Are dentist required to tell their patient when they break an instrument off in the tooth; as in a file with a root canal?

I saw my x-ray and I asked the assistant what was in my tooth. She said, "Oh, it's just part of the file that broke off. Nothing to worry about." The pain feels like a thorn. The crown doesn't allow me to fully bite down but I if I did, it hurts too much. When the dentist did the x-rays, he didn't use the "apron" to protect me. I'm upset I wasn't told about the file. I had a right to know, at the time it happened. If I'd not seen the x-ray, I don't think I would have been told at all.