If only it were as easy to whiten teeth as it is to whiten teeth in Photoshop. After opening your image in Photoshop, follow the steps described here to quickly and easily whiten teeth in Photoshop.
Use the Lasso Tool to roughly select the area of the image that includes the teeth.
Create a new Hue/Saturation adjustment layer.
Click the drop-down menu that says Master and choose Yellows. Drag the Saturation slider all the way over to the left so that the number is -100.
Go back to Master in the drop-down menu and drag the Lightness slider to the right a bit.
The image will now appear something like this:
Go to Edit in the menu and click Fill.
Choose Black in the drop-down menu in the Contents section. Click OK.
Select the Brush Tool.
Make sure that the foreground color is set to white.
Adjust the size and hardness of the brush.
Paint over the teeth to whiten them.
If you make a mistake, set the foreground color to black and paint over the mistake.
If the teeth are too white, adjust the opacity to lower the intensity of the whitening.
Photo by SuperFantastic.