ABSTRACT
Objective To study the effects of different root control attachment on root control and periodontal ligament （PDL） stress during canine distal translation in plastic aligner-based orthodontic treatment. Methods Through three-dimensional (3D) finite element technology, 11 models composed of 4 attachments and 3 kinds of loading were established. Namely, attachment A: no attachments; attachment B: traditional vertical rectangular attachment; attachment C: 1/4 spherical double optimized attachment; attachment D: double optimized door arch attachment; load a: 0.15 mm distal translation of the canine; b: load a+ application of 30 N·mm counterclockwise torque to stress surface of the attachment; load c: load a+ application of 30 N·mm counterclockwise torque to the entire crown. The root control effect of distal translation of the right maxillary canine was simulated with plastic aligner under different loads. Results Displacement modes of all models were distally tipped translation. The double optimized door arch attachment showed the optimal root control effect during canine distal translation. The root control effect for two groups of double optimized attachment was better than that of traditional rectangular attachment. The effect of adding attachments on root control of the canine was better than that of applying only counterclockwise couple. The PDL stress mainly appeared in distal alveolar ridge and root apex without attachment, while the PDL stress mainly appeared in distal alveolar ridge with attachment. Conclusions The most suitable measure to improve the effect of root control during canine distal translation is to use the double optimized door arch attachment in clinic.