The Influence of Post Bleaching Treatments in Stain Absorption and Microhardness

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 ± 3.7^a	3.71 ± .34^a	12.13 ± .38^a
Group 1 (Fluoride)	Visual	5.06 ± 2.9^A	.10 ± .31^A	.76 ± .35^A	5.40 ± .27^A
Group 2 (Fractional CO₂ laser)	Digital	11.19 ± 5.3^a	4.54 ± .30^a	3.07 ± .14^a	8.49 ± .50^ab
Group 2 (Fractional CO₂ laser)	Visual	5.30 ± 2.4^A	.36 ± 0.2^A	2.20 ± .38^A	3.46 ± .40^B
Group 3 (Nanohydroxyapatite)	Digital	11.20 ± 4.9^a	3.26 ± .19^a	2.73 ± 1.6^a	12.13 ± .58^a
Group 3 (Nanohydroxyapatite)	Visual	5.03 ± 3.9^A	.53 ± .29^A	.43 ± .03^A	4.06 ± .41^B
Group 4 (Control)	Digital	11.57 ± 7.7^a	-	8.30 ± .42^b	6.71 ± .58^b
Group 4 (Control)	Visual	5.60 ± 3.5^A	-	3.40 ± .38^A	2.8 ± .048^B

a,A - There is no significant statistic differences between similar characters.

Small letter for digital evaluation and capital letter for visual evaluation.