CAD/CAM - international magazine of digital dentistry

24 I I case report _ CAD/CAM fixed prosthetics DentalDesignerusesavirtualarticulator(Fig.11). The virtual articulator mimics movements the same way as a real articulator does. In addition, you can use the colour-marking feature to detect contact areas. Movements can be simulated automatically or by moving the mouse. The software also contains preset values for configuring, for example, the strength of pontics and alerts the user if these pre-sets are changed. Figure12showsacompletedbridgereadytobesent for milling and Figure 13 the complete abutment, combining the anatomy from the library files and the created plan. The fact that today we can mill custom-made abutments and screw-retained bridges from zirconia is the result of a cross-disciplinary ef- fort between dental technology and engineering. After years of hard work, we are now able to mill parts to tolerances of less than 5 µm. The milling of implant bridges requires a five-axis milling ma- chine. The STL file generated by the CAD system is only one of the steps in creating the final product (Fig. 14). The complete zirconia abutment sits completely passively on the model after correctly executed computer-aideddesign,millingandsintering(Fig.15). As part of quality control, the completed abutment is test-tightened to the correct torque on the model. The flexural strength of carefully modified custom-made abutments can be up to twice as high as that of standard zirconia abutments. Stress tests conducted at the University of Turku strained the abutments at a 45-degree angle using up to 1,500 N of force. The completed abutments accurately matched the design, including the opposing arch and the gingival margin. In this particular case, the abut- ments were coloured using regular colour (Fig. 16). The veneering work was performed at Turun Teknohammas’s laboratory using conventional methods (Fig. 17). The ceramic used was IPS e.max (Ivoclar Vivadent) and the work was performed by Jaakko Siira, the technician in charge. The completed screw-retained bridge and the abutment were tried on the model (Fig. 18), as was the screw-retained zirconia crown (Fig. 19). Then the completed work was ready to be sent to the clinic (Fig. 20). Figure 21 shows the final clinical situation of the completed product, tightened to the desired torque._ Fig. 16_The completed abutments accurately matched the design. Fig. 17_The veneering work was performed at the laboratory using conventional ceramic methods. Fig. 18_The completed screw-retained bridge and the abutment on the model. Fig. 19_The screw-retained zirconia crown. Fig. 20_The completed work ready to be sent to the clinic. Fig. 21_The final clinical photograph. CAD/CAM 1_2014 Tero Rakkolainen Käsityöläiskatu 7 20100Turku Finland www.intodental.fi CAD/CAM_contact Fig. 21 Fig. 18Fig. 16 Fig. 17 Fig. 19 Fig. 20 CAD0114_22-24_Rakkolainen 14.04.14 11:46 Seite 3