Leucite crystallization during processing of a heat-pressed dental ceramic

Area of Science:

• Dental Materials Science
• Ceramic Engineering
• Materials Processing

Background:

• Heat-pressed dental ceramics, such as IPS Empress, are widely used.
• Understanding the strengthening mechanisms during processing is crucial for optimizing material properties.
• Leucite (KAlSi2O6) is a key crystalline phase influencing the properties of these ceramics.

Purpose of the Study:

• To elucidate the mechanism of strengthening in heat-pressed dental ceramics (IPS Empress) during processing.
• To investigate the effect of various processing steps on leucite content.
• To correlate changes in leucite content with observed increases in flexural strength.

Main Methods:

• Quantitative X-ray Diffraction (XRD) was employed to determine leucite content.
• Analysis of Variance (ANOVA) was used to assess the statistical significance of processing effects.
• Post-hoc tests (Student-Neuman-Keuls, Duncan's Multiple Range) were performed for detailed comparisons.

Main Results:

• Processing significantly affected leucite content (P < .0001).
• Leucite content did not change after initial pressing but increased significantly after the first colorant firing (P < .05).
• A second colorant firing further increased leucite content (P < .05), with no further significant increases after subsequent firings.

Conclusions:

• Firing, particularly with colorants, leads to a significant increase in leucite content in heat-pressed dental ceramics.
• The observed increase in leucite content after firing is consistent with reported increases in flexural strength.
• This study provides insight into the microstructural changes that contribute to the strengthening of IPS Empress during fabrication.