title: [Aging of silorane- and methacrylate-based composite resins: effects on color and translucency].
abstract: OBJECTIVE
  To evaluate the color stability and translucency of silorane-based low shrinkage composite after in vitro aging procedures of thermal cycling and water storage respectively, and to compare with those of conventional methacrylate-based posterior composite.
  
  
  METHODS
  Three light-cured composite resins, dimethacrylate-based composite A (Filtek™ Z350), B (Filtek™ P60) and silorane-based composite C (Filtek™ P90), were tested in this study. Ten specimens (10 mm in diameter, 1 mm in height) of each composite were prepared. The ten specimens in each group were then divided into two subgroups (n = 5). One subgroup underwent thermal cycling [(5.0 ± 0.5)~(55.0 ± 1.0) °C, 10 000 cycles] and the other was stored in 37 C° distilled water for 180 days. With a spectrophotometer, the CIE L * a * b * parameters of the specimens were tested before and after artificial aging against white, medium grey and black backgrounds, respectively. △E, TP and △TP were calculated and data were analyzed using independent-samples t test and partial analysis (P < 0.05).
  
  
  RESULTS
  With regard to color stability, silorane-based composite showed color alteration above the clinically acceptable levels (△E > 3.3), and also showed higher △E with a statistically significant difference in comparison with the other composites (B and C) (P < 0.05) after artificial aging. With regard to translucency, composite C showed more alteration compared with composite B (P < 0.05) after thermal cycling.
  
  
  CONCLUSIONS
  It may be concluded that the silorane-based composite underwent greater alteration with regard to color stability and translucency.
authors.affiliation: Department of General Dentistry, Peking University School and Hospital of Stomatology, Beijing 100081, China.
authors.forename: Chang
authors.initials: C
authors.lastname: Liu
authors.forename: Jie
authors.initials: J
authors.lastname: Pan
authors.forename: Hong
authors.initials: H
authors.lastname: Lin
authors.affiliation: Center of Stomatology, Peking University Hospital, Beijing 100871, China; Email: shensong@pku.edu.cn.
authors.forename: Song
authors.initials: S
authors.lastname: Shen
mesh_terms: D000375:Aging; D003116:Color; D003188:Composite Resins; D008027:Light; D008422:Materials Testing; D008689:Methacrylates; D062047:Silorane Resins; D013053:Spectrophotometry; D013499:Surface Properties; D014867:Water
chemical_list: D003188:Composite Resins; C438835:Filtek P60 Composite Resin; D008689:Methacrylates; D062047:Silorane Resins; C544925:filtek P90; C533204:filtek Z350; D014867:Water