I think it'd be hard to see and tell if there's a worm in a tooth root. Although I could visualize that it would be a nice place for a worm to live in. A secure fortress if you will.
Trying to tie a string around a worm that's located in your mouth would be very tricky.
A trick my dentist taught me: take a tea bag, dunk it in warm water, remove the tag, wrap the string around the bag to make a tube and place that on the affected area.
Into the tea bag you could add some parasite killing herbs before you roll it. This way the herbs would be concentrating in your mouth area.