title: Higher-concentration carbamide peroxide effects on surface roughness of composites.
abstract: BACKGROUND
  Ten percent carbamide peroxide has been used extensively within the dental profession for the purpose of bleaching teeth. Although this method has been successful, the use of higher-concentration carbamide peroxides (20-35%) for home bleaching has increased substantially in the past few years. The purpose of this study was to evaluate changes in surface roughness of a hybrid and a microfilled composite after exposure to bleaching agents containing higher concentrations of carbamide peroxide.
  
  
  METHODS
  Sixty-eight circular, resin-based composite specimens (8 mm x 2 mm) were prepared against a Mylar surface. Half of the specimens were fabricated from a hybrid composite material and the other half with a microfilled composite. Specimens were polished with aluminum oxide finishing disks, divided into four groups, and then exposed either to 20% carbamide peroxide for 3 hours per day for 14 days or to 35% carbamide peroxide for 1 hour per day for 14 days. The mean surface roughness (Ra) was determined for each specimen before and after exposure to bleaching agents, using mechanical profilometry. Data were analyzed by two-way analysis of variance (ANOVA) for differences between composite type, carbamide peroxide concentrations, and interaction of the two factors with respect to average surface roughness. All data analysis was performed at alpha = 0.05.
  
  
  RESULTS
  Mean change from baseline of surface roughness (Ra) of microfilled composite and 20% carbamide peroxide was -0.03 microm +/- 0.10 microm; microfilled composite and 35% carbamide peroxide: 0.01 microm x 0.02 microm; hybrid composite and 20% carbamide peroxide: -0.43 microm x 0.91 microm; hybrid composite and 35% carbamide peroxide: -0.19 microm x 0.43 microm. Surface roughness of hybrid or microfilled composite did not change significantly from baseline with either concentration of carbamide peroxide (p = .300).
  
  
  CONCLUSIONS
  Higher-concentration carbamide peroxide bleaching agents, used as intended by the manufacturer, pose no significant risk to resin composite restoration surfaces.
authors: Resetorative Dentistry, Department of General Dentistry, Lackland Air Force Base, Texas 78236-5551, USA.
authors: Robert E
authors: RE
authors: Langsten
authors: William J
authors: WJ
authors: Dunn
authors: Grant R
authors: GR
authors: Hartup
authors: David F
authors: DF
authors: Murchison
mesh_terms: D000537:Aluminum Oxide / Q000737:chemistry; D000704:Analysis of Variance; D000077463:Carbamide Peroxide; D003188:Composite Resins / Q000737:chemistry* / Q000145:classification; D003775:Dental Polishing; D004338:Drug Combinations; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008422:Materials Testing; D016877:Oxidants / Q000008:administration & dosage / Q000737:chemistry*; D010545:Peroxides / Q000008:administration & dosage / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry; D013499:Surface Properties; D013997:Time Factors; D014073:Tooth Bleaching; D014508:Urea / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000737:chemistry*
chemical_list: D003188:Composite Resins; D004338:Drug Combinations; D016877:Oxidants; D010545:Peroxides; D011108:Polymers; C099128:Prodigy; C074741:Silux Plus; D000077463:Carbamide Peroxide; D014508:Urea; D000537:Aluminum Oxide