| Summary: | 碩士 === 國立臺灣大學 === 臨床牙醫學研究所 === 88 === An in vitro study was undertaken to evaluate the effects of different alloys, wire sizes and angulations between the bracket slots and arch wires on the dynamic frictional resistance. Stainless steel (SS), conventional nickel-titanium (Ni-Ti), -titanium (-Ti) and thermoelastic nickel-titanium wires with different phase-transformation temperatures (Copper nickel-titanium 27℃, 35℃, 40℃) were tested in the standard cast bracket slots (1830 mil). The wire sizes tested included .016 inch, .018 inch, .016 .022 inch and .017 .025 inch. In addition, the angulations between the slot and wire were set in 0, 2 and 4, respectively. All tests were conducted in wet (water-immersed) condition at the temperature of 37℃. The wires were ligated into the slots with elastomeric rings. One-way analyses of variance and Scheffe’s multiple comparisons procedure were used to determine the individual effects of wire alloy, wire size and slot/ wire angulation. In 0 degree angulation (parallel condition), the Ni-Ti alloy showed the highest dynamic frictional resistance, followed by thermoelastic nickel-titanium, -Ti alloys and the SS alloy produced the least frictional resistance. In non-parallel condition, the dynamic frictional resistance of the titanium alloys, in general, was higher than SS alloy. The angulation between the bracket slots and wires had a significant effect on frictional resistance: the higher angulation , the more frictional resistance. Regardless of angulation, the nearly full-size arch wires (.017 .025 inch) showed the highest dynamic frictional resistance and the .016 inch round wire usually produced the least frictional resistance.
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