ABSTRACT
In recent years, traditional procedures in dentistry are facing a challenge through the application of Reverse Engineering (RE) techniques together with Computer Aided Design and Manufacturing (CAD/CAM) (Wu et al. 2001). The geometry of the single tooth as well as the whole oral cavity can be digitized and transformed into a three-dimensional virtual model by a digitising device. In dentistry, contactless scanners are commonly preferred to contact digitizers because they require shorter scan time and they are adequate for even soft and brittle materials (Persson et al. 2006). These devices are based on the projection of a laser or a white light over the scan object. At the same time one or more digital cameras capture an image of the light stripe or pattern that is deformed by the object surface. This technology is limited by the optical characteristics of the surface that has to be dry and opaque to assure a correct readability by the scanner. Due to the complexity of dental geometries, multiple scans are usually required from different viewpoints to digitize optical occlusions areas. Computer software is then used to merge together different scans using a matching function. The availability of a virtual model opens up new opportunities: it can be used to design customized dental devices. Moreover, after converting the CAD model into STL format,
frame and completed with mould guide posts and a sprue area. The mounted coupon is refined, hand fitted, and hand polished. After inspection, it is referred as a master mould. Thereafter, the working mould is produced from the master mould in a similar way, that is by fabricating the epoxy mandrel, spraying, electroplating and refining. The refining step includes the final hand-applied finishpolish operation. The mould surfaces have a highdefinition of the artificial teeth to be produced, but it takes approximately twelve to fourteen weeks to make the master mould, and six weeks to make a working mould from it.
