# Transfer Accuracy of Two 3D Printed Trays for Indirect Bracket Bonding--An In Vitro Pilot Study
## 3 Results
### Bracket Bonding Accuracy (Linear Measurements)
#### 3.2.1 Impact of Crowding  
Linear discrepancies were higher in the no crowding (median: 0.14 mm, Q1-Q3: \(-\)0.06-0.30 mm) compared to the crowding (median: 0.10 mm, Q1-Q3: \(-\)0.06-0.23 mm) group (\(p<0.001\)). When splitting the data to assess the impact of crowding for the two types of trays and the respective tooth types, significant differences were found in occlusal/gingival direction, i.e., for hard and soft trays at front teeth (\(p=0.015\), \(p=0.001\), respectively), and for soft trays in the molar region (\(p=0.007\)). For hard trays, a significant difference was noted in buccal-oral direction at molars (\(p=0.029\)) (Table 1). Figure 7: Boxplots detailing the accuracy of bracket transfer for lingual measurements. Results are summarized for the cannines, front teeth, molars, and premolars and split up into hard/soft trays and no crowding/crowding. A positive/negative value indicates mesial/distal, buccal/oral or occlusal/gingival displacement, respectively. \begin{table}
\begin{tabular}{c c c c c c c} \hline
**Tooth Type** & **Tray** & **Measurement** & **MD** & **IQR** & **MD** & **IQR** & **\(p\)-Value** \\ \hline \multicolumn{7}{c}{No crowding (LII \textless{}3)} & Crowding (LII \textgreater{}7) & Crowding vs. no crowding \\ \hline Hard & Angulation (\({}^{\circ}\)) & 4.02 & 1.33 & 5.07 & 2.88 & 0.529 \\ \hline Soft & Angulation (\({}^{\circ}\)) & 1.86 & 2.07 & 2.04 & 2.59 & 0.445 \\ \hline \multicolumn{7}{c}{\(p\)-value hard vs. soft tray (r)} & \textless{}0.001 (0.58) *** & \textless{}0.001 (0.56) *** & \\ \hline Hard & Buccal/oral (mm) & 0.24 & 0.2 & 0.21 & 0.09 & 0.201 \\ \hline Soft & Buccal/oral (mm) & 0.27 & 0.29 & 0.23 & 0.18 & 0.698 \\ \hline \multicolumn{7}{c}{\(p\)-value hard vs. soft tray (r)} & 0.968 & \multicolumn{3}{c}{0.327} \\ \hline Hard & Mesial/distal (mm) & 0.04 & 0.54 & 0.06 & 0.24 & 0.989 \\ \hline Soft & Mesial/distal (mm) & 0.06 & 0.45 & 0.07 & 0.38 & 0.678 \\ \hline \multicolumn{7}{c}{\(p\)-value hard vs. soft tray (r)} & 0.495 & \multicolumn{3}{c}{0.841} \\ \hline Hard & Oclusal/gingival (mm) & 0.16 & 0.37 & 0.15 & 0.24 & 0.799 \\ \hline Soft & Oclusal/gingival (mm) & 0.10 & 0.29 & 0.04 & 0.21 & 0.211 \\ \hline \multicolumn{7}{c}{\(p\)-value hard vs. soft tray (r)} & 0.398 & \multicolumn{3}{c}{0.005 (0.45) **} \\ \hline Hard & Torque (\({}^{\circ}\)) & 4.32 & 2.63 & 4.7 & 3.32 & 0.461 \\ \hline Soft & Torque (\({}^{\circ}\)) & 3.52 & 3.04 & 2.51 & 5.04 & 0.341 \\ \hline \multicolumn{7}{c}{\(p\)-value hard vs. soft tray (r)} & 0.289 & \multicolumn{3}{c}{0.096} \\ \hline Hard & Angulation (\({}^{\circ}\)) & 1.96 & 1.7 & 2.46 & 2.25 & 0.053 \\ \hline Soft & Angulation (\({}^{\circ}\)) & 1.59 & 1.19 & 1.29 & 1.64 & 0.178 \\ \hline \multicolumn{7}{c}{\(p\)-value hard vs. soft tray (r)} & 0.308 & \multicolumn{3}{c}{0.001 (0.39) **} \\ \hline Hard & Buccal/oral (mm) & 0.32 & 0.15 & 0.27 & 0.14 & 0.083 \\ \hline Soft & Buccal/oral (mm) & 0.30 & 0.30 & 0.3 & 0.24 & 0.722 \\ \hline \multicolumn{7}{c}{\(p\)-value hard vs. soft tray (r)} & 0.065 & \multicolumn{3}{c}{0.923} \\ \hline Hard & Mesial/distal (mm) & 0.09 & 0.38 & 0.05 & 0.15 & 0.607 \\ \hline Soft & Mesial/distal (mm) & 0.06 & 0.22 & 0.05 & 0.26 & 0.624 \\ \hline \multicolumn{7}{c}{\(p\)-value hard vs. soft tray (r)} & 0.384 & \multicolumn{3}{c}{0.769} \\ \hline Hard & Oclusal/gingival (mm) & 0.26 & 0.43 & 0.02 & 0.32 & 0.015 (0.27) * \\ \hline Soft & Oclusal/gingival (mm) & 0.12 & 0.45 & \(-0.07\) & 0.37 & 0.001 (0.36) * \\ \hline \multicolumn{7}{c}{\(p\)-value hard vs. soft tray (r)} & 0.554 & \multicolumn{3}{c}{0.068} \\ \hline Hard & Torque (\({}^{\circ}\)) & 2.31 & 2.01 & 3.28 & 2.49 & 0.028 (0.25) * \\ \hline Soft & Torque (\({}^{\circ}\)) & 1.64 & 2.34 & 1.54 & 2.07 & 0.439 \\ \hline \multicolumn{7}{c}{\(p\)-value hard vs. soft tray (r)} & 0.312 & \multicolumn{3}{c}{\textless{}0.001 (0.41) ***} \\ \end{tabular}
\end{table} 
Table 1: Descriptive statistics for the subgroup analysis of the bracket transfer accuracies for linear and angular measurements.