable composite; C110370:belleGlass; C009753:fiberglass; C065770:Herculite XR