Densaugeo

Densaugeo is the hex that gave Hermione Granger one of the more humiliating and clarifying moments of her Hogwarts career. The incantation builds on Latin dens (tooth) and augere (to grow, increase), producing a name that announces itself: the hex makes teeth grow. The cast strikes the target's mouth, and within seconds the front teeth begin lengthening past the lips, past the chin, into something between rabbit-tusk and walrus-tusk.

The famous on-page cast comes in Goblet of Fire, in the same corridor exchange that hit Goyle with Furnunculus boils. Draco Malfoy's Densaugeo collides mid-air with Harry's Furnunculus, and Hermione catches the rebound. Her front teeth start growing past her chin in seconds. The scene's lasting cruelty, however, is not the cast — it is Snape's response when the trio arrives in his classroom. Looking at Hermione, whose teeth are now visibly grotesque, he says simply that he sees no difference. The line is one of the worst things Snape says to a student in the entire series, and the moment crystalizes Hermione's relationship with her own appearance: she has Madam Pomfrey shrink her teeth slightly past their original size before fixing them, finally, the way she always wanted them.

Treatment for Densaugeo requires dedicated dental healing, generally administered at the Hospital Wing or by a healer specializing in physical-augmentation curses. Standard Finite Incantatem will halt the growth but not reverse what has already happened, and untreated Densaugeo'd teeth do not return to normal on their own. The hex is one of those mid-tier offensive spells that does no permanent harm if treated promptly but can produce serious dental work if ignored.

Densaugeo is treated as a Hex rather than a Curse — its effects are reversible, no lasting damage if treated, no Dark Magic involved. But it is firmly on the unpleasant end of the curriculum, and most schools and dueling clubs treat unprovoked casting of it as more serious than the classification suggests.