title: Effect of home-bleaching gels modified by calcium and/or fluoride and the application of nano-hydroxyapatite paste on in vitro enamel erosion susceptibility.
abstract: OBJECTIVE
  This in vitro study compared the effect of bleaching agents modified by the addition of calcium and/or fluoride and the application of a nano-hydroxyapatite paste after bleaching, on the susceptibility of enamel to erosion.
  
  
  METHODS
  Bovine enamel cylindrical samples (3 mm diameter) were assigned to six groups (n = 20 specimens/group) according to the bleaching agent: no bleaching (C-control), 7.5% hydrogen peroxide gel (HP), HP with 0.5% calcium gluconate (HP+Ca), HP with 0.2% sodium fluoride (HP+F), HP with calcium and fluoride (HP+Ca+F) and HP followed by the application of a nano-hydroxyapatite agent (HP+NanoP). The gels were applied on the enamel surface (1 h) followed by cyclic erosive challenges (Sprite Zero®-2 min), for 14 days. The paste was applied after bleaching for 5 min (HP+NanoP). The enamel surface alteration was measured by contact profilometry (µm) (after 7 and 14 days).
  
  
  RESULTS
  C-control (mean ± SD: 2.29 ± 0.37 at 7 days/4.86 ± 0.72 at 14 days) showed significantly lower loss compared to the experimental groups. HP+Ca (3.34 ± 0.37/6.75 ± 1.09) and HP+F (4.49 ± 0.92/7.61 ± 0.90) presented significantly lower enamel loss than HP (4.18 ± 0.50/10.30 ± 1.58) only for 14 days and HP+Ca+F (4.92 ± 1.03/8.12 ± 1.52) showed values similar to the HP+F group. The HP+NanoP (5.51 ± 1.04/9.61 ± 1.21) resulted in enamel loss similar to the HP after 14 days.
  
  
  CONCLUSIONS
  It was found that 7.5% hydrogen peroxide increased the susceptibility of enamel to erosion. The addition of calcium or fluoride to the bleaching gel reduced the erosion effect, while the nano-hydroxyapatite agent did not provide any protective effect.
authors.affiliation: a 1 Department of Restorative Dentistry, Institute of Science and Technology, Univ Estadual Paulista UNESP , São José dos Campos, SP, Brazil.
authors.forename: Luciana Floriani Thives Freitas
authors.initials: LF
authors.lastname: Santos
authors.affiliation: a 1 Department of Restorative Dentistry, Institute of Science and Technology, Univ Estadual Paulista UNESP , São José dos Campos, SP, Brazil.
authors.forename: Carlos Rocha Gomes
authors.initials: CR
authors.lastname: Torres
authors.affiliation: a 1 Department of Restorative Dentistry, Institute of Science and Technology, Univ Estadual Paulista UNESP , São José dos Campos, SP, Brazil.
authors.forename: Taciana Marco Ferraz
authors.initials: TM
authors.lastname: Caneppele
authors.affiliation: b 2 Department of Biological Sciences, Bauru School of Dentistry, USP , Bauru, SP, Brazil.
authors.forename: Ana Carolina
authors.initials: AC
authors.lastname: Magalhães
authors.affiliation: a 1 Department of Restorative Dentistry, Institute of Science and Technology, Univ Estadual Paulista UNESP , São José dos Campos, SP, Brazil.
authors.forename: Alessandra Buhler
authors.initials: AB
authors.lastname: Borges
mesh_terms: D000818:Animals; D002125:Calcium Gluconate / Q000627:therapeutic use*; D002417:Cattle; D003743:Dental Enamel / Q000187:drug effects* / Q000648:ultrastructure; D004198:Disease Susceptibility; D017886:Durapatite / Q000627:therapeutic use*; D005782:Gels; D006244:Hardness; D006861:Hydrogen Peroxide / Q000627:therapeutic use*; D008422:Materials Testing; D049329:Nanostructures / Q000627:therapeutic use*; D020011:Protective Agents / Q000627:therapeutic use; D012969:Sodium Fluoride / Q000627:therapeutic use*; D013997:Time Factors; D058205:Tooth Bleaching Agents / Q000627:therapeutic use*; D014077:Tooth Erosion / Q000517:prevention & control*
chemical_list: D005782:Gels; D020011:Protective Agents; D058205:Tooth Bleaching Agents; D012969:Sodium Fluoride; D017886:Durapatite; D006861:Hydrogen Peroxide; D002125:Calcium Gluconate
keywords: Enamel; erosion; hydrogen peroxide; tooth bleaching; tooth wear