Thanks Joe for the reply. I guess my confusion was because searching based on the ingredients of crowns for teeth sounds like the crowns themselves often contain mercury. Maybe I'll try calling my dentist to see if they would know based on their records what was used for the crowns. Fortunately I'm pretty sure all my crowns came from the same place and pretty close to the same time.
I think I'll just try to schedule an evaluation with a bio-dentist and see what my options are. I know the husband won't agree to anything in the thousands, but if insurance might possibly cover some of it maybe it'll be sellable.
Thanks again for taking your time to help us newbs!