Methods: The in vitro stain removal efficacy was assessed by a modified Pellicle Cleaning Ratio (PCR) method. Bovine enamel blocks were pre-etched and stained in a mixture of mucin, ferric chloride, instant coffee and tea at 37 degree centigrade with rotation for 4 days. Specimens, with L value between 30 and 40, were brushed on a brushing machine with test dentifrice slurries (25/40 dentifrice/water) for 400 strokes at a normalized pressure of 150 grams. The PCR score of each test dentifrice was calculated as follows, PCR=Delta L(dentifrice)/Delta L(ADA std)*100. An ADA standard was prepared by adding 10 grams ADA reference standard calcium pyrophosphate to 50 grams of 0.5% CMC solution. The pH-stat crystal growth inhibition study was conducted to confirm the anticalculus efficacy of DEW. Hydroxyapatite seed treated with dentifrice supernant was placed into a supersaturated solution of calcium and phosphate with respect to hydroxyapatite. Calculus inhibiting ingredients in the dentifrice adsorb onto the seed surface and inhibit the hydroxyapatite crystal growth rate. Both study used the same negative control, a regular Silica, non-tartar control fluoride dentifrice.
Results: The PCR scores for DEW and the negative control were 105(13), 90(16), respectively. Statistical analysis showed that DEW was significantly better (p<0.05) than the negative control in stain removal. In the Crystal Growth Inhibition study, DEW produced a 69.6% reduction in hydroxyapatite crystallization compared with negative control.
Conclusions: These results demonstrate that DEW was more effective in tooth stain removal than regular silica fluoride dentifrice, and also provide support for the anticalculus efficacy of this new dentifrice.