In vitro assessment of the effectiveness of whitening dentifrices for the removal of extrinsic tooth stains.

This in vitro study evaluated the effectiveness of whitening dentifrices for the removal of extrinsic tooth stains. Twenty dental blocks (4 x 4 mm), including enamel and dentine, removed from freshly extracted bovine incisors, were randomly divided into 4 groups: G1--distilled water, G2--Colgate, G3--Crest Extra Whitening and G4--Rapid White. In all specimens, the dentin was covered with colorless nail polish, and the enamel was left exposed. Next, the specimens were immersed in a solution of black tea, which was changed every 24 h, for a period of 6 days. After this period, a photo-reflectance reading was taken (Time 1) with a spectrometer. The stained specimens were then submitted to linear brushing movements (5,000 cycles) using brushes (Oral B-Soft) coupled to an automatic toothbrushing machine, under a static axial load of 200 g and with a speed of 4 movements/second, at 37 degrees C, with the dentifrice or water being injected every 60 s. When toothbrushing ended, a second photo-reflectance reading was taken (Time 2). The results were submitted to two-criteria analysis of variance (ANOVA) and to the Tukey test ( = 0.05). When the two times for a same group were compared, Time 2 presented the highest reflectance values with statistical difference only for G3 and G4. Among the dentifrices tested, only the Rapid White group differed from the control group, presenting the highest reflectance values. Only the whitening dentifrice Rapid White was effective for the removal of extrinsic stains.