## 3 Results  
A descriptive analysis of each type of bracket investigated is reported in Table 3. Each type comprised a sample of 10 brackets (n = 10). The range of measurements made was expressed as the mean and SD range, from a minimum of 0.558 \(\pm\) 0.001 mm (IH3 DB2) and 0.558 \(\pm\) 0.002 mm (IH3 DB2) up to a maximum of 0.0578 \(\pm\) 0.004 mm (Legend Mini and Inspire Ice brackets) and 0.0578 \(\pm\) 0.002 mm (Damon Q2 self-ligating). Considering the minimum and maximum variation in the measured height as a percentage of the nominal height, there was a range from \(-0.36\%\) (IH3 DB1 and IH3 DB2) to 4.30% (Primo, Legend Mini, Carriere SLX 3D and Inspire Ice) (Table 3).  
Considering each individual type of bracket, there was a statistically significant difference between the real, measured slot height and the nominal, declared slot height (\(p<0.05\)) for all the bracket samples investigated, with the exception of IH3 DB1 (\(p=1\)) and IH3 DB2 (\(p=0.317\)) (Table 3). In other words, the 3D-printed brackets presented the greatest accuracy in terms of slot height. Comparing the four different groups of brackets (Group 1: metal, conventional; Group 2: metal, self-ligating; Group 3: ceramic; and Group 4: IH3D), the Kruskal-Wallis test revealed statistically significant differences in slot height accuracy (H3 = 43.994, \(p<0.001\), n = 70) (Figure 3). Subsequent pairwise comparisons showed significant differences between the following pairings: Group 1 vs. Group 4 (\(p<0.01\)), Group 2 vs. Group 4 (\(p<0.01\)), and finally, Group 3 vs. Group 4 (\(p<0.01\)) (Table 4).  
\begin{table}
\begin{tabular}{l c} \hline \hline  & **Type of Bracket** & \(p\)**-Value** \\ \hline Primo SWM & 0.18 \\ \hline Legend Mini & 0.157 \\ \hline Damon Q2 & 0.157 \\ \hline Carriere SLX 3D & 0.157 \\ \hline Inspire ICE & 0.157 \\ \hline IH3 DB 1 & 0.157 \\ \hline IH3 DB 2 & 1.0 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Analysis of the repeatability of measurements by [PERSON]’s non-parametric test (\(p<0.05\)).  
Figure 3: Accuracy of slot height in the various groups.  
\begin{table}
\begin{tabular}{c c c c c c c c c c c c c} \hline \hline  & **Type of** & **Bracket** & **n** & **Mean** & **DS** & **Minimum** & **Maximum** & **CL (95\%)** & **SE** & **Minimum** & **Maximum** & **Percentage** & **Percentage** \\  & **Bracket** & **n** & **(mm)** & **(mm)** & **Value** & **(mm)** & **(mm)** & **(mm)** & **(mm)** & **Variation** & **Variation** & **Variation** & **_p-Value_ \\ \hline  & Primo & SWM & 10 & 0.571 & 0.007 & 0.564 & 0.582 & 0.543–0.601 & 0.0021 & 1.08\% & 4.30\% & 0.005 \({}^{*}\) \\ \cline{2-11}
**Group 1** & Legend & Mini & 10 & 0.578 & 0.004 & 0.572 & 0.582 & 0.549–0.607 & 0.0011 & 2.51\% & 4.30\% & 0.004 \({}^{*}\) \\ \hline  & Damon & 10 & 0.578 & 0.002 & 0.574 & 0.580 & 0.549–0.607 & 0.0007 & 2.87\% & 3.94\% & 0.005 \({}^{*}\) \\ \cline{2-11}
**Group 2** & Carrier & SLX & 10 & 0.576 & 0.005 & 0.566 & 0.582 & 0.547–0.605 & 0.0016 & 1.43\% & 4.30\% & 0.005 \({}^{*}\) \\ \hline
**Group 3** & Inspire & ICE & 10 & 0.578 & 0.004 & 0.572 & 0.582 & 0.549–0.607 & 0.0011 & 2.51\% & 4.30\% & 0.005 \({}^{*}\) \\ \cline{2-11}
**Group 4** & IH3 DB 1 & 10 & 0.558 & 0.002 & 0.556 & 0.560 & 0.530–0.586 & 0.0005 & \(-0.36\%\) & 0.36\% & 1 \\ \cline{2-11}  & IH3 DB 2 & 10 & 0.558 & 0.001 & 0.556 & 0.560 & 0.530–0.586 & 0.0004 & \(-0.36\%\) & 0.36\% & 0.317 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Descriptive analysis of each type of bracket investigated. SD: standard deviation; CL: confidence limit; SE: standard error and comparative analysis of measured and nominal slot heights for each type of bracket investigated (_p_ < 0.05 \({}^{*}\)).  
Finally, the slot height accuracy of brackets belonging to the same group (Groups 1, 2, and 4) was compared. This highlighted statistically significant differences in Group 1, the conventional metal brackets (\(p<0.001\)) (Table 5).