Lindsey Vonn just showed off the dental procedure she had to undergo to get new chompers ... and it's gnarly as hell!!!

The Olympic gold medalist put drill to teeth Monday, filming the whole process ... and in the video, you can see it doesn't appear to be the most pleasant experience.

The dentist ground down Vonn's two front teeth into little nubs ... and even Lindsey had to acknowledge it's some "pretty gross content."

Fortunately, the doc was able to build Vonn's teeth back up ... and afterward, the 35-year-old showed the pearly whites were no worse for wear!!