title: [Color property evaluation of 7 kinds of resin-based composite products].
abstract: OBJECTIVE
  To investigate the color stability and opacity of seven resin-based composite products after ultraviolet irradiation.
  
  
  METHODS
  Seven kinds of light-cured resin-based composite products (Aelite Flo, Filtek Z350 Flowable, Clearfil AP-X, Dyract AP, Z100, Durafill VS, Filtek Z350 Universal) were tested in the study (five for each group). Changes in color and opacity of test samples were determined before and after 8, 16 and 24 h ultraviolet irradiation using the CIE 1976 L*a*b* system and CIE 1931 XYZ system by a colorimeter.
  
  
  RESULTS
  The color of resin disks suffering ultraviolet irradiation was different in different irradiating time. Color difference values ranged from 1.85-3.21 for 8 h ultraviolet irradiation to 2.88-4.55 for 24 h ultraviolet irradiation. Opacity values ranged from 0.75-0.82 before ultraviolet irradiation to 0.80-0.98 after 24 h ultraviolet irradiation. Among all the groups, Z100 and Filtek Z350 Flowable showed the biggest color change, while Filtek Z350 Universal showed the highest opacity.
  
  
  CONCLUSIONS
  It can be concluded that for some products, ultraviolet irradiation leads to color instability and opacity variation.
authors.affiliation: Institute of Stomatology, Nanjing Medical University, Nanjing 210029, China.
authors.forename: Hai-feng
authors.initials: HF
authors.lastname: Xie
authors.forename: Xin
authors.initials: X
authors.lastname: Zhang
authors.forename: Ye
authors.initials: Y
authors.lastname: Zhu
authors.forename: Fei-min
authors.initials: FM
authors.lastname: Zhang
authors.forename: Feng
authors.initials: F
authors.lastname: He
mesh_terms: D003116:Color; D003124:Colorimetry; D003188:Composite Resins; D006801:Humans; D008027:Light; D008422:Materials Testing; D008689:Methacrylates
chemical_list: C112828:Clearfil AP-X; D003188:Composite Resins; D008689:Methacrylates; C533204:filtek Z350; C039734:Durafill