Just like a dirty sanchez, but dirtier! It's when you rub your fingers in your ass and wait for someone to grin, then you wipe it across their teeth. They won't be smiling now!
That guy had a dumbass grin on his face, so I wiped it off with a dental sanchez!
A dental sanchez is when you stick your finger in your own ass, then wipe it on your someones teeth, causing there lips to rise up. Which makes it look likes there are smiling.
I just gave that dude a dental sanchez.