Effectiveness of single versus double attachments in the correction of premolar rotation in adult patients: A retrospective study

OBJECTIVE: Rotational movements, particularly in premolars, remain among the most challenging tooth movements to achieve with clear aligners. This study aims to evaluate the clinical effectiveness of single versus double attachments in the correction of premolar rotation using clear aligner therapy. METHODS: A total of 100 patients with premolar rotation who underwent clear aligner therapy between 2022 and 2025 were screened. Only those who met the predefined inclusion and exclusion criteria were included in the final analysis. Digital impressions at baseline (T0) and completion of the rotational movement (T1) were analyzed using 3D software to evaluate premolar rotational movement. Intergroup comparisons were performed using the Mann-Whitney U test, while intragroup comparisons between expected and achieved outcomes used the Wilcoxon signed-rank test. RESULTS: Of the 29 eligible patients, 47 rotated premolars were analyzed. Significant differences between predicted and achieved premolar rotation were observed in both groups (P<0.001). The single-attachment group showed a predicted 14.31°±5.81° versus an achieved 5.41°±4.88°, while the double-attachment group had predicted 18.02°±7.41° versus an achieved 11.00°±6.88°. Notably, the double attachment group achieved greater rotational correction, P<0.01, and higher treatment efficiency, median 60.61%, P<0.01. CONCLUSIONS: Clear aligners demonstrate limited predictability for correcting premolar rotation. Double attachments significantly improve rotational outcomes and treatment efficiency compared with single attachments. These findings support the clinical use of double attachments for challenging premolar rotations. ETHICAL APPROVAL: This study was approved by the Ethics Committee of Xiangya Stomatological Hospital, Central South University (Approval No. LYEC2025-K0027).