Comparison of ΔE Values
The average ∆E values of the teeth in the treatment and control groups and their statistical comparisons are presented in Table Comparison of ∆E values of the treatment and control groupsThe Kruskal–Wallis test statistic and independent t-test were used. Lower case letters indicate in-group evaluation between rows; capital letters indicate evaluation between the columns. The same letters indicate that there is no statistically significant difference (∆E1a: Colour difference between before treatment and immediately after treatment∆E2a: Colour difference between before treatment and 1 month after treatment∆E3a: Colour difference between before treatment and 3 months after treatment∆E4a: Colour difference between before treatment and 6 months after treatment