Influence of angulation on the resistance to sliding fixed appliances

The resistances to sliding were studied as a function of five angulations ( 0 degrees, 3 degrees, 7 degrees, 11 degrees, and 13 degrees) using nine dif ferent couples made of stainless steel, single crystal sapphire, or polycry stalline alumina brackets against stainless steel, nicker titanium, or beta -titanium arch wires. After 22 mil brackets were mounted to fixtures and 21 x 25 mil arch wires were ligated with 10 mil stainless steel ligatures, th e arch wires were slid through the brackets at 1 cm/minute in the dry state at 34 degrees C, The resistance to sliding was measured by one computer wh ile five normal forces (nominally 0.2, 0.4, 0.6, 0.8, and 1.0 kg) were seri ally maintained by another computer. A second couple was prepared for each material combination with five normal forces that were each 0.1 kg less. St atistical fits of linear regressions were such that p < .001 for most tests . When couples were in the passive configuration at low angulations, all st ainless steel wire-bracket couples once again had the least resistance to s liding. When the angulation exceeded about 3 degrees, however, the active c onfiguration emerged and binding quickly dominated as the resistance to sli ding increased over 100-fold, Under these conditions, the relative rankings among the materials transposed; couples of stainless steel had the most re sistance to sliding, whereas, couples of the more compliant alloys, such as nickel titanium wire, had the least. Results suggested that the active con figuration and subsequent binding emerged when no bracket clearance remaine d. This binding component increased in importance with angulation and was a dditive to the frictional component, that is, they followed the principle o f superposition.