You could go to a biologic dentist who is familiar with procedures that will keep the mercury out of your saliva, etc. In a relative sense, you have that Amalgam in your mouth now, where it releases mercury when you breathe, eat, talk, etc. -- it is active even without removing it. And if you remove it, you can have it filled with a safer composite (most dentists do this nowadays, or you should be able to ask for it over amalgam)) so your post-extraction bioburden will be less.
Apart from the Amalgam fear, make sure you do some immune-boosting before and after the extraction. The mouth is a gateway for the rest of the body and mouth wounds are ways for infection to get in more easily. Not a huge deal for a healthy person -- but I know when my husband got his wisdoms and when he gets his teeth cleaned, even (he has a heart condition and there is some link to possible infection...) out he was placed on Antibiotics before and after the procedure.
If you don't like Antibiotics , you can megadose with C before and after (I buy Emergen-C and take 9-10 packs a day, very easy!) ; rinse with diluted Iodine solution; and/or use Colloidal Silver the day of and afterwards. E-mail me for more specifics!
And the number one thing I recommend for mouth/tooth health is oil pulling. Check out the forum. It is an easy, cheap, and extremely effective way to reduce bacteria in the mouth. You can do it before to get the mouth clean and most important, after the extraction to keep the mouth clean and prevent germs from getting into the bloodstream. It's one of the few cleansing/detox protocols I will do if I get pregnant again! A lot of people on the forum, too, report having to get dental work (like root canals) done and then oil pulling for a while and then not having to get the work done after all -- it is just great for mouth/tooth health in general (plus makes teeth whiter). If you do it with coconut oil you'll get antimicrobial protection galore -- I (personally) would do that and not take the Antibiotics they may offer. (Not on principle but because I've taken some of this stuff instead of using antibiotics before, so I do have a lot of faith from experience!)
If you do opt for antibiotics, follow up with probiotics and also the coconut oil (also an antiviral and antifungal, which helps us to avoid yeast infections that can occur when the "good" flora is eliminated with the bad stuff!)
Best, and good luck -- it will be fine! Your body also has heightened immunity when you are pregnant....