## 4 Discussion
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multicolumn{2}{c}{**Within-Group Comparisons**} & \multicolumn{2}{c}{**Mean (mm)**} & \multirow{2}{*}{**72-T3 (mm)**} & \multirow{2}{*}{**95\% CI**} & \multirow{2}{*}{\(p\)-Value**} & \multicolumn{2}{c}{**72-T3 (\%)**} & \multicolumn{2}{c}{**\% Relative**} \\ \multicolumn{2}{c}{**T2 – T3**} & & \(\pm\) SD & & & & & **Predictability:** & **(T3-T1 \(\times\) 100/T2-T1)** \\ \hline \multirow{8}{*}{Bilateral Crossbite} & \multirow{2}{*}{Canine} & T2: PRED & 34.05 \(\pm\) 2.04 & \multirow{2}{*}{0.77} & \multirow{2}{*}{0.17 to 1.37} & \multirow{2}{*}{0.011} & \multirow{2}{*}{2.31\%} & \multirow{2}{*}{54.17\%} \\ \cline{3-3} \cline{5-8}  & T3: POST & 33.28 \(\pm\) 1.89 & & & & & & \\ \cline{2-8}  & 1 st & T2: PRED & 41.94 \(\pm\) 2.60 & \multirow{2}{*}{0.73} & \multirow{2}{*}{\(-\)0.01 to 1.47} & \multirow{2}{*}{0.053} & \multirow{2}{*}{1.77\%} & \multirow{2}{*}{82.28\%} \\ \cline{3-3} \cline{5-8}  & Premolar & T3: POST & 41.21 \(\pm\) 2.69 & & & & & \\ \cline{2-8}  & 2 nd & T2: PRED & 47.18 \(\pm\) 3.06 & \multirow{2}{*}{0.80} & \multirow{2}{*}{\(-\)0.20 to 1.80} & \multirow{2}{*}{0.145} & \multirow{2}{*}{1.70\%} & \multirow{2}{*}{86.02\%} \\ \cline{3-3} \cline{5-8}  & Premolar & T3: POST & 46.39 \(\pm\) 3.17 & & & & & \\ \cline{2-8}  & 1 st & T2: PRED & 51.03 \(\pm\) 3.44 & \multirow{2}{*}{0.74} & \multirow{2}{*}{\(-\)0.32 to 1.79} & \multirow{2}{*}{0.239} & \multirow{2}{*}{1.45\%} & \multirow{2}{*}{84.40\%} \\ \cline{3-3} \cline{5-8}  & 1 st & T3: POST & 50.30 \(\pm\) 3.20 & & & & & \\ \hline \multirow{8}{*}{Single-Tooth Crossbite} & \multirow{2}{*}{Canine} & T2: PRED & 33.53 \(\pm\) 1.85 & \multirow{2}{*}{0.33} & \multirow{2}{*}{\(-\)0.15 to 0.80} & \multirow{2}{*}{0.243} & \multirow{2}{*}{0.99\%} & \multirow{2}{*}{75.37\%} \\ \cline{3-3} \cline{5-8}  & T3: POST & 33.20 \(\pm\) 2.10 & & & & & & \\ \cline{1-1} \cline{2-8}  & 1 st & T2: PRED & 40.99 \(\pm\) 2.63 & \multirow{2}{*}{0.32} & \multirow{2}{*}{\(-\)0.21 to 0.87} & \multirow{2}{*}{0.365} & \multirow{2}{*}{\(-\)0.53\%} & \multirow{2}{*}{90.15\%} \\ \cline{1-1} \cline{2-8}  & Premolar & T3: POST & 40.67 \(\pm\) 2.53 & & & & & \\ \cline{1-1} \cline{2-8}  & 2 nd & T2: PRED & 46.39 \(\pm\) 3.01 & \multirow{2}{*}{0.39} & \multirow{2}{*}{\(-\)0.15 to 0.94} & \multirow{2}{*}{0.213} & \multirow{2}{*}{0.85\%} & \multirow{2}{*}{89.74\%} \\ \cline{1-1} \cline{2-8}  & Premolar & T3: POST & 46 \(\pm\) 2.91 & & & & & \\ \cline{1-1} \cline{2-8}  & 1 st & T2: PRED & 51.16 \(\pm\) 3.48 & \multirow{2}{*}{0.39} & \multirow{2}{*}{\(-\)0.39 to 1.18} & \multirow{2}{*}{0.58} & \multirow{2}{*}{2.79\%} & \multirow{2}{*}{65.76\%} \\ \cline{1-1} \cline{2-8}  & T3: POST & 49.77 \(\pm\) 3.53 & & & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 4: _Cont._portion of the aligner, with losses increasing from 0.1 to 0.3 mm for every prescribed mm from incisors to premolars, and to 0.5 mm for every mm of prescribed movement for first molars. Similar results were found in the systematic review by [PERSON] et al. [23] on the efficacy of arch expansion with clear aligners. The predictability of the treatment outcome was highest for measurements at the premolar level in all crossbite groups (79.19% for the second premolar in the unilateral crossbite group, 86.02% for the second premolar in the bilateral crossbite group, and 90.15% for the first premolar in the single-tooth crossbite group). The predictability was lowest for measurements at the canine level (\(-93\%\) in the unilateral crossbite group and 54% in the bilateral group). [PERSON] et al. [1] described similar predictability results of 80.3% at the first premolar level and 81% at the second premolar level, observing the lowest predictability at the second molar level, which they attributed to the correct position of this molar in 90.4% of their series. It would be of interest to include measurements of permanent second molars in future research. [PERSON] et al.