Reclast infusion after a root canal.

I had two extractions months ago, and was ready to schedule my Reclast infusion soon. During a dental cleaning yesterday they found a tooth in front of the extracted tooth needed a root canal, and might have a fracture. The dentist said I can schedule the Reclast because the root canal is going to be an easy procedure, and he doesn't see any fractures. I've had Reclast infusions twice before, and this will be the last I think. Will this be safe? I don't know how they missed the problem with that tooth when they did x-rays for the teeth to be extracted.