title: Interexaminer reproducibility of ordinal and interval-scaled plaque indices.
abstract: BACKGROUND
  Although many plaque scoring indices have been proposed for clinical or research purposes, only few of them are commonly used in the dental literature. Owing to the ordinal nature of these established indices, only nonparametric tests can be performed, while statistical analysts usually prefer parametric methodologies. Furthermore, these indices do not discriminate between the proximal and the broad surfaces of the teeth.
  
  
  OBJECTIVE
  The aim of this study was to assess the interexaminer reproducibility for one established ordinal plaque index and two recently proposed interval-scaled indices.
  
  
  METHODS
  Six subjects received a professional tooth cleaning and stopped all oral hygiene measures during 48-62 h. Accumulated plaque was disclosed and separately scored on all teeth except third molars by two examiners using the visual plaque index (VPI), the axial plaque extension index (APEI) and the proximal plaque extension index (PPEI). In total, 168 teeth (48 molars, 48 premolars, 24 canines and 48 incisors) were scored.
  
  
  RESULTS
  Statistically significant differences were found between the means of buccal VPI (p<0.05, Wilcoxon test), mesiobuccal, mesiolingual and distolingual APEI, and distobuccal, mesiolingual and distolingual PPEI (p<0.05, t-test). Spearman correlation values between the duplicate VPI measurements were 0.84 for buccal and 0.64 for lingual VPI, while Pearson correlation values varied between 0.51 and 0.83 for APEI and between 0.48 and 0.74 for PPEI. For VPI, 71% of the buccal (kappa=0.60) and 74% of the lingual (kappa=0.53) scores were identical. For APEI and PPEI scores, a linear regression was found with slopes ranging between 0.50 and 0.80. Mean measurement errors were 7.7% for buccal and 0.4% for lingual VPI, and ranged between 0.9% and 46.1% for APEI and PPEI.
  
  
  CONCLUSIONS
  The interexaminer reproducibility of all three indices showed fair to good agreement. Buccal VPI and buccal APEI in particular showed good agreement.
authors.affiliation: Free University of Brussels, School of Dental Medicine, Department of Periodontology, Laarbeeklaan 103, B-1090 Brusssels, Belgium.
authors.forename: B
authors.initials: B
authors.lastname: Dombret
authors.forename: S
authors.initials: S
authors.lastname: Matthijs
authors.forename: M Moradi
authors.initials: MM
authors.lastname: Sabzevar
mesh_terms: D000328:Adult; D003774:Dental Plaque Index; D005260:Female; D006801:Humans; D016014:Linear Models; D008297:Male; D015588:Observer Variation; D015203:Reproducibility of Results; D018709:Statistics, Nonparametric