All teeth develop in a sac and when they do not erupt (and are not removed) the sac remains and can expand with fluid and cause a cyst around the wisdom tooth.

Cysts can grow to ping- pong ball size and displace teeth and cause jaw fractures. Often cyst development is painless and patients don’t know about them until an x-ray is taken to check for impacted wisdom teeth. Occasionally a cyst will weaken the jaw so much that the jaw bone fractures.