I've come across this article which relates the amount of scaling you have to AF:
(I hope this link comes out)
Apparently there's a reduction in AF development of about 30% in those who go to the hygienist once a year and 65% in those who go twice or more a year.
It might be too late for those who already have AF. But if you're going for an ablation, if you want to remain AF free it would seem to make a lot of sense to get your teeth really clean and get rid of gum disease.