a Photographs of teeth under treatment of vibration in (top) pure deionized water and (bottom) turbid liquid of BTO nanoparticles for 0, 1, 3, and 10 h, respectively. These photographs are successive images of the same tooth. Variation in b luminance L, c color value of red–green axis a, d color value of blue-yellow axis b and e color difference ΔE at vibration time of 0, 1, 3 and 10 h. f The setup we used to simulate daily teeth cleaning behaviors. g Photograph of teeth brushed with pure deionized water (top) and BTO nanoparticles turbid liquid (bottom), respectively. The comparison of brushed zone, marked by circles, reveals that the piezo-catalysis with electric toothbrush was effective to tooth whitening. The difference of ΔE at each time point was calculated by t-test, p < 0.01. Scale bars are 1 cm. Error bars = standard deviation (n = 3).