I have an otherwise beautiful client that has a green cast to her teeth. I'm really not sure how to handle this while still keeping her natural smile looking natural. Dodging mids just makes them a lighter shade of green. There's really no nice tooth material to sample and clone. Have you ever had to deal with such a thing? Maybe I could sample someone else's teeth and use that to hide her discoloration? How far would you go with it? I don't want to offend her by completely changing the way her smile looks.

TheKrowe, welcome to RetouchPRO! Nice to have you aboard and hope you enjoy.

If you are using Photoshop, select the teeth
Ctl+U (OR Image>Adjustments>Hue/Saturation)
where it says "Master" click the little arrow and change it to Green and adjust the saturation and lightness sliders till the teeth are the appropriate color.. sometimes you may need to adjust the yellow and red also.. click OK then deselect

Is the cast only on her teeth or is it on the entire image. If the former, then a selective color adjustment layer may be the quickest most effective way. If the latter, then a global curve, or gray point adj may be best. Can you upload the image or a section of it?
Regards, Murray