[Electronic surveying of digital partially dentate casts]

To develop a method of surveying the digitalized partially dentate cast in order to accomplish computer aided design (CAD) of removable partial denture (RPD) frameworks.

The stone cast of a partially dentate patient was scanned using a three-dimensional laser scanner. Points on the surface of the digitalized cast, termed as a "point cloud", were obtained. The point cloud was then imported into self-developed Tanglong software to sample and uniform. New module of identifying the surveying lines was specially written in Tanglong using C++. A straight line was created in the center of the cloud point. Then the cloud point surrounding the straight line was divided into many parts. Local coordinates were established to indicate the information of angle and distance of every point to the straight line. Surveying lines were produced step by step electronically by identifying the closest and farthest points relative to the straight line and then connected together. Different surveying lines were obtained by adjusting the angle of the straight line. After the surveying lines were decided, the undercut areas could be marked and the depth of undercut was calculated automatically. The blockout of the undercuts could also be achieved by moving the location of the point cloud in undercut area.

Survey lines of digitalized partially dentate casts were generated in computer. The undercut area and its depth were identified and the undercut could be blocked out. The shape of survey lines on the digitalized casts was similar to that on the physical casts drawn using traditional method.

The new module in Tanglong software was developed specifically for surveying partially dentate casts. It had a user-friendly interface with the easy-to-understand menus. The success of surveying dental casts digitally would make it possible to CAD of RPD frameworks.