Purpose: To investigate the location of center of resistance(CRe) of six upper anterior teeth.
Methods: A three-dimensional finite element model of premaxillary bone and anterior teeth was established in ANSYS 8.1 software. Anterior teeth were fixed with stainless archwire of 2 mm × 2 mm. A horizontal retraction force of 150 g was applied bilaterally to the segment through hooks of 2 to 14 mm. After loading, solution was done and displacement and maximum principle stress were calculated.
Results: Displacement and stress distribution of anterior teeth varied according to the increase of height of horizontal retraction force. Labiolingual displacement of incisors varied from crown lingual tipping to lingual translation and lingual controlling root movement, while canine mainly showed lingual crown tipping. The displacements of teeth increased with the length of hook but their moving tendency remained unchanged. Stress distribution in PDL was in accordance with direction and magnitude of teeth displacement. In all cases, lingual displacement and stress in PDL were most homogeneous when hook was 10 mm long.
Conclusion: The results of this study suggest that perpendicular location of center of resistance of six upper anterior teeth is about 14 mm gingivally to incisal edge of central incisor.