title: Measurement of stain on extracted teeth using spectrophotometry and digital image analysis.
abstract: OBJECTIVE
  The aim of this study was to assess the reliability and validate a customized image analysis system, designed for use within clinical trials of general dental hygiene and whitening products, for the measurement of stain levels on extracted teeth and to compare it with reflectance spectrophotometry.
  
  
  METHODS
  Twenty non-carious extracted teeth were soaked in an artificial saliva, brushed for 1 min using an electric toothbrush and a standard toothpaste, bleached using a 5.3% hydrogen peroxide solution and cycled for 6 h daily through a tea solution. CIE L* values were obtained after each treatment step using the customized image analysis system and a reflectance spectrophotometer. A statistical analysis was carried out in SPSS.
  
  
  RESULTS
  Fleiss' coefficient of reliability for intra-operator repeatability of the image analysis system and spectrophotometry was 0.996 and 0.946 respectively. CIE L* values were consistently higher using the image analysis compared with spectrophotometry, and t-tests for each treatment step showed significant differences (P < 0.05) for the two methods. Limits of agreement between the methods were -27.95 to +2.07, with a 95% confidence of the difference calculated as -14.26 to -11.84. The combined results for all treatment steps showed a significant difference between the methods for the CIE L* values (P < 0.05).
  
  
  CONCLUSIONS
  The image analysis system has proven to be a reliable method for assessment of changes in stain level on extracted teeth. The method has been validated against reflectance spectrophotometry. This method may be used for pilot in vitro studies/trials of oral hygiene and whitening products, before expensive in vivo tests are carried out.
authors.affiliation: Department of Oral Health and Development, School of Clinical Dentistry, University of Sheffield, Claremont Crescent, UK. d.lath@sheffield.ac.uk
authors.forename: D L
authors.initials: DL
authors.lastname: Lath
authors.forename: R N
authors.initials: RN
authors.lastname: Smith
authors.forename: Y H
authors.initials: YH
authors.lastname: Guan
authors.forename: M
authors.initials: M
authors.lastname: Karmo
authors.forename: A H
authors.initials: AH
authors.lastname: Brook
mesh_terms: D002151:Calorimetry; D006801:Humans; D007091:Image Processing, Computer-Assisted; D023861:Photography, Dental; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013053:Spectrophotometry; D013662:Tea; D014073:Tooth Bleaching; D014075:Tooth Discoloration / Q000473:pathology*
chemical_list: D013662:Tea