Chemical and microstructural evaluation of dental ceramics before and after multiple firing cycles.

The study evaluated the leucite content in the powder of EX-3, Cerabien, and Omega 900 dental ceramics, as well as in samples subjected to 3, 8, and 13 firing cycles. Chemical composition of the ceramics before the sintering process and after firing cycles was verified. SEM analyses, combined with energy-dispersive X-ray microspectroscopy and X-ray diffraction, were conducted on unfired powder and sintered samples to determine the semi-quantitative chemical composition. Origin 5.0 software and Peak fitting 5.0 were used to quantify the crystalline phase. EX-3, Cerabien, and Omega 900 ceramics showed the following chemical elements in decreasing average order (%): O, Si, K, Al, Na, Ca, and Mg. Omega 900 showed Ba as an intermediary between Na and Ca. Ceramics also showed the oxides: SiO2, K2O, Al2O3, Na2O, CaO, MgO, and BaO. EX-3 showed leucite and cristobalite crystalline phases, Cerabien cristobalite crystalline phase, and Omega 900 leucite. EX-3 showed a significant increase in leucite content between 3 and 8, as well as between 8 and 13 firing cycles (p<0.05). Cerabien showed a significant increase in cristobalite content between 3 and 8 firing cycles, while Omega 900 showed a significant increase in the leucite content between 3 and 8 firing cycles. Significant decrease between 8 and 13 firing cycles was shown (p<0.05). In conclusion, firing cycles did not change the ceramics chemical compositions, showing microstructure with amorphous and crystalline phases. Ex-3 showed leucite and cristobalite phases, Cerabien cristobalite phase, and Omega 900 leucite phase. The increase in firing cycles promoted changes in the ceramic crystalline phase.