title: The effect of at-home bleaching on the microhardness of six esthetic restorative materials.
abstract: BACKGROUND
  The authors conducted an in vitro study to evaluate the effect of an at-home bleaching product on the microhardness of six restorative materials under different surface treatments.
  
  
  METHODS
  Four resin-based composite materials (a hybrid, flowable, microhybrid and nanohybrid), an ormocer (organic modified ceramic) material and a ceramic material were bleached with 15 percent carbamide peroxide. The authors prepared two groups of samples (polished and unpolished) (n = 7) from each resin-based composite material and the ormocer. The authors polished all of the samples in the ceramic group. Two samples from each group served as negative controls. The authors measured the microhardness of the samples before bleaching, after eight hours and 56 hours of bleaching, and 24 hours and one month after the end of bleaching.
  
  
  RESULTS
  The statistical analysis showed that the at-home bleaching technique did not have a statistically significant effect on the microhardness of any of the restorative materials tested (hybrid, P = .0679; flowable, P = .5088; microhybrid, P = .0601; nanohybrid, P = .6166; ormocer, P = .2154; ceramic, P = .9943).
  
  
  CONCLUSIONS
  At-home bleaching with 15 percent carbamide peroxide did not cause any harmful changes to the microhardness of tooth-colored restorative materials.
  
  
  CONCLUSIONS
  Clinicians do not need to replace resin-based composite, ormocer or ceramic restorations after at-home bleaching treatment when the restorations are in posterior teeth.
authors.affiliation: Department f Operative Dentistry and Periodontology, Albert-Ludwigs University of Freiburg, Germany. olga.polydorou@uniklinik-freiburg.de
authors.forename: Olga
authors.initials: O
authors.lastname: Polydorou
authors.forename: Elmar
authors.initials: E
authors.lastname: Hellwig
authors.forename: Thorsten Mathias
authors.initials: TM
authors.lastname: Auschill
mesh_terms: D000704:Analysis of Variance; D000077463:Carbamide Peroxide; D002516:Ceramics; D003188:Composite Resins; D003742:Dental Devices, Home Care; D003776:Dental Porcelain; D003793:Dental Restoration, Permanent; D004338:Drug Combinations; D006244:Hardness; D063225:Organically Modified Ceramics; D016877:Oxidants; D010545:Peroxides; D012821:Silanes; D014073:Tooth Bleaching; D014508:Urea / Q000031:analogs & derivatives
chemical_list: D003188:Composite Resins; D004338:Drug Combinations; D063225:Organically Modified Ceramics; D016877:Oxidants; D010545:Peroxides; D012821:Silanes; D003776:Dental Porcelain; D000077463:Carbamide Peroxide; D014508:Urea