Laboratory assessment of tooth whitening by sodium bicarbonate dentifrices

The increasing emphasis on dental aesthetics has made tooth whitening an important function of a dentifrice. This laboratory study investigated the whitening effect of toothbrushing with sodium bicarbonate-based dentifrices compared with standard dentifrices that do not contain sodium bicarbonate. Six dentifrices and a distilled water control were tested for their ability to whiten teeth with intrinsic stain. The dentifrices contained different abrasive systems: (1) 45% NaHCO3; (2) 65% NaHCO3 (Arm and Hammer Dental Care); (3) 94% NaHCO3; (4) 94% NaHCO3 + 1.5% H2O2; (5) silica (Crest Regular Toothpaste); and (6) dicalcium phosphate (Colgate Regular Toothpaste). After a thorough rubber cup cleaning with a pumice slurry, the intrinsic color of the test teeth with a Vita shade of A3 or darker was measured with a spectrophotometer using the standard L*a*b* color scale. Measurements were taken on a total of 12 teeth per test dentifrice before treatment, and after 30, 60, 90 and 120 minutes of mechanical toothbrushing. No changes in L* (lightness/brightness) or a* (red-green hue) occurred, but significant differences in b* (yellow-blue hue) were observed over time. Compared to baseline tooth color, all four sodium bicarbonate-based dentifrices were significantly effective in removing the yellow intrinsic tooth stain, while the water control, silica dentifrice, and dicalcium phosphate dentifrice demonstrated no significant change. Between-group comparisons showed that the four dentifrices containing sodium bicarbonate were significantly more effective than the water and dicalcium phosphate dentifrice groups. The commercial dentifrice containing 65% sodium bicarbonate was also more effective than the commercial silica dentifrice. Although continued toothbrushing from 30 to 120 minutes resulted in additional stain removal, most of the tooth whitening by the sodium bicarbonate-based dentifrices occurred in the first 30 minutes of brushing. In the studies conducted, dentifrices containing high concentrations of sodium bicarbonate were more effective at removing intrinsic tooth stain than dentifrices that do not contain sodium bicarbonate.