my 18 year old had 2 crowns after root canals about 6 months apart. A new dentist (and a dental assistant to an endodontist, who glanced at they xray) said that there was a gap between the crown and the tooth and it needed to be redone. Can they possibly just patch it up, or does it need to be fully redone? What is the urgency- does it need to be redone next week, within a few years, or only if there is an issue? What is the detriment to the existing tooth if the original doctor redoes it & he does a bad job again, & it needs to be redone another time?