How does dietary calcium benefit the teeth?

My dentist recommends I get enough calcium for my teeth, but how exactly does calcium benefit my teeth? I realize that enamel and dentin are largely made of calcium, but then I hear that dietary calcium doesn't actually travel to the teeth to make them stronger. Or does it? The enamel is practically "dead" tissue, and the dentin is mostly dead too. Only the pulp and nerves of the tooth and the gums are alive. I do realize that fluoride helps make tooth enamel stronger though, and use fluoride toothpaste and ACT for this.