Like most things in Photoshop there are always a number of different ways to achieve an end result, and I think it comes down to each persons individual preference. However to do it without the using the dodge tool I'd suggest:

-New dupe layer.
-Mask, paint over your teeth area then feather 1 or 2 pixels dependent on how big the gnashers are in relation to the rest of the image.
-Curves, adjust till he/she looks like an 'Osmond'.
-Set opacity to your desired level.

However in cases where it looks like they could chew an apple through a tennis racquet I'd consider whipping them out and giving them a new set, but that's a whole different technique.

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Richard