Well, I was a skeptic. Despite sage advice Brian has posted here many times, I dismissed this idea.
No more.
Had a root canal last week. Molar, 3 roots. It was a disaster initially (had to be sent to an Endodontist -- the "other endo" -- after my dentist failed). In any case, here it is a week later, healing up nicely, and lo and behold I've become more insulin sensitive for no other apparent reason.
Of course, this isn't definitive, but the correlation is there. That infected tooth had to be infected for some time. Now it's not, it's the only real difference in my health from last week, and if this continues I'll have to adjust my IC on my pump.
Sorry to hear about your root canal. I wish I could have given you advice that would have avoided the root canal. Sadly I still struggle with dental problems. My diabetes and dental struggles just seem gripped in a deadly cycle and my dentist and periodontist are putting their kids through college with my help.