Comparative Effectiveness of Invisalign and Fixed Appliances in First-Premolar Extraction Cases

The fundamental aims of orthodontic treatment are to correct dent al mal occl usi on and achieve a stable, dynamic functional equilibrium. The introduction of preadjusted appliances in the 1970s was evolutionary in this sense, because they were desi gned for three-dimensional control of tooth positions without the need for wire-bending.1 Many torque and tip pre-scriptions have been proposed since then, but some have tended to produce an undertorqued ap-pearance. To address this issue, the MBT* prescription increased pala-tal root torque on the upper inci-sors; it also increased buccal root torque on the lower incisors to avoid tipping in the leveling stage.