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Fast tooth contour extraction for CT images which suitable for simulation is basded on the feature of CT images, reconstruct the lost contour between the tissues semi-automaticly.This research, we used Amira? three-dimension modeling software to reconstruction the tooth from CT images, analyzed the gray range of dental arch, and contrasted the data we had got, find several factors which affect the tooth contour extaction.On the crown, for reconstructing the contours, which are invisible in CT images due to high identity in the density value, between adjoining teeth, this paper gives a simple, and feasible method: First, the intersecting points, which were formed by the adjoining contours being parts of outer continuous contour extracted from a tooth-array cross-section in a CT image, were find out according to the saltation of the tangent vector directions on the points. Second, a B-spline, as the representation of a piece of outer contour, was built with two neighboring intersection-points as the end-points, and the outer-contour points as the interpolating points. Third, the one-order derivatives of two adjoining B-splines at common end-point were resolved respectively, and then a mean derivative at the point was computed. And then, cubic Hermit curves, as the replace of invisible contours between adjoining teeth, were built with a pairs of the opposite intersecting point as end-points; finally, construct a new B-spline of the teeth, to make sure C1 continuity of teeth contour. The fact of reconstructing 3D teeth based on the contours rebuilt with the method mentioned above has proven that a satisfying result was obtained.
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