Basic concepts….
1.Space
closure occurs during the first 6 months after
extraction. It is best to insert the appliance as soon as possible following the exttraction.
2.Loss
of space occurs primarily due to a tipping movement of teeth (mesially or distally). In the maxillary molar region, space loss occurs due to rotation (mesial-in) in conjunction with mesial tipping.
3.Erupting
premolars usually require 4-5 months to move
through 1mm of bone as measured on a BWXR.