title: Comparison of the ability of different colour indices to assess changes in tooth whiteness.
abstract: OBJECTIVE
  The study investigates the suitability of different whiteness indices and colour parameters in assessing changes in tooth whiteness using a digital-colour imaging system.
  
  
  METHODS
  Forty-six male and female subjects aged 18-70 years participated in the study and were divided into two groups. The control group was given a standard "non-whitening" dentifrice (Colgate Great Regular Flavour) and the test group received whitening strips (crest white strips). The latter contained 6% hydrogen peroxide and were worn for 30 min twice daily on the six maxillary anterior teeth. Digital images of teeth were captured using a Jai 3CCD digital camera with annular LED illumination array and the data obtained was used to calculate colour parameters (L*, a* and b*) and whiteness indices (WIC, WIO, W). Colour differences (delta L, delta a, delta b and delta E) and differences in whiteness indices were obtained and were compared between the test and control groups. Reliability and repeatability of the instrument were checked by comparing the digital data to the clinical data and also by comparing data obtained from different camera views for the same tooth.
  
  
  RESULTS
  The test group showed significant changes in the colour parameters and whiteness indices over the 2-week period. It also showed significant correlation between the digital data obtained from lateral and central camera views for the same teeth. Digital data showed a similar trend to that of clinical data. The WIO index demonstrated the strongest discrimination between the test and control groups.
  
  
  CONCLUSIONS
  The WIO index is appropriate for assessing changes in tooth whiteness. The digital imaging system is reproducible and reliable in evaluating changes in whiteness of teeth.
authors.affiliation: School of Design, Centre for Colour Design and Technology; University of Leeds, United Kingdom.
authors.forename: Wen
authors.initials: W
authors.lastname: Luo
authors.forename: Stephen
authors.initials: S
authors.lastname: Westland
authors.forename: Paul
authors.initials: P
authors.lastname: Brunton
authors.forename: Roger
authors.initials: R
authors.lastname: Ellwood
authors.forename: Iain A
authors.initials: IA
authors.lastname: Pretty
authors.forename: Naveen
authors.initials: N
authors.lastname: Mohan
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D003116:Color; D003124:Colorimetry; D003481:Cuspid / Q000033:anatomy & histology; D003802:Dentifrices / Q000627:therapeutic use; D005260:Female; D006801:Humans; D006861:Hydrogen Peroxide / Q000627:therapeutic use; D007091:Image Processing, Computer-Assisted / Q000295:instrumentation / Q000379:methods*; D007180:Incisor / Q000033:anatomy & histology; D008297:Male; D008875:Middle Aged; D016877:Oxidants / Q000627:therapeutic use; D023861:Photography, Dental / Q000295:instrumentation / Q000379:methods*; D015203:Reproducibility of Results; D012824:Silicic Acid; D012822:Silicon Dioxide / Q000627:therapeutic use; D012969:Sodium Fluoride / Q000627:therapeutic use; D014070:Tooth / Q000033:anatomy & histology*; D014073:Tooth Bleaching / Q000145:classification*; D014100:Toothpastes
chemical_list: C488279:Crest whitestrips; D003802:Dentifrices; D016877:Oxidants; D014100:Toothpastes; C546060:hydrated silica gel-based toothpaste; D012824:Silicic Acid; D012822:Silicon Dioxide; D012969:Sodium Fluoride; D006861:Hydrogen Peroxide