I think what your seeing/feeling or whatever is VG not plaque because ....
"Dental plaque is a sticky and invisible film made of bacteria covering the teeth." ( from e-how.com)
And PG & VG are both anti-microbial and DON"T promote plaque .
I have been to the dentist & the oral hygienist since I started vaping (VGmostly here too) & my plaque indexes (ya know when they use the dye & chart your mouth) have never been as LOW as the are NOW !!
I have been in a constant (@least 4 x's a yr.) dental program for the last 16 years @ the local dental college. So this is an amazing thing to them. I have explained e-cigs several times to several students & professors , we think that the pg/vg doesn't allow the plaque to form. And since I am staying saturated in it

....TADA there ya GO !
They said we would have to see if my plaque levels stay this good b-4 they REALLY make an official conclusion tho .
I thought it was cool ....
and my cleaning consisted of talking to everyone, not really cleaning ... cuz there wasn't really anything to clean !
So I think what you are feeling is just excess vg ,
I just drink more water & brush when I start feeling slimy
