Table 2: ∆L means (standard deviation) according to bleaching agent and enamel thickness for each time evaluated.

Bleaching agent Enamel thickness Time
∆L1 ∆L2 ∆L3
10% Carbamide
Peroxide		 0 mm enamel (D) *15.65 (4.17) a *23.40 (4.23) a 32.24 (4.53) a
0.5 mm enamel (0.5E) *10.30 (2.89) b *15.89 (3.45) b 25.95 (2.59) b
1 mm planned enamel (1E) *9.70 (1.53) b *16.02 (3.22) b *24.55 (3.33) b
1 mm unplanned enamel (aprismatic) (1AE) 5.47 (2.15) c *10.58 (3.70) c 19.75 (3.21) c
35% Hydrogen
Peroxide		 0 mm enamel (D) 8.54 (2.32) a 19.58 (3.48) a 28.02 (4.32) a
0.5 mm enamel (0.5E) 4.32 (1.24) b 9.62 (3.00) b 21.94 (2.08) b
1 mm planned enamel (1E) 4.71 (2.55) b 9.88 (3.50) b 14.84 (3.50) c
1 mm unplanned enamel (aprismatic) (1AE) 4.46 (1.63) b 7.16 (2.20) c 19.54 (2.89) bc

Means followed by different lowercase letters comparing thickness within bleaching agent and evaluated time indicate significant difference (p ≤ 0.05). *It differs from 35% hydrogen peroxide in the same thickness and time (p ≤ 0.05).