Something that's sanitized is so clean that it's free of harmful germs. Your dentist only uses sanitized instruments in your mouth (hopefully!).
There are many things that are safer or cleaner if they're sanitized. A sanitized swimming pool is one that you're comfortable swimming in, and knowing a brain surgeon has sanitized hands is even more reassuring. You can also use this adjective in a derogatory way, to mean "changed to make people more comfortable," as in a sanitized art exhibit that's pretty but doesn't convey the artist's original messy and disturbing vision.