Midpalatal absolute anchorage system for postero-superior movement of the maxillary dentition. A, Orthodontic force was applied postero-superiorly to the maxillary arch by attaching power chains from the hooks of the power arm to the spurs on the modified lingual arch; B, close-up view.

SMS, Safe-multifunctional-solid screw; M-LA, modified lingual arch; PA, power arm; PC, power chain.