# Evaluation of Tooth Movement Accuracy with the F22 Aligner System: A Retrospective Study
## 2 Materials and Methods  
### Sample Selection  
The study group, retrospectively selected from the University of Ferrara Orthodontics Clinic's electronic database, consisted of adult patients with complete permanent dentition treated via CAT between 2016 and 2020. The study design was approved by the University of Ferrara Postgraduate School Ethics Committee (registration number 9/2020), and the research was conducted in conformity to the Declaration of Helsinki.  
The inclusion criteria used for the retrospective selection of patients were:  
* Class I dental malocclusion with minimal crowding (\(\leq\)3 mm) in both arches [32], treated with a series of 12-20 aligners per arch.
* No use of auxiliaries (derotation elastomeric chains, inter-arch elastics or extrusion elastics), miniscrews, cantilevers or vestibular or lingual fixed partial appliances.
* Grip points and IPR (interproximal reduction) were permitted.
* Planned derotation of rounded teeth \(\leq 20^{\circ}\) (premolars and canines) is included.
* The use of grip points positioned for derotation \(\geq 10^{\circ}\) of rounded teeth and \(>\)20\({}^{\circ}\) for mandibular incisors and maxillary lateral incisors, which have a mesiodistally narrow clinical crown. The triangular grip points were applied with the long side in the direction of force application.
* No previous or active periodontal disease at the beginning of orthodontic therapy.
* Presence of at least one posterior tooth (first or second molar) per quadrant that had not been planned to move.
* F22 Aligners were worn for 2 weeks prior to passing to the following step.
* F22 Aligner therapy completed with adequate patient compliance (20-22 h per day), as documented in a personal diary.  
This retrospective selection resulted in a final sample of 120 patients (64 female and 56 male; mean age 35.2 years \(\pm\) 7.4), starting from 254 cases affected by dental Class I Malocclusion treated via F22 Aligners. A flow chart of retrospective sample selection is graphically illustrated in Figure 1.  
Figure 1: Flow chart regarding the retrospective selection of the final sample investigated.  
Each patient expressed written consent for the use of their records for research; the setup for each case was performed by two specialists in orthodontics, experts in CAT and certified by the Italian Board of Orthodontic Aligners.  
Digital planning involved digitally positioning the center of rotation between the apical one-third and middle-root one-third in single-rooted teeth, and 2 mm apical to the function in multirooted teeth, and the tooth movements planned were mainly coronals. Pure radicular movements, such as root torque and mesial-distal root tipping, were thus avoided [33].  
The clinical staging used involved a step every 2\({}^{\circ}\) for the following investigated movements: inclination (buccal-lingual crown tipping), angulation (mesial-distal crown tipping) and rotation.  
Each patient enrolled retrospectively in the study was treated with polyurethane F22 Aligners with vestibular grip points created using GRADIA DIRECT LoFlo flow composite (GC Orthodontics Europe GmbH, Harkortstrasse, Germany).  
Grip points were used are for both stabilization (rectangular shaped) and derotation (triangular shaped). The former were usually used in posterior teeth when anterior intrusion was planned; the regular dimension was 3 mm in length and 1 mm in height, and usually positioned in the center of the clinical crown. The latter were triangular-shaped and applied on teeth that had to be rotated, especially rounded teeth (canines and premolars); regular dimension was 1 mm in height, with a longer surface oriented towards the opposite side of rotation, spanning about 3 mm in length.  
Considering the whole sample mean number of aligners, the mean IPR values and mean number of grip points for both arches used in the first phase of CAT with F22 aligners have been reported.