. 2026 Mar 2;34:e20250513. doi: 10.1590/1678-7765-2025-0513

Table 4. Mean (standard deviation) of superficial Knoop microhardness (KHN) as a function of group and time.

Group	Time
	Initial	Final
	Mean (standard deviation)	Mean (standard deviation)
No bleaching	284.44 (7.47)^Aa	284.61 (9.06)^Aa
7.5% HP	280.55 (7.59)^Aa	254.49 (6.27)^Bb
7.5% HP + Chi	282.02 (7.72)^Aa	284.46 (5.55)^Aa
7.5% HP + Ca	282.00 (7.48)^Aa	251.44 (6.98)^Bb
7.5% HP + Ca + Chi	280.53 (6.17)^Aa	282.48 (7.84)^Aa

Distinct letters (uppercase horizontally and lowercase vertically) indicate statistically significant differences (p≤0.05). p(group<0.0001; p(time)<0.0001; p(interaction)<0.0001.