there have been links to dental work and premature labour. A research study in a hospital in WA has discovered that an enzyme in your mouth can cause pre term labour. This may only be a factor to consider in your 3rd trimester - so best speak to OB about it.

They ran a story on the Sunday program several years ago about reason for prem births - and this is one of the factors that they discovered. The story caught my attention as my twins were born prem. I then started to freak when they talked about this link as I went to the dentist the day before I went into pre-term labour at 30 weeks.
So what I am saying is not to freak you out. You have to weigh up the health risks of having an infected tooth against the risk of preterm labour.

I would be very surpised if you would be able to find a dentist to perform a root canal on you whilst pg anyway. I just have one done and they took several x-rays as well as local to numb the area.

Perhaps it is an abcess which they may be able to aleviate with anti-biotics until after your babe is born.
Good luck and let us know how you go