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Abstract
BackgroundThe aim of this study is to compare the biomechanical effects of the conventional 0.019 × 0.025-in stainless steel archwire with the dual-section archwire when en-masse retraction is performed with sliding mechanics and skeletal anchorage.MethodsModels of maxillary dentition equipped with the 0.019 × 0.025-in archwire and the dual-section archwire, whose anterior portion is 0.021 × 0.025-in and posterior portion is 0.018 × 0.025-in were constructed. Then, long-term tooth movement during en-masse retraction was simulated using the finite element method. Power arms of 8, 10, 12 and 14 mm length were employed to control anterior torque, and retraction forces of 2 N were applied with a direct skeletal anchorage.ResultsFor achieving bodily movement of the incisors, power arms longer than 14 mm were required for the 0.019 × 0.025-in archwire, while between 8 and 10 mm for the dual-section archwire. The longer the power arms, the greater the counter-clockwise rotation of the occlusal plane was produced. Frictional resistance generated between the archwire and brackets and tubes on the posterior teeth was smaller than 5% of the retraction force of 2 N.ConclusionsThe use of dual-section archwire might bring some biomechanical advantages as it allows to apply retraction force at a considerable lower height, and with a reduced occlusal plane rotation, compared to the conventional archwire. Clinical studies are needed to confirm the present results.
Highlights
The aim of this study is to compare the biomechanical effects of the conventional 0.019 × 0.025-in stainless steel archwire with the dual-section archwire when en-masse retraction is performed with sliding mechanics and skeletal anchorage
When incisors are retracted in sliding mechanics with direct skeletal anchorage, power arms have the effect of increasing the incisor torque expression
The present study showed that the use of power arms produced a deflection of the archwire (Fig. 6), so that its anterior portion is lifted in an apical direction and twisted in the third order of space
Summary
The aim of this study is to compare the biomechanical effects of the conventional 0.019 × 0.025-in stainless steel archwire with the dual-section archwire when en-masse retraction is performed with sliding mechanics and skeletal anchorage. Retraction of the anterior teeth with orthodontic fixed appliances is often associated with several undesirable side effects such as deepening of the bite, rotation of the occlusal plane, archwire bowing and loss of posterior anchorage [1]. Based on biomechanical studies, several authors have suggested the use of power arms of different lengths depending on the desired type of anterior tooth movement This would enable clinicians to achieve controlled tooth movement with fewer side effects during space closure in sliding mechanics [10]. The use of extremely long power arms, which becomes necessary for improving controlled movements of the anterior teeth, might compromise patient comfort [7, 12]
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