Yup I just had a root canal done at 35 weeks... When I mentioned I was having dental issues to my ob she almost kicked my but straight into the dentist office
They say it's better to get your dental work done than to let it go and possibly cause infection! Especially if you got white fillings... I don't think they use Mercury in silver fillings anymore but I know they used to, but not white fillings! Anyways, you'll definitely be fine. I drank and smoked like crazy while I was pregnant without knowing I was and my son is perfectly healthy!
I work at Dentist office there is no risk at all..
It should be fine! Some dentists will do work even if they know your pregnant. I don't think there's any real risk to be worried about if it was just the one time.