title: Reaction kinetics of sodium ascorbate and dental bleaching gel.
abstract: OBJECTIVE
  The aim of this study was to establish the reaction kinetics of 35% hydrogen peroxide and sodium ascorbate and to determine the mass of antioxidant required to neutralize the bleaching gel.
  
  
  METHODS
  The method used to quantify sodium ascorbate was based on the United States Pharmacopeia (1995)(26). Oxidation-reduction titration was used to confirm the concentration of hydrogen peroxide and sodium ascorbate and to determine the reaction kinetics between them.
  
  
  RESULTS
  The results indicated a direct correlation between the mass of hydrogen peroxide and that of the antioxidant agent. In addition, 5 min of contact was sufficient to neutralize the hydrogen peroxide used.
  
  
  CONCLUSIONS
  This in vitro study showed that the amount of sodium ascorbate required for reduction of hydrogen peroxide is directly related to the concentration of the latter. In addition, the reaction kinetics between oxidant and antioxidant showed that a longer application time for sodium ascorbate does not influence the effectiveness of the reaction and that 5 min is sufficiently long for this antioxidant to exert an antioxidant effect.
authors: School of Dentistry, Pontifical Catholic University of Parana, Curitiba, Parana, Brazil. andreavfreire@yahoo.com.br
authors: Andrea
authors: A
authors: Freire
authors: Evelise M
authors: EM
authors: Souza
authors: Danilo Biazzetto
authors: DB
authors: de Menezes Caldas
authors: Edvaldo Antônio Ribeiro
authors: EA
authors: Rosa
authors: Cynthia França Wolanski
authors: CF
authors: Bordin
authors: Ricardo Marins
authors: RM
authors: de Carvalho
authors: Sergio
authors: S
authors: Vieira
mesh_terms: D000465:Algorithms; D000975:Antioxidants / Q000737:chemistry*; D001205:Ascorbic Acid / Q000737:chemistry*; D006801:Humans; D006861:Hydrogen Peroxide / Q000737:chemistry*; D007202:Indicators and Reagents; D007455:Iodine; D007700:Kinetics; D008422:Materials Testing; D016877:Oxidants / Q000737:chemistry*; D010084:Oxidation-Reduction; D013997:Time Factors; D017186:Titrimetry; D014073:Tooth Bleaching
chemical_list: D000975:Antioxidants; D007202:Indicators and Reagents; D016877:Oxidants; D007455:Iodine; D006861:Hydrogen Peroxide; D001205:Ascorbic Acid