title: Effects of a 10% carbamide peroxide bleaching agent on roughness and microhardness of packable composite resins.
abstract: OBJECTIVE
  Bleaching agents containing 10% carbamide peroxide may be applied to the surface of preexisting packable resin-based composite restorations. The aim of this in vitro study was to evaluate the effect of a 10% carbamide peroxide bleaching agent (Review, SS White, Rio de Janeiro, Brazil) on surface roughness and microhardness of three packable resin-based composites (Fill Magic condensable, Vigodent, Rio de Janeiro, Brazil; Alert, Jeneric Pentron, Wallingford, CT, USA; Definite, Degussa, Hanau, Germany).
  
  
  METHODS
  For the control (no bleaching) and experimental (bleaching treatment) groups, 12 specimens of each material were prepared in cylindrical acrylic molds. The experimental specimens were exposed to the bleaching agent for 6 hours a day for 3 weeks. During the remaining time (18 h), they were stored in artificial saliva. The control specimens remained immersed in artificial saliva throughout the experiment. Surface roughness and microhardness measurements were performed on the top surface of each specimen.
  
  
  RESULTS
  Analysis of variance and the Tukey test showed no significant differences in roughness among the packable composites evaluated (p = .18), but those submitted to the treatment with a 10% carbamide peroxide bleaching agent displayed significantly higher mean surface roughness than did the corresponding control group for each material. For the microhardness tests, there were significant differences among materials (p < .0001). Alert showed the highest microhardness values followed by Definite and Fill Magic condensable.
  
  
  CONCLUSIONS
  Ten percent carbamide peroxide bleaching agents may change the surface roughness of packable composites, but they do not alter their microhardness.
  
  
  CONCLUSIONS
  Under the conditions of this study, a 3-week bleaching regimen with 10% carbamide peroxide agents affected the roughness of packable composites. Nevertheless, the surface microhardness was not affected, although there were differences among the materials evaluated inherent to their composition.
authors.affiliation: Dentistry Research Center, São Leopoldo Mandic, Campinas, SP, Brazil. rbasting@yahoo.com
authors.forename: Roberta Tarkany
authors.initials: RT
authors.lastname: Basting
authors.forename: Camila
authors.initials: C
authors.lastname: Fernandéz Y Fernandez
authors.forename: Glaucia Maria Bovi
authors.initials: GM
authors.lastname: Ambrosano
authors.forename: Inger Teixeira
authors.initials: IT
authors.lastname: de Campos
mesh_terms: D000077463:Carbamide Peroxide; D003188:Composite Resins / Q000737:chemistry; D004338:Drug Combinations; D006244:Hardness; D016877:Oxidants; D010545:Peroxides; D012833:Siloxanes / Q000737:chemistry; D013499:Surface Properties; D013729:Terpenes / Q000737:chemistry; D014073:Tooth Bleaching; D014508:Urea / Q000031:analogs & derivatives*
chemical_list: C406265:Alert composite resin; D003188:Composite Resins; C421785:Definite composite resin; D004338:Drug Combinations; C481898:Fill Magic; D016877:Oxidants; D010545:Peroxides; C506184:Review (bleaching agent); D012833:Siloxanes; D013729:Terpenes; D000077463:Carbamide Peroxide; D014508:Urea