The reason has to do with blood supply between the mouth area and the heart.
In about 98% of the heart attack cases they find the same bacteria causing problems in the mouth, in the heart tissue.
This is also why you don’t want to have root canals if you can avoid it. Bacteria from those deep bloody operations can find their way to your heart.
It’s been a significantly underestimated risk.
So when the dentist says you need a root canal, what is the alternative?
Any competent dentist will prescribe antibiotics prior to a root canal. Good luck finding a competent dentist.