# Predictability of Maximly Expansion with Invisalign(r) First: Treatment Planning vs. Outcome
## 4 Discussion
According to [PERSON] et al., the average accuracy for cuspid level expansion movements is 82.9%, while for gingival margin-level expansion it is 62.7% [15]. These results are in line with [PERSON] et al., who stated that the overall accuracy of expansion treatment with Invisalign(r) is 70%, regardless of the type of tooth [16]. [PERSON] and [PERSON] reported significant differences between the planned and achieved expansion and observed a predictability that ranged from 68% to 79% for crown movements, while the predictability of bodily movement for the first upper molar was 36% [17]. Limited studies in the literature have evaluated maxillary expansion with the Invisalign(r) First protocol. In the investigation conducted by [PERSON] et al., a consistent amount of body expansion for amines, deciduous molars, and first permanent molars was observed. Molar inclination was also assessed due to its correlation with potential periodontal issues and was found to be comparable to that achievable with other traditional expansion techniques. It was speculated that the Invisalign(r) First system could lead to a physiological adaptation similar to that achieved with slow maxillary expanders [18]. [PERSON] et al. compared the effectiveness and efficiency of clear aligners and 2 \(\times\) 4 fixed appliances in correcting maxillary incision position irregularities in mixed dentition. Clear aligners and 2 \(\times\) 4 mechanics showed similar effectiveness and efficiency in correcting maxillary incision positions in mixed dentition. The choice of appliance should be guided by the preferences of the orthodontist and the patient's family [19]. Another comparison of different techniques was made in the retrospective study by [PERSON] et al., with the aim to analyze morphological changes in the upper arch in mixed dentition after two expansion protocols, the Invisalign(r) First system, and rapid maxillary expansion (RME). Through morphometric analysis, it was found that Invisalign(r) First induced changes in the shape of the upper arch during expansion, while RME did not [20]. Treatment with aligners resulted in an improvement in the shape of the maxillary arch, while RME maintained the initial triangular shape. Therefore, it was observed that RME widened the palate and tilted the upper first molars more vestibular, while clear aligners caused a greater increase in canine width. In addition, Invisalign(r) First appears to be more efficient than RME in terms of expansion at the anterior segment of the arch, with better control of molar tipping and greater palatal width increase. The prospective cohort study by [PERSON] et al. compared the dento-skeletal effects of using the Invisalign(r) First system with Hass-type appliances [21]. According to the authors, both Hass-type appliances and Invisalign(r) First could effectively expand the maxilla in mixed dentition. The Hass-type expander show significant better efficiency for dental arch expansion, while no significant difference was reported regarding arch depth. According to [PERSON] et al., with Invisalign(r) First, it is possible to expand the arches effectively without affecting molar inclination, even though the increase in the palatal surface area is not significant. [PERSON] et al. observed that interceptive treatment with Invisalign(r) is predictable and clinically effective for arch expansion, even though more sets of aligners could be required to obtain the outcome planned with the Clincheck(r) 9. Another investigation from [PERSON] et al. reported that the overall predictability of maxillary expansion with Invisalign(r) First is 62.6%; however, maxillary expansion was measured only at the cuspidal level [22]. In the present investigation, the predictability of maxillary expansion with Invisalign(r) First ranged from 45% to 67%. A lower predictability was observed when expansion was measured at the gingival margin, as a probable consequence of a more prominent tipping movement in the crown.