# Evaluation of Tooth Movement Accuracy with the F22 Aligner System: A Retrospective Study
## 4 Discussion
As for rotation, lower predictability was found for the canines, both maxillary and mandibular, and the mandibular premolars (range 40.6-45.1%, n = 445), whereas the rotation of the mandibular incisors (range 58.4-62.8%, n = 307), maxillary incisors and maxillary premolars (range 49.5-53.9%, n = 472) was more predictable. These results seem to be due to the coronal morphology of the rounded teeth, which do not lend themselves to derotation with CAs, as reported by [PERSON] [42]. The application of grip points does not seem to be detrimental in this regard, as reported by [PERSON] et al. [7], and in fact would seem to increase the predictability of mandibular incisor rotation \(>\) 20\({}^{\circ}\), although the number of observations was limited (n = 20). Nevertheless, the same benefit was seen for the \(>\)20\({}^{\circ}\) rotation of the maxillary incisors and premolars (from 49.5 to 53.9% to 58.4 to 62.8%, n = 88), so clinicians should consider their application in these cases. A further objective of the study was to evaluate the influence of age and gender on F22 Aligner system accuracy. Age did seem to have an influence on either inclination or angulation accuracy. For both, there was a relatively lower predictability in the 13-23.5-year group than in the intermediate age group (23.5-33.5 years for inclination and 23.5-53.5 years for -angulation), in which predictability was also greater than the older age group (33.5-64 years for inclination and 53.5-64 years for angulation). The same trend was found for rotation, with the F22 Aligner system being more predictable in the intermediate age group than in both the younger and older groups. This trend contrasts with that reported by [PERSON] et al. with the Invisalign system, as they found an S-shaped cubic relationship between age and the percentage movement obtained, which becomes quadratic and U-shaped in women and more linear in men [43]. Those authors recorded a lower predictability of movements in intermediate age, the opposite trend to that which we, like both [PERSON] et al. and [PERSON] et al., found [44; 45]. A potential explanation for the latter case could be the joint effect of biological response, which is more favorable in younger patients [46]., and compliance, which is usually greater in adults than in adolescents and pre-adolescents [47]. That being said, [PERSON] et al. investigated a sample that was four times lesser than that with respect to the current study, and they investigated the Invisalign system [43]. Another interesting observation was the gender difference found in the older group with regard to rotation. Specifically, a greater percentage of prescribed rotation was achieved in females (44.7-49.6%, n = 366) than in males (34.9-39.8%, n = 109), likely due to greater compliance by females [48]. Moreover, in females the predictability of movements increased with advancing age, while in males the trend found was precisely the opposite. This effect could be due to elderly females having a lower mineralized bone component, with a decrease in bone quality (osteoporosis) and consequently reduced resistance to orthodontic movement. In males, on the other hand, the opposite condition would be more frequent, i.e., a reduction in the clastic component (osteoporosis) [43]. As for intra-arch widths, F22 aligners demonstrated adequate expansive capacity, with average imprecision that was less than 1 mm in all cases. The only statistically significant difference between prescribed (T1) and achieved movement (T2) in this regard was the inter-premolar distance at the mandibular first premolars. This may be due to the morphology of the mandibular first premolars, which have a reduced crown height on the lingual thrust side [41], but in any case, the difference may be considered clinically minimal (0.24 mm). These conclusions are comparable with those by both [PERSON] et al. and [PERSON] et al.