title: Whitening effect and morphological evaluation of hydroxyapatite materials.
abstract: OBJECTIVE
  To measure the efficacy of the whitening effect of non-oxidizing and non-acidic nano- and micro-hydroxyapatite materials on the enamel surface and to evaluate the surface changes after treatment.
  
  
  METHODS
  Three hydroxyapatite suspensions and two hydroxyapatite mixtures in dissolvable polymer films were applied to a total of 30 extracted caries-free human premolars. After the last material application, a hydrodynamic shear force was generated and applied for 2 minutes to all teeth to simulate mechanical loading of the surface. The tooth color was measured with a dental spectrophotometer. The mean changes of the L*a*b* values between different measurements in each group were expressed as delta E and were analyzed with ANOVA and the Tukey's post-hoc test.
  
  
  RESULTS
  The groups of the nano-hydroxyapatite, the hydroxyapatite-nanocrystals and the tricalcium-phosphate exhibited significant delta E values between baseline and after hydrodynamic shear force application (P<0.05). In conclusion, the materials used in the study are very promising alternatives to oxidizing bleaching agents.
authors.affiliation: Ludwig Maximilians University, Faculty of Dentistry, Department of Operative Dentistry and Periodontology, Goethe Str. 70, D-80336 Munich, Germany.
authors.forename: Alp
authors.initials: A
authors.lastname: Dabanoglu
authors.forename: Claudia
authors.initials: C
authors.lastname: Wood
authors.forename: Franklin
authors.initials: F
authors.lastname: García-Godoy
authors.forename: Karl-Heinz
authors.initials: KH
authors.lastname: Kunzelmann
mesh_terms: D000704:Analysis of Variance; D001641:Bicuspid; D003124:Colorimetry / Q000379:methods; D003799:Dental Stress Analysis; D006801:Humans; D006882:Hydroxyapatites; D008855:Microscopy, Electron, Scanning; D033081:Shear Strength; D013053:Spectrophotometry; D018709:Statistics, Nonparametric; D014073:Tooth Bleaching / Q000379:methods*
chemical_list: D006882:Hydroxyapatites