Comparison of frictional forces during the closure of extraction spaces in passive self-ligating brackets and conventionally ligated brackets using the finite element method.

Sl Gomez-Gomez,N Sanchez-Obando,Ma Alvarez-Castrillon,Cm Ardila,Y Montoya-Goez

doi:10.4317/jced.55739

Sl Gomez-Gomez, N Sanchez-Obando + Show 3 more

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https://doi.org/10.4317/jced.55739

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Abstract

BackgroundThis study compared the frictional force resulting from the bracket/archwire interface and the stress at the root/periodontal ligament/bone interface, between passive self-ligating brackets and conventionally ligated brackets, during the space closure stage.Material and MethodsA cone beam tomography was taken to a female patient that required extraction of upper first premolars and passive self-ligating system; three months after its activation, a cone beam tomography was taken again. The designs of the maxillary bone and the entire system were possible through tomography images and stereomicroscopic photographs. Validation of the Finite Element Method (FEM) was achieved comparing the amount of movement seen through tomography images and the FEM. Space closure was simulated for each system through the FEM and a comparison was made between the frictional force at the bracket/archwire interface, and the root/periodontal ligament/bone interface.ResultsThe most significant representation of frictional force at bracket/archwire interface and bone stress was found at the conventionally ligated system, while the passive self-ligating system accounted for the highest distribution of stress over the root.ConclusionsThe FEM is an accurate tool used to quantify frictional force and stress concentration during the orthodontic closure. The passive self-ligating system was seen less frictional during the closure state compared to conventional brackets. Key words:Friction, orthodontic bracket, finite element analysis.

Highlights

Friction has been defined as the resistance to movement when an object is moved with respect to another one and it operates at the direction opposite to the movement on contact surfaces [1,2,3,4]
Based on the images obtained from the cone-beam scans (CB) scan in T1, Computer assisted design (CAD) reconstruction of the maxillary bone/teeth set, performing extrusion and casting operations was possible with the Solid-Edge St6 software; the periodontal ligament was modeled with a 0.2 mm thickness [10,11,12]
Considering that there are no significant differences between dental movement, seen with tomography and Finite Element Method (FEM), it has been concluded that the numerical method simulates the real physical phenomenon. -Frictional Resistance in Bracket/Archwire Interface Comparing cutting forces, as a measurement of frictional resistance, a general tendency at specific points of the arch was not detected in any of the systems evaluated; the maximum cutting force was found in the two types of dental system, on upper canines, with a stronger presence in the conventionally ligated system, with 4.69 MPa, compared to the passive ligation system, with 2.98 MPa; this accounts for 36.5% more of frictional resistance, in the conventional ligated system, compared to the self-ligating system (Fig. 3)

Summary

Introduction

Friction has been defined as the resistance to movement when an object is moved with respect to another one and it operates at the direction opposite to the movement on contact surfaces [1,2,3,4]. This study compared the frictional force resulting from the bracket/archwire interface and the stress at the root/periodontal ligament/bone interface, between passive self-ligating brackets and conventionally ligated brackets, during the space closure stage. Space closure was simulated for each system through the FEM and a comparison was made between the frictional force at the bracket/archwire interface, and the root/periodontal ligament/bone interface. Results: The most significant representation of frictional force at bracket/archwire interface and bone stress was found at the conventionally ligated system, while the passive self-ligating system accounted for the highest distribution of stress over the root. The passive self-ligating system was seen less frictional during the closure state compared to conventional brackets

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