My iPad icons have disappeared.

The icons Safari, mail, photo and music have disappeared from the bottom of my iPad desktop.

I have the most updated version and I have not been playing with the restrictions.

However, after reading some posts in the forum I have disabled and enabled restrictions for Safari and the icon has been showed again.

But there is no restriction option for mail, music and photo, so I can't recover these icons.

In the search option the applications can be started, so it is somewhere but I can't find it.

I have alread reset my iPad and recovered the backup, but when I recover it, the icons disappears again, as it was some configuration that is being stored in the backup.

Can someone help me with this?

Thanks!