Although the origin of the first treatments with clear aligners is dated back to 1945 when Dr. Kesling published his article on the dental positioner, the digital technological advancement of the last twenty years has been responsible for making invisible orthodontics capable of addressing complex orthodontic malocclusions, not only mild to moderate crowding or diastema closures as indicated in its beginnings.
Virtually all present-day invisible orthodontic systems feature versatile planning software that meets orthodontists' requirements and expectations, with research focusing on the development of new plastic materials with improved elastic, mechanical, and shape memory properties, as well as on the influence of other factors affecting aligner biomechanics, such as the design of the cut line or the thickness of the appliances.
One of the assumed concepts about clear aligners is that they alone have limitations in achieving optimal outcomes, and that the use of external auxiliary elements to the system, such as temporary skeletal anchorage devices or intermaxillary elastics, allows for improved control of tooth movement and proper management of complex cases like extraction space closures or distalizations.
The aligner systems themselves, such as the Invisalign system with its "SmartForce features", have also incorporated internal auxiliary elements that can be attached to the teeth (such as attachments, power arms, or buttons) or integrated into the aligner (bite ramps, indentations, pressure points, precision cuts, integrated buttons...).
Thanks to the use of composite attachments, it is possible to better control the point of force application closer to the center of resistance, enabling more precise tooth movement or improving the retention of the aligners.
However, many biomechanical applications of attachments are still unknown, and innovations in invisible orthodontic technology require a constant update in the theoretical framework and established paradigms.
Therefore, the objective of this narrative review was to gather, translate, and analyze all articles related to the configuration and biomechanics of composite attachments in clear aligner treatment, in order to assist orthodontists in updating their knowledge in the field.
