before you decide the problem is the shader rather than your expectations, i'd suggest using the shader in an image where you actually duplicate an unaltered image.  pretty much everything in the media is altered, and our expectations have completely skewed accordingly.  it may be that with that lighting angle, her teeth would be shadowed by her lips to that point. 

metallic spandex is in development. i think the shaders are done, so i'm rendering stuff now.