Anchorage Loss Evaluation during Maxillary Molars Distalization Performed by Clear Aligners: A Retrospective Study on 3D Digital Casts

Abstract

The purpose of the research was to analyze the premolar and canine anchorage loss observed during maxillary molars distalization in subjects with Class II malocclusion treated with clear aligners. A total of 49 subjects (27 females, 22 males, mean age 14.9 ± 6 years) derived from the Department of Orthodontics of the University of Rome “Tor Vergata” were selected according to the following inclusion criteria: Caucasian ancestry, Class I or minor Class II skeletal malocclusion, Class II occlusal relationship, permanent dentition with fully erupted second molars, and good compliance with aligners. Each patient underwent the same non-extractive molar distalization protocol with no auxiliaries other than attachments and Class II elastics. Prior to treatment (T1) and at the end of the first maxillary molars distalization movement (T2), digital dental casts were taken by using an iTero intraoral scanner. Linear measurements were performed in order to evaluate the anchorage loss at the level of the second and first premolars and the canines. The statistical comparison of T2 and T1 values was obtained using a paired t-test (p < 0.05). A statistically significant distalization of the maxillary first permanent molars (2.5 mm) was observed; a slight and not significant anchorage loss of the first and second premolars was assessed, while a statistically significant mesial movement of upper canines (1.33 mm) was highlighted. Clear aligner treatment was effective in obtaining a molar distalization movement. However, during molar distalization, an anchorage loss at the level of upper canines was observed.