Allahyar Geramy; Ahmad Sodagar; Omid Mortezaee
Abstract
Aim: Anchorage management is a challenging problem while retracting anterior segment in orthodontic treatments. The purpose of this study is to evaluate the effect of anterior teeth labiolingual inclination on the amount of anchorage loss and distance of anterior retraction.Methods and Materials: Six ...
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Aim: Anchorage management is a challenging problem while retracting anterior segment in orthodontic treatments. The purpose of this study is to evaluate the effect of anterior teeth labiolingual inclination on the amount of anchorage loss and distance of anterior retraction.Methods and Materials: Six 3D computer models of an upper anterior segment were designed in SolidWorks 2006 (SolidWorks, Concord, Massachusetts, USA).The models contained supporting structure, upper central and lateral incisors, their PDLs, the brackets and an anterior retraction arch wire with two vertical open loops. The models were the same except for the torque of anterior teeth which were 0, 5, 10, 15, 22, and 35 degrees consequently. ANSYS Workbench Version 12.1 (ANSYS Inc., Southpointe, Canonsburg, PA, USA) was selected for the analysis. At each analysis, the end points of the arch wire were displaced distally simulating the anterior retraction arch wire activation. The displacement produced in the labio-mesio-incisal point angle and the mesializing force applied to the terminal molar was assessed.Results: Torque degree of 0 to 22 exerting almost equal force on anchorage unit during retraction while 35 degrees of torque causing more reciprocal force. Ten degrees of anterior torque resulted in maximum displacement of anterior segment.Conclusions: To have maximum anchorage and faster anterior teeth movement during retraction degree of torque suggested to be about average and neither too protruded nor uprighted.
Allahyar Geramy; Tahura Etezadi; Ahmad Reza Shamshiri; Mohammad Javad Kharazifard
Abstract
Introduction: An appropriate force system is a perquisite of desirable and predictable tooth movements during orthodontic treatment. Complete knowledge about the generated forces and moments by loops is essential to choose the best one for every situation.The aim of this study was to establish a mathematical ...
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Introduction: An appropriate force system is a perquisite of desirable and predictable tooth movements during orthodontic treatment. Complete knowledge about the generated forces and moments by loops is essential to choose the best one for every situation.The aim of this study was to establish a mathematical equation to bring about a relationship between the L-loop height, width, activation and the produced force.Materials and methods: Six 3D finite element models were designed for L-loop without preactivation bends. Loops were designed with different widths (w) and heights (h). The cross section of wire was 0.016”× 0.022”. The distal end of each model was activated 1 mm in 0.1 mm intervals. The force produced by activation in a 0.1 millimeter increment was recorded. Results: Force findings were different according to the loop parameters defined. The produced force varies from 0.106 to 0.228 N for a 0.1 millimeter of activation and increased from 1.07 to 2.27 N in 1.0 mm of activation.Conclusion: The magnitude of force by L-loop can be estimated through adjustment of vertical part and activation as Increments of activation increased the delivered force while Increasing L-loop height decreased the generated force.
Allahyar Geramy; Tahoora Etezadi
Abstract
Desirable tooth movements need optimal force systems. Loops are employed to move teeth properly. L-loop is used frequently due to its ease of fabrication. The aim of this study is to assess the expected forces and moments when a definite length of wire is bent to form L-loop. In other words, the effect ...
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Desirable tooth movements need optimal force systems. Loops are employed to move teeth properly. L-loop is used frequently due to its ease of fabrication. The aim of this study is to assess the expected forces and moments when a definite length of wire is bent to form L-loop. In other words, the effect of loop height and width on the produced force and moment is evaluated by the finite element method (FEM). Materials and methods: Six 3D finite element models were designed of an L-loop without pre-activation bends keeping the total lengths of wire equal to 24.34+/- 0.5 mm. The cross section of wire was 0.016”× 0.022”. The force produced by activation in a 0.1 millimeter increment was recorded. Results: In model L1, the findings start with 0.086 N in 0.1 mm of activation and increased to 0.88 N in 1mm of loop opening. The pattern of findings was almost the same for other loop designs (L2 through L6) with an increase in findings. M/F ratios were almost constant in a loop design along its activation starting with 3 in L1 and reaching about 1.9-2 in L6. Conclusions: Moment to force ratios were almost constant in a loop design along its activation. increasing width and decreasing height with almost the same length of loop wire can increase force and therefor reduce M/F ratio.
Allahyar Geramy; Reza Jelodar; Hasan Salehi
Abstract
Aim: The aim of this study was to assess the effects of different loop forms in continuous arch technique on its force characteristics in the anterior retraction arch wires.Material and Method: Six 3D finite element models were designed of an anterior retraction arch wire formed and included four average ...
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Aim: The aim of this study was to assess the effects of different loop forms in continuous arch technique on its force characteristics in the anterior retraction arch wires.Material and Method: Six 3D finite element models were designed of an anterior retraction arch wire formed and included four average sized anterior brackets and the palatal wall of the bracket slot of the canines. The models were similar except for the height and angle of the loop legs. The left side loop was kept constant in all stages of the study while modifying the right side loop height or vertical leg's angulations. SolidWorks 2006 was selected for the modeling phase and ANSYS Workbench Ver. 11.0 for the calculations. Mesializing force on molar, medially directed force on canine, and anterior retraction forces were evaluated.Results: According to the results, loop height in one side cannot affect the other side loop force characteristic directly; A gradual increase of the force difference between two side of the anterior retraction arch wire is shown. The mesializing force on molar is also increased with almost the same manner. The other findings related to loop leg divergence shows a difference between two sides but the differences are almost the same with varying degrees of divergence. Although the forces are not the same in both sides but the difference remained almost constant.
Conclusion: Arch wires may seem to be symmetric but may act asymmetric. Difference in anterior teeth retraction may be due to some asymmetries in arch wire fabrication which needs further considerations.
Allahyar Geramy; Seyed Amir Reza Fatahi Meybodi; Amir Hooman Sadr Haghighi
Abstract
Aim: To analysis the effect of unilateral shortening (Asymmetric Length, AL type) vs. expansion of head-gear outer-bow (Asymmetric Expansion, AE type) in delivering unilateral distal force.Methods: In 36 situations, composed or different outer-bow shortening, expansion and different neck contour and ...
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Aim: To analysis the effect of unilateral shortening (Asymmetric Length, AL type) vs. expansion of head-gear outer-bow (Asymmetric Expansion, AE type) in delivering unilateral distal force.Methods: In 36 situations, composed or different outer-bow shortening, expansion and different neck contour and position, the resultant distal force was analyzed. Applying an analysis described by Haack and Wienstein, the ratio by which the resultant distal force was divided between 2 terminal molars was calculated.Results: In AL type head-gear a greater portion of force was delivered to contra-lateral terminal while in AE type headgear the ratio of force delivery between two molars could not be higher than 1.04 due to geometrical limitations.Conclusion: AL type head-gear is a predictable and effective way for asymmetric distal force delivery. The greater force will be received by the contra-lateral terminal to the shorter arm of the outer-bow. AE type is not suggested for distal force delivery due to its geometric limitation and relative ineffectiveness.
