I met her in NinhNhat, NinhBinh province, VietNam. Couple of dozen years before, chewing petel nut was a signal of adult and use it as type of cake at any events such as ceremony, wedding or party to get luckily because of red color after chewing petel nut. A recently years, it have not been to become common but we can meet it in oldest people who chewing betel nut along time, teeth would be black color and never comeback to white, for newbie if eat or chew petel nut would drunk at any time.