Detailed information about a 1st tooth cake design

Since you say that you know they're edible, I'd say that the tooth and crown are most likely made of gum paste, not fondant.

The curves on the points of the crown would likely droop really badly if made of fondant because it never solidifies. Gum paste does. So, once you have it molded to the shape you want, you let it dry out and then it stiffens to a candy-like finished product. Here's an outline of the difference between the two and when you should use one over the other.

As to how to make them, the crown can be made by following any of a number of guides on the web. They generally involve cutting a strip of gum paste in the shape you like and wrapping it around a cylinder of the diameter you need until it dries.

The detailed decorations on the cake and crown and the crown on the tooth are probably made very easily with gum paste using molds.

The tooth itself will likely be the most difficult thing as it will take a lot of artistic talent and patience. Making figures is very complicated, particularly if you have no experience working with fondant/gum paste or with something similar like clay.

There are general guides here, though none of them are for teeth, they should give you an idea of how the process works.