Crown lengthening failure

I have a tooth that had a root canal treatment and a crown about a year ago. I wanted to replace it with a porcelain crown. When the dentist took the old crown off, the remaining tooth was very soft and pulpy underneath. The dentist said I should have a crown lengthening procedure done to enable more of the tooth to be present for the crown to be attached to. He sent me to a periodontist to have this done.

I had the procedure done last month. Since then, I felt sensitivity and throbbing pain from the tooth and into the jaw. After a few days, I developed a pocket of infection. I was given stronger antibiotics. I also noticed a bad smell when I floss from the the gums where the procedure was done. How likely is it that the procedure failed? How long until my gums are fully healed? I have also wondered if there is an underlying problem with the root canal. Any ideas on this? I would be grateful for any answers!