A new index for measuring extrinsic stain in clinical trials

A staining index has been 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 eight incisor teeth were enlarged to scale (magnification X 4) and each tooth face divided into 4-mm squares. All areas of extrinsic stain were drawn by the examiner on the grid system. This method has been tested in three clinical trials and the reproducibility investigated. In 161 duplicate examinations a total of 1,830 stained squares were scored by one examiner, compared with 1,853 squares by the second 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 two dentifrices; one was a normal commercial product with an abrasivity against dentin approximately two-thirds that of the other paste. The proposed Extrinsic Stain Index provides data which can be analyzed by appling parametric or nonparametric tests.