Average Leeway Space

# The average "Leeway space" available in each half of the maxilla is approximately:
a) 0.9 mm
b) 4.0 mm
c) 2.9 mm
d) 6.9 mm 

The correct answer is A. 0.9 mm.

The combined mesiodistal width of the permanent canines and premolars is usually less than that of deciduous canines and molars and this difference is known as Leeway Space of Nance. This space is used by the permanent lower molars during late mesial shift from end-on occlusion to class-I relation. The amount ot leeway space is about 1.8 mm (0.9 mm on each side of arch) in maxillary arch and about 3.4 mm in mandibular arch (1. 7 mm on each side of arch). 

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