An operation will damage your immune system and so will a prolonged dry fast.It will get better after but that’s is not the point here. If your idea is a short dry fast I would first ask your doctor, there could be multiple variables after the operation,hygiene, area of operation hydratation, general soreness, you previous conditions etcA dry fast will probably help healing but I would not suggest it after such operation.
I did a dry fast after removal of wisdom teeth and it worked for me, but the principles were simple, no eating, no opening mouth, and nothing touching the operation area. Clearly will heal faster ( and it was a particularly painful operation since my teeth was in an awkward spot)