In vitro Pellicle Cleaning Ratio (PCR) Testing and evaluation of toothpaste stain removal from human or bovine enamel samples
The Pellicle Cleaning Ratio (PCR) can be used to evaluate stain removal performance of dentifrices such as toothpastes or toothpowders. Stain build-up occurs when chromophores from food and drinks bind to the protein pellicle layer on the enamel surface. Dentifrices typically contain mild abrasives which help to removed stains during brushing. The PCR test is a means of comparing abrasivity against a reference abrasive or benchmark products.
The consumer desire for whiter teeth has driven the appearance of many new dentifrice products on the market. A robust, quick, reproducible test is required that can rank stain removal capability and guide formulation development or provide support for marketing claims.
Our oral care laboratory team routinely performs Pellicle Cleaning Ratio (PCR) testing to evaluate stain removal performance of dentifrice products.
Bovine enamel slabs approximately 9mm square are embedded in plastic/acrylic blocks and stained with a mixture of tea, coffee, mucin and iron chloride. Stain is measured using a chromameter that records L*a*b* colour parameters and blocks (up to 16 per test cell) are stratified to test dentifrices and reference cells. Stained blocks are then brushed using an artificial brushing machine under specific conditions of load, speed and duration, with slurries of the dentifrices made by mixing toothpaste or toothpowder with water. After brushing the L*a*b* parameters are re-measured and changes are calculated in terms of overall colour change (ΔE). Mean ΔE values for each dentifrice are calculated and compared to the reference abrasive thereby yielding a PCR value, which may fall into low, medium or high categories.
PCR results can be statistically compared if required and are provided to the client in a fully signed-off report.
For over 18 years our Clinical Research Services group has been bringing quality and safety to life as a trusted partner for developers and manufacturers of oral care products. We provide a one source solution for both in vitro studies and human trials providing robust data to support the efficacy and safety of novel treatments.