title: Monitoring of demineralized dentin microhardness throughout and after bleaching.
abstract: OBJECTIVE
  To evaluate the effect of six bleaching agents: Nite White [NW] 10% and 22% Excel 2Z (Discus Dental), Rembrandt (REM) 10% and 22% (DenMat), Opalescence (OPA) 10% and 20% (Ultradent) and a placebo agent on demineralized dentin microhardness at different time intervals.
  
  
  METHODS
  105 human dentin slabs (3 x 3 mm) were embedded, planed and submitted to cariogenic challenges, composed of de- and remineralization cycles. For 42 days, specimens were exposed to bleaching agents, consisting of applying them daily for 8 hours, removing and storing the specimens in artificial saliva for 16 hours. At the end of the bleaching treatment, specimens were kept in artificial saliva for 14 days. Knoop Microhardness tests were performed on specimens' surface before (baseline), during (8 hours, 7, 14, 21, 28, 35 and 42 days) and after bleaching procedures (7 and 14 days).
  
  
  RESULTS
  The ANOVA for split-plot showed significant effect on the interaction between bleaching agent and time (alpha =0.05). Tukey's test revealed no significant differences on demineralized dentin microhardness exposed to bleaching agents until Day 7. Regression analyses demonstrated that NW 10% and 22% and OPA 10% and 20% increased dentin microhardness in different magnitudes, whereas REM 10% and 22% induced mineral loss during bleaching agent application, followed by microhardness recovery in the post-treatment period.
authors.affiliation: Department of Restorative Dentistry, School of Dentistry of Piracicaba, State University of Campinas, Brazil.
authors.forename: Patricia Moreira
authors.initials: PM
authors.lastname: de Freitas
authors.forename: Cecilia Pedroso
authors.initials: CP
authors.lastname: Turssi
authors.forename: Anderson Takeo
authors.initials: AT
authors.lastname: Hara
authors.forename: Mônica Campos
authors.initials: MC
authors.lastname: Serra
mesh_terms: D000704:Analysis of Variance; D000077463:Carbamide Peroxide; D003804:Dentin / Q000737:chemistry / Q000187:drug effects*; D004338:Drug Combinations; D006244:Hardness / Q000187:drug effects; D006801:Humans; D016877:Oxidants / Q000008:administration & dosage / Q000009:adverse effects*; D010545:Peroxides / Q000008:administration & dosage / Q000009:adverse effects*; D012044:Regression Analysis; D014073:Tooth Bleaching / Q000009:adverse effects*; D017001:Tooth Demineralization; D014508:Urea / Q000008:administration & dosage / Q000009:adverse effects* / Q000031:analogs & derivatives*
chemical_list: D004338:Drug Combinations; D016877:Oxidants; D010545:Peroxides; D000077463:Carbamide Peroxide; D014508:Urea