title: Fracture toughness of posterior resin composites.
abstract: OBJECTIVE
  The purpose of this study was to evaluate and compare the resistance to crack propagation, as measured by the fracture toughness, of some packable posterior resin composites with other posterior resin composite materials.
  
  
  METHODS
  Fracture toughness determinations were made for the 5 packable and the other posterior resin composites using 3-point flexure of beams with a standardized central single-edge notch. Ten beams of each material were tested on an Instron test machine. The maximum loads were determined, from which the fracture toughness values (KIC) were calculated. The data were analyzed statistically using ANOVA and t tests.
  
  
  RESULTS
  The resin composites tested demonstrated a range of KIC values. The materials were separated according to the mean KIC values into 5 groups that were statistically different. While 2 packable resin composites had KIC values that were among the highest, the other packables were substantially lower than nonpackables. The intermediate value group consisted of 3 of the conventional posterior resin composites.
  
  
  CONCLUSIONS
  There was a very weak correlation between fracture toughness and reported volume concentration of particulate reinforcing elements. The posterior resin composites tested exhibited a spectrum of KIC values. The packable resin composites were distributed along this spectrum, with 2 products exhibiting high potential for resistance to crack propagation.
authors.affiliation: Division of Restorative Dentistry, University of California School of Dentistry, Los Angeles, California 90095, USA. edbonilla2@juno.com
authors.forename: E D
authors.initials: ED
authors.lastname: Bonilla
authors.forename: G
authors.initials: G
authors.lastname: Mardirossian
authors.forename: A A
authors.initials: AA
authors.lastname: Caputo
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry; D000704:Analysis of Variance; D003188:Composite Resins / Q000737:chemistry*; D003764:Dental Materials / Q000737:chemistry*; D003793:Dental Restoration, Permanent; D003799:Dental Stress Analysis / Q000295:instrumentation; D006801:Humans; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry; D018583:Pliability; D011140:Polyurethanes / Q000737:chemistry; D012822:Silicon Dioxide; D013223:Statistics as Topic; D013314:Stress, Mechanical; D013499:Surface Properties; D014783:Viscosity; D015040:Zirconium
chemical_list: D000180:Acrylic Resins; C406265:Alert composite resin; C084111:Charisma composite resin; C029012:Composite Dental Resin; D003188:Composite Resins; D003764:Dental Materials; D008689:Methacrylates; D011140:Polyurethanes; C099128:Prodigy; C113049:Solitaire composite resin; C403464:SureFil packable composite; C121818:Tetric ceram; C083568:Z100 composite resin; C078905:Bisfil; C029824:urethane dimethacrylate luting resin; D012822:Silicon Dioxide; D015040:Zirconium