Before there were grills everyday people who needed dental work had their teeth pulled and replaced with gold teeth. Many black people opted for this option rather than spending lots of money for expensive dental repair and  so gold teeth were prevalent in black communities. During the late 1980's gold teeth gained popularity and exposure as rappers like Flava Flav of Public Enemy and others began to show off their gold teeth (along with their gold chains, rings, etc.) as bling was the style of the time.  Gold teeth quickly went from a dental solution to a fashion statement as more rappers included sets of false teeth in their gold and jewelry arsenal.  After Nelly made the song "Grillz" in 2005, the rest was history.