I dented it and the bumper came off

Is it common to dent the bottom?

Small dents are pretty common, but if the dent is severe and causes a problem, go into a music shop to get it fixed.

I had lots of dents fixed on my alto sax so I wouldn't see why not take it to a good shop & ask a pro. Any brass can be welded that's the beauty of metal take it from a master fabricator metal is longer than life if taken care of. Peace

Quit asking the same question over and over again. Once is enough.

If you have enough money it can be repaired to new condition.

I dented it and the bumper came off

Is it common to dent the bottom?