Then, around 80 million years ago, modern birds emerged without teeth. It turns out that while developing a beak, birds lost their teeth.
Normal chick (left), mutant jaw (right) shows teeth
CREDIT: John F. Fallon and Matthew P. Harris
John Fallon of the University of Wisconsin was able to conduct an experiment in 2005 that induced tooth growth in normal developing chickens by tweaking the genes. The chicks were not allowed to fully develop, but their teeth looked like reptilian teeth and shared many of the same genetic traits.
A direct application of this research could be re-growing teeth in people who have lost them through accident or disease.
The Development of Archosaurian First-Generation Teeth in a Chicken Mutant - http://www.cell.com/current-biology/retrieve/pii/S0960982206000649