Bracket, ligation, and misaligned straight wires effects on load systems during orthodontic sliding mechanics

Objective: The objectives of this study were to measure and compare the complete, not solely friction, load components (forces and moments) experienced by brackets as they slide along straight wires that are angled relative to the path of bracket travel. Materials and Methods: Three types of brackets (stainless steel mandibular canine and central incisor, and an all-ceramic mandibular canine) were ligated with stainless steel or elastomeric modules to 2 sizes of stainless steel wire (0.021” x 0.021” and 0.016” x 0.016”) at 0°, 1° and 2° bracket-wire misalignments. All 3 force and 3 moment components experienced by the brackets were measured as they slid along the wire. Results: Overall, all 36 permutations of the 3 brackets, 2 ligations, 2 wires and 3 alignments produced statistically different (predominantly P < .0001) load components on the bracket. Conclusions: The type of bracket, wire, ligation, and relatively small misalignments (1° and 2°) between bracket and wire affect all force and moment components applied to the bracket. Traditional friction-focused “pull through” studies miss the attendant effects on the other 5 load components