J. Soc. Cosmet. Chem. 26, 217-225 (1975) i•) 1975 Society of Cosmetic Chemists of Great Britain A parametric test to measure cleaning power of toothpaste the W. B. DAVIS and D. A. REES* Presented on 26-30th •lugust 1974 in London at the IFSCC I•IIIth International Congress on 'Cosmetics--Quality and Safety' organized by the Society of Cosmetic Chemists of Great Britain. Synopsis---A sensitive IN VIVO method was developed to quantify the cleaning power of dentifrices. Volunteers built up natural STAIN on their TEETH over a period of 5 weeks by replacing their usual TOOTHPASTE with a non-abrasive paste. The estimated •o area of the incisors covered by stained pellicle was observed to increase, especially towards the end of this build-up period. The natural stain was progressively removed by a series of 10 s BRUSHING periods using an electric TOOTHBRUSH and the pastes to be tested. The logarithm of the area of stain was plotted against the duration of brushing with the test paste and found to conform to a linear trace. Thus an equation for stain removal may be of the form S=ae t't with the coefficient b being an expression of the ability of the test paste to remove stain. INTRODUCTION Over thirty years ago, Manly (1) observed that the 'brown pellicle' which formed regularly on the teeth of some people who did not use denti- frice abrasives could be readily removed by one or two brushings with a dentifrice grade calcium carbonate or phosphate but not by brushing with a dry or moistened brush without a dentifrice. Lobene (2), and later Van Abb6 et al. (3) who slightly modified Lobene's technique, employed direct visual observation to assess the removal of stained material from teeth using a toothpaste under controlled brushing conditions. Wilkinson and Pugh (4) used both photographic recording and * Beecham Products Applied Research and Evaluation Laboratories, RandalIs Road, Leather- head, Surrey. 217

218 IOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS a photometric method to assess the extent of stain on teeth cleaned for 2 weeks with a test toothpaste, after an initial scale and polish. These techiques detected differences in the stain-removing properties of toothpastes, but employed non-parametric data. Moreover, stain colour and intensity, and the presence of plaque complicated the assessment. A technique has now been developed which uses quantitative measure- ment on a parametric basis, to generate a value of cleaning power for tooth- paste. It is uncomplicated by stain colour and intensity or plaque and gives repeatable results. EXPERIMENTAL Formation of stain for study of cleaning power When volunteers used a non-abrasive toothpaste for cleaning their teeth, a natural stain, not related to their smoking habits, developed visibly in approximately one-third of the subjects and increased in area during the course of 1 month. Satisfactory plaque removal and oral hygiene was achieved, however, with no adverse effect on the gingivae. Quantitative assessment of stain By examining the incisors of each volunteer through a horizontally mounted Nikon stereoscopic binocular microscope (model SMZ-2), fitted with double spotlight tungsten illumination, the stained areas were easy to identify. Ektachrome X photographic transparencies of the teeth were taken with a Miranda Sensomat camera through the binocular microscope using crossed polaroid screens over the Multiblitz photographic flash* and objec- tive lens. This method of illumination eliminated specular reflection and permitted clear identification of the stained areas, although giving a slightly out-of-focus effect. Examiners were trained to estimate visually the percentage area of the labial surfaces of the eight incisors covered by stain and their estimates were found not to differ from the planimeter-derived measurements by more than one-sixth. The percentage area of the labial surfaces of the eight incisor teeth covered by stain was calculated from planimeter measurements of boundary * Dr Ing. D. A. Mannesmann, GmbH & Co. KT, Porz-Westhoven, West Germany.