A comparative in vitro study of the frictional characteristics of two types of self-ligating brackets and two types of pre-adjusted edgewise brackets tied with elastomeric ligatures.

The aim of this in vitro study was to investigate the frictional characteristics of two types of self-ligating brackets ('A' Company Damon SL and Adenta Time brackets) and two types of pre-adjusted edgewise brackets (TP Tip-Edge and 'A' Company Standard Twin brackets). The test brackets were glued to steel bars and aligned using a preformed jig. Five combinations of archwire size and material were used (0.014-inch nickel titanium, 0.0175-inch multistrand stainless steel, 0.016 x 0.022-inch nickel titanium, 0.016 x 0.022-inch stainless steel and 0.019 x 0.025-inch stainless steel wires). The wires were drawn through the brackets and the frictional resistance was measured using an Instron 1193 testing machine. The data were analysed using a one-way analysis of variance and Scheffe's multiple comparison of means test. The results revealed that the Damon brackets demonstrated the lowest friction for all dimensions of test wires followed by the Time bracket. The 'A' Company Standard Twin brackets produced the highest friction with all wire dimensions tested, followed by the Tip-Edge bracket. With all brackets the 0.016 x 0.022-inch nickel titanium wires produced a higher frictional resistance than the 0.016 x 0.022-inch stainless steel wires. The results indicate that these self-ligating brackets produce less frictional resistance than elastomerically-tied pre-adjusted edgewise brackets.