only once, a young kid going to a clinic.
A friend told me that she had a "device attached to her neck" and told me her experience... and I had to disimule my interest.
And finaly, I saw a adolescent in the subway who had brackets, and some kind of "structure" to enlarge his maxilar, and was conected like, I don´t know, nails or something, the iron get into his cheeks, I suposed that that kind of device has to leave the skin with scars.