dkcamoli... there should be no more risk associated with teeth extraction being on levothroxine than not being on it. I've been on thyroid hormone medication for 8 yrs and have had several extractions, plus other dental surgery and have had no trouble.
If you're having dental x-rays, you might want to ask for a thyroid shield, to eliminate radiation.
There should be no reason to do a fresh thyroid scan prior to doing dental work.
Talk to your doctor and/or dentist prior to having work done, in case you have extenuating circumstances...