Anchorage loss in maxillary premolar and anterior teeth during maxillary molar distalization in clear aligner treatment

Introduction: This study aimed to assess the anchorage loss in the premolars and anterior teeth during maxillary molar distalization using clear aligners combined with miniscrews, provided that no virtual movement was designed for these teeth. Methods: A total of 38 maxillary quadrants of 21 participants were analyzed. Digital models were gathered pre-treatment and before the designed initial movement of the premolars and anterior teeth and superimposed using the palatal rugae area. The predicted, achieved, and unachieved molar distal movements, as well as the linear, anterior, and lateral movements of premolars and actual movement of anterior teeth, were compared and analyzed. Results: Approximately 0.8 mm of maxillary molar distalization was unachieved. The unachieved distalization of the first and second molars (0.53 ± 0.41 mm and 0.82 ± 0.64 mm, respectively), the lateral and anterior movement of the first (0.14 ± 0.28 mm and 0.32 ± 0.37 mm, respectively) and second (0.25 ± 0.31 mm and 0.29 ± 0.32 mm, respectively) premolars were significantly greater than 0. There were significant positive linear regression relationships between the unachieved distal movement of molars and the anterior movement of premolars, as well as between the unachieved distal movement of molars and the actual movement of the anterior teeth (P <0.05). In addition, significant positive linear regression relationships were found between the anterior movement of the premolars and the actual movement of the anterior teeth. Conclusions: Significant anterolateral movement tendencies were observed in premolars. Premolar anterior anchorage loss may mediate the interactions between molar distalization and anchorage loss in the anterior teeth.