Enhancing the predictability of tooth movements with clear aligners-part 1: Biomechanical considerations and...

Clear aligner (CA) therapy has undergone remarkable developments over the past 2 decades, transforming from a simple alignment modality into a mainstream orthodontic treatment capable of addressing complex malocclusions. Despite these innovations, the predictability of aligner tooth movements remains one of the most challenging aspects of clinical practice. This review explains the biomechanical considerations and clinical determinant factors that underline the variability in tooth movement predictability with CAs. From a biomechanical standpoint, 3 fundamental conditions-anchorage adequacy, stress continuity, and sufficient aligner-to-tooth contact-collectively determine the accuracy with which aligner biomechanics are translated into clinical reality. This proposed anchorage-stress-contact triad provides the biomechanical rationale for evaluating aligner predictability. The predictability of aligner tooth movements is clinically governed by a multifactorial interplay among aligner-related factors (material properties and shape design), practitioner-related factors (digital setup precision, attachment design, aligner staging, and clinical monitoring), and patient-related factors (compliance and biological variability). Understanding how these determinants interact provides a comprehensive basis for interpreting inconsistencies between digitally programmed and clinically achieved outcomes, offering insights to optimize aligner tooth movements and enhance aligner treatment outcomes.