## 4 Discussion  
This study evaluated the influence of rapid high-intensity curing on the DC of orthodontic adhesive systems. The findings confirm that rapid curing leads to lower DC values, especially under metal brackets. Material composition was the most influential factor. The \"exposure reciprocity\" principle did not hold at higher intensities, likely due to bimolecular termination and radical quenching. The null hypotheses were rejected since the rapid curing protocol and presence of a metal bracket resulted in lower short-term and 24 h DC values for all materials and groups except for the 24 h DC values for Transbond XT in the CG, where both curing protocols led to statistically similar results. The observed short-term (44.4-64.4% for conventional curing and 43.0-60.0% for rapid curing, Figure 2) and 24 h DC values (54.4-82.8% for the conventional curing protocol and 49.7-81.4% for the rapid curing protocol, Figure 4) in this study fell within the ranges reported in prior literature [14; 17; 31; 38; 39; 40; 41]. This consistency indicated that the polymerization efficiency observed in the present study is as expected. However, a more detailed comparison with previously published data is limited because differences in sample preparation, curing conditions, and other incompletely specified study variables can considerably influence the reported values [12; 31]. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Factor** & \(\mathbf{p}\)**-Value * ** & **Partial \(\mathbf{\eta^{2}}\)** \\ \hline Material & \textless{}0.001 & 0.933 \\ \hline Bracket & \textless{}0.001 & 0.968 \\ \hline Curing protocol & \textless{}0.001 & 0.901 \\ \hline Time point & \textless{}0.001 & 0.840 \\ \hline Material \(\times\) Bracket & \textless{}0.001 & 0.931 \\ \hline Material \(\times\) Curing protocol & \textless{}0.001 & 0.221 \\ \hline Bracket \(\times\) Time point & \textless{}0.001 & 0.080 \\ \hline Material \(\times\) Bracket \(\times\) Curing protocol & \textless{}0.001 & 0.417 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Partial eta-squared values describing the effect size of different factors on short-term DC values. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Factor** & \(\mathbf{p}\)**-Value * ** & **Partial \(\mathbf{\eta^{2}}\)** \\ \hline Material & \textless{}0.001 & 0.994 \\ \hline Bracket & \textless{}0.001 & 0.603 \\ \hline Curing mode & \textless{}0.001 & 0.615 \\ \hline Material \(\times\) Bracket & \textless{}0.001 & 0.259 \\ \hline Material \(\times\) Curing protocol & \textless{}0.001 & 0.201 \\ \hline Bracket \(\times\) Curing protocol & \textless{}0.001 & 0.247 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Partial eta-squared values describing the effect size of different factors on 24 h DC values. Lower short-term and 24 h DC values observed with the rapid curing protocol in both groups could be attributed to lower total energy received during curing. Regardless of higher radiant exitance in rapid curing compared to conventional curing, the total energy received was lower by approximately 4600 J/cm\({}^{2}\) (2 \(\times\) 10 s \(\times\) 1100 J/cm\({}^{2}\) = 22,000 J/cm\({}^{2}\); 2 \(\times\) 3 s \(\times\) 2900 J/cm\({}^{2}\) = 17,400 J/cm\({}^{2}\); 22,000 - 17,400 = 4600 J/cm\({}^{2}\)). These findings are in accordance with another study [23] where lower DC values were also obtained with a high-intensity curing protocol. Nevertheless, considering the very thin material layer (0.2 mm), both protocols should have provided sufficient energy for complete polymerization [6; 7]. Hence, the observed differences could be attributed to the negative effects of rapid polymerization, like increased rate of bimolecular termination--a phenomenon commonly associated with high-intensity curing modes with modern LED LCUs [13]. High-intensity light activates a greater number of photoinitiator molecules and generates more free radicals, accelerating the polymerization reaction.