This study was designed to analysis the displacement and stress distribution of individual tooth by orthodontic force during distal en masse movement of the maxillary dentition. In this study, three dimensional finite element analysis was used. Author made the finite element model of maxillary teeth, periodontal ligament, alveolar bone and bracket with anatomic and physiologic characteristics on computer. Author analysed and evaluated the displacement and stress distribution of individual tooth when extraoral force, Class II intermaxillary elastics, ideal arch wire, MEAW and tip back bend were used for distal en masse movement of the maxillary dentition. These analyses were also applied in the case of the maxillary second molar were not extracted. Author compared the results of the cases which maxillary second molar were extracted or not. The results were expressed quantitatively and visually. Author obtained following results,
1. When anterior headgear was applied, the posterior translation, posterior tipping, and vertical displacement of teeth were produced more in the anterior segment of the dentition.
2. When Class II intermaxillary elastics were applied in the ideal arch wire, the teeth disp acement were usually produced in the anterior segment. But when tip back bend were added in the ideal arch , the orthodontic force produced
by elastics were transmitted to the posterior segment. As increasing the tip back bend, posterior translation and lingual tipping of anterior teeth were decreased, posterior translation and tipping displacement of posterior teeth were increased, and extrusion of anterior teeth by Class II elastics x -,re decreased.
3. When MEAW and Class II elastics were applied, the teeth movement were similar with the case of ideal arch wire and Class II elastics, but more small and uniform teeth displacement were produced. Compared with the ideal arch wire, posterior tipping of the posterior segment were more produced than lingual tipping displacement of the anterior segment.
4. When the maxillary second molar without orthodontic appliance existed, the displacement of maxillary first molar were decreased
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