Not that it is anything like, say, hare lipped, but recently I saw a woman (and I’m sure that there are people of both genders like this) who appeared, when her mouth was closed, to have no teeth.
Any of you who’ve seen someone with false teeth can tell when that person has their dentures in or out, based on how their face looked. I recently saw a woman, whom I would have sworn had taken her teeth out, based on the structure of her face, were it not for the fact that when she opened her mouth, you could see that she essentially had a full (or nearly so) set of teeth.
I know that certain facial conditions, such as a brachygnathia (which might or might not appear unattractive, based on other characteristics) have a name, so I’m assuming that this has a medical description as well.