I had my wisdom teeth removed when I was in my early 20's and for me, the first sign was a dull ache in my jaw. My jaw and cheeks ached all the time, and it got so bad that I walked around all the time massaging the back of my cheeks with my hands. But, mine were coming in underneath my other teeth, so it may be different for some people. It also hurt to open and close my mouth. The surgery to remove them was pretty easy....they knocked me out and I woke up asking "when are they going to take my teeth out?"! After a few days of recovery, my mouth felt sooooo much better!
