The Effect of Different Sintering Protocols on the Surface Morphology of Multilayered Monolithic Zirconia
Burcu Kizilirmak, Asst. Prof. Neslihan Guntekin, Prof. Ali Riza Tuncdemir
Necmettin Erbakan University, Faculty of Dentistry, Department of Prosthodontics, Konya
Objectives
The next generation zirconias, introduced after 4th and 5th generation monolithic zirconias, are multilayered zirconias with a polychromatic structure. These zirconias, incorporating 3Y-TZP, 4Y-TZP, 5Y-TZP, enable speed sintering per manufacturer instructions, though the impact of this process remains unclear. The aim of this study is to determine the effect of speed and repetitive sintering on the structural and optical properties of multilayered monolithic zirconias.
Materials and Methods
In this study, multilayered zirconia blocks, including Katana Zirconia YML (Kuraray, J) (YML), and IPS e.max ZirCAD Prime (Ivoclar Vivadent, FL) (Prime), were used with both speed (SS) and conventional (CS) sintering protocols. Samples were designed using ExoCAD software (Exocad DentalCAD, Germany) and manufactured using a CAD/CAM milling machine. All samples (Ø12×1 mm) were randomly divided into two groups and subjected to three sintering cycles. (n:14, N:56) L*, a*, b* values were measured with a spectrophotometer post 1st, 2nd and 3rd sintering, while X-ray diffraction (XRD) and Scanning Electron Microscope (SEM) data were collected. Translucency (TP) values were statistically analyzed using three-factors ANOVA to evaluate the effects of sintering speed and repetition. IBM SPSS Statistics software was employed for statistical analysis.
Results
The TP value of YMLCS is significantly higher than YMLSS and PrimeCS.PrimeSS has a higher TP value compared to PrimeCS, but the difference is not significant. In SEM images, particle sizes have increased in the repeated YMLSS and YMLCS groups. The particle size of Prime is noticeably smaller than all groups of YML. XRD analysis revealed a change of monoclinic and tetragonal phases in YMLCS, YMLSS, and repeated sintering.
Conclusions
In clinical practice, conventional sintering is highly reliable for Katana Zirconia YML, whereas for the IPS e.max ZirCAD Prime group, the effect of speed and conventional sintering on translucency values is not significant. In repetitive sintering, an increase in translucency is observed.