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. 2020 Oct-Dec;11(4):320-326.
doi: 10.4103/ccd.ccd_197_19. Epub 2020 Dec 20.

Is There a Need to Increase Palatal Root Torque of Upper Incisors in Lingual Appliance? A Finite Element Analysis

S P Lekshmi  1 , Elbe Peter  1 , G Suja Ani  1
Affiliations

Is There a Need to Increase Palatal Root Torque of Upper Incisors in Lingual Appliance? A Finite Element Analysis

S P Lekshmi et al. Contemp Clin Dent. 2020 Oct-Dec.

Abstract

Objectives: To understand the effect of the biomechanical differences by assessing pre and post retraction torque, amount of retraction and arch width changes in both techniques.

Methodology: A three-dimensional geometric model of maxilla with all upper teeth except first premolar was generated based on computed tomography radiograph of a dry skull using the computer program Hypermesh. 13.0. Virtual models of 0.022 "Roth labial brackets and 0.018 "ORMCO 7th generation lingual brackets; and for labial brackets 0.019 × 0.025" SS archwire and for lingual brackets 0.016 × 0.024" SS archwire were constructed. Sliding mechanics was used during en-masse retraction by applying a 300 g distal force on both sides of the dentition from canine to the second premolar brackets in the labial and lingual simulation. The finite element program ANSYS 12.1 was used to calculate the torque and displacement.

Results: The results stipulated that in transverse direction there was lingual tipping of anteriors, mild buccal flaring in second premolars and first molars and lingual tipping in second molar in lingual appliance. In the sagittal plane, the greater distal movement of posteriors and an up-righting tendency of molars were observed in lingual appliance. Extrusion of anterior teeth were observed in both appliances. Regarding the premolars and first molars, labial movements and relative intrusion were observed in lingual appliance compared to labial appliance.

Conclusion: In lingual treatment, it is crucial to increase the lingual root torque. The amount of retraction and arch widening were more in lingual appliance compared to labial technique.

Keywords: En masse retraction; finite element analysis; labial appliance; lingual appliance.

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Conflict of interest statement

There are no conflicts of interest.

Figures

Figure 1
Figure 1
Creation of finite element model of maxilla for labial appliance. (a) Front view, (b) occlusal view, (c) rear view, (d) side view
Figure 2
Figure 2
Creation of finite element model of maxilla for lingual appliance. (a) Front view (b) occlusal view, (c) rear view, (d) side view
Figure 3
Figure 3
Torque assessment (a) labial appliance, (b) lingual appliance[14]
Graph 1
Graph 1
Graphical representation of torque changes observed in labial appliance
Graph 2
Graph 2
Graphical representation of torque changes observed in lingual appliance
Figure 4
Figure 4
Position of teeth before and after loading in X direction: (a) Labial appliance and (b) Lingual appliance
Figure 5
Figure 5
Position of teeth before and after loading in Y-direction: (a) Labial appliance and (b) lingual appliance; position of teeth before and after loading in Z-direction, (c) labial appliance and (d) lingual appliance
See this image and copyright information in PMC

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