title: The effect of aging on the fracture toughness of esthetic restorative materials.
abstract: OBJECTIVE
  To compare the fracture toughness (KIc) of tooth-colored restorative materials based on a four-point bending; to assess the effect of distilled water and a resin surface sealant (G-Coat Plus) on the resistance of the materials to fracture.
  
  
  METHODS
  Specimens were prepared from six materials: Quix Fil; Dyract (Dentsply), Freedom (SDI), Fuji VII (GC), Fuji IX (GC); Fuji II LC (GC). Fuji II LC and Fuji IX were tested both with and without applying G-Coat Plus (GC). The specimens were divided into the three groups which were conditioned in distilled water at 37 degrees C for 48 hours, 4 and 8 weeks. The specimens were loaded in a four-point bending test using a universal testing machine. The maximum load to specimen failure was recorded and the fracture toughness calculated.
  
  
  RESULTS
  There were significant differences among most of the materials (P < 0.001). Quix Fil had the highest mean KIc value and Fuji VII the lowest. Immersion in distilled water for the resin composite and polyacid-modified resin composites caused a significant decrease in KIc as the time interval increased. For glass-ionomer cements, KIc decreased significantly after 4 weeks, and after 8 weeks immersion slightly increased. G-Coat Plus affected Fuji II LC positively while it had no effect on the Fuji IX.
authors: Department of Restorative Dentistry, Dental School, Shiraz University of Medical Science, Shiraz, Iran. bagherir@unimelb.edu.au
authors: Rafat
authors: R
authors: Bagheri
authors: Mohammad R
authors: MR
authors: Azar
authors: Martin J
authors: MJ
authors: Tyas
authors: Michael F
authors: MF
authors: Burrow
mesh_terms: D020099:Coated Materials, Biocompatible; D020770:Compomers; D003188:Composite Resins; D003793:Dental Restoration, Permanent; D003799:Dental Stress Analysis; D005899:Glass Ionomer Cements; D008422:Materials Testing; D018583:Pliability; D019279:Resin Cements; D013997:Time Factors; D014867:Water
chemical_list: D020099:Coated Materials, Biocompatible; D020770:Compomers; D003188:Composite Resins; C000618651:G-Coat Plus; D005899:Glass Ionomer Cements; D019279:Resin Cements; D014867:Water