Isolate
We now want to have our teeth on a new layer so that we can work on them without affecting the rest of the image, so we use the Layer Via Copy command [CTRL+J] to copy the contents of our selection to a new layer. We’ll rename this layer to “Teeth” by double clicking on the name of the layer in the Layers Palette and then typing your new name.
Step 3 – Desaturate
Now, we need to get rid of that horrible browny yellow colour. Some tutorials will tell you to use Color Balance for this but that is a long winded and almost painful process – particularly if you have a number of images to work on – so we’ll go quick and dirty – we’ll simply desaturate, thereby removing all colour information from this layer. We’ll re-introduce a little of the colour later. For now, just desaturate either by going Image>Adjustments>Desaturate or (and I always prefer keyboard shortcuts) by pressing [SHIFT]+[CTRL]+[U]. Then we’ll perform an AutoContrast command on the teeth by pressing [ALT]+[SHIFT]+[CTRL]+[L], thereby brightening up the layer.