Introduction. Self-ligating brackets have been promoted by the manufactures for being less frictional than any other orthodontic fixed appliances. Resistance to slide (RS) between bracket and wire depends in-vitro mainly on two determinants (1): the force of ligation and the force of binding (BI) (1, 2). BI occurs when the wire first contacts both opposing edges of the slot (active configuration) due to angulation between bracket-slot and the wire (3). Several in-vitro studies demonstrated that as the forces of binding increase due to the increased bracket angulation, the relative role of ligation within the RS decreases to the point where frictional resistance is dominated by this binding (2, 4). Thus, there is no difference between self-ligating and conventional brackets in terms of RS recorded. This occurred with high stiffness wire such as 18x25 SS, 21x25 SS, NiTi and TMA. The aim of this in-vitro study was to investigate the resistances (RS) to slide expressed by self-ligating and conventional ligation systems as a function of five 2° order angulations using typical alignment wires in a 3-bracket model. We also wanted to verify how the main components of the RS act in both systems when these wires are used. Materials and Methods. The brackets tested were all interactive self-ligating with closed and opened slide to simulate conventional brackets; the ligatures used with the conventional system were elastomeric modules (int. diam. 1 mm). The tested wires were all 0.14 NiTi heat-activated (Af set at 36° by manufacture). A home-made “Instron” machine was used to measure frictional resistance. Tests were repeated 5 times for each angulation simulated. All data were analyzed statistically. Results/Discussions. RS increased significantly as the angulation increased in both groups (p < 0.0001). RS measurements were significantly higher at each angulation (p < 0.0001) with the conventional ligation system. Moreover, no differences were found between 7°-10°, 7°-13° and 10°-13° settings with conventional brackets (p > 0.05). Our results suggest that self-ligating brackets enable a better sliding of the wire even if binding forces add up to classical friction. Also, with conventional brackets, the ligation forces exerted from the elastomeric modules are able to inhibit the binding forces partially when alignment wires are tested. Conclusions. Despite the relevance of the binding phenomenon, the forces released by the ligatures affect RS the most when low-stiffness wires are used.

In vitro analysis of resistance to sliding produced by self-ligating and conventional ligation methods during dental alignment

MATARESE, Giovanni;MILITI, Angela;NUCERA, RICCARDO;PORTELLI, Marco;FABIANO, FRANCESCA
2012-01-01

Abstract

Introduction. Self-ligating brackets have been promoted by the manufactures for being less frictional than any other orthodontic fixed appliances. Resistance to slide (RS) between bracket and wire depends in-vitro mainly on two determinants (1): the force of ligation and the force of binding (BI) (1, 2). BI occurs when the wire first contacts both opposing edges of the slot (active configuration) due to angulation between bracket-slot and the wire (3). Several in-vitro studies demonstrated that as the forces of binding increase due to the increased bracket angulation, the relative role of ligation within the RS decreases to the point where frictional resistance is dominated by this binding (2, 4). Thus, there is no difference between self-ligating and conventional brackets in terms of RS recorded. This occurred with high stiffness wire such as 18x25 SS, 21x25 SS, NiTi and TMA. The aim of this in-vitro study was to investigate the resistances (RS) to slide expressed by self-ligating and conventional ligation systems as a function of five 2° order angulations using typical alignment wires in a 3-bracket model. We also wanted to verify how the main components of the RS act in both systems when these wires are used. Materials and Methods. The brackets tested were all interactive self-ligating with closed and opened slide to simulate conventional brackets; the ligatures used with the conventional system were elastomeric modules (int. diam. 1 mm). The tested wires were all 0.14 NiTi heat-activated (Af set at 36° by manufacture). A home-made “Instron” machine was used to measure frictional resistance. Tests were repeated 5 times for each angulation simulated. All data were analyzed statistically. Results/Discussions. RS increased significantly as the angulation increased in both groups (p < 0.0001). RS measurements were significantly higher at each angulation (p < 0.0001) with the conventional ligation system. Moreover, no differences were found between 7°-10°, 7°-13° and 10°-13° settings with conventional brackets (p > 0.05). Our results suggest that self-ligating brackets enable a better sliding of the wire even if binding forces add up to classical friction. Also, with conventional brackets, the ligation forces exerted from the elastomeric modules are able to inhibit the binding forces partially when alignment wires are tested. Conclusions. Despite the relevance of the binding phenomenon, the forces released by the ligatures affect RS the most when low-stiffness wires are used.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11570/2375021
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