## 3 Results  
Our analysis included 43 patients (10 men and 33 women; age range: 18-44 years; mean age: 28.8 \(\pm\) 11.2 years). ICC was measured twice by the same examiner at 14-day intervals. The ICCs (1.1) for cortical bone thickness on the successful and unsuccessful sides were 0.988 and 0.993, respectively. Likewise, the ICC (1.1) values for alveolar bone density on the successful and unsuccessful sides were 0.999 and 0.999, respectively. These results confirmed the validity of the measurements. Table 1 and Table S1 present the descriptive statistics for the successful and unsuccessful sides. The cortical bone thickness was 1.01 \(\pm\) 0.27 mm on the successful side and 0.93 \(\pm\) 0.27 mm on the unsuccessful side without a significant difference. In addition, Grp. 1 (0.71 \(\pm\) 0.11 mm, range: 0.47-0.85 mm) had 31 (successful: 11, unsuccessful: 20) sides, Grp. 2 (0.97 \(\pm\) 0.054 mm, range: 0.86-1.05 mm) had a total of 27 (successful: 17, unsuccessful: 10) sides, and Grp. 3 (1.27 \(\pm\) 0.20 mm, range: 1.07-1.78 mm) had a total of 28 (successful: 15, unsuccessful: 13) sides (Table S2). There was no significant correlation between mini-screw stability and cortical bone thickness (Table 2). The bone density was 1317.89 \(\pm\) 332.23 mg/cm\({}^{3}\) on the successful side and 1059.64 \(\pm\) 202.64 mg/cm\({}^{3}\) on the unsuccessful side (Table S1). It was significantly higher on the successful side than on the unsuccessful side. Meanwhile, Grp. 1 (891.72 \(\pm\) 110.44 mg/cm\({}^{3}\), range: 674.7-1073.1 mg/cm\({}^{3}\)) had 29 sides (successful: 13, unsuccessful: 16); Grp. 2 (1149.22 \(\pm\) 46.66 mg/cm\({}^{3}\), range: 1078.6-1228.9 mg/cm\({}^{3}\)), 29 (successful: 9, unsuccessful: 20) sides; and Grp. 3 (1506.65 \(\pm\) 238.91 mg/cm\({}^{3}\), range: 1229.4-1910.3 mg/cm\({}^{3}\)), 28 (successful: 21, unsuccessful: 7) sides (Table S2). The regression analysis shows there was no significant correlation between mini-screw stability and bone density (Table 2). As for the habitual chewing side, 39 out of 43 patients had a habitual chewing side, while 4 had no chewing preference. Of the 39 patients with a habitual chewing side, 27 had a successful mini-screw on the habitual chewing side, while 12 had an unsuccessful mini-screw on the habitual chewing side. There was a significant association between screw stability and habitual chewing side (Table 2). Compared to the preferred side, the non-preferred side had a 2.25 (95% CI = 1.14-4.442) times significantly higher PR for failure. \begin{table}
\begin{tabular}{c c c c} \hline \hline  & **Success** & **Unsuccessful** & **Total (n)** \\ \hline Habitual chewing (n) & 43 & 43 & 86 \\ Preferred side (\%) & 69.2 & 30.8 & 39 \\ Non-preferred side (\%) & 30.8 & 69.2 & 39 \\ No preference (\%) & 50 & 50 & 8 \\ \hline Cortical bone thickness (n) & 43 & 43 & 86 \\ Grp. 1 (\%) & 35.5 & 64.5 & 31 \\ Grp. 2 (\%) & 63 & 37 & 27 \\ Grp. 3 (\%) & 53.6 & 46.4 & 28 \\ \hline Bone density (n) & 43 & 43 & 86 \\ Grp. 1 (\%) & 44.8 & 55.2 & 29 \\ Grp. 2 (\%) & 31 & 69 & 29 \\ Grp. 3 (\%) & 75 & 25 & 28 \\ \hline Insertion site (n) & 43 & 43 & 86 \\ Between U5 and U6 (\%) & 50 & 50 & 76 \\ Between U6 and U7 (\%) & 50 & 50 & 10 \\ \hline Years of experience (n) & 43 & 43 & 86 \\ Grp. 1 (\%) & 50 & 50 & 44 \\ Grp. 2 (\%) & 50 & 50 & 16 \\ Grp. 3 (\%) & 50 & 50 & 26 \\ \hline \hline \end{tabular} Abbreviations: U5, upper second premal; U6, upper first molar; U7, upper second molar.  
\end{table} 
Table 1: Cross table with comparison of the successful and unsuccessful sides in patients with unilateral mini-screw failure. This association remained significant after all variables were included in the same model (PR = 2.22, 95% CI = 1.12-4.41). Furthermore, the mini-screw was inserted between the second premolar and first molar in 38 patients and between the first and second molars in 5 patients. There was no significant correlation between screw stability and the implantation site (Tables 1 and 2).