Hi everyone

I really need some help with post processing an image. I have some photos I have done for a friend and they have stained teeth. I have tried the teeth whitening brush in lightroom three but the stains still look bad and now un natural. Please does anyone have any recommendations on how to make them look natural. The stains are like lines through the bottoms of the top teeth.
Please please help. Im still very new to this.

Thankyou