Table 4b. P-values of comparisons between DE values of materials for lighter and darker teeth are presented in the lower left (below dashes) and upper right half (above dashes) of the table, respectively. P-values <0.05 indicate significant difference .

Before bleaching/After bleaching	Opalescence Oh	Treswhite Supreme	Hollywood Smiles
Opalescence Oh	-	0.021	0.000
Treswhite Supreme	0.162	-	0.039
Hollywood Smiles	0.000	0.000	-
After bleaching/After staining	Opalescence Oh	Treswhite Supreme	Hollywood Smiles
Opalescence Oh	-	1.000	0.000
Treswhite Supreme	1.000	-	0.001
Hollywood Smiles	0.049	0.044	-