# Predictability of Maximly Expansion with Invisalign(r) First: Treatment Planning vs. Outcome
## 4 Discussion  
The purpose of this study was the evaluation of the predictability of maxillary expansion with Invisalign(r) First. The Invisalign(r) First system, introduced by Align Technology in 2018, was designed to carry out Phase I orthodontic treatment using aligners. Phase I treatment is typically performed with arch expanders and represents interceptive treatment for growing patients. Using clear aligners, it is possible to perform simultaneous movements in all three spatial dimensions. This means it can address a range of common orthodontic issues such as dental crowding, diastema, deep overbite, open bite, and increased overjet. In addition, clear aligners offer other advantages over traditional fixed appliances, such as reducing negative effects on the periodontitis, enabling better oral hygiene, and providing a more comfortable and esthetic treatment alternative [10]. \begin{table}
\begin{tabular}{l c c c c c} \hline \hline  & **Planned Expansion** & **Achieved Expansion** & \(\Delta\) & **\%** & \(p\)**-Value** \\ \hline Deciduous canine dental width & 3.72 & 2.22 & 1.5 & 59.68\% & \(p<0.05\) \\ \hline First deciduous molars dental width & 4.37 & 2.78 & 1.5 & 63.77\% & \(p<0.05\) \\ \hline Second deciduous molars dental width & 4.5 & 3.01 & 1.48 & 66.99\% & \(p<0.05\) \\ \hline First permanent molars dental width & 4.52 & 2.51 & 2 & 55.61\% & \(p<0.05\) \\ \hline Deciduous canine gingival width & 3.59 & 1.79 & 1.8 & 49.87\% & \(p<0.05\) \\ \hline First deciduous molars gingival width & 4.22 & 2.24 & 1.98 & 53.11\% & \(p<0.05\) \\ \hline Second deciduous molars gingival width & 4.29 & 2.29 & 2 & 53.36\% & \(p<0.05\) \\ \hline First permanent molars gingival width & 4.12 & 1.86 & 2.26 & 45.16\% & \(p<0.05\) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Results from the comparison between the planned and achieved expansion. Upper arch expansion with clear aligners is one of the most discussed topics in modern orthodontics. With Invisalign(r), it is possible to expand the maxillary arch in the permanent dentition, but the increase is mainly due to tipping movements [11]. In the systematic review by [PERSON] et al. [12], it was observed that the use of aligners is recommended for simple malocclusions. Treatment with aligners is effective in aligning and leveling arches in non-growing subjects. Intrusion movement is comparable with fixed orthodontics, while the control of extrusion and rotation movements is not as predictable. The use of attachments, elastics, and IPR is essential to enhance the predictability of orthodontic movements. The results obtained by [PERSON] et al. [13] are consistent with what [PERSON] et al. stated regarding the effectiveness of maxillary arch expansion with aligners. It was observed that the mechanical behavior of the distal portion of the aligners is similar to that of traditional fixed appliances. Furthermore, the amount of overcorrection for mild and moderate cases and the aligner change interval were evaluated. For most movements, a 7-day change interval is sufficient, while for torque and rotation control, a 14-day interval is required. The systematic reviews by [PERSON] and [PERSON] and [PERSON] et al. also stated that the effectiveness of clear aligners in achieving maxillary transverse expansion is a feasible option for addressing dental crowding [11; 14]. The effectiveness of expansion is higher in the premolar area. Maximillary expansion decreases from the anterior to the posterior segments, and the presetting of sufficient buccal root torque of the posterior teeth can result in improved expansion efficiency. When planning maxillary arch expansion with Invisalign(r), it is necessary to consider overcorrection because Clincheck(r) software tends to overestimate the expansion movement compared to the clinical outcome, making movement predictability lower. There are few studies in the literature that have assessed the discrepancy between planned expansion in ClinCheck(r) and the actual results achieved with Invisalign(r) aligners in adults.