Fig. 5: Nondestructive characterization.
The scanning electron microscope images of an identical tooth a before whitening treatment, b after piezo-catalysis whitening in BTO turbid liquid for 3 h, and c after further whitening by 30% H2O2 for 2 h. The images at the bottom are the enlarged view of the marked identical zone. Scale bars are 100 μm (top) and 50 μm (bottom).
