Item Title "Refresh"?

[kb5cth]

I used a Title expression to generate item titles combining a string from an attribute and the creation date. I then changed the title expression to remove the string. How do I tell the existing items to update to the new title expression on the template? If there's no way, how do I manually change the item title? I tried changing the actual Item Title value on the item attribute window, but it doesn't propagate to the tree.

Bill