Can all recursive functions be re-written as tail-recursions?

Possible Duplicate:
Are there problems that cannot be written using tail recursion?

From my understanding, tail recursion is an optimization you can use when a recursive call does not need information from the recursive calls that it will spam.

Is it possible then to implement all recursive functions using tail-recursion? What about something like DFS, where you need the innermost child to return before the parent can?