Table 3. Relation between the logarithm of the surface gloss and the average surface roughness.

Staining	Toothpaste	Time	Correlation coefficient	p-value
Control	RT	T1	-0.76	0.0001
		T2	-0.72	0.0004
		T3	-0.49	0.0288
		T4	-0.73	0.0002
	AC	T1	-0.49	0.0276
		T2	-0.84	<0.0001
		T3	-0.73	0.0002
		T4	-0.83	<0.0001
	HP	T1	-0.78	<0.0001
		T2	-0.76	0.0001
		T3	-0.66	0.0016
		T4	-0.77	<0.0001
Coffee	RT	T1	-0.76	0.0001
		T2	-0.54	0.0128
		T3	-0.37	0.1092
		T4	-0.44	0.0503
	AC	T1	-0.52	0.0199
		T2	-0.88	<0.0001
		T3	-0.84	<0.0001
		T4	-0.86	<0.0001
	HP	T1	-0.66	0.0015
		T2	-0.77	<0.0001
		T3	-0.75	0.0001
		T4	-0.80	<0.0001

RT: Regular toothpaste; AC: Activated Charcoal Toothpaste; HP: Hydrogen Peroxide Toothpaste; RS: Remineralizing solution. T1: before brushing; T2: after brushing; T3: after staining or after seven days in RS; T4: after staining or after 14 days in RS.