Will crown lengthening (removing/shaving down bone) weaken endodontically treated natural teeth?

I recently had emax dental crowns placed in front. They look terribly bulky and one of my central teeth in front shows black around gum line. My dentist said the darl line was from endodontically treated tooth. He said he was unable yo place the thick emax further under gum. He is now suggesting I see a periodontist for crown lengthening. Is this necessary? Will I lose bone? Will he break my natural teeth trying to remove these adhesivesly bonded crowns?