## 3 Results  
The results of CIELCh on a white background are shown in Table 2.  
Regarding \(\Delta\)E, the results are shown in Figure 2. At t1, MF(P1) and MH(P2) achieved the highest \(\Delta\)E(t0/t1), but only NX3L showed a colour difference between P1 and P2 (\(p\) = 0.04). At t7, the \(\Delta\)E(t0/t7) values of each tested RLA were different from the \(\Delta\)E(t0/t1) ones. In particular, RXL and RXD showed the highest \(\Delta\)E(t0/t7) both in P1 and P2. RXD and MF showed different \(\Delta\)E(t0/t7) values in P1 and P2 (RXD, \(p\) = 0.00; MF, \(p\) = 0.00), but only RXD was above the PTC (RXD = 17.964 \(\pm\) 0.318; MF = 0.640 \(\pm\) 0.107), while only \(\Delta\)E(t0/t1) of MF (P1) and MH (P2) exceeded the PTC, and the \(\Delta\)E(t0/t7) values for each RLA were above this value. Then, all RLAs tested changed the colour after 7 days of storage in water (\(p\) < 0.05). \begin{table}
\begin{tabular}{c c c c|c c c} \hline  & \multicolumn{2}{c|}{**t0**} & \multicolumn{2}{c}{**t0**} & \multicolumn{2}{c}{**t7**} \\ \hline  & **L** & **C** & **h** & **L** & **C** & **h** \\ \hline \multicolumn{7}{c}{**P1**} \\ \(\mathrm{NX3L}\) & 89.02 (0.33) & 1.17 (0.09) & 167.35 (3.94) & 95.58 (0.16) & 1.56 (0.13) & 135.11 (1.81) \\ \(\mathrm{NX3D}\) & 82.33 (0.34) & 1.33 (0.26) & 69.51 (4.86) & 89.83 (0.21) & 5.66 (0.15) & 94.27 (0.60) \\ \(\mathrm{RXL}\) & 80.76 (0.35) & 14.14 (0.22) & 99.19 (0.18) & 88.01 (0.12) & 19.71 (0.31) & 97.64 (0.26) \\ \(\mathrm{RXD}\) & 83.67 (0.44) & 2.52 (0.04) & 130.92 (0.76) & 93.76 (0.27) & 4.57 (0.28) & 103.25 (0.26) \\ \(\mathrm{MF}\) & 82.08 (0.25) & 0.61 (0.02) & 30.70 (6.83) & 90.71 (0.15) & 2.92 (0.10) & 84.29 (0.87) \\ \(\mathrm{MH}\) & 81.75 (0.19) & 2.91 (0.12) & 88.93 (1.24) & 89.16 (0.07) & 6.68 (0.04) & 93.62 (0.14) \\ \hline \multicolumn{7}{c}{**P2**} \\ \(\mathrm{NX3L}\) & 89.16 (0.20) & 0.99 (0.12) & 179.24 (7.33) & 95.31 (0.27) & 1.53 (0.04) & 135.97 (0.81) \\ \(\mathrm{NX3D}\) & 82.28 (0.32) & 0.72 (0.06) & 38.63 (14.49) & 90.16 (0.22) & 4.59 (0.29) & 95.78 (1.11) \\ \(\mathrm{RXL}\) & 80.54 (0.36) & 14.34 (0.20) & 99.04 (0.19) & 93.80 (0.19) & 2.75 (0.19) & 107.89 (0.86) \\ \(\mathrm{RXD}\) & 83.51 (0.36) & 1.59 (0.14) & 158.46 (5.11) & 93.78 (0.23) & 2.77 (0.31) & 107.57 (0.91) \\ \(\mathrm{MF}\) & 83.12 (0.18) & 0.96 (0.06) & 61.61 (4.36) & 90.57 (0.03) & 3.53 (0.20) & 85.86 (0.86) \\ \(\mathrm{MH}\) & 80.94(0.73) & 2.90(0.21) & 88.74(1.42) & 88.93(0.16) & 6.70(0.13) & 94.15(0.47) \\ \hline \multicolumn{7}{c}{**NX3L = NX3L light-cure, NX3D = NX3 dual-cure, RXL = RelyX Veneer, RXD = RelyX Ultimate, MF = Enamel Plus HRi Flow, MH = Enamel Plus HRi.**} \\ \end{tabular}
\end{table} 
Table 2: CIELCh parameters of the tested resin lute agents cured with traditional curing protocol (P1) and step luting protocol (P2). L*, C* and h* values are expressed as means (standard deviation), and they were recorded on white background before (t0) and after 7 days (t7) of storage in water. Figure 2: \(\Delta\)E(t0/t1) and \(\Delta\)E(t0/t7) results of tested resin luting agents cured with traditional curing protocol (P1) and step luting protocol (P2). Different letters identify statistical differences between P1 groups. Different symbols (\(\#\), \(\$\) and \(\&\)) identify statistical differences between P2 groups. Bars identify a statistical difference between P1 and P2 (\(p\) < 0.05). NX3L = NX3 light-cure, NX3D = NX3 dual-cure, RXL = RelyX Veneer, RXD = RelyX Ultimate, MF = Enamel Plus HRi Flow, MH = Enamel Plus HRi. The translucency values are summarised in Table 3. At t1, only MF(P2) showed a different translucency than in t0 (\(p<0.05\)). At t7, the TPc of all RLAs with P1 and P2 changed, except for NX3D (\(p<0.05\)). However, the translucency trend remained the same in both P1 and P2 (NX3L \(<\) RXL \(<\) RXD \(<\) MH \(<\) MF \(<\) NX3D (opaque \(<\) translucent)). Only NX3L (P2), NX3D (P1 and P2) and MH (P1) showed a \(\Delta\)TPc (t0/7) below the PTT.