Evaluation of innovative techniques for dental crowns manufacturing

Recently, Reverse Engineering (RE) and Additive Manufacturing (AM) have proven to be interesting techniques alternative to traditional procedures in dental applications, such as crown manufacturing. The geometry of a stone replica can be digitized by a three-dimensional scanner. From the points clouds a Virtual Model (VM) is generated and tooth caps could be designed on it and manufactured by Computer Aided Manufacturing (CAM) or employing AM techniques. The sequence from replica digitization (VM) to cap fabrication involves many production steps, each one inevitably inducing dimensional errors. However, the information given by systems suppliers or present in literature is lacking and does not allow comparison among different manufacturing systems. Therefore, it becomes important to investigate new technologies to quantify their accuracy and precision. Currently, there is not a standard methodology for evaluating the error introduced by each step of the manufacturing cycle, from the scanning of the replica to the final dental device. Moreover, to have comparable data, a suitable benchmark must be defined (Atzeni et al., 2009). In literature a few benchmarks based on standard geometries were proposed for dental applications (Brosky et al., 2002; DeLong et al., 2003), but they appear lacking because differences from posterior and anterior teeth shapes, tooth position along the dental arch, and three dimensional arrangement of teeth are disregarded.