In the dental field, the 3D tooth model in which each tooth can be manipulated individually is an essential component for
the simulation of orthodontic surgery and treatment. To reconstruct such a tooth model from CT slices, we need to define
the accurate boundary of each tooth from CT slices. However, the global threshold method, which is commonly used in
most existing 3D reconstruction systems, is not effective for the tooth segmentation in the CT image. In tooth CT slices,
some teeth touch with other teeth and some are located inside of alveolar bone whose intensity is similar to that of teeth.
In this paper, we propose an image segmentation algorithm based on B-spline curve fitting to produce smooth tooth
regions from such CT slices. The proposed algorithm prevents the malfitting problem of the B-spline algorithm by
providing accurate initial tooth boundary for the fitting process. This paper proposes an optimal threshold scheme using
the intensity and shape information passed by previous slice for the initial boundary generation and an efficient B-spline
fitting method based on genetic algorithm. The test result shows that the proposed method detects contour of the
individual tooth successfully and can produce a smooth and accurate 3D tooth model for the simulation of orthodontic
surgery and treatment.
In this paper we present a micromirror fabrication technique without using silicon-on-insulator (SOI) wafers. Torsional electrostatic micromirrors have been fabricated using a combination of chemical mechanical polishing (CMP) process and anodic bonding. The size of fabricated silicon mirror plate was 610×400 μm2 and 20 μm thick. The steering electrodes have been fabricated in the dry etched trench on the glass wafer by electroplating process and CMP processing without damage of electrodes during anodic bonding process. The surface roughness of polished silicon micromirror(Ra) was 3.19nm. The single crystal silicon mirrors are electrostatically actuated with parallel bottom electrodes placed 8 μm below the mirror plate, and they could be stably operated in a ±1.1°. The pull-in voltage has been measured as 520 V. The resonant frequency of the fabricated torsion mirror was 47.3 kHz.