[The identification of electronic surveying lines on 3-D digital models of dentition defects]

To develop a mathematical algorithm and a software package for the process of electronically surveying a scanned point cloud cast. To provide a principal premise to the subsequent computer aided design and computer aided manufacture (CAD/CAM) of removable partial denture framework, and to provide a method to improve quality control in the dental laboratory.

Point cloud data of a partially edentulous cast, a mandibular Kennedy Class II Modification 2 arch, was captured using an optical scanning system with projective grating and high-resolution digital camera. Using commercial CAD/CAM software system (Geomagic Studio 6), this point cloud data was processed and the 3-D digital model of partially edentulous cast was reconstructed. From a suggested surveying angle the contour points of height were identified, and then the digital surveying lines were traced using Projection and Contour Extraction software package. The depth of undercut was measured and defined to determine the clasp termination of retainer.

Electronic surveying line of 3-D digital dentition defect model was achieved. Digital surveying line defined the cast into undercut and non-undercut areas. Different virtualized paths of insertion could be automatically suggested when the cast was surveyed and analyzed from different angles. The depth of undercut was automatically measured and the retentive clasp termination was determined.

The mathematical algorithm and the software package in this study can be used to survey and analyze 3-D digital models of dentition defects, and to identify an electronic surveying line.