Biomechanical concept of Aligners: A review

Even when aligners move teeth effectively, they operate on displacement-driven mechanics rather than force-driven mechanics. As a result, their moment-to-force ratios and patterns of force application differ from those observed in fixed orthodontics. In this short video, I review the concept of the moment-to-force ratio and apply it to aligner mechanics, highlighting why achieving high M/F ratios with thermoformed aligners can be challenging. This limitation may explain the increased incidence of uncontrolled tipping in complex cases and the presence of unwanted side effects when couples are not applied consistently through the aligner system. These biomechanical constraints justify the frequent use of attachments in thermoformed aligner therapy. However, they also open the door to innovations—such as active memory polymers in workflows like LuxCreo that may allow for reduced attachment use while maintaining biomechanical control. I welcome your feedback and suggestions on both the concepts presented and ways to improve these videos. Read more on my blog: https://discoverortho.com/