## 4 Discussion  
As a result of maxillary expansion with an RME appliance, the increase in the perimeter of the dental arch was on average 3.99 mm, with a standard deviation of 2.84. The increase in maxillary width achieved with the RME appliance is 4.41 mm, with a standard deviation of 1.63 mm in the molar area. The result correlates with the results obtained by [PERSON] values [86], as well as with those of other researchers [87; 88; 89; 90; 91]. [PERSON], in a scoping review, reports an increase in the width of upper permanent molars by 5.4 mm through RME [89]. [PERSON] found an interpolar width increase of 5.21 \(\pm\) 1.55 mm [90]. Most of the research in the literature explores only the changes in transversal dimensions achieved with RME appliances. [PERSON] [84] observed in a long-term evaluation the changes in dental arch dimensions in 112 patients treated with RME appliances. In its research, the methodology is described in detail and examines all the parameters of the dental arch. After the active phase with the RME appliance, the dental arch perimeter is increased by 7.5 mm. At the same time, the interpolar width increases by 4 mm. In a long-term stability evaluation, the increase of 6 mm in the dental arch perimeter in the upper jaw is proven to be stable. In contemporary orthodontics, as described in the present study, the phase of the creation of physical casts and their transfer through digitalization preceding the stage of measurements is eliminated by intraoral scanning. There is no image deformation, and the data is more accurate and precise. The chance of human error decreases, and the variations due to deformation of the physical model, such as material modification by  
Figure 6: Scatter plot and linear regression model between PA2-PA1 and PP2-PP1. (R\({}^{2}\) = 0.576). time--constriction or impaired physical integrity--are eliminated. The measurements can be made almost immediately after intraoral scanning, which takes a few minutes of clinical time. The treatment goals may be visualized and presented to the patients before the start of the treatment. That gives more accessible information. It is really helpful in cases where there is more than a single option for orthodontic treatment. After visualization of treatment objectives (VTO), the patients are more motivated, and the compliance level increases. The patients really give their informed consent and know what the clinician wants to achieve at the end of the treatment. That is helpful for the right attitude about treatment outcomes. In the [PERSON] [84] study, the Haas-type RME appliance was used. The expansion screw was incorporated in the same place by the dental technician laboratory team. In the present study, digital planning gives the opportunity for individual placement of expansion screws according to clinical needs. It may be moved in three dimensions (transversal, sagittal, and vertical), and the zooming options give excellent visualization from different perspectives. The orthodontist can make the appliance design by itself or at the same time with the dental technician. They can open the file, discuss the appliance design, and work on it from different offices. The different elements can be incorporated into appliance design and can be used after the expansion is achieved [11; 13; 14; 15]. The results closest to ours are those provided by [PERSON] [85]. In a prospective long-term study, an evaluation of the effects of rapid maxillary expansion in the early mixed dentition was made. He reported that the dental arch perimeter in the upper jaw increased by 4 mm, which is the same as the results of the present study. The methodology of measurements described in the [PERSON] study [84] was used. The RME expander with acrylic splint was used on 51 patients. The used appliances are different in two investigations--in the [PERSON] study, it is a Haas-Type RME, and in the Geran examination, it is an RME expander with an acrylic splint. In the present study, the RME is digitally assisted and printed on a 3D printer.