Here's a link that has some pretty good pictures showing how deer are aged by tooth wear. What a deer eats and where it lives has a big influence on tooth wear. A deer that is mainly eating crops will not have the wear that a deer in the northern woods that is eating cedar a number of months during the winter to survive will have. A deer that is eating in sandy type soil will also have faster tooth wear that one that has plenty of food and doesn't have to have close contact with the ground.

http://www.bing.com/images/search?q=...hart&FORM=IGRE