Some people never develop Wisdom Teeth others can have up to four or less.
Wisdom Teeth are last permanent teeth to erupt so there is often not enough space in your mouth for them. This can cause the Wisdom Teeth to become full or partially impacted or stuck.
Wisdom Teeth that only partially emerge or come through crooked can cause pain and swelling in the surrounding tissues and gum overlying the tooth, this is called Pericoronitis.
Pericoronitis is a dental infection that occurs when the tooth is partially erupted and the gum covers part of the tooth. This allows food and germs to become lodged underneath the gums. You could experience a bad taste in your mouth, swollen glands in your neck, swollen face or pus could come out from the surrounding area. If this happens antibiotics maybe prescribed and the tooth extracted. The symptoms could disappear in the early stages after antibiotic treatment, however this problem will continue until the tooth is removed.
Another problem associated with Wisdom Teeth is decay because they are so far back and can sometimes erupt on funny angles they may be impossible to get to with your toothbrush so they get decayed. If you are really unlucky you not only get decay of the wisdom tooth, but if the wisdom tooth is on a funny angle against the tooth in front and food gets stuck in between it is almost impossible to remove and it ends up causing decay in both teeth. Often deep near the gum near the tooth in front of the wisdom tooth. As the decay is deep down it can be hard to repair reliably and in worst cases the tooth along with with the wisdom tooth both end up needing extraction. However this additional tooth extraction could be prevented if the wisdom tooth was removed early enough. If you have a Wisdom Tooth that is not functional in your bite when you chew it can also over erupt, that involves another risk to the healthy teeth in front.