Stress Distribution and Displacement of Maxillary Anterior Teeth During En-masse Intrusion and Retraction: A FEM Study

Abstract

Background: Space closure by en masse intrusion and retraction in orthodontics is of particular interest. Aim: The aim of this study was to evaluate the stress distribution and displacement of maxillary anterior teeth. Materials and Methods: Four different finite element models of maxillary arch were constructed to understand the nature of stresses and displacement patterns of anterior teeth during en masse intrusion and retraction on force application with different combinations of mini-implants and retraction hooks. Results: In this study, tensile stresses were seen in the cervical region and various movements of teeth such as lingual crown tipping, bodily movement, lingual root tipping, intrusion, and extrusion were observed. Conclusion: Nature of stresses changes from tensile to compressive from cervical area to apical area. Various tooth displacements suggest that different combinations of mini-implants and retraction hooks affect the direction of the tooth movement.

The Effect of Varied Positioning of Mini-screw, Anterior Retraction Hook, and Resultant Force Vector on Efficient En-Masse Retraction Using Finite Element Method: A Systematic Review

“…Six studies have used 150 g of force for the retraction. Namburi et al 20 and Bohara et al 23 used intrusion force (60 g) from the anterior region in addition to the retraction force. Chetan et al 17 showed retraction component of force reduces by around 1% and the intrusion component of force increases by around 0.3% for each millimeter apical placement of the screw.…”

“…But on the contrary, Chetan et al 17 suggested that the position of the implant in the vertical plane will have very little effect on the type of tooth movement. Bohara et al 23 showed force vector passing away from the center of resistance (CR) will show tipping movement independent of implant position. (Table 5 Continued)…”

“…Parashar et al, Sreevats et al, and Bohara et al used MIMICS software for simulation. Zhang et al, 13 Sung et al, 14 Kojima et al, 15 Ashekar et al, 16 Chetan et al, 17 Hedayati et al, 19 Namburi et al, 20 Bohara et al, 23 and Suzuki et al 24 used ANSYS software for simulation, whereas Jain et al have not mentioned the software used for the study. Kojima et al, 15 Suzuki et al, 24 and Parashar et al 18 designed an FEM model based on the CT scan and converted it into a 3D model, while other studies such as Ashekar et al, 16 Chetan et al, 17 and Hedayati et al 19 designed a model based on Wheeler's dental anatomy textbook.…”

“…Kojima et al, 15 Suzuki et al, 24 and Parashar et al 18 designed an FEM model based on the CT scan and converted it into a 3D model, while other studies such as Ashekar et al, 16 Chetan et al, 17 and Hedayati et al 19 designed a model based on Wheeler's dental anatomy textbook. Jain et al 22 and Bohara et al 23 did not quote the model design. Namburi et al 20 compared the stresses on the 2-implant systems with 3-implant systems for retraction.…”

“…The method of retraction and force used for retraction varied in the studies. The force of 150 gm was used in studies conducted by Zhang et al, 13 Ashekar et al, 16 Chetan et al, 17 Hedayati et al, 19 Shreevats et al, 21 Jain et al, 22 Bohara et al, 23 and Suzuki et al 24 Sung et al 14 and Parashar et al 18 used 200 gm of force and Namburi et al 20 used 120 g for retraction and 60 gm for the intrusion. Jain et al 22 showed the method of en-masse retraction using NiTi spring in comparison with the power chain.…”