I have a gummy smile. What type of dentist can fix this and how can it be done?

Your question is a good one, and I applaud you
for seeking answers from specialist. You should contact a periodontist, a type
of dentist who specializes in caring for the supporting structures of the
teeth. A periodontist can diagnose the cause of your gummy smile and create a
treatment plan based on that cause. Without photos. it isn't possible to say
what would be the best option in your case, but gummy smile correction can
involve gum contouring or lip lowering surgery. BOTOX® Cosmetic injections also
offer a temporary solution. But the first step is to schedule a consultation
with a periodontist. Good luck.

If you smile is very gummy simple gingivectomy may not correct it .   But there is a procedure called a lip tack that is a very simple and will correct it . A periodontist should be familiar with this. I have seen this with good results .

Posting a photo would really help in answering your question. Most dentists can do a gingivectomy and remove excess gum tissue. If there needs to be bone removed it becomes more of a surgical procedure and usually a periodontist would do the surgery. Start with your dentist and ask their opinion. The problem may also not be excess gum tissue, it could be an over active lip or the size of your upper jaw bone. These problems require different treatment to correct them.