title: Optical effects of experimental light-activated bleaching procedures.
abstract: OBJECTIVE
  The purpose of this study was to evaluate the efficiency of experimental light-activated bleaching procedures.
  
  
  BACKGROUND
  The improved color effect may be attributed to the potential photochemical effect of light-emitting diode (LED405), organic LED (OLED), and femtosecond laser rather than to the photothermal effect of conventional lights used for tooth bleaching.
  
  
  METHODS
  Specially made pastilles of hydroxylapatite were immersed in green tea for 8 h and randomly divided into four groups (n=50) specified by the type of light source applied during a 30 min bleaching treatment: LED405, OLED, and femtosecond laser, or its absence (control group). Each group was treated with five bleaching gels: 10%, 16%, and 30% carbamide peroxide (CP), and 25% and 38% hydrogen peroxide (HP). Changes in color were determined by red-green-blue (RGB) colorimeter and ultraviolet-visible-near-infrared (UV/Vis/NIR) spectroscopy.
  
  
  RESULTS
  Regardless of the applied bleaching gel, LED405 produced a larger increase in the value of RGB index than did OLED and bleaching without light activation (p<0.05). Femtosecond laser also produced significantly better results in combination with 16% CP and 38% HP. Furthermore, application of a bleaching agent with a higher concentration of peroxide boosted the value of the RGB index. Spectroscopic measurements revealed similar results, although treatments with OLED were rated relatively better than in RGB analysis.
  
  
  CONCLUSIONS
  The mechanisms of light-activated bleaching procedures had a significant effect on the color change. The bleaching activation with LED405 and higher concentrations of peroxide in bleaching agents promoted better whitening effect.
authors.affiliation: 1 Department of Endodontics and Restorative Dentistry, School of Dental Medicine, University of Zagreb , Zagreb, Croatia .
authors.forename: Eva
authors.initials: E
authors.lastname: Klaric
authors.forename: Mario
authors.initials: M
authors.lastname: Rakic
authors.forename: Marijan
authors.initials: M
authors.lastname: Marcius
authors.forename: Mira
authors.initials: M
authors.lastname: Ristic
authors.forename: Ivan
authors.initials: I
authors.lastname: Sever
authors.forename: Zrinka
authors.initials: Z
authors.lastname: Tarle
mesh_terms: D055117:Curing Lights, Dental; D017886:Durapatite; D007834:Lasers; D008027:Light; D013057:Spectrum Analysis; D014073:Tooth Bleaching / Q000379:methods*
chemical_list: D017886:Durapatite