A new index for measuring extrinsic stain in clinical trials

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Abstract
A staining index was proposed which is simple to use clinically and yet is sensitive enough to detect small changes in staining levels between different groups. Accurate scale drawings from an atlas of tooth form were reproduced. Outlines of the labial and lingual surfaces of all 8 incisor teeth were enlarged to scale (magnification .times. 4) and each tooth face divided into 4-mm squares. All areas of extrinsic stain were drawn by the examiner on to the grid system. This method was tested in 3 clinical trials and the reproducibility investigated. In 161 duplicate examinations a total of 1830 stained squares were scored by one examiner, compared with 1853 squares by the 2nd examiner; the reproducibility ratio was 0.155 and the coefficient of correlation was 0.956. The method proved sufficiently sensitive to record differences in staining levels in groups using 2 dentifrices; one was a normal commercial product with an abrasivity against dentin approximately 2/3 that of the other paste. The proposed Extrinsic Stain Index provides data which can be analyzed by applying parametric or nonparametric tests.