inCoris ZI Research Articles

Reaction of Dental Zirconia with Phosphate-Bonded Investments for Heat Pressing Technique

The aim of the study was to investigate the reaction of phosphate bonded investment to zirconia during for the heat-pressing technique. Two kinds of dental zirconia were used in this study (inCoris ZI and P-NANOZR). Zirconia was invested into the three kinds of phosphate-bonded investment (Ceravety, PC-15 and Norivest). The investments were fired at several different temperatures. The X-ray diffraction peaks due to monoclinic ZrO2 were not detected on the waxed-up side of zirconia discs. It demonstrates that no low temperature degradation occurred during the heating of the investment. X-ray diffractometry revealed that the peak assigned to ZrP2O7 was detected on the contact side of zirconia discs fired with phosphate-bonded investment at 850 and 950°C. It also revealed that diffraction peak assigned to YPO4 and the monoclinic ZrO2 were detected in the same side of zirconia discs contacted with phosphate-bonded investment fired at 1100 °C. It can be concluded that the reduction of Y caused the transformation from tetragonal to monoclinic phase and the reduction of strength.

Chipping behaviour of all-ceramic crowns with zirconia framework and CAD/CAM manufactured veneer

Objectives The aim of this in vitro study was to assess the ultimate load to failure of zirconia based crowns veneered with CAD/CAM manufactured ceramic. Methods 32 identical, anatoform zirconia (Sirona inCoris ZI, mono L F1) frameworks (thickness 0.6 mm) were constructed (Sirona inLab 3.80). Afterwards, 16 crowns were completed using a CAD/CAM manufactured lithium disilicate ceramic veneer (IPS e.max CAD, Ivoclar Vivadent). The remaining 16 frames were veneered using conventional manual layering technique. For the CAD/CAM manufactured veneers, the connection between framework and veneer was accomplished via a glass fusion ceramics. Before fracture tests, half of the specimens underwent thermocycling and chewing simulation (1.2 million chewing cycles, force magnitude F max = 108 N). To further investigate the new technique, finite element computations were carried out on the basis of the original geometry. Results Nearly all (87.5%) conventionally veneered crowns failed already during chewing simulation, whereas crowns with CAD/CAM manufactured veneers were non-sensitive to artificial ageing. Crowns veneered with lithium disilicate ceramic displayed ultimate loads to failure of about 1600 N. Conclusion The CAD/CAM production of veneers for restorations with zirconia framework is a promising way to reduce failures originating from material fatigue.