Stress distribution analysis in anterior teeth caused by several retraction mechanics.

Rafael Golghetto Domingos,Jorge Abrão,Dalva Cruz Laganá,Almir Lima Júnior,João Batista De Paiva,José Rino Neto

doi:10.1590/2177-6709.26.5.e212042.oar

Rafael Golghetto Domingos, Jorge Abrão + Show 4 more

Open Access

https://doi.org/10.1590/2177-6709.26.5.e212042.oar

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Abstract

ABSTRACTIntroduction: Orthodontic retraction of the anterior teeth is indicated when the patient has a malocclusion with protrusion of the incisors. Several mechanics are indicated to perform this retraction. Objective: The objective of this study was to compare the strains generated by four different types of retraction mechanics along the roots of the anterior teeth.Methods: A photoelastic model simulating an arch with first premolars extraction was made. Sixty retraction archwires were prepared, including fifteen for each type of mechanics evaluated: sliding, teardrop loop spring, T-loop spring and double key loop archwire. The strains were observed in two perspectives: occlusal and oblique. In the occlusal perspective, strains were compared among the six anterior teeth. From the oblique perspective, strains were compared among the thirds of the left canine root.Results: In the occlusal perspective, the teardrop loop spring mechanics presented greater strains, followed by T-loop spring, double key loop archwire and sliding mechanics. In all mechanics, strains were more concentrated in the canines than in the incisors. From the oblique perspective, the teardrop loop mechanics generated greater strains in the cervical regions of the canine, and in the apical regions, no differences were found in strains among the four types of mechanics. In the same mechanics, greater strains were present in the cervical zones. Conclusion: The teardrop loop spring retraction mechanic presented the greatest mean strain, and the sliding retraction mechanic presented the lowest mean strain on the root of anteroinferior teeth in the occlusal and oblique perspectives.

Highlights

Orthodontic retraction of the anterior teeth is indicated when the patient has a malocclusion with protrusion of the incisors
The 0.021 x 0.025-in steel archwire used during the construction of the model was removed, and an orthodontic archwire diagram was made with it as reference for the retraction archwires used on the subsequent mechanical tests
The analysis of the four retraction techniques evaluated in this study revealed interesting results for understanding the behavior of the strains generated during the correction of malocclusions where orthodontic retraction of anterior teeth is indicated

Summary

Introduction

Orthodontic retraction of the anterior teeth is indicated when the patient has a malocclusion with protrusion of the incisors. Patients with excessive incisors buccal inclination frequently present abnormalities in masticatory function, such as lack of anterior guidance and unsatisfactory facial aesthetics due to lips protrusion and unaesthetic teeth exposure at rest.[1,2,3,4,5] Intending to correct these features, orthodontic treatment plans have been designed to reduce incisor protrusion. In this context, first premolar extractions are often proposed, followed by retraction of the anterior teeth.[1,3]. Among the existing techniques to retract the anterior teeth, the following techniques can be cited: sliding mechanics,[6,7,8] teardrop loop spring,[9,10,11,12] T-loop spring[5,13,14,15] and double key loop archwire.[16,17,18]

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