Cephalometric radiograph taken after the midpalatal absolute anchorage system was placed in situ. CR, Collective center of resistance of the maxillary dentition; LAIF1, the line of action of the postero-superior orthodontic force distal to the center of resistance of the maxillary arch; LAIF2, the line of action of the postero-superior orthodontic force mesial to the center of resistance of the maxillary arch.