title: Influences of composite-composite join on light transmission characteristics of layered resin composites.
abstract: OBJECTIVE
  The purposes of this study were: (1) to determine the light transmission characteristics (straight-line and diffusion transmission) of bulk-filled and layered resin composites, and (2) to evaluate the effect of layering filling on translucency and color appearance of resin composites.
  
  
  METHODS
  Three light-cured resin composites (EsteliteΣ, Tokuyama Dental; Beautifil II, Shofu and Clearfil Majesty, Kuraray Medical) in A2 and OA2 shades were used in this study. 2 mm-thick resin composite discs were prepared by two methods; bulk filling technique (2 mm filling at one time), layering technique (two layers each 1 mm thickness). The transmitted light intensity of each resin composite disc was measured using a goniophotometer, and diffusion factor (DF), an indicator for diffuse transmission property, and peak gain (G0) for straight-line transmission were calculated from the light distribution graphs. Color was measured according to the CIELAB color scale on a spectrophotometer, and the translucency parameter (TP) and color difference (ΔE(*)) between bulk-filled and layered specimens were calculated. The data were statistically analyzed using three-way ANOVA, and Dunnett's T3 and t-test for post-hoc test.
  
  
  RESULTS
  Three-way ANOVA revealed that the layered specimens had significantly lower G0 values and higher DF values than the bulk-filled specimens, and significantly reduced TP values. The color differences (ΔE(*)) ranged from 1.07 to 1.85 between the bulk-filled and layered specimens.
  
  
  CONCLUSIONS
  Resin composite placed in layers exhibited reduced straight-line light transmission and increased diffusion transmission compared with bulk-filled resin composite. The layering technique affected the translucency and color rendition of resin composite.
authors: Cariology and Operative Dentistry, Department of Restorative Sciences, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, 1-5-45, Yushima, Bunkyo-ku, Tokyo 113-8549, Japan.
authors: Kanako
authors: K
authors: Horie
authors: Masatoshi
authors: M
authors: Nakajima
authors: Keiichi
authors: K
authors: Hosaka
authors: Kimisuke
authors: K
authors: Kainose
authors: Azusa
authors: A
authors: Tanaka
authors: Richard M
authors: RM
authors: Foxton
authors: Junji
authors: J
authors: Tagami
mesh_terms: D017609:Barium Compounds / Q000737:chemistry; D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D055598:Chemical Phenomena; D003116:Color; D003188:Composite Resins / Q000737:chemistry* / Q000528:radiation effects; D001840:Dental Bonding; D003764:Dental Materials / Q000737:chemistry* / Q000528:radiation effects; D006801:Humans; D008027:Light; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D055620:Optical Phenomena; D010783:Photometry; D011092:Polyethylene Glycols / Q000737:chemistry; D011109:Polymethacrylic Acids / Q000737:chemistry; D012822:Silicon Dioxide / Q000737:chemistry; D013053:Spectrophotometry
chemical_list: D017609:Barium Compounds; C470433:Beautifil composite resin; D003188:Composite Resins; D003764:Dental Materials; C507124:Estelite sigma; D011109:Polymethacrylic Acids; C102738:barium glass filler; C541508:clearfil majesty; C020946:triethylene glycol dimethacrylate; D011092:Polyethylene Glycols; D017438:Bisphenol A-Glycidyl Methacrylate; D012822:Silicon Dioxide