In vitro tooth whitening by a sodium bicarbonate/peroxide dentifrice

The main purpose of this laboratory study was to determine the tooth whiten ing effect of a baking soda dentifrice containing stabilized 1% hydrogen pe roxide Following repeated applications to intrinsically stained teeth. Addi tional objectives were to investigate (1) the influence of tooth surface cu rvature and moisture on color measurements, (2) preliminary treatment param eters using 1% hydrogen peroxide solution, and (3) the relationship between Vita(R) shade guide standards and instrumental color readings. Human tooth specimens with intrinsic stain were specially prepared and measured for co lor (L*a*b*) by means of diffuse reflectance spectrophotometry. Specimens w ere measured under wet and dry conditions with natural and flattened enamel surfaces. A preliminary test was conducted with 1% H2O2 solution to establ ish tooth whitening versus treatment time. Then, new tooth specimens were t reated repeatedly with slurries of silica, baking soda, or baking soda/pero xide dentifrices at 30-minute intervals, and color measurements were taken under both wet and dry conditions after 4, 8, 16 and 24 hours. L*a*b* color measurements of the Vita(R) shade guide teeth were also made in order to r elate laboratory color changes to clinical effects. The parameter testing r esults showed that flattening the enamel surface had no effect on tooth col or, but the teeth rapidly became lighter and less yellow upon air-drying. T he 1% H2O2 solution caused both a significant decrease in yellow (b*) and a n increase in lightness (L*). Since the reduction for b* occurred more rapi dly and to a greater extent than the L* factor, the b* component may be the more important indicator of tooth whitening by bleaching. Compared to the silica and baking soda dentifrices, the baking soda/peroxide dentifrice sig nificantly decreased the yellow color (b*) of the teeth after 8 or more hou rs of topical treatment. The instrumental color readings of the Vita Shade guide teeth showed that the color differences between the standards were no t linear or consistent, and their accuracy for assessing clinical changes i n tooth whiteness is questionable.