Teeth develop high in the jaw bone and must travel a long way to reach their correct location. Teeth sometimes get lost and become stuck against other teeth or other structures in your mouth.
This results in failure of that particular tooth to erupt through into the mouth, and the corresponding primary tooth not shedding.
Leaving an impacted tooth long term results in considerable damage to the teeth that’s blocking it, cystic formation in the bone as well as eventual failure of the affected primary tooth.
Early detection and intervention (around 9-11) is very important. When diagnosed early, treatment can be as simple as an expander plate, or partial braces. Sometimes, it will be recommended to remove the primary tooth to encourage the adult tooth to erupt correctly.
When diagnosed and treated later in life, treatment often involves exposure of the tooth and orthodontically moving the impacted tooth into place. This is often done with braces, but can be completed in Invisalign in special cases.