You can easily play dentist and whiten a person's teeth.
Be sure to check off as you go along.
1) Preserve your original file.
If you haven't already done so, go to Preserve Your Original File.
2) Create a Background copy layer.
If you haven't already done so, go to Create a Background Copy Layer.
3) Enlarge the teeth with the Zoom tool.
1) Select the Quick Selection tool.
2) Select an appropriate brush size.
3) Click, hold, and drag on the teeth.
Make sure the brush doesn't touch the gums.
4) If the selection is too large, make sure the Add to selection icon is selected in options bar/Tool Options.
Press and hold the Alt key to change the brush to a minus brush.
Place the brush outside the selection, click, hold, and drag to make the selection smaller.
5) Be sure to save the selection if you may need to return to do more work.
If you haven't already done so, go to Save the Selection.
6) Create a Hue/Saturation adjustment layer.
7) In the Hue/Saturation window, change Master to Yellows.
8) Decrease the saturation, the middle slider in the Hue/Saturation window.
7) Check to make sure the teeth are not being overly whitened.
8) If needed, you can increase the Lightness slider in the Hue/Saturation window to whiten the teeth further.
9) You can use the Sponge tool to desaturate any remaining areas of the teeth that are still discolored.
Change the Mode to Desaturate in options bar/Tool Options.
Here's the whitened version.
If you haven't already done so, go to Saving Files.