Filing and chipping the front teeth to sharpened points is a body modification practice that is very widespread throughout the world. The tradition was, and in some places still is common in equatorial Africa, Southeast Asia, among the Mayans and associated people and from time to time among the Australian Aborigines.
How and why? Well the how part is quite easy. Usually a sharp instrument, sometimes bespoke and sometimes not, is employed to delicately chip away at the enamel until the desired effect is achieved. Painful and brain jarring at the very least, one can imagine that a few hours of that would send you to bed with a headache and a toothache.
Why is a little different. In some cases, teeth were filed down to a nub in order to reduce the impression of anger and hostility, and in other cases to increase the same effect. The practice was certainly cosmetic, because it offered absolutely no advantage in battle or in the business of hunting, or in eating meat. In fact, the removal of so much essential enamel from the tooth surface simply exposes it to enhance risk of decay and disintegration, and after that, hot and cold sensitivity must be awful.
There has in recent years, with the popularity of body modification, been an upsurge in the business of tooth sharpening, but with the advantage of modern dentistry, the same effect can be achieved without necessarily exposing the inner material of the tooth.
Nonetheless, here we have yet another challenging body modification undertaken for whatever specific reason, and another questionable chapter in the pursuit of ideal beauty.