title: Effect of thermocycling on optical parameters of resin composites by the brand and shade.
abstract: OBJECTIVE
  To evaluate the difference in changes of optical properties of varied shades from varied brands of resin composites after thermocycling, and to determine the influence of the optical parameters, such as color coordinates, chroma and translucency, and the changes in these parameters on the color change.
  
  
  METHODS
  Eight light-curing resin composites (41 shades) were investigated. Color of 1-mm thick specimens was measured according to the CIELAB color scale over a white and over a black background on a reflection spectrophotometer before and after 5,000 cycles of thermocycling. Translucency parameter (TP) was calculated. The influence of the brand and shade on the changes in color, color coordinates, chroma, and TP was determined. Multiple regression analysis was performed to determine the influence of the optical parameters and the changes in these parameters on the color change.
  
  
  RESULTS
  Color change was in the range of 1.1 to 4.6 deltaE*ab units, and TP change was in the range of -3.8 to 0.1. Changes in optical parameters investigated were influenced by the brand of resin composite (P < 0.05). Several brands showed no significant difference by the shade depending on the optical parameter (P > 0.05). Based on multiple regression analysis, deltab*, deltaL*, deltaTP and L*-baseline significantly influenced the color change (P < 0.05).
authors.affiliation: Department of Dental Biomaterials Science and Dental Research Institute, School of Dentistry, Seoul National University, Seoul, Korea.
authors.forename: Seung-Hun
authors.initials: SH
authors.lastname: Lee
authors.forename: Yong-Keun
authors.initials: YK
authors.lastname: Lee
mesh_terms: D003116:Color; D003188:Composite Resins / Q000737:chemistry*; D003764:Dental Materials / Q000737:chemistry*; D006801:Humans; D008027:Light; D008422:Materials Testing; D055620:Optical Phenomena; D013053:Spectrophotometry; D013696:Temperature
chemical_list: C520091:CeramX; D003188:Composite Resins; D003764:Dental Materials; C474035:Filtek Supreme; C470230:Gradia; C533204:filtek Z350; C471182:glacier hybrid composite; C533205:gradio; C451741:point 4 composite resin; C507210:premise composite resin