First, we open the image in Photoshop .
Select the teeth with the tool Lazo of the Tool panel . We can zoom in on the area and use other selection tools if we want to be more precise with the selection.
Photoshop: loop tool

We set a fade radius of 1 pixel. To do this, we display the Selection menu , click on the Modify option and choose Fade .

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We create an adjustment layer type tone and saturation from the Panel Settings .
Photoshop: Adjust Hue and Saturation

In this panel we choose to work with yellow tones . Next, we drag the Saturation regulator until the yellow shade of the teeth is eliminated.
Photoshop: Adjust Hue and Saturation

Photoshop: Adjust Hue and Saturation

We select the All option again in the Edit menu of the Settings Panel and drag the Brightness regulator to the right until the desired effect is achieved.

Photoshop: Adjust Hue and Saturation

Example: