Development of methods to enhance extrinsic tooth discoloration for comparison of toothpastes

BACKGROUND: Extrinsic staining of teeth is considered to be unsightly and a number of 'whitening' toothpastes have been formulated to inhibit or remove such tooth discoloration. The aim of this study was to compare the stain prevention of two toothpastes. METHOD: The study was a single-blind, randomised, placebo-controlled, crossover design, balanced for residual effects involving 24 healthy dentate volunteers. The treatments were as follows: (1) a whitening toothpaste product, (2) an experimental toothpaste formulation and (3) water. For each 4-day rinse period, subjects were rendered stain free on the teeth and tongue. Approximately on the hour from 09:00 to 16:00 hours, subjects rinsed with chlorhexidine mouth rinse for 1 min followed by warm black tea for 1 min. The treatment interventions were at 09:00 and 16:00 hours and before the chlorhexidine rinse. The toothpastes were rinsed as 3 g/10 ml water slurries and water as a 10 ml rinse each for 2 min. On day 5, subjects were scored for tooth and tongue stain intensity and area, and the product of these was calculated. The washout period was at least 9 days. RESULTS: Treatment differences for the teeth were highly significant but not for the tongue. Paired contrasts for tooth stain intensity, area and product were mostly all significantly in favour of reduced staining by the experimental formulation compared with water and the whitening product. There were no significant differences between water and the whitening product. CONCLUSIONS: Using a forced dietary staining method, the data support a tooth stain-inhibitory/-removal action for the experimental formulation, but not the whitening product.