[Analysis of tip back bend on initial displacement of the maxillary first molar in Tip-Edge force system by three-dimensional finite element method].

The aim of this study was to analyze the initial displacement of the maxillary first molar by tip back bend in Tip-Edge force system and to explore the relationships between the displacement and the degree or position of tip back bend.The Tip-Edge three-dimensional finite element model was constructed by CT scan of a dry skull with all teeth. The conditions of five types of degree (20 degrees, 30 degrees, 40 degrees, 50 degrees, 60 degrees) and four types of position (2, 4, 6, 8 mm) of tip back bend were added to the three-dimensional finite element model and the initial displacements of the maxillary first molar were calculated.Under the effect of tip back bend, distal and extrusive displacement of the maxillary first molar occurred. The distal and extrusive movement increased as the degree of tip back bend increased or the position of tip back bend moved distally.The initial displacement of the maxillary first molar could be controlled by the precise control of the degree and position of tip back bend.