Second order root control of self-ligating brackets and traditional brackets: a "typodont" study.

AIM: Aim of the study was to evaluate if self-ligating brackets (SLB) and conventional brackets (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 anatomic root structure were placed in them. Resin 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 arches. Models were put in warm 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 radiographies 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 order 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.

A "typodont" study of rate of orthodontic space closure: self-ligating systems vs. conventional systems.

AIM: The aim of this study was to compare the effectiveness of space closure of two bracket systems, self-ligating and conventional ones, considering two systems with the same design and prescription. The experimental model of this study aims to identify in general if one type of system is more suitable for planning the extractive therapy, without considering the clinical aspect necessary for an adequate orthodontic approach. METHODS: A resin maxilla without the first premolars was used to test the self-ligating and conventional brackets system. Space closure was achieved on 0.016x0.022" in stainless steel wires with nickel-titanium coil springs 150 grams in strength and 10 mm in length. Two experiment settings have been prepared. The first setting was made bonding conventional bracket on the right side and self-ligating on the left; the last one was made bonding self-ligating bracket on the right side and conventional on the left. All measurements (runs) have been repeated seven times for both settings. RESULTS: During the closing phase of extraction spaces both systems are equable since there are no significant statistical differences (P=0.70). CONCLUSION: Our typodont model showed no significant difference in the efficiency of space closure between the self-ligating bracket and conventional bracket tied with stainless steel ligatures.