Evaluation of accuracy and variability of scoring-area-based plaque indices - A laboratory model

Background: Plaque scoring, using a variety of indices and methods, is wide ly used in clinical dentistry. There is limited information on inter- and i ntra-examiner variability and almost no data on examiner accuracy. Aims: The aim of this study, was to determine the inter- and intra-examiner variability and accuracy of 15 examiners, of differing plaque-scoring expe rience, in recording and judging plaque areas from simulated plaque on toot h charts. Methods: Plaque, shaded red, was drawn onto tooth charts of 8 simulated "pa tients" and measured by planimetry by 1 investigator. For each tooth for ea ch "patient", examiners subjectively copied the plaque onto blank charts an d scored plaque in 5% increments for the global plaque index. This was repe ated on 2 occasions. Drawn plaque areas were determine by the investigator and comparisons made with the actual areas and % scores of plaque. Results: For both plaque recording methods, intra-examiner variability was low and slighly better than inter-examiner variability. Reproducing plaque areas showed a high level of accuracy in most examiners, as was judging are as in 5% increments, albeit slightly less accurate than area drawing. Overa ll examiner experience had little influence on judging plaque areas. Conclusion: The data suggest that area-based plaque indices can be scored o r recorded accurately and with minimal variability within or between examin ers. The laboratory model could be used to train and assess examiners.