An occlusal plaque index. Measurements of repeatability, reproducibility, and sensitivity.
PURPOSE: To evaluate a new, computerized method of measuring dental plaque on occlusal surfaces which exhibit the highest caries prevalence. METHODS: In 16 patients (6-9 years of age), plaque on the occlusal surfaces of permanent molars was stained (Mira-2-Tone) and photographed with an intra-oral camera. In a conventional picture editing program (PC/Adobe PhotoShop 6.0), the occlusal surface and plaque were measured in pixels and the relative proportion of occlusal plaque was calculated (ANALYSIS 3.0). The repeatability and reproducibility of the method were analyzed by re-taking and analyzing four images by two examiners four times via intra- and inter-examiner correlation coefficients and by re-analyzing 10 images. Sensitivity was tested by re-taking and analyzing the images of the same occlusal surfaces in all patients after instructed brushing with an electric toothbrush. RESULTS: Intra- and inter-examiner correlation coefficients for repeatability and reproducibility of the analysis were excellent (ICC> 0.997 and ICC=0.98, resp.; 95% confidence interval: 0.955-0.995). The inter- and intra-examiner coefficients for the whole procedure including the re-taking of images were also high (ICC > 0.90). The method was also highly sensitive, proving a statistically significant plaque reduction after brushing (before: mean 29.2% plaque, after: 14.7% plaque; t-test, P= 0.025).