Body modification takes many forms, from simple ear piercing and small tattoos to much more involved processes like the "cat people" you read about. Body modification is not something to be taken lightly because the effects aren't always easy to get rid of. Even pierced earlobes will still show a slight scar if you let the hole close up.
More serious body modification is even harder to fix. Implanted spikes, forked tongues, eye (scleral) tattoos, filed fangs, and other changes take a lot of work. You thought removing a tattoo took a long time? That's nothing compared to what has to be done in these other cases.
So if you're considering serious body modification, such as filing your teeth into fangs, think carefully. Here's what you'd have to go through to have those teeth fixed if you were to change your mind.
One option, especially if the front teeth are the only ones modified, is to have veneers added. This should be used only if your teeth were not weakened by the filing, which is a very common side effect. Remember, if you file your teeth, you're removing enamel, and if you file them down enough to change the shape, you could be removing enough of the tooth structure to make them difficult to care for.
But if they are still strong, and most of the tooth is still there (for example, maybe you had your already pointy canines contoured a bit, rather than actually grinding it down) adding a veneer to give the tooth a more normal shape may work. You'll need a dentist to evaluate the tooth first, of course.
Extraction and Implants (or Bridges/Dentures)
However, if the tooth is weak or too small, the veneers would be useless -- it would be difficult to eat with them, for example. A drastic option if you're dealing with a few teeth could be to extract them and have implants added, or to get dentures or a bridge. Again, this is drastic, but if you are really having trouble with your sharpened teeth, it may be a necessary evil.
If your teeth were not filed into fangs but mildly reshaped as part of the modification, you may be able to fill in the rest of the regular tooth shape as if you were dealing with a chip. Dentists can restore chipped tooth corners with material similar to that used in composite fillings. This is best for small modifications, however.
So if all those descriptions have you sucking your lips in to protect your teeth as if you just heard nails on a chalkboard, that's a sign that maybe you shouldn't get your teeth modified. There are plenty of temporary makeup tricks you can use to make your teeth look like they've been changed, and it would be a lot better for your mouth if you went with those instead of permanent modification. Contact a dentist, like Dr. Mahnaz Rashti, for more help.