Allahyar Geramy; Hannane Ghadirian
Abstract
Aim: Bent root forms are always a challenging point in an orthodontic treatment. The main aim of this study has been to assess the stress effects of a dilaceration in apical third of an upper central incisor in orthodontic movement.Materials and Methods: Three FEM models of an upper central incisor were ...
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Aim: Bent root forms are always a challenging point in an orthodontic treatment. The main aim of this study has been to assess the stress effects of a dilaceration in apical third of an upper central incisor in orthodontic movement.Materials and Methods: Three FEM models of an upper central incisor were designed with cortical and spongy bone, PDL, and teeth. The only difference between 3D models was the anatomy of the apical fourth of their root. A 30-deg (the first model) and a 60-degree (the second model) dilaceration in the apical fourth of the root were designed in a labial direction. The calculation was in ANSYS Workbench Ver. 11.0. A 1.0 N labio-palatal force was applied in 45 degrees to the horizontal plane in the labial side of the crown. Von mises stress was evaluated along a path of nodes starting at the mid root area at labial moving towards the apex and continuing to reach the mid root lingual region on root surface.
Results: The apical stress did not show a dramatic increase in dilacerated form models starting from 0.11 MPa in normal model to 0.17 MPa in a 60-degree dilacerations model. Moving away from the apex, the stress findings increased which was noticeable between the normal model (0.48 MPa) and the 60-degree model (2.11 MPa).Conclusion: Based on the findings of this FEN! study, It was shown that the increase in the stress in areas away from the apex can be interpreted as the reason to the start of the external root resorption. There may be other models of the pointed apex root forms to show an increase in the apical area stress which was not the case in this model.
Allahyar Geramy; Amir hooman Sadr Haghighi; Saeede Mokhtari Khoee
Abstract
Aim: Orthodontic treatment outcomes are combination of advantages and disadvantage. The force implied during treatment could affect dental pulp status. Amount of changes in pulp complex depend on the types of tooth movements and whether the apex is open or not. The aim of this study is to compare the ...
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Aim: Orthodontic treatment outcomes are combination of advantages and disadvantage. The force implied during treatment could affect dental pulp status. Amount of changes in pulp complex depend on the types of tooth movements and whether the apex is open or not. The aim of this study is to compare the effects of different orthodontic tooth movements in two kinds of open and normal apices by 3D Finite element analysis.
Materials and Methods: Two three-dimensional Finite element models of an upper central incisor were modeled based on average dimensions. The models contained cortical and spongy bone, uniform thickness PDL of 0.25 mm and an upper central incisor. The differences between the models was the apex development which was complete in the first model and open in the second one in Solid- works 2006 and transferred to ANSYS Workbench Ver. 11.0. Different force systems to produce tipping, bodily and intrusion were applied in the tooth crown. The Von Mises stress was assessed along two defined paths.
Results: Maximum amount of the stress along the long axis of pulp belonged to open apex by tipping movement then intrusion with normal apex and finally bodily movement in open apex samples. In evaluation as regard of stress along apical third of PDL the highest stress created by intrusion in normal apex group.
Conclusion: In open apex, tipping and bodily movement could induce much more stress and in normal apex the concern of root resorption by intrusion was more than other types of tooth movements.
Allahyar Geramy
Abstract
Aim: Introduction of new bracket designs in market and use with a range of inciso-apical dimension and base thickness arises a question in mind as "Is it necessary to standardize various bracket bases from torque delivery efficiency?"
Materials and Methods: Two bracket bases of different incio-apical ...
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Aim: Introduction of new bracket designs in market and use with a range of inciso-apical dimension and base thickness arises a question in mind as "Is it necessary to standardize various bracket bases from torque delivery efficiency?"
Materials and Methods: Two bracket bases of different incio-apical dimension (3 and 6 mm.) and also two different base thicknesses (1.6 and 3.5 mm.) were modeled and moments were applied. All displacements along a defined incio-apical path were monitored to be evaluated.
Results and Conclusion: No difference was found between the displacements along the defined path in each phase of study. In this way, it was concluded that torque delivery of different brackets is not related to their base size (inciso-apical) and dimenson which is in complete agreement and confirmation of the principle of free vectors. (IJO 2006; 1: 71 - 74)
Hossein Ravanmehr; Amir Hossein Mirhashemi; Allahyar Geramy; Ahmad Sodagar
Ahmad Sodagar; Allahyar Geramy; Ehsan Karimian
Allahyar Geramy
Abstract
Aim: Being aware of the active and reactive forces and moments in an applied force system helps minimizing side effects and informing patients of future happenings. Wire bends are still used in clinical orthodontics in different ways.
Material and Methods: Three models were designed in SolidWorks 2006. ...
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Aim: Being aware of the active and reactive forces and moments in an applied force system helps minimizing side effects and informing patients of future happenings. Wire bends are still used in clinical orthodontics in different ways.
Material and Methods: Three models were designed in SolidWorks 2006. A step bend of 0.5 mm, a model of two central incisors with their supporting structures, and two blocks with a space and a wire with a combination of two step bends to modify the tooth angulation. Then the models were transferred to ANSYS Workbench Ver. 11.0 for calculations. Different positions of a step bend and the force systems produced by them were assessed.
Results: A gradual decrease of force produced by the step bend between 316 and 308 grams was shown to exist in central step bend position and the extreme one. The moment followed almost the same pattern starting from 15.125 N.mm in center bend position to 14.135 N.mm in its extreme position. In combined step bend model, extrusive/ lingualized movment in one side and intrusive/ labialized in the other side and tipping of the crowns in one and the apices to other side was also shown.
Conclusion: Step bend is not sensitive to its position and almost the same force system is produced in different bend positions (IJO 2006;1: 194-7).
Allahyar Geramy
Abstract
Aim: Several bracket characteristics are now in market. Preformed archwires are used without frequent need to add bends. V-bends are used in many situations. This bend as a basic maneuver is assessed thoroughly in this study.Materials and Methods: Finite Element Method (FEM) was selected to analyze the ...
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Aim: Several bracket characteristics are now in market. Preformed archwires are used without frequent need to add bends. V-bends are used in many situations. This bend as a basic maneuver is assessed thoroughly in this study.Materials and Methods: Finite Element Method (FEM) was selected to analyze the situation. A 3D model of two maxillary central incisors with their supporting structures and an archwire were modeled. A V-bend in different positions relative to the teeth was defined. Forces produced were monitored.Results: Center V-bend (a/L=1/2) produced two moments in opposite direction. Moving towards one tooth added vertical forces in opposite direction. At a/L ˜˷115, intrusive movement was noticed; while signs of intrusion and change in angulation was detected at 1/10< a/L<1/5. When a/L reached 0.42/6.408 same direction of moments were shown.Conclusion: V-bend force system is quite sensitive to its position.
