Figure 1. Off-centered, stepped T-loop (A) before and (B) after activation. PB is premolar bracket, CB is canine bracket.
Comparison between forces and moments of plain and stepped 8 3 8 mm T-loops with 12 mm interbracket distance at premolar bracket (PB) and canine bracket (CB). During activation, the CB was moved inline and the PB was moved to the left until 100 g horizontal force was obtained. Deformed loop shapes are shown in gray.
CONCLUSIONS
N Step bends can dramatically change force systems (vertical force and M/F ratio) of off-centered closing loops by creating intrusive forces on the CB, extrusive forces on the PB, and clockwise moments on both CB and PB. N The force system of a T-loop with a vertical step bend is a combination of the V-bend effect from the position of the T-loop and the step bend. N Step bends affect the force system of closing loops more when the vertical step is increased, horizontal loop length decreased, or T-loop size reduced from 10 x 10 mm to 8 x 8 mm.