• The korean journal of orthodontics
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• v.25 no.2 s.49
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• pp.143-152
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• 1995

This study was performed, by Finite Element Method, to evaluate the stress distribution on the periodontal tissue according to activation of the various closing loops and to predict the pattern of movement of maxillary incisors. At the same time, bull loop, key-hole loop, T-loop, combination loop and asymmetrical T-loop which were used for retraction of maxillary incisors was analysed by Finite Element Method. The following results were obtained 1. Horizontal force was the greatest in bull loop, the followed by key-hole loop, combination loop, T-loop and initial tooth movement exhibited uncontrolled tipping. 2. Horizontal force in asymmetrical T-loop compared to other closing loops was remarkably decreased, and the intrusive force on the incisors occurred. 3. As torque was increased, the moment was increased as a linear increment. 4. As moment was increased, initial movement of tooth changed to root movement from uncontrolled tipping.

• The korean journal of orthodontics
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• v.34 no.1 s.102
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• pp.33-45
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• 2004

The purpose of this experimental study was to determine appropriate magnitude of the Gable bends to produce maximum retraction of the anterior teeth. The Calorific Machine was used to illustrate the tooth movement in three dimension. The experimental teeth except the first premolar were embedded in the artificial alveolar bone part. In a series of experiments, the extraction space was closed using arch wires with bull loops into which the gable bends of $10^{\circ},\;20^{\circ},\;30^{\circ}$ degrees were incorporated. The experiments were repeated three times for each degree of the gable bend. Before and after the space closure, radiographs were taken in the sagittal and occlusal directions using occlusal films. Analysis of variance and Scheffe post hoc test were used to determine significant differences among the three groups. The following results were obtained. 1. As magnitudes of the gable bends increased, more bodily anterior tooth movement was seen and the distance of retraction also increased. 2. As magnitudes of the gable bends increase, the amount of posterior tooth protraction decreased while intrusive and buccal movement increased. 3. The arch was coordinated by distal-in rotation of the canine and mesial-in rotation of the second premolar adjacent to the extraction space.

• The korean journal of orthodontics
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• v.35 no.5 s.112
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• pp.371-380
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• 2005

The purpose of this experimental study was to evaluate aㅜd compare maxillary arch dimensional and positional changes between first and second premolar extraction groups. The Calorific Machine was used to illustrate tooth movement in three dimensions. The experimental teeth except the first or second premolars were embedded in artifical alveolar bone. The extraction space was closed using arch wires with bull loops into which 15 degree gable bends were placed. Before and after space closure, radiographs were taken in the sagittal and occlusal directions using occlusal films. The results showed greater mean maxillary incisor retraction and less anchorage loss in the maxillary first premolar extraction group than in the maxillary second premolar extraction group. Mesiopalatal rotation of anchor teeth was greater after extraction of a maxillary second premolar than a maxillary first premolar (P<.001).

• The korean journal of orthodontics
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• v.37 no.6
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• pp.407-420
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• 2007

The aim of this study was to compare the differences in closing extraction spaces between maxillary first premolar and second premolar extractions using 3-dimensional finite element analysis (FEA). Methods: Maxillary artificial teeth were selected according to Wheeler's dental anatomy. The size and shape of each tooth, bracket and archwire were made from captured real images by a 3D laser scanner and FEA was performed with a 10-noded tetrahedron. A $10^{\circ}$ gable bend was placed behind the bull loop on a $0.017"{\times}0.025"$ archwire. The extraction space was then closed through 12 repeated activating processes for each 2mm of space. Results and Conclusions: The study demonstrated that the retraction of anterior teeth was less for the second premolar extraction than for the first premolar extraction. The anterior teeth showed a controlled tipping movement with slight extrusion, and the posterior teeth showed a mesial-in rotational movement. For the second premolar extraction, buccal movement of posterior teeth was highly increased.