[useryman]

> They inject something in the gums that removes sensitivity there so you feel nothing

I've never heard this called "freezing". I assume you're being injected with lidocaine, the dentist's non-psychoactive best friend. https://en.wikipedia.org/wiki/Lidocaine

This family of molecules is well known for causing numbness in motor and sensor nerves; https://www.youtube.com/watch?v=KEI4qSrkPAs