title: An In Vitro Evaluation of Human Enamel Surfaces Subjected to Erosive Challenge After Bleaching.
abstract: OBJECTIVE
  This study aimed to evaluate whether tooth enamel bleached with hydrogen peroxide (H2O2) is more susceptible to erosion when compared with unbleached tooth enamel; and whether the presence of calcium (Ca) in the bleaching gel influenced this process.
  
  
  METHODS
  Enamel blocks were prepared from human molars, and submitted to surface microhardness analysis (baseline). Blocks were prepared and randomly divided into four treatment groups (n = 20): G1 and G2-bleached with 7.5% H2O2, with and without Ca, respectively; G3 and G4-bleached with 35% H2O2, with and without Ca, respectively. After bleaching, these groups were submitted to an erosive challenge with 1% citric acid. G5 and G6 (n = 20, each) were the negative (without bleaching) and positive controls (without bleaching, but with erosion), respectively. The percentage of surface hardness loss (%SHL), the 3D non-contact profilometry and Scanning Electron Microscopy (SEM) analyses were performed.
  
  
  RESULTS
  G2 showed the highest %SHL after bleaching. G1 presented the lowest %SHL in comparison with G2, G3, G4, and G6 after erosion (p < 0.05), which was confirmed only by the SEM analysis.
  
  
  CONCLUSIONS
  It is suggested that low concentration of H2O2with calcium can be recommended for at-home bleaching agents, which may avoid the mineral loss of bleached enamel after an erosive challenge.
  
  
  CONCLUSIONS
  Low concentration of H202with calcium can be recommended for at-home bleaching agents, which may avoid the mineral loss of bleached enamel after an erosive challenge. (J Esthet Restor Dent 29:128-136, 2017).
authors.affiliation: Department of Professional Master's Course in Dentistry, Dental School, Universidade Veiga de Almeida, Rio de Janeiro, RJ, 20271-020, Brazil.
authors.forename: Maria
authors.initials: M
authors.lastname: de Fátima Carvalho Vasconcelos
authors.affiliation: Department of Pediatric Dentistry and Orthodontics, Dental School, Universidade Federal do Rio de Janeiro, Ilha do Fundão, Rio de Janeiro, RJ, 21949-900, Brazil.
authors.forename: Andréa
authors.initials: A
authors.lastname: Fonseca-Gonçalves
authors.affiliation: Department of Pediatric Dentistry and Orthodontics, Dental School, Universidade Federal do Rio de Janeiro, Ilha do Fundão, Rio de Janeiro, RJ, 21949-900, Brazil.|School of Dentistry, Universidade Salgado de Oliveira, Niterói, RJ, 24030-060, Brazil.
authors.forename: Adílis Kalina Alexandria
authors.initials: AKA
authors.lastname: de França
authors.affiliation: Department of Preventive and Communitary Dentistry, Dental School, Universidade do Estado do Rio de Janeiro, Rio de Janeiro, RJ, 20551-030, Brazil.|Department of Preventive and Social Dentistry, Dental School, Universidade Federal do Rio de Janeiro, Ilha do Fundão, Rio de Janeiro, RJ, 21949-900, Brazil.
authors.forename: Urubatan Vieira
authors.initials: UV
authors.lastname: de Medeiros
authors.affiliation: Department of Pediatric Dentistry and Orthodontics, Dental School, Universidade Federal do Rio de Janeiro, Ilha do Fundão, Rio de Janeiro, RJ, 21949-900, Brazil.
authors.forename: Lucianne Cople
authors.initials: LC
authors.lastname: Maia
authors.affiliation: Department of Professional Master's Course in Dentistry, Dental School, Universidade Veiga de Almeida, Rio de Janeiro, RJ, 20271-020, Brazil.|School of Dentistry, Universidade Salgado de Oliveira, Niterói, RJ, 24030-060, Brazil.
authors.forename: Celso Silva
authors.initials: CS
authors.lastname: Queiroz
mesh_terms: D003743:Dental Enamel / Q000737:chemistry*; D006244:Hardness; D006801:Humans; D066298:In Vitro Techniques; D008964:Molar, Third; D013499:Surface Properties; D014073:Tooth Bleaching