Abstract
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.
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