title: [Study on color stability of composite resins for a facing crown polymerized with high output photo-curing unit].
abstract: OBJECTIVE
  This study investigated the color stability of composite resins for a facing crown cured with a high output photo-curing unit (Hyper LII, YAMAHACHI DENTAL MFG., CO.).
  
  
  METHODS
  Four brands of composite resins for a facing crown after polymerization with Hyper LII were immersed in coffee. Color measurement was carried out before and 1, 2, and 4 weeks after immersion, and the results were compared.
  
  
  RESULTS
  1. After immersion in coffee, the L* values decreased gradually, the a* values showed little change, and the b* values increased gradually in all resins. 2. The difference in the color difference values (deltaE*ab) between each material became greater with time; the deltaE*ab after 4 weeks immersion were from 3.0 [Dentacolor (DEC), dentin specimen] to 6.3 [Solidex (SOL), enamel specimen] on polished surfaces, and from 0.9 [Gradia (GRA), dentin specimen] to 5.2 (SOL, enamel specimen) on non-polished surfaces. However, the deltaE*ab were 1/3 to 1/5 better than those of our previous studies. 3. The enamel specimens showed larger color differences than the dentin specimens. 4. When polished surfaces were compared with non-polished surfaces, Cesead II (CEII), DEC and SOL showed almost equal color differences while GRA showed larger color differences.
  
  
  CONCLUSIONS
  This study suggests that composite resins for a facing crown cured with a high output photo-curing unit result in a decrease of color changes with time and an improvement of color stability.
authors.affiliation: Department of Prosthodontics, Showa University School of Dentistry. namie@senzoku.showa-u.ac.jp
authors.forename: Namie
authors.initials: N
authors.lastname: Yoshimoto
authors.forename: Ayako
authors.initials: A
authors.lastname: Akasaka
authors.forename: Kenji
authors.initials: K
authors.lastname: Warita
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Ishiura
authors.forename: Daisuke
authors.initials: D
authors.lastname: Higuchi
authors.forename: Shuhai
authors.initials: S
authors.lastname: Hu
authors.forename: Tadaharu
authors.initials: T
authors.lastname: Kawawa
mesh_terms: D000180:Acrylic Resins; D003116:Color; D003188:Composite Resins; D003442:Crowns; D011108:Polymers; D011140:Polyurethanes
chemical_list: D000180:Acrylic Resins; C029012:Composite Dental Resin; D003188:Composite Resins; D011108:Polymers; D011140:Polyurethanes