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.
Allahyar Geramy; Amir Hooman Sadr haghighi; Seyed Amir Reza Fatahi Meybodi; Hasan Salehi
Abstract
Aim: Canine retraction is an important part of orthodontic treatments and should be coincided with preservation of posterior anchorage, The strain energy input of different appliance designs in teeth PDL is assessed.Materials and methods: Eight 3D finite element (FE) models of upper right maxillary molars ...
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Aim: Canine retraction is an important part of orthodontic treatments and should be coincided with preservation of posterior anchorage, The strain energy input of different appliance designs in teeth PDL is assessed.Materials and methods: Eight 3D finite element (FE) models of upper right maxillary molars and second premolar were designed. The models contained teeth, their PDL, and bone with their attachments. Combinations of wire cross scetion(round and rectangular), force application on the first or second molar, including or excluding the second molar, and adding the second molar to the system via ligature wire is considered in different models. The strain energy input to the PDL of different teeth was evaluated.Results: Engagement of all teeth, force application to the second molar resulted in 0.00017129 mJ and shifting toward applying force to the first molar resulted in 0.00017398 mJ. When the second molar was free from wire but laced; this energy finding was 0.00014499 mJ which increase to 0.0003991 mJ when the second molar was really out of the system. Findings for the rectangular wire were 0.00000084, 0.000001148, 0,0001026, and 0.0002929 respectively.Conclusion: Rotation prevention of the second molar is the key point in using its anchorage value.
Tahereh Hosseinzadeh-Nik; Seyed Amir Reza Fatahi Meybodi; Negin Shahsavari
Abstract
Aim: This article is aimed at geometrical evaluation of antero-posterior displacement of incisor inferioris (Ii) and pogonion (Pog) following mandibular rotation and introducing a simple method to predict post surgical Holdaway ratio to evaluate the need for genioplasty.Materials and Method: First the ...
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Aim: This article is aimed at geometrical evaluation of antero-posterior displacement of incisor inferioris (Ii) and pogonion (Pog) following mandibular rotation and introducing a simple method to predict post surgical Holdaway ratio to evaluate the need for genioplasty.Materials and Method: First the geometrical factors affecting the displacement of a landmark following the mandibular rotation are discussed; namely α (the amount of mandibular rotation), r (the distance of the landmark from the center of rotation), and θ (the angle of the radius of the landmark from true horizontal line), Then the amount of displacement is calculated as d=2r[sirt(α/2)sin(α/2+θ)]. Finally prediction method of post surgical Holdaway ratio is described as adding the amount of "d " for Pog and Ii to pre surgical Holdaway ratio. This ratio in addition to position of Pog relative to facial skelton was used to predict the need for genioplasty. The application of this method is also demonstrated on an open bite patient as an example and the outcome is compared with manual prediction method.Results: The described method predicted the need for genioplasty the same way as manual prediction method.Conclusion: The geometrical prediction method can be of great value in determining the need of genioplasty following surgical mandibular rotation.
