My dentist said he never does dental work in the first trimester, except for cleanings. Do you know if they will be giving you any gas or anesthesia? If so you should reschedule because it can cause miscarriage early on. You can also call the dentist and see what they say.
You can buy a test for 1$ at the dollar store. Or wait until the day of your appointment and tell the doctor you might be pregnant and if it is safe during pregnancy he will go ahead with removing them and if its not he will tell you he can't do it.