## 3 Results
### Impact of Nitrogen Generator  
A significant difference between the group with a 30 min curing time with a nitrogen generator and the same curing time group without a nitrogen generator was found (median value 0.66 mm IR [0.42, 0.94] and 0.61 mm IR [0.47, 0.89], respectively, Mann-Whitney U-test \(p\)-value = 0.004). Particularly, significant differences were found at the following reference points: 1.6 MP, 1.5 FIS, 1.3 I, 1.2 V, 1.2 I, 2.6 MB, 2.6 MP, 2.6 DB, 2.3 I, 2.2 I, and 2.1 I (see Table 4).  
\begin{table}
\begin{tabular}{c c c c} \hline
**1.6** & **Without N2** & **With N2** & **\(p\)-Value** \\ \hline MB & 0.51 [0.51, 0.56] & 0.51 [0.51, 0.56] & 0.910 \\ MP & 0.61 [0.61, 0.61] & 0.70 [0.66, 0.75] & 0.007 \\ DB & 0.56 [0.56, 0.61] & 0.51 [0.51, 0.56] & 0.125 \\ DP & 0.66 [0.61, 0.66] & 0.66 [0.66, 0.70] & 0.515 \\ FIS & 0.75 [0.75, 0.75] & 0.80 [0.70, 0.84] & 0.443 \\ V & 0.56 [0.51, 0.56] & 0.51 [0.51, 0.51] & 0.221 \\
1.5 & Without N2 & With N2 & \(p\)-Value \\ B & 0.56 [0.56, 0.56] & 0.61 [0.56, 0.61] & 0.324 \\ P & 0.61 [0.61, 0.61] & 0.61 [0.61, 0.61] & 0.317 \\ FIS & 0.79 \(\pm\) 0.02 & 0.73 \(\pm\) 0.04 & 0.028 \\ V & 0.51 [0.51, 0.51] & 0.51 [0.51, 0.56] & 0.519 \\
1.4 & Without N2 & With N2 & \(p\)-Value \\ B & 0.56 [0.51, 0.56] & 0.61 [0.56, 0.61] & 0.100 \\ P & 0.56 [0.56, 0.61] & 0.66 [0.66, 0.66] & 0.081 \\ FIS & 0.80 [0.75, 0.80] & 0.80 [0.66, 0.80] & 0.435 \\ V & 0.51 [0.51, 0.51] & 0.51 [0.51, 0.56] & 0.288 \\
1.3 & Without N2 & With N2 & \(p\)-Value \\ I & 0.56 [0.51, 0.56] & 0.61 [0.61, 0.61] & 0.014 \\ V & 0.56 [0.56, 0.56] & 0.56 [0.56, 0.56] & 0.606 \\
1.2 & Without N2 & With N2 & \(p\)-Value \\ I & 0.56 [0.56, 0.61] & 0.66 [0.66, 0.66] & 0.011 \\ V & 0.66 [0.66, 0.66] & 0.56 [0.56, 0.61] & 0.037 \\
1.1 & Without N2 & With N2 & \(p\)-Value \\ I & 0.66 [0.66, 0.70] & 0.70 [0.66, 0.75] & 0.230 \\ V & 0.75 [0.75, 0.75] & 0.75 [0.70, 0.75] & 0.093 \\
2.1 & Without N2 & With N2 & \(p\)-Value \\ I & 0.75 [0.70, 0.75] & 0.94 [0.84, 0.94] & 0.010 \\ V & 0.75 [0.70, 0.75] & 0.75 [0.75, 0.80] & 0.059 \\
2.2 & Without N2 & With N2 & \(p\)-Value \\ I & 0.61 [0.56, 0.61] & 0.66 [0.61, 0.70] & 0.033 \\ V & 0.61 [0.61, 0.66] & 0.66 [0.61, 0.66] & 0.316 \\
2.3 & Without N2 & With N2 & \(p\)-Value \\ I & 0.56 [0.56, 0.56] & 0.61 [0.61, 0.66] & 0.014 \\ V & 0.56 [0.56, 0.56] & 0.56 [0.51, 0.56] & 0.093 \\ \hline \end{tabular}
\end{table}
Table 4: Local thickness values at reference points for the different curing conditions (30 min curing time with and without nitrogen generator). Results are expressed in mm as Mean \(\pm\) Standard Deviation or Median [Interquartile Range]. \(p\)-value: Student’s \(t\)-test, or Mann–Whitney U test, \(p\)-value; MB: mesiobuccal cusp tip; MP: mesiopalatal cusp tip; DB: distobuccal cusp tip; DP: distob-palatal cusp tip; FIS: mesiodistal centre of the central fissure; V: central point of the facial surface; B: buccal cusp tip; P: palatal cusp tip; I: most coronal, central point of the incision edge.  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline
**1.6** & **Overall** & **15 Min** & **20 Min** & **25 Min** & **30 Min** & **40 Min** & **50 Min** & \(p\)**-Value** \\ \hline FIS & 0.71 \(\pm\) 0.08 & 0.69 \(\pm\) 0.02 & 0.76 \(\pm\) 0.04 & 0.69 \(\pm\) 0.06 & 0.78 \(\pm\) 0.10 & 0.62 \(\pm\) 0.13 & 0.69 \(\pm\) 0.07 & 0.050 \\ \hline V & 0.56 & 0.56 & 0.51 & 0.51 & 0.56 & 0.56 & 0.56 & 0.56 \\  & [0.51, 0.56] & [0.56, 0.56] & [0.51, 0.56] & [0.51, 0.51] & [0.56, 0.56] & [0.56, 0.61] & [0.51, 0.56] & 0.010 \\ \hline \end{tabular}
\end{table}
Table 3: _Cont._