The effects of third-order torque and self - Saint Louis University

added. Similarly, Bunkall 15 noted reductions in average
kinetic friction and maximum static friction of 35 to 70%.
Second-Order Angulation, Binding and Notching
Several studies have shown that, as second-order
angulation between the bracket-slot and the archwire
increases, friction also increases. 5,21,24,31,33,44,80,90
Classical friction from ligating force is largely
responsible for frictional resistance when the second-order
angulation is less than the angle at which binding occurs. 5
This angle is called “critical” and is defined as the
second-order angulation at which the wire just contacts two
diagonally opposing edges of the bracket-slot, reducing the
wire-slot clearance to zero. 91 When the angle exceeds the
critical value for the bracket-archwire combination,
binding becomes an influential factor in resistance to
sliding. 92 Factors that affect binding are archwire size,
bracket-slot geometry, and interbracket distances. 57
Thorstenson and Kusy 93 reported that ligation type seemed to
have an effect on only classical friction because they did
not influence binding when the brackets were positioned at
an angulation beyond the critical contact angle.
If the wire-slot angulation substantially exceeds the
critical contact angle, a physical deformation of a round
29