Fig. 4

Biomechanical effects of mere elastic force on the bimaxillary space closure. A Vector diagram reflecting the displacement directions and distances of teeth displacement under 150 g and 500 g elastic forces. B Schematic diagram of different biomechanical effects of elastic force on the upper and lower dentition. The tipping movement and the root control are different concept in this work. The use of elastic force would cause larger instantaneous teeth tipping; the root control was actually enhanced, which means, compared with the moderate group, retracting same distance in direct strong anchorage group could cause less anterior teeth tipping