Table 1. Results of repeated measures ANOVA (Greenhouse-Geisser) on effects of veneering porcelain thickness and background shade on color attributes .

Color attributes	Source	Type III Sum of Squares	df	Mean Square	F	p
L *	Background	28.408	2	14.204	405.724	<0.0001
	Thickness	85.285	3	28.428	730.376	<0.0001
	Background × Thickness	40.892	6	6.815	184.953	<0.0001
	Error	1.990	54	0.037
a *	Background	4.066	2	2.033	66.276	<0.0001
	Thickness	34.622	3	11.541	455.834	<0.0001
	Background × Thickness	18.023	6	3.004	114.294	<0.0001
	Error	1.419	54	0.026
b *	Background	17.017	2	8.509	67.090	<0.0001
	Thickness	185.051	3	61.684	875.827	<0.0001
	Background × Thickness	70.659	2.946	23.981	158.146	<0.0001
	Error	4.021	26.518	0.152
∆E	Background	16.480	2	8.240	170.256	<0.0001
	Thickness	79.102	3	26.367	490.950	<0.0001
	Background × Thickness	57.409	6	9.568	191.446	<0.0001
	Error	2.699	54	0.050