title: Fracture toughness comparison of six resin composites.
abstract: OBJECTIVE
  This study investigated the Mode I and II fracture toughness values of resin composites used for the restorations of anterior teeth by the Brazilian disk test method.
  
  
  METHODS
  The Brazilian disk test was performed on six commercially available dental resin composites, Venus (hybrid resin composite), Durafill (micro-filled resin composite), Gradia (micro-filled/hybrid resin composite), Point4 (hybrid resin composite), Supreme (nano-particle resin composite) and Filtek Z250 (resin composite with zirconia particles). Five resin composite disks of 25 mm in diameter and 2mm in thickness with chevron notches were prepared for each fracture mode per material. The specimens were stored in distilled water for 24h at 37 degrees C, and then tested by a Zwick testing machine under compression mode with a constant crosshead speed of 0.25 mm/min at room temperature. The stress intensity factors under combined Modes I and II fracture toughness were calculated by the formula presented by Atkinson et al. The fracture patterns of two specimens randomly selected from each test group were examined using a scanning electron microscope. A one-way analysis of variance (ANOVA) was performed for the statistical evaluations followed by the post-hoc Tukey's Student Range (HSD) test.
  
  
  RESULTS
  The highest mean Mode I and II fracture toughness values were found in Filtek Z250 and Filtek Supreme and they were significantly higher than other materials (comparisons significant at the 0.05 level). The intermediate group consisted of Point4, Venus and Gradia ANTERIOR, whereas Durafill, statistically, had the lowest mean value for fracture toughness.
  
  
  CONCLUSIONS
  Fracture toughness values of hybrid and nano-particle resin composites are significantly higher than those of micro-filled resin composites. This suggests that the latter should be used for non-stress bearing areas.
authors: Department of Adult Restorative Dentistry, University of Nebraska Medical Center College of Dentistry, 40th and Holdrege Streets, Lincoln, Nebraska 68583, USA. hwatanabe@unmc.edu
authors: Hidehiko
authors: H
authors: Watanabe
authors: Satish C
authors: SC
authors: Khera
authors: Marcos A
authors: MA
authors: Vargas
authors: Fang
authors: F
authors: Qian
mesh_terms: D000704:Analysis of Variance; D003188:Composite Resins / Q000737:chemistry*; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis; D006244:Hardness; D008422:Materials Testing; D018709:Statistics, Nonparametric
chemical_list: D003188:Composite Resins