Table 4.

Results of the color stability of the zirconia and PEEK crowns.

Color Stability	Crown Materials				p Value
	Zirconia		PEEK
	Mean (SD)	Median (IQR)	Mean (SD)	Median (IQR)
Control (C)	17.71 (0.68)	17.85 (0.62)	9.58 (0.51)	9.50 (0.65)	<0.001 *
Thermocycled (T)	14.72 (0.85)	14.65 (1.12)	6.23 (0.40)	6.20 (0.58)	<0.001 *
Thermocycled + Worn (T + W)	11.88 (0.81)	11.90 (1.15)	5.28 (0.60)	5.10 (0.93)	<0.001 *
Friedman Test (p value)	<0.001 *		<0.001 *

SD = standard deviation, IQR = interquartile range. * Significant differences at p value < 0.05.