RELATIVE KINETIC FRICTIONAL FORCES BETWEEN SINTERED STAINLESS-STEEL BRACKETS AND ORTHODONTIC WIRES

The level of kinetic frictional forces generated during in vitro trans lation at the bracket-wire interface were measured for two sintered st ainless steel brackets as a function of two slot sizes, four wire allo ys, and five to eight wire sizes. The two types of sintered stainless steel brackets were tested in both 0.018-inch and 0.022-inch slots. Wi res of four different alloy types, stainless steel (SS), cobalt chromi um (Co-Cr), nickel-titanium (Ni-Ti), and beta-titanium (beta-Ti), were tested. There were five wire sizes for the 0.018-inch slot and eight wire sizes for the 0.022-inch slot. The wires were ligated into the br ackets with elastomeric ligatures. Bracket movement along the wire was implemented by means of a mechanical testing instrument, and time dep endent frictional forces were measured by a load cell and plotted on a n X-Y recorder. For most wire sizes, lower frictional forces were gene rated with the SS of Co-Cr wires than with the beta-Ti or Ni-Ti wires. Increase in wire size generally resulted in increased bracket-wire fr iction. There were no significant differences between manufacturer for the sintered stainless steel brackets. The levels of frictional force in 0.018-inch brackets ranged from a low of 46 gm with 0.016-inch Co- Cr wire to a high of 157 gm with 0.016 x 0.025-inch beta-Ti wire. In c omparing the data from a previous study by Kapila et al. 1990 performe d at OUHSC with the same apparatus, the friction of sintered stainless steel brackets was approximately 40% to 45% less than the friction of the conventional stainless steel brackets.