Can you have a fractured tooth root if there's no pain to speak of and are they dangerous?

My two bottom teeth that are as far in the back as possible have gold crowns that are decades old. If I brush them or chew on them too much they can ache briefly , like for ten minutes. This has been going on with these two teeth for a year! Could I have fractured roots with so infrequent discomfort and could it be dangerous? I could have decay under the crowns but X-rays do not pick up decay under gold crowns!