When canines are engaged, the canines are depressed and the first premolars are elevated. Thus all the distal tipping forces on premolars and molars are neutralized by the depressing force on the canines. This depression is neither too rapid as it has very large root with well supported alveolar bone. Now arch wire lies gingival to the incisors brackets.
If second order bends are placed in the maxillary arch without Class-II elastics, the uncontrolled forces move the root apices of the teeth in the buccal segment in mesial direction without distal movement of the crown. In such instances it will leads to mesial displacement of the teeth in the buccal quadrants of both arches resulting bimaxillary protrusion.