RESUMO
<p><b>OBJECTIVE</b>To investigate the reliability of a newly developed grating projection system 3DSS-STD-II by three-dimensional reconstruction of dental cast, so as to offer some evidence for dental computer aided design and computer aided manufacturing (CAD/CAM).</p><p><b>METHODS</b>Five groups' data of mandibular dentition cast from different angle: Occlusion, right lateral dentition, anterior dentition, left lateral dentition and posterior of the cast were scanned and acquired by 3DSS-STD-II new measuring system. The five groups of acquired data were then under simplification and combination process and the digital dental cast was finally reconstructed by the reverse engineering software Geomagic 6.0. After the reconstruction process, the plaster dental cast and digital reconstructed dental cast were then manually and digitally measured respectively by different items: Width of incisors, width of anterior dental arch, width of buccal segment, length of anterior dental arch and length of buccal segment. The manual process was undergone by vernier caliper and the digital process was by reverse engineering software. The statistical analysis was then undergone in order to evaluate the reliability, repeatability and scan-precision of the new grating projection system.</p><p><b>RESULTS</b>With the statistical analysis results, the grating projection system 3DSS-STD-II showed its good reliability and repeatability in three-dimensional reconstruction of dental plaster cast. There were no significant differences between the data acquired by 3DSS-STD-II digital scanning system and manual measurement by vernier caliper in the precision.</p><p><b>CONCLUSION</b>The new grating projection system of 3DSS-STD- II equipped with high reliability and fast speed can meet the need of the fast data acquisition and three-dimensional reconstruction of dental cast and CAD process.</p>