Children erupt their front teeth first and in many cases crowding and rotations develop with these first teeth. The reason for this is that primary front teeth are smaller than their permanetn successors AND....if growth is not sufficient to compensate for this size differential, then crooked front teeth result.
The amazing thing that changed the number of permanent teeth being extracted was when dentists startedundestanding and preserving "leeway" space. "Leeway" space is the extra space you gain if you realize that the back "baby molars" are bigger than the permanent teeth that replace them. So.....if you allow this space to be held with space maintainers then, we can ultimately unravel the crowded front teeth into the preserved extra space!!! This combined with early expansion allows children to experience broader smiles with a lower extraction rate!!!
Lower Lingual Holding Arch (LLHA)
The lower lingual holding arch is attached to the lower molar teeth via orthodontic bands. The bar extends along the inside of the lower teeth. The anterior part rests along the lingual surfaces of the front teeth and thus prevents forward migration of the molars once the baby teeth are lost.
The Nance or upper holding arch is attached to the upper molar teeth via orthodontic bands. The wire extends along the inside of the upper teeth and is stopped by an acrylic piece on the palate. This piece of acrylic acts as an anchor so the back teeth cannot move forward; thus preserving space.