Restoring default fonts without reinstalling OS X?

I recently uninstalled a trial version of Microsoft Office, and followed an online tutorial to delete any and all files associated with it. However, by mistake, I deleted some of my default fonts. I've tried using Font Book to recover them but it keeps returning the same error message; "Please reinstall Mac OS X to recover default fonts". I am currently running Mountain Lion, and do not have a bootable version of it with which to reinstall.

I'd like to know if there's an easier way of restoring all my fonts at once, or at least determining which ones are missing so that I could reinstall them each at a time.