In the last few years, the acceptance of ceramic inlays next to plastic and gold inlays has increased perceivably. Ceramic restorations possess an inconspicuous appearance like natural teeth and exhibit similar hardness. Furthermore, in contrast to amalgam ceramic inlays they have no toxical pertinence and a long durability. Proportionally to this market the number of dental labs using CAD/CAM-systems for tooth restorations, like crowns or inlays, has grown. Using CAD/CAM systems shortens the design and the manufacturing time. As a result, the costs of a restoration are being reduced as well. Conventional systems in contrast require a more or less amount of user interaction as well as three-dimensional power of imagination for the construction of an inlay.
ViRus constitutes a CAD-software for the fully automatic design of tooth restorations allowing the use of the patient's personal tooth anatomy. In addition to the automated process the Fraunhofer Institute and Hint-Els want the user to be able to design the restoration according to his own esthetic principles. Therefore the initial restoration is proposed as a suggestion which can be modified by the user at any time. Every modification leads to a viewer update, so that changes can be seen immediately. The user interaction and therefore the learning curve are very low. On that account the dentists and dental technicians can save a lot of time and money for the handling compared to similar systems.
ViRus is a part of the CAD/CAM system for tooth restoration offered by Griesheim-based Hint-ELs. The Hint-Els system consists of a scanner, the construction software for bridges, crowns and inlays and a milling machine. With the scanner, the dentist or dental technician digitizes the prepared tooth. Then he designs the tooth restoration using ViRus. Finally, the restoration is produced out of the desired material with a milling machine or by selective laser melting.
The main challenge designing a tooth restoration is the reconstruction of the defective tooth surface. An automatic tooth reconstruction process is only possible if the typical geometry of the teeth is known by the system. The innovative approach of the CAD-system developed at IGD implies the explicit use of dental medical knowledge in the form of a small number of tooth models. These models have the ability to adapt to the patient's tooth anatomy automatically. Therefore the original shape of a tooth surface is being reconstructed by the model and adjusted to the remaining intact tooth surface.
This means, for constructing a restoration, the user only has to choose an appropriate model out of the available tooth library and start the adaptation process. All further steps are done automatically. Basis of the reconstruction is a three-dimensional model of the patient's dentition made by the dentist using an intra-oral camera or by scanning a gypsum model. The model shows the affected tooth, the two adjacent teeth, as well as the antagonists.
Instead of reshaping the replacement the dentist simply selects from the database the model that resembles best the patient's natural tooth. This piece is automatically superimposed in the virtual model and adjusted to the affected tooth and the surrounding teeth. To be able to execute final manual corrections ViRus provides various tools to individually adjust the identations and tooth edges. Even an individual tooth database for particular patients is realizable with ViRus. If such a database has been set up for a patient, the dentist can, if necessary, implant an exact copy of the original tooth.
As one of the 20 Nominees for the European IST Grand Prize 2006, Fraunhofer IGD was given the opportunity to exhibit ViRus during the European IST Prize Exhibition at the European Commission in Brussels on 30 November - 1 December 2005. More details on this award-winning dental CAD software can be found at the Fraunhofer IGD Web site.