COLOR STABILITY OF PRESSED IPS E.MAX LITHIUM DISILICATE CERAMICS AFTER REPEATED FIRING CYCLES

Abstract

Objectives: To determine and compare color difference CIEDE2000 (DE00) of pressed IPS E.max lithium disilicate ceramic material after repeated firing cycles. To determine and evaluate correlation of CIELAB and CIEDE2000 values analyzed by XRite Color i5 Spectrophotometer, VITA EasyShade® Advance 4.0 (VITA Zahnfabrik) and Adobe Photoshop CC. Materials and methods: 36 specimens 8mmX10mm at 1.5mm thickness (12 specimens of pressed IPS e.max® Press Lithium Disilicate MT Monochromatic ingots and 24 specimens pressed IPS e.max® Multi Press Lithium Disilicate Multichromatic ingots. Specimens were exposed to repeated firing cycles up to 7 cycles. Color analysis was performed after 1st,2nd,3rd,5th, and7th firing cycle. CIE L*a*b* values measured by X-Rite Color i5 Spectrophotometer, VITA EasyShade® Advance 4.0 (VITA Zahnfabrik) and Adobe Photoshop CC. CIELAB (D*ab) and CIEDE2000 (D00) calculated to measure color difference. Results: Linear regression and multiple comparison analysis (Tukey’s HSD test) showed a significant color difference (D*ab) and CIEDE2000 (D00) with (p-value <0.001), after v multiple firing cycles, between instruments used and in different shades groups. Moreover, significant different in interactive effect between different shades tested by different instrument, different shades tested after multiple firing cycles and different instruments after multiple firing cycles. Conclusion: IPS E.max lithium disilicate material shows significant color difference after repeated firing cycle tested by three color analysis instruments. Measuring instruments used to evaluate CIE L*a*b* color values showed significant different in color values analysis which may lead to altered level of interpretation, particularly to determine perceptibility and clinical acceptability thresholds.