Is a fiberotomy necessary after braces, or just wear a retainer?

Yes good idea: Fibers between the teeth are elastic in nature. With braces you can close the spaces and wear retainer but you need to remove cause of spaces.

Keep teeth straight: It can be a good idea if your teeth had to move a lot to be straightened. A retainer will be necessary as well.

Edward's works: The edward's procedure or supercrestal fiberotomy was described in 1970 and assists in retaining problematic, rotated teeth. This small procedure is usually only accomplished for 1 or 2 teeth. The need, the process, and the risk/benefits should be discussed with your orthodontic and periodontal specialist.