In the field of orthodontic treatments, it is indisputable that compared to cases where there is no extraction, extraction cases present more difficulties. In fact, in the treatments without extraction, most significant movements are concentrated especially in the upper arch, since the lower arch does not present problems that require large displacements. Accordingly, in these cases, all the lower arch is a stable reference point for assessing the progress of treatment. On the contrary, in cases with extraction, reference points change continuously, since teeth move in all four quadrants and this means a greater chance of “making mistakes”. If in these situations you have a biomechanical system, such as bi-dimensional, allowing control of the movements and the anchors in a systematic way, which is reproducible and relatively simple, it will be much easier to control even the most complex cases.
(Rev Esp Ortod. 2012;42(4):218-228)