Importance of Attachments in Treatment with Clear Aligners: A Narrative Review: Attachments in clear aligner therapy (running title)

Abstract

Objectives At present, clear aligners are widely used for treatment of complicated orthodontic cases such as severe crowding, and class II or III malocclusion. However, some movements such as extrusion, derotation, torque formation, or closing of large spaces are still challenging to perform with clear aligners. Resin attachments, elastics, some certain gingival margin designs, and thermopliers have been suggested to increase the predictability of tooth movement with aligners. At present, it is well understood that attachments are a non-negligible part of treatment with aligners. Different experimental and clinical studies have assessed these features, but there is still no exact guideline for indications of each feature, or their effectiveness. Thus, the aim of this study was to review in vitro and clinical studies and to discuss the best approach to achieve more predictable tooth movement with clear aligners. Methods Different databases including PubMed, Google Scholar and Scopus were searched and articles evaluating retention of aligners, different approaches to increase retention, and characteristics of attachments were included in this review. Results 39 experimental and clinical studies were included for this narrative review. Conclusion The composition of aligner material probably plays a more important role than material thickness in retention. However, more comprehensive studies should be performed to confirm this. There is no doubt upon the necessity of using attachments to increase the retention of aligners and predictability of tooth movements. It seems that rectangular attachments are more efficient than ellipsoid ones. Also, quarter-sphere shaped attachments are preferred for rotational and root movements