Leeway Space
One important factor is loss of leeway space due to early loss of primary molars.
Leeway space. Medicine and health dentistry. The difference in combined width between the primary canine first molar and second molar and their permanent successors the permanent canine and premolars. The leeway space provides adequate space to resolve crowding that is present in the mixed dentition in the majority of individuals.
Leeway space in a dictionary of dentistry. In caucasians it is greater in the primary dentition by about 1 1 5mm in the maxilla and 2 2 5mm in the mandible. This space can be maintained by preserving arch length with a lingual arch as the primary teeth begin to exfoliate unless conditions such as the premature loss of a primary canine require earlier intervention.