Comparison of two different distalization methods in the treatment of class II malocclusion with clear aligners

The aim of the present study was to compare the dentoskeletal effects of Class II elastic anchorage and infrazygomatic crest (IZC) miniscrew anchorage in sequential maxillary molar distalization using clear aligners. A total of 22 patients with Angle Class II malocclusion treated with clear aligners and maxillary molar distalization were included. The patients were divided into two groups based on anchorage method: Class II elastics or IZC miniscrew. Lateral cephalometric radiographs and digital models were obtained from all patients at the beginning of treatment (T0) and after distalization of the second premolars (T1). Skeletal and dental changes were assessed using cephalometric radiographs and digital maxillary models. The digital models were superimposed using the "local best fit" algorithm with Geomagic Control X software. Comparison of cephalometric measurements demonstrated significant differences between the groups in incisor mandibular plane angle (IMPA) and overbite. In the intermaxillary elastic group, the upper second molar was distalized by 1.72 ± 0.64 mm, upper first molar by 1.87 ± 0.78 mm, and upper second premolar by 1.55 ± 0.8 mm. In the IZC miniscrew group, the upper second molar was distalized by 2.24 ± 0.87 mm, upper first molar by 2.19 ± 0.74 mm and upper second premolar by 1.84 ± 0.71 mm. In both groups, greater than predicted maxillary molar intrusion was observed. In the transverse direction, the buccal movement of the maxillary first molars exceeded the planned amount in the intermaxillary elastic group, while both maxillary molars and second premolars showed greater movement than planned in the miniscrew group. No significant differences in achieved tooth movements were observed between the groups except for more distal movement and less distal rotation of the maxillary second molars in miniscrew group compared to intermaxillary group. More distal movement of the maxillary second molar was achieved with miniscrews than intermaxillary elastics. In cases where overbite reduction and control of lower incisor inclination are critical, miniscrew anchorage is more advantageous during maxillary molar distalization with clear aligners. Keywords: Class II malocclusion; Clear aligner; Distalization; Miniscrew anchorage