Comparison of the frictional coefficients for selected archwire-bracket slot combinations in the dry and wet states.

Coefficients of friction were evaluated in the dry and wet (saliva) states for stainless steel, cobalt-chromium, nickel titanium, and beta-titanium wires against either stainless steel or polycrystalline alumina brackets. For both operators' experiments, an 0.010" stainless steel ligature wire pressed each archwire into the 0.018" or 0.022" bracket slot at 34 degrees C. In the dry state and regardless of slot size, the mean kinetic coefficients of friction were smallest for the all-stainless steel combinations (0.14) and largest for the beta-titanium wire combinations (0.46). The coefficients of the polycrystalline alumina combinations were generally greater than the corresponding combinations that included stainless steel brackets. In the wet state, the kinetic coefficients of the all-stainless steel combinations increased up to 0.05 over the dry state. In contrast, all beta-titanium wire combinations in the wet state decreased to 50% of the values in the dry state. The mixed reports that saliva may promote adhesive and lubricious behaviors may have some substance.