Temperature effect on thermal changes and phase analysis of 3Y-TZP zirconia restorations

This study aimed to investigate the effect of final sintering on the thermal properties and phase composition of yttrium-stabilized zirconium dioxide. Totally 15 yttrium-stabilized zirconium oxide standard ovoid samples were studied (3Y-TZP, IPS e.max ZirCAD LT, Ivoclar Vivadent, Schaan, Liechtenstein). This material contains the following components: ZrO2 - 87.0 - 95.0%, Y2O3 - 4.0 - 6.0%, HfO2 - 1.0 - 5.0%, Al2O3 - 0.0 - 1, 0%. Initially, X-ray diffraction analysis was performed. After that, differential scanning calorimetry was carried out up to a temperature of 900°C. X-ray diffraction analysis was performed to assess the effect of the firing process on the phase analysis of zirconia samples (Selected samples were tested on an X-ray diffraction instrument (EMPYREAN, PANalytical, Lelyweg, The Netherlands) The thermal changes study in zirconia samples resulting from repetitive firing processes was performed then. Samples were placed in a differential scanning calorimeter (NETZSCH STA 409 PC Luxx, Bavaria, Germany) and heated at a rate of 10°C/min from 50°C to 900°C.) Then, differential scanning calorimetry data (the mass and structural changes of zirconia samples depending on temperature) was recorded. The percentage of the monoclinic phase increases on average from 3.6% to 7.5%, but this difference is not statistically significant (p=0.1). Two exothermic peaks were observed when the samples were heated from 50°C to 900°C. The final firing of 3Y-TZP zirconium crown up to 900°C slightly increases the content of the monoclinic phase and causes exothermal changes.