title: Changes in the stiffness of demineralized dentin following application of tooth whitening agents.
abstract: OBJECTIVE
  The purpose of this study was to evaluate the effect of the bleaching agents on the elastic modulus of bovine demineralized dentin matrix (EMDM).
  
  
  METHODS
  Eighty-five slices were obtained from 17 bovine teeth. The slices were divided randomly into five experimental groups (n = 17): unbleached control group (CG), 4% hydrogen peroxide (HP4), 4% hydrogen peroxide + 0.05% Ca (HP4 + Ca), 7.5% hydrogen peroxide + ACP (HP7.5) and 10% carbamide peroxide (CP10). The HP4, HP4 + Ca and CP10 groups were treated with the bleaching agents for 8 h/day (14 days), while the samples of HP7.5 group were exposed to bleaching agent for 30 min twice a day (14 days). The CG was kept in 100% humidity. After bleaching treatments, the enamel of the samples was removed and 85 dentin beams (0.5 × 1.7 × 7.0 mm) were prepared. Afterwards, the beams were immersed in 10% phosphoric acid solution (5 h) and rinsed with water (10 min). The beams were tested after 24 h, 7 and 14 days of storage in distilled water, using three-point bend method. Data were statistically analyzed using ANOVA and Fisher's test.
  
  
  RESULTS
  All bleaching treatments reduced the EMDM. After 14 days post-bleaching, the EMDM increased for HP4 and HP4+Ca groups.
  
  
  CONCLUSIONS
  The use of bleaching agents promoted a decrease in EMDM, which indicates that the bleaching treatment interacts with the dentin organic matrix. The EMDM measurement for the specimens of the 7.5% hydrogen peroxide group that were immersed in water at 14 days post-bleaching did not recover the EMDM values when compared to the control group.
authors.affiliation: Department of Restorative Dentistry, School of Dentistry, University of North Parana, Londrina, PR, Brazil.
authors.forename: Sandrine Bittencourt
authors.initials: SB
authors.lastname: Berger
authors.forename: Sabrina
authors.initials: S
authors.lastname: Pavan
authors.forename: Cristina de Mattos Pimenta
authors.initials: Cde M
authors.lastname: Vidal
authors.forename: Paulo Henrique Dos
authors.initials: PH
authors.lastname: Santos
authors.forename: Marcelo
authors.initials: M
authors.lastname: Giannini
authors.forename: Ana Karina
authors.initials: AK
authors.lastname: Bedran-Russo
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D000077463:Carbamide Peroxide; D002417:Cattle; D016009:Chi-Square Distribution; D003804:Dentin / Q000187:drug effects*; D055119:Elastic Modulus / Q000187:drug effects; D006244:Hardness / Q000187:drug effects; D006861:Hydrogen Peroxide / Q000008:administration & dosage / Q000633:toxicity; D008422:Materials Testing; D010545:Peroxides / Q000008:administration & dosage / Q000633:toxicity; D018583:Pliability / Q000187:drug effects; D011897:Random Allocation; D014073:Tooth Bleaching / Q000009:adverse effects*; D058205:Tooth Bleaching Agents / Q000633:toxicity*; D014508:Urea / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000633:toxicity
chemical_list: C093073:Demineralized Dentin Matrix; D010545:Peroxides; D058205:Tooth Bleaching Agents; D000077463:Carbamide Peroxide; D014508:Urea; D006861:Hydrogen Peroxide