I had crown lengthening done once. The procedure is basically cutting away your gum to expose more of the bottom of the tooth (gives more surface area for a crown to attach). The "cutting" with a laser, so it's basically just burning away the gums. I could see actual smoke rising out of my mouth and it distinctly smelled like cooking bacon. It was very surreal because I didn't FEEL anything.

Cauterization of the wound, I'd expect. Stops bleeding via cooking you.