# Comparison of Root Parallelism in Extraction Cases Treated with Clear Aligners vs. Fixed Appliances
## 4 Results
\begin{table}
\begin{tabular}{c c c c c} \hline \hline  & Aligner & Fixed & Aligner & Fixed \\  & 47 Extraction Sites & 56 Extraction Sites & 38 Extraction Sites & 64 Extraction Sites \\ \hline Group & P\({}_{1}\) & P\({}_{1}\) & NP\({}_{1}\) & NP\({}_{1}\) \\ \hline P\({}_{2}\) & 26 (55.3\%) & 38 (69.1\%) & 17 (44.7\%) & 35 (55.6\%) \\ NP\({}_{2}\) & 21 (44.7\%) & 18 (30.9\%) & 21 (55.3\%) & 29 (44.4\%) \\ Total & 47 (100\%) & 56 (100\%) & 38 (100\%) & 64 (100\%) \\ \hline \hline \end{tabular}
\begin{tabular}{c c c c c} \hline \hline  & Aligner (\(n=28\)) & Fixed (\(n=30\)) & & \\  & T3–T5 Angulation & & & \\  & 85 Extraction Sites & 120 Extraction Sites & & \\ \hline Variable & Count (Percentage) & Count (Percentage) & \(\chi^{2}\) & \(df\) & \(p\) \\ \hline SP & 43 \({}_{\text{a}}\) (50.6\%) & 74 \({}_{\text{a}}\) (61.7\%) & & \\ AC & 5 \({}_{\text{a}}\) (5.9\%) & 18 \({}_{\text{b}}\) (15.0\%) & & \\ AD & 37 \({}_{\text{a}}\) (43.5\%) & 28 \({}_{\text{b}}\) (23.3\%) & & \\ Total & 85 (100\%) & 120 (100\%) & 11.157 & 2 & 0.004 ** \\ \hline \hline \end{tabular} (1) SP, satisfactory parallelism; AC, apical convergence; AD, apical divergence. (2) The subscript letters a and b represent a subset of the categories between groups. Identical subscripts indicate no statistically significant difference between groups. At the level of 0.05, there is no significant difference in proportion between groups. (3) ** Statistically significant at \(p<0.01\).  
\end{table} 
Table 3: Comparison of the difference in the root-angulation categories of the canines and the second premolars after treatment (chi-square test). \begin{table}
\begin{tabular}{c c c c} \hline \hline  & Aligner & Fixed & Aligner & Fixed \\  & 47 Extraction Sites & 56 Extraction Sites & 38 Extraction Sites & 64 Extraction Sites \\ \hline Group & P\({}_{1}\) & P\({}_{1}\) & NP\({}_{1}\) & NP\({}_{1}\) \\ \hline P\({}_{2}\) & 26 (55.3\%) & 38 (69.1\%) & 17 (44.7\%) & 35 (55.6\%) \\ NP\({}_{2}\) & 21 (44.7\%) & 18 (30.9\%) & 21 (55.3\%) & 29 (44.4\%) \\
47 (100\%) & 47 (100\%) & 56 (100\%) & 38 (100\%) & 64 (100\%) \\ \hline \hline \end{tabular}
\begin{tabular}{c c c c c c} \hline \hline  & Aligner (\(n=28\)) & Fixed (\(n=30\)) & & & \\  & T3–T5 Angulation & & & \\  & 85 Extraction Sites & 120 Extraction Sites & & \\ \hline Variable & Count (Percentage) & Count (Percentage) & \(\chi^{2}\) & \(df\) & \(p\) \\ \hline SP & 43 \({}_{\text{a}}\) (50.6\%) & 74 \({}_{\text{a}}\) (61.7\%) & & & \\ AC & 5 \({}_{\text{a}}\) (5.9\%) & 18 \({}_{\text{b}}\) (15.0\%) & & & \\ AD & 37 \({}_{\text{a}}\) (43.5\%) & 28 \({}_{\text{b}}\) (23.3\%) & & \\ Total & 85 (100\%) & 120 (100\%) & 11.157 & 2 & 0.004 ** \\ \hline \hline \end{tabular} (1) SP, satisfactory parallelism; AC, apical convergence; AD, apical divergence. (2) The subscript letters a and b represent a subset of the categories between groups. Identical subscripts indicate no statistically significant difference between groups. At the level of 0.05, there is no significant difference in proportion between groups. (3) ** Statistically significant at \(p<0.01\).  
\end{table} 
Table 2: Comparison of the root-parallelism percentages between the canine and the second premolar after treatment (chi-square test). Figure 2: Root-angulation categories of canines and second premolars after treatment between the aligner and fixed appliance with regard to nonparallel angulation. The aligner mainly showed apical divergence (AD), while the fixed appliance mainly showed apical convergence (AC). were used, non-tipping and mesial tipping accounted for the vast majority, which indicated that the dental crown of the maxillary molars had a tendency toward mesial inclination. In comparison, the mandibular first molars mainly showed non-tipping and distal tipping for both appliances, and the mandibular second molars mainly showed non-tipping in the clear aligner treatment, while they showed non-tipping and distal tipping in the fixed appliance treatment (Table 6). during treatment with aligners, especially in the cases of second premolar extraction.