title: A study of hydrogen peroxide chemistry and photochemistry in tea stain solution with relevance to clinical tooth whitening.
abstract: OBJECTIVE
  Tooth whitening using hydrogen peroxide is a complex process, and there is still some controversy about the roles of pH, temperature, chemical activators, and the use of light irradiation. In this work the basic interactions between whitening agents and stain molecules are studied in simple solutions, thus avoiding the physics of diffusion and light penetration in the tooth to give clarity on the basic chemistry which is occurring.
  
  
  METHODS
  The absorbance of tea stain solution at 450 nm was measured over a period of 40 min, with various compositions of whitening agent added (including hydrogen peroxide, ferrous gluconate and potassium hydroxide) and at the same time the samples were subjected to blue light (465 nm) or infra-red light (850 nm) irradiation, or alternatively they were heated to 37°C.
  
  
  RESULTS
  It is shown that the reaction rates between chromogens in the tea solution and hydrogen peroxide can be accelerated significantly using ferrous gluconate activator and blue light irradiation. Infra red irradiation does not increase the reaction rate through photochemistry, it serves only to increase the temperature. Raising the temperature leads to inefficiency through the acceleration of exothermic decomposition reactions which produce only water and oxygen.
  
  
  CONCLUSIONS
  By carrying out work in simple solution it was possible to show that ferrous activators and blue light irradiation significantly enhance the whitening process, whereas infra red irradiation has no significant effect over heating. The importance of controlling the pH within the tooth structure during whitening is also demonstrated.
authors.affiliation: Philips Research Laboratories, 101 Cambridge Science Park, Milton Road, Cambridge CB4 0FY, UK. nigel.young@philips.com
authors.forename: Nigel
authors.initials: N
authors.lastname: Young
authors.forename: Peter
authors.initials: P
authors.lastname: Fairley
authors.forename: Veena
authors.initials: V
authors.lastname: Mohan
authors.forename: Coline
authors.initials: C
authors.lastname: Jumeaux
mesh_terms: D002863:Chromogenic Compounds / Q000737:chemistry / Q000528:radiation effects; D005296:Ferrous Compounds / Q000737:chemistry / Q000528:radiation effects; D006358:Hot Temperature; D006801:Humans; D006861:Hydrogen Peroxide / Q000737:chemistry* / Q000528:radiation effects; D006863:Hydrogen-Ion Concentration; D006878:Hydroxides / Q000737:chemistry / Q000528:radiation effects; D007259:Infrared Rays; D008027:Light; D016877:Oxidants / Q000737:chemistry* / Q000528:radiation effects; D010083:Oxidants, Photochemical / Q000737:chemistry / Q000528:radiation effects; D055668:Photochemical Processes; D017680:Potassium Compounds / Q000737:chemistry / Q000528:radiation effects; D013662:Tea / Q000737:chemistry*; D013997:Time Factors; D014073:Tooth Bleaching; D058205:Tooth Bleaching Agents / Q000737:chemistry* / Q000528:radiation effects
chemical_list: D002863:Chromogenic Compounds; D005296:Ferrous Compounds; D006878:Hydroxides; D016877:Oxidants; D010083:Oxidants, Photochemical; D017680:Potassium Compounds; D013662:Tea; D058205:Tooth Bleaching Agents; D006861:Hydrogen Peroxide; C011819:ferrous gluconate; C029943:potassium hydroxide