Unlike us, horses have teeth that grow throughout their lives. In the wild equines forage constantly on tough plants, which causes them to wear their molars down. Domesticated horses don't get the same chewing regime and can wear their teeth down unevenly, causing sharp hooks or points in the tooth surface. This can cause chewing difficulty, bitting problems or pain, so most middle-aged horses get treated to a tooth job, or 'floating' once a year.
Floating, or filing the teeth, is done either by hand with a rasp, or with a coin-sized filing head on the end of a power drill. To make this safer for both horses and humans involved, the horses are sedated. The vet then suspends the horse's head in a padded halter-sling and fits a speculum to hold open the mouth.
The actual filing takes about 5mins and is painless for the horse. The sedation and headgear are used because most horses are not on board with the whole giant electric toothbrush thing.
And by afternoon they're generally back to (almost) normal.
Jennifer Landels, Maestra di Scuderia
Academie Duello Cavaliere Program