¿Why is it unsafe to have dental work during first trimester?

I hear that it is ok, and definitly not okay to have certain dental work done during the first trimester and think last. When I asked a Dentist, he said because of abortion (miscarriage). As I have stated in another question I am in need of emergency dental work due to that fact that my wisdom is pushing all my other teeth and that well it's broken completely and I kid you not, it's like a horrible throbing, yanking pain. Even my saliva causes agony pain. Please if anyone has been through this I would appriciate your in put. I am to see the Another dentist on Wednesday, but in the meanwhile, I think I should get some info for precautions. Thank you.

¿Why is it unsafe to have dental work during first trimester?
DRUGS. depending on the dentist and what they end up doing to you. but it sounds like your going to have to at least get the wisdom teeth pulled. so that means they will most likely put you under. well its not like fully under, your awake but you remember nothing. but to get to the point even Novocain has been believed to be linked to miscarriages, and you would be getting allot more than that.