## 2 Materials and Methods
The final guide models were exported in STL file format and processed using CHITUBOX software (version 64, Shenzhen CBD Technology Co., Ltd., Shenzhen, China) to generate the printing file. The guides were printed using a Form 2 stereolithography 3D printer (Formlabs, Millbury, OH, USA) with a layer thickness of 50 \(\upmu\)m, employing a CE-certified Surgical Guide Resin (Formlabs). The printing process was performed according to the manufacturer's guidelines. After printing, the guides underwent post-processing, including a 10 min isopropyl alcohol wash to remove residual resin, support removal, manual polishing, and a final 5 min light-curing cycle in a Form Cure unit (Formlabs, Millbury, OH, USA) at 60 \({}^{\circ}\)C. The surgical guides were designed to incorporate metal bushings provided by the miniscrew manufacturer (HDC, Thiene, VI, Italy), enabling precise coupling with a dedicated pick-up driver for controlled miniscrew insertion. Following the administration of local infiltration anesthesia with articaine 4% without vasoconstrtictor (Ubistesin, 3M ESPE, Seefeld, Germany) to the palatal mucosa adjacent to the planned insertion sites, a pilot osteotomy was performed using a stainless steel lance drill (\(\O\) 1.1 mm, HDC, Thiene, VI, Italy) at a rotational speed of 1500 rpm under continuous sterile saline irrigation. Predrilling was carried out to ensure controlled cortical perforation, reduce insertion torque, and improve the positional accuracy of the miniscrew. Subsequently, palatal miniscrews (Regular Plus Konic, HDC, Thiene, VI, Italy) with a length of 10 mm and a diameter of 2.0 mm were inserted manually through the metal sleeves of the surgical guide using a dedicated pick-up driver provided by the manufacturer. Insertion was performed under strict aseptic conditions, with each screw advanced until its collar reached the guide sleeve surface, ensuring appropriate primary stability and optimal axial positioning. The insertion torque was manually controlled using a mechanical torque gauge and maintained within a range of 10-15 Ncm, following clinical safety recommendations for palatal miniscrew placement. Figure 1: BlueSky Plan Software interface, overlaying digital maxillary models and CBCT volumes. Once the orthodontic miniscrews were positioned, two dedicated scan bodies (HDC, Thiene, VI, Italy) made of medical-grade polyether ether ketone (PEEK) and measuring 5 mm in height were attached to the miniscrews. The position and angulation of the miniscrews were then registered by acquiring a new intraoral scan using a Medit i500 intraoral scanner (Medit, Seoul, Republic of Korea). The scanning protocol included a high-resolution setting with a scan resolution of 20 \(\upmu\)m, starting from the occlusal surfaces of the maxillary teeth and extending to the palatal area, ensuring the optimal acquisition of the scan bodies' profiles for precise digital superimposition (Figure 2). The post-insertion intraoral scan was used to digitally position two virtual analogs of the miniscrews in correspondence with the recorded scan body positions. These virtual analogs were then superimposed onto the preoperative planned miniscrew positions using the superimposition tool of BlueSkyPlan Software (version 4.7, Blue Sky Bio, LLC, Grayslake, IL, USA). The superimposition was performed using a best-fit surface-based alignment protocol on the surrounding palatal anatomy to ensure precise registration of pre- and post-operative datasets. Outcome measurements were performed bilaterally on both the right and left sides of each patient. The primary outcome, which was the maximum insertion angle discrepancy (MAD), was determined by visualizing and measuring the angular deviation between the long axis of the planned miniscrew and the actual inserted analog on the matched 3D models within the software interface. Angular measurements were expressed in degrees (\({}^{\circ}\)) and recorded for both sides of each case (Figure 3).