Impact of Molar Distalization with Clear Aligners on Periodontal Ligament Stress and Root Resorption Risk: A...

Background/Objectives: Molar distalization with clear aligners is increasingly used for Class II malocclusions, yet the associated periodontal ligament (PDL) stress and potential root resorption risk remain unclear. Three-dimensional finite element analysis (3D FEA) provides insight into these factors, but variations in attachments and anchorage strategies merit systematic evaluation. To determine whether molar distalization with clear aligners exceeds the PDL stress thresholds for root resorption and to assess how different attachments and anchorage methods influence stress distribution. Methods: In accordance with the PRISMA 2020 guidelines, four electronic databases were searched without language or date restrictions. Studies were included if they (1) employed 3D FEA, (2) analyzed PDL stress during aligner-based molar distalization, and (3) assessed root resorption risk or stress thresholds. Two reviewers independently screened and extracted data, yielding eight studies. Results: Attachments lowered PDL stress and distributed forces more evenly, reducing root resorption risk compared with no attachment cases. Micro-implants shifted stress to molars and protected anterior teeth; palatal mini-screws achieved greater distalization but higher stress, requiring caution, while buccal mini-screws showed lower stress in first premolar roots. Placing a mini-screw between first and second molars yielded the lowest, most uniform stress. Class II elastics-with precision cuts-demonstrated low compressive stress and improved anchorage, although some resorption risk persisted in maxillary anteriors. Conclusions: Clear aligner-based molar distalization can elevate PDL stress to potentially resorptive levels. Although attachments, micro-implants, and Class II elastics improve stress distribution and lessen root resorption risk, it is not fully eliminated. Careful, individualized treatment planning remains essential, and further clinical validation is needed to establish definitive guidelines.