There are many ways to treat a gummy smile, so before you have the procedure done, get good advice. That may mean you need to do your research. The key is that you can get black triangles after crown lengthening so you need to know exactly what to expect. We can not guarantee results but we can give you an idea of what we think, so you are prepared.
When you do crown lengthening you can get rid of the gummy smile but you need to know if your teeth are small, if they had delayed erruption, if your top jaw is misaligned, etc. Why do you have a gummy smile?
Depending on what challenges you are dealing with, that will affect the outcome. When the surgeon does crown lengthening, if your papillae(the area of gum inbetween your teeth) are altered, you can get black triangles. You need to find find out what your needs are and go from there.
You can sometimes treat a gummy smile with Botox. Black triangles can sometimes be solved with bonding and/or veneers as well. Good luck.