Analysis of information sources in references of the Wikipedia article "Teeth blackening" in English language version.
Among post-1975 refugee communities, the older ladies, especially those from Tonkín, can still be found with blackened teeth...
And the ebony bark, in its core beneath Was never so black as thy shiny teeth.
As for northern Vietnam, archaeological data of some dental remains show that betel-nut chewing and tooth-blackening (nhuộm răng) were practicsed in the Núi Nấp archaeological site considerably later, as early as 400 BCE (Oxenham, Locher, Nguyen, and Nguyen 2002) in the Đông Sơn era.
'The teeth [of women from Hanoi] were dyed up to a shiny black as the cockroach wings.' At the time, 'teeth as black as custard-apple seeds' were the most desirable traits of a beautiful girl. 'In the 1920s, most of Hanoi girls had blackened teeth'
Cách đây 230 năm, ngày 22-12-1788, trước khi chỉ huy nghĩa quân Tây Sơn hành quân ra Bắc đánh đuổi quân xâm lược nhà Thanh, Nguyễn Huệ đã lên ngôi Hoàng đế và khảng khái tuyên thệ trước ba quân tướng sĩ: "Đánh cho để dài tóc/ Đánh cho để đen răng/ Đánh cho nó chích luân bất phản/ Đánh cho nó phiến giáp bất hoàn/ Đánh cho sử tri Nam quốc anh hùng chi hữu chủ".
