Second order root control of self-ligating brackets and traditional brackets : a “typodont” study

Aim. Aim of the study was to evaluate if self-li- gating brackets (SLB) and conventional brack- ets (CB) have the same degree of second order root control in closing extraction spaces. Methods. Two resin models, left and right sides of an upper arch, with two wells in the premolar area, were used. Wells have been filled with wax and resin premolars with ana- tomic root structure were placed in them. Res- in premolars were bonded with CB and SLB. We performed 20 pairwise runs: CB on one side against SLB on the other side. We tested 0.018 and 0.016x0.022 stainless steel arch- es. Models were put in worm water to allow teeth to move in the softened wax by the force excerpted by NiTi coils. Root control in the second order was evaluated with the aid of metallic markers on the roots and digital ra- diographies taken before and after each run. Results. On 0.018 wires CB moved 4.0 mm (SD 1.06 mm), mean root control angle was 14.8° (SD 9.15°), while SLB moved 4.1 mm (SD 1.33 mm), mean angle in the second or- der was 11.8° (SD 5.01°). On 0.016x0.022 wires CB moved 3.6 mm (SD 1.24 mm), mean angle in the second order was 9.7° (SD 5.48°) while SLB moved 3.4 mm (SD 1.05 mm), mean angle was 10.7° (SD 3.92°). Conclusion. It seems that, on typodont, CB and SLB are equally efficient in moving teeth crowns and have the same degree of second order root control, both when 0.018 and 0.016x0.022 stainless steel wires are used.