title: Effect of at-home bleaching with different thickeners and aging on physical properties of a nanocomposite.
abstract: OBJECTIVE
  To evaluate the influence of 16% carbamide peroxide (CP) containing different thickeners on the physical characteristics of a nanocomposite resin submitted or not to accelerated artificial aging (AAA).
  
  
  METHODS
  One hundred samples were randomly distributed into two groups (n = 50) according to AAA. Each group was divided into 5 subgroups (n = 10) depending on the bleaching/thickener treatment: CP + carbopol, CP + natrosol, carbopol, natrosol, and no treatment (control). The physical properties tested were color (ΔE), gloss (GU), mean roughness (Ra), and Knoop microhardness (KHN). The resin surface was performed with atomic force microscopy (AFM).
  
  
  METHODS
  The color (variable Δ E) was assessed with two-way analysis of variance (ANOVA) and additionally with Tukey's and Dunnett's tests, the roughness values were submitted to Kruskal-Wallis, Dunn's, and Mann-Whitney's tests. Data on gloss and KHN were submitted to two-way ANOVA and Tukey's test (α = 0.05).
  
  
  RESULTS
  Among the physical properties evaluated, CP + carbopol promoted a reduction in composite microhardness only, thus differing statistically from the controls. As for CP + natrosol, such a change was not observed. The aging process reduced all the physical properties, thus differing statistically from the nonaging group. CP + carbopol increased the roughness and decreased the gloss of aged resins, whereas natrosol reduced gloss only, which differed statistically from the controls.
  
  
  CONCLUSIONS
  AFM showed evidence of the loss of organic matrix and exposure to load particles in the aged samples. Therefore, the replacement of carbopol with natrosol provided maintenance of the composite microhardness following bleaching. The aging process reduced the physical properties evaluated, and some changes were enhanced by the application of bleaching.
authors.affiliation: Department of Restorative Dentistry, Piracicaba Dental School, University of Campinas, FOP/Unicamp, Piracicaba, SP, Brazil.
authors.forename: Thayla Hellen Nunes
authors.initials: THN
authors.lastname: Gouveia
authors.affiliation: Department of Restorative Dentistry, Piracicaba Dental School, University of Campinas, FOP/Unicamp, Piracicaba, SP, Brazil.
authors.forename: Juliana do Carmo
authors.initials: JDC
authors.lastname: Públio
authors.affiliation: Department of Social Dentistry/Statistics, Piracicaba Dental School, University of Campinas, FOP/Unicamp, Piracicaba, SP, Brazil.
authors.forename: Glaucia Maria Bovi
authors.initials: GMB
authors.lastname: Ambrosano
authors.affiliation: Department of Restorative Dentistry, Piracicaba Dental School, University of Campinas, FOP/Unicamp, Piracicaba, SP, Brazil.
authors.forename: Luís Alexandre Maffei Sartini
authors.initials: LAMS
authors.lastname: Paulillo
authors.affiliation: Department of Restorative Dentistry, Piracicaba Dental School, University of Campinas, FOP/Unicamp, Piracicaba, SP, Brazil.
authors.forename: Flávio Henrique Baggio
authors.initials: FHB
authors.lastname: Aguiar
authors.affiliation: Department of Restorative Dentistry, Piracicaba Dental School, University of Campinas, FOP/Unicamp, Piracicaba, SP, Brazil.
authors.forename: Débora Alves Nunes Leite
authors.initials: DANL
authors.lastname: Lima
keywords: Accelerated aging; bleaching agents; color stability; composite resin; gloss; microhardness; surface roughness