## 2 Materials and Methods  
This retrospective cross-sectional CBCT study was conducted according to the principles of the Declaration of Helsinki. Its protocol was reviewed and approved by the Ethics Committee of Messina (prot. 33-2020). The University clinic's database was searched, and records of patients showing the following criteria were selected: Caucasian subjects with permanent dentition (excluding third molars) who had undergone a CBCT exam for planning skeletal palatal anchorage with two miniscrews placed in the anterior palatine vault, aged between 14 and 22 y.o., with no history of previous orthodontic treatment, as well as the absence of craniofacial abnormalities or congenital syndromes, such as cleft lip and palate, cysts, or maxillary tumors. Moreover, the included subjects had the following records in their folders: digital models obtained with an intra-oral scanner, a supplementary maxillary scan taken for scan body position registration, and a CBCT scan of the maxilla stored as a DICOM file. Twenty-four cases met the inclusion criteria; their records were checked for quality and integrity, and they were included in this investigation. Patients were stratified by gender and ordered by age within each group. A random sequence generator was used to create two lists of randomized numbers, each with 11 and 13 units. The final sample size was determined through a preliminary power analysis, using data obtained from the first 10 patients included in the study. To ensure the robustness of the results, an additional evaluation was carried out based on studies available in the literature. The parameters considered for the analysis are as follows: 0\({}^{\circ}\) (planned miniscrew angulation), 2.3\({}^{\circ}\) (maximum angular discrepancy between the planned and final miniscrew axis), and 2.6 (common standard deviation). The power level was set at 0.8, and the significance level was set at 5%. The results of the analysis indicated that a sample of 21 cases would be sufficient to achieve the desired statistical power. To minimize the risk of false negative results, the sample size was increased to 24 subjects (12 females and 12 males). Case enrollment was performed using a balanced randomization system based on patient gender. The final sample included 24 subjects (mean age 18.4 \(\pm\) 3.15 years), with 12 male subjects (mean age 17.7 \(\pm\) 3.06 years) and 12 female subjects (mean age 19 \(\pm\) 3.56 years). The overall sample included 8 subjects with skeletal Class I, 10 subjects with skeletal Class II, and 6 subjects with skeletal Class III. CBCT and lateral cephalogram records were generated using the Kavo OP 3D Pro CBCT scanner (Kavo Dental Technologies, Imaging Sciences International, Hatfield, PA, USA). The CBCT scans were acquired with a voxel size of 0.3 mm and a field of view (FOV) of 8 \(\times\) 9 cm. The acquisition parameters for the CBCT examinations were set as follows: 90 kV, 6.3-8 mA, and an exposure time ranging from 5 to 8 s. Lateral cephalometric radiographs were performed using the following settings: 90 kV, 10 mA, and an exposure time of 16 s.  
Digital maxillary models were obtained using an intraoral scanner (Medit i500, Medit, Seoul, Republic of Korea) and exported in STL file format with a resolution of 20 \(\upmu\)m.  
DICOM files and a maxillary digital model were imported into a specific software used for planning the 3-dimensional position of miniscrews (BlueSkyPlan software version 4.7, Blue Sky Bio, LLC, Grayslake, IL, USA). Subsequently, Blue Sky Plan software was used to superimpose maxillary digital models and CBCT volumes (Figure 1). The software (internationally registered as a medical device) used an algorithm to automatically superimpose the digital maxillary model and the CBCT volume scan. Blue Sky Plan software was also used to design the surgical guide. The surgical guides were digitally designed using BlueSkyPlan software (version 4.7, Blue Sky Bio, LLC, Grayslake, IL, USA), a CE-certified medical software for 3D orthodontic planning and surgical guide design.