First of all, it's over-simplified to divide the brain into zones just by the sensory inputs they serve. There are lobes wose function is one or two layers above, or which deal with stuff like fight-or-flight reflexes or whatnot.
Second, neurons can and routinely do take new functions, if needed. If you lose a bunch of brain matter from the part that, say, ought to deal with your right foot normally, another part of the brain can learn to do that function instead.
The most extreme case was that of a French civil servant who pretty much didn't have much brain left. Yet he could still function as a normal human. Admittedly an IQ 70 human, but nevertheless.
The brain is pretty much a self-organizing machine, and an amazing one at that. It can learn to deal with inputs or outputs that don't resemble anything it had to use before. E.g., the signals from a CCD camera sensor is _nothing_ like the pre-processed image from a normal retina, but there have been implants of such a CCD camera sensor in blind people and the brain eventually learns to "see" through it. E.g., I remember reading about an experiment where brain tissue from a rat learned to control a toy truck. It's nothing like a rat body, but the neurons will figure out how to use it anyway.
(Sadly I'm not allowed to post links to the BBC articles yet, to support that statement, but let's say it's a quick googling exercise if anyone is curious enough.)
What I'm getting at is that even if you didn't have the brain cells dedicated to wisdom teeth (e.g., because you had a mini-stroke in that part of the brain), some neurons from somewhere else could take over the function.
