title: Influence of staining solutions and whitening procedures on discoloration of hybrid composite resins.
abstract: OBJECTIVE
  The aim was to evaluate the color stability and water uptake of two hybrid composite resins polymerized in two different conditions after exposure to commonly consumed beverages. In addition, the effect of repolishing and bleaching on the stained composite was evaluated.
  
  
  METHODS
  Eighty specimens (12 mm × 12 mm × 3 mm) were made from two hybrid composite resins of shade A2. Forty specimens of each composite were divided into two groups (n = 20 per each) according to the curing method used (hand light cure HLC or oven light cure OLC). Then each group (HLC or OLC) was sub-divided randomly into four sub-groups (n = 5), which were immersed for 60 days in different beverages (distal water, coffee, tea and pepsi) and incubated at 37°C. Water uptake was measured during this time and followed by measurement of color difference (ΔE) by using a spectrophotometer. After complete staining, repolishing (grit 4000 FEPA at 300 rpm under water) and bleaching (40% hydrogen peroxide bleaching gel) were conducted. The repolished and bleached specimens were submitted to new color measurements.
  
  
  RESULTS
  Color value of the specimens immersed in tea displayed the highest statistically significant (p < 0.05) mean color difference (ΔE) compared to other beverages, whereas the ΔE value of pepsi was significantly lower than the others. After staining of the composite resins, both the bleaching and repolishing were able to reduce the ΔE value.
  
  
  CONCLUSIONS
  All beverages used affected the color stability of tested composite resins. The effect of beverages on color change of composites depends on type of beverage and water uptake value of resins used. A superior whitening effect was obtained with repolishing technique compared to bleaching.
authors.affiliation: Department of Biomaterials Science and BioCity Turku Biomaterials Research Program, Institute of Dentistry, University of Turku, Turku, Finland. sufgar@utu.fi
authors.forename: Sufyan
authors.initials: S
authors.lastname: Garoushi
authors.forename: Lippo
authors.initials: L
authors.lastname: Lassila
authors.forename: Marwa
authors.initials: M
authors.lastname: Hatem
authors.forename: Muneim
authors.initials: M
authors.lastname: Shembesh
authors.forename: Lugane
authors.initials: L
authors.lastname: Baady
authors.forename: Ziad
authors.initials: Z
authors.lastname: Salim
authors.forename: Pekka
authors.initials: P
authors.lastname: Vallittu
mesh_terms: D001628:Beverages; D003116:Color; D003188:Composite Resins / Q000737:chemistry*; D003775:Dental Polishing / Q000379:methods; D006861:Hydrogen Peroxide; D055115:Light-Curing of Dental Adhesives; D008422:Materials Testing; D058105:Polymerization; D013053:Spectrophotometry; D014073:Tooth Bleaching / Q000379:methods; D017155:Wettability
chemical_list: D003188:Composite Resins; D006861:Hydrogen Peroxide