## 2 Materials and Method  
### Subjects  
A sample of thirty-nine adult patients (31 females, 8 males), treated with TADs to distalize dentition at the orthodontic department at Yonsei University Dental Hospital, Seoul, Korea, were selected as subjects in this study. In total, 28 patients had maxillary TADs to distalize the whole maxillary dentition. A total of 25 patients had mandibular TADs, whereas 14 of these 25 patients had maxillary TADs at the same time (Table 1). All patients met the following inclusion criteria: (1) patients older than 18 years at initial status, (2) intact permanent dentition including second molars, (3) without extraction of the premolars or other teeth except the third molars, (4) minimal crowding (<4 mm), (5) followed at least 1 year for post-retention, and (6) no syndrome or skeletal disharmony. The mean age at the beginning of treatment was 25.5 years (range: 18.3-32.3), and the mean treatment period was 24.5 months (range: 16-34 months). The mean period during which total arch distalization force was applied was 12.1 months (range: 6-22 months), and the mean retention period was 29.3 months (range: 14-52 months). All patients were given lingual fixed retainers between the canines and removable circumferential retainers for retention. The Yonsei Dental Hospital institutional review board (CRNo: 2-2020-0013) approved this study, and informed consent agreements were signed by the participants. The minimum sample size was calculated using G*Power 3 (Dusseldorf, Germany) with a significance level of \(p\) < 0.05 and a power of 80%, and it was confirmed as 25. The descriptive data of the patients are given in Table 1 and the characteristics of the patients are shown in Table 2. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Patients** & **Sex** & **Age** & **Location of** & **Duration of Force** & **Duration of** \\  & & & **TADs Placement** & **Application** & **Retention** \\ \hline
1 & F & 25 Y 2 M &
\begin{tabular}{c} \#15-16 B, \#25-26 B \\ Lt. R, Rt. R \\ \#16-17 B, \#25-26 B \\ \#35-36 B, \#45-46 B \\ \end{tabular} & 15 M & 30 M \\
2 & F & 18 Y 5 M &
\begin{tabular}{c} \#15-16 B, \#25-26 B \\ \#35-36 B, \#45-46 B \\ \#15-16-17 B, \#25-26-27 B \\ \#36-37 B, \#46-47 B \\ \end{tabular} & 9 M & 21 M \\
3 & F & 25 Y 2 M &
\begin{tabular}{c} \#15-16-17 B, \#25-26-27 B \\ \#35-36 B, \#45-46 B \\ \end{tabular} & 14 M & 26 M \\
4 & F & 32 Y 3 M &
\begin{tabular}{c} \#16-17 B, \#26-27 P \\ \#35-36 B, \#45-46 B \\ \end{tabular} & 18 M & 19 M \\
5 & F & 25 Y 6 M &
\begin{tabular}{c} \#15-16 B, \#25-26 B \\ \#36-37 B, \#46-47 B \\ \end{tabular} & 11 M & 48 M \\
6 & M & 28 Y 6 M &
\begin{tabular}{c} \#15-16-17 B, \#25-26-27 B \\ \#35-36 B, \#45-46 B \\ \end{tabular} & 22 M & 43 M \\
7 & F & 25 Y 2 M &
\begin{tabular}{c} \#16-17 B, \#25-27 B \\ \#35-36 B, \#45-46 B \\ \end{tabular} & 16 M & 22 M \\
8 & F & 24 Y 11 M &
\begin{tabular}{c} \#15-16-17 B, \#25-26-27 B \\ \#36-37 B, \#46-47 B \\ \end{tabular} & 12 M & 24 M \\
9 & M & 24 Y 9 M &
\begin{tabular}{c} \#15-16 B, \#25-26 B \\ \#15-16-17 B, \#25-26-27 B \\ \end{tabular} & 8 M & 24 M \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Descriptive distribution of the patients. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Patients** & **Sex** & **Age** & \multicolumn{2}{c}{**Location of**} & **Duration of Force** & **Duration of** \\  & & & **TADs Placement** & **Application** & **Retention** \\ \hline
10 & F & 28 Y 4 M & \#15-16 B, \#25-26 B & 17 M & 36 M \\
11 & F & 18 Y 7 M & \#15-16 B, \#25-26 B & 13 M & 27 M \\  & & & \#35-36 B, \#45-46 B & & \\
12 & F & 28 Y 3 M & \#15-16 P, \#25-26 P & 12 M & 24 M \\
13 & F & 29 Y 7 M & Midpalatal & 9 M & 18 M \\  & & & \#36-37 B, \#46-47 B & & \\  
& 22 Y 9 M & \#36-37 B, \#46-47 B & 19 M & 39 M \\ \hline \end{tabular}
\end{table} 
Table 1: _Cont._