Intra-examiner reproducibility of 4 dental plaque indices

The aim of the present study was to assess the intra-examiner reproducibility for 2 established ordinal plaque indices and 2 newly proposed interval plaque indices.

15 subjects received a professional tooth cleaning and interrupted all oral hygiene measures for 48 to 62 hours. Plaque accumulation was scored 2x for all canines, premolars and 1st and 2nd molars in the 1st and 3rd quadrants with the visual plaque index (VPI), the modified navy plaque index (mNPI), the axial plaque extension index (APEI) and the proximal plaque extension index (PPEI). 147 teeth (57 molars, 60 premolars, 30 canines) were scored.

No statistically significant differences were found for duplicate measurements with all indices, except for buccal and lingual VPI (p < 0.05. Wilcoxon test) and for buccal APEI (p < 0.01, t-test). High correlations existed between all duplicate measurements with r-values ranging from 0.76 to 0.94. For the VPI, 78% of buccal (kappa = 0.70) and 89% of lingual (kappa = 0.75) scores were identical, whereas this was the case for 88% of buccal (kappa = 0.81) and for 73% of lingual (kappa = 0.62) mNPI scores. For APEI and PPEI scores a linear regression was found with slopes ranging between 0.76 and 1.00. For these indices, the mean measurement error ranged between 0.4 and 9.1%. Results were comparable for VPI, mNPI and PPEI, whereas APEI appeared slightly less reproducible.

In conclusion, a high intra-examiner reproducibility was found for all plaque indices tested, both the ordinal and the interval indices.