One or more teeth in the upper arch fit too far to the inside of the lower teeth.
There is not enough space in the mouth for permanent teeth to erupt straight.
The upper front teeth do not make contact with the lower front teeth when biting down.
The upper front teeth excessively overlap the lower front teeth when biting down.
Gaps between teeth caused by small, missing, or impacted teeth, or by excess tissue.
The lower front teeth/jaw are positioned too far forward in relation to the upper front teeth/jaw.