Miley Cyrus -- Gets Yanked by Dentist After Online Tooth Shaming

Miley Cyrus has unlocked the secret to free dental advice -- post your X-ray online and let dental experts weigh in, but be warned ... it might not be all good news.

Miley posted the shot on Instagram and it didn't take long for the reviews to pour in, and several blasted her mouth work. We spoke to one reviewer, a dental assistant named Ashley, who gave us this dental Yelp:

-- Miley has veneers on all her upper teeth and had a root canal at some point
-- She might want to get another set of X-rays ... she could have a few cavities
-- Her wisdom teeth need to come out soon (the top ones are impacted and could be a big problem for her other molars if not dealt with soon)

Miley might have taken that advice ... she posted a pic Wednesday of a few teeth she got pulled.

Fun Fact(ish): A recent study said the Tooth Fairy pays West coast kids $4.68/tooth, on average. Don't it spend all in one place, Miley.