title: Bleaching agent action on color stability, surface roughness and microhardness of composites submitted to accelerated artificial aging.
abstract: OBJECTIVE
  The purpose of this study was to evaluate the bleaching agent action on color stability, surface roughness and microhardness of composites (Charisma, Filtek Supreme and Heliomolar - A2) submitted to accelerated artificial aging (AAA).
  
  
  METHODS
  A Teflon matrix (12 x 2 mm) was used to fabricate 18 specimens (n=6) which, after polishing (Sof-Lex), were submitted to initial color reading (ΔE), Knoop microhardness (KHN) (50 g/15 s load) and roughness (R(a)) (cut-off 0.25 mm) tests. Afterwards, the samples were submitted to AAA for 384 hours and new color, microhardness and roughness readings were performed. After this, the samples were submitted to daily application (4 weeks) of 16% Carbamide Peroxide (NiteWhite ACP) for 8 hours and kept in artificial saliva for 16 hours. New color, microhardness and roughness readings were made at the end of the cycle, and 15 days after bleaching.
  
  
  RESULTS
  Comparison of the ΔE means (2-way ANOVA, Bonferroni, P<.05) indicated clinically unacceptable color alteration for all composites after AAA, but without significant difference. Statistically significant increase in the KHN values after AAA was observed, but without significant alterations 15 days after bleaching. For R(a) there was no statistically significant difference after AAA and 15 days after bleaching.
  
  
  CONCLUSIONS
  The alterations promoted by the bleaching agent and AAA are material dependent.
authors.affiliation: Graduate Student, Department of Dental Materials and Prosthodontics, Dental School of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP, Brazil.
authors.forename: Raphael Mendes Bezerra
authors.initials: RM
authors.lastname: Rattacaso
authors.forename: Lucas
authors.initials: L
authors.lastname: da Fonseca Roberti Garcia
authors.forename: Fabiano Gamero
authors.initials: FG
authors.lastname: Aguilar
authors.forename: Simonides
authors.initials: S
authors.lastname: Consani
authors.forename: Fernanda
authors.initials: F
authors.lastname: de Carvalho Panzeri Pires-de-Souza