Table 2: Mean values of shade changes (Δ-Values) ± standard deviations for all groups and at each tested time

Type of post bleaching surface treatment Shade evaluation Post bleaching ΔE,ΔV (T2-T1) After surface treatment
ΔE,ΔV (T3-T2)
After tea restaining
ΔE,ΔV(T4-T3)
After tea restaining with baseline
ΔE,ΔV(T4-T1)
Group 1 (Fluoride) Digital 11.80 ± 6.1 a 5.17 ± 3.7a 3.71 ± .34a 12.13 ± .38a
Visual 5.06 ± 2.9A .10 ± .31A .76 ± .35A 5.40 ± .27A
Group 2 (Fractional CO2 laser) Digital 11.19 ± 5.3 a 4.54 ± .30a 3.07 ± .14a 8.49 ± .50ab
Visual 5.30 ± 2.4A .36 ± 0.2A 2.20 ± .38A 3.46 ± .40B
Group 3 (Nanohydroxyapatite) Digital 11.20 ± 4.9 a 3.26 ± .19a 2.73 ± 1.6a 12.13 ± .58a
Visual 5.03 ± 3.9A .53 ± .29A .43 ± .03A 4.06 ± .41B
Group 4 (Control) Digital 11.57 ± 7.7 a - 8.30 ± .42b 6.71 ± .58b
Visual 5.60 ± 3.5A - 3.40 ± .38A 2.8 ± .048B

a,A - There is no significant statistic differences between similar characters.
Small letter for digital evaluation and capital letter for visual evaluation.

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