CAD/CAM - international magazine of digital dentistry

The above images show the original tooth in transparent with the optimal tooth preparation inside, colour coded by depth, i.e. how much material that has been removed. (Photos courtesy of Staffan Björkenstam, Chalmers) I 15 news _ 3-D software I CAD/CAM 3_2011 to achieve the objective without colliding with the teeth or mouth parts.” The software is based on advanced mathemati- cal models and on state-of-the-art visualisation technology. The researchers have based their work on international guidelines on how teeth should be shaped before being fitted with dental crowns. The guidelines cover the ratios between the height and width of the tooth and the extent to which a layer needs to be ground down in order to leave enough space for the crown, for example. Theresearchersreporttheyhaveconvertedevery guideline into an equation, dividing each tooth into 10,000 sections. From that, the software performs an optimisation, leaving as much of the tooth as possible. “Most dentists are very skilful, but no hu- man being can achieve this sort of optimisation as efficiently as a computer program,” said Chalmers researcher and dentist Matts Andersson. “If the tooth does not have a good fit with the crown, bac- teria can accumulate in the gaps, resulting in caries and loosening of the teeth. A bad fit can also lead to problems with the jaw joint—or to the dental crown simply falling off.” According to the researchers, their new method should therefore reduce the risk of such problems. Itwouldalsoshortenthetimeneededfortreatment and save large amounts of money. “I estimate that the treatment sessions would be10percentshorter,”saidAndersson.“Thatwould resultinsavingsofUS$27millionperyear.However, the biggest benefit would probably be an improve- ment in quality, increasing the life of the dental crowns and reducing the number of remakes.” The researchers have also produced 3-D soft- ware that dental students can use for learning how to grind teeth. Currently, students have no access to simulation programs with defined objectives. “There are other simulation tools available but the main contribute of our simulator is that we have defined objectives i.e. the student can immediately see how close they get to the optimal result, and they know what to aim for,” Chalmers researcher Staffan Björkenstam told CAD/CAM. The research into tooth grinding is based on methods originally produced for vehicle manufac- turing and derived from automatic path planning for industrial robots, something that production researchers and mathematicians at Chalmers are working on jointly with the motor industry. The project is a cross-disciplinary collabora- tion, financed by Nobel Biocare and VINNOVA, a Swedishgovernmentagencythatadministersstate funding for research and development. The colla- boration partners are the Department of Product and Production Development at Chalmers, the Fraunhofer–Chalmers Research Centre for Indus- trial Mathematics, and Nobel Biocare._ Editorial note: A 3-D animation demonstrating the precise manœuvring of the grinding tool is available on www.dental-tribune.com/articles/content/id/6619 or simplyscantheQRcodewithyoursmartphone. Fraunhofer-Chalmers Centre Chalmers Science Park Sven Hultins Gata 9D 41288 Göteborg Sweden www.chalmers.se CAD/CAM_contact