This is common in children while their adult teeth start to erupt.
One or more of the upper adult teeth may erupt with the incorrect angulation and end up behind the lower front teeth.
This bite is very uncomfortable for the child as it prevents them from attaining their natural bite. When left, the involving teeth experience more wear and gum defects.
Left long term can lead to unfavourable jaw growth or asymmetrical facial development. Early treatment (around 7-11 years old) is recommended.
Treatment when young is usually very simple with a specialised plate to flick the involved teeth across. Treatment is usually complete in less than 6 months.
More advanced anterior crossbite may require braces or Invisalign to fully correct.