## 2 Materials and Methods  
The proposed appliance is made of several additively manufactured parts: a main structure that is anchored to the palatal bone by means of 3 miniscrews inserted in the relative bushings, two rods that extend in a distal direction towards the molars and two molar tubes attached to the molar bands (Figure 1). The molar tubes can slide along the rods, to permit a mesial movement of the molars. Hooks are present on the molar tubes and on the anterior portion of the rods to attach elastic chains that generate the force for mesial molar movement. To take full advantage of this appliance, an innovative workflow was developed, that is summarized and compared to the conventional approach in Figure 2. Initially, in the proposed workflow, an integrated geometric model is obtained by aligning a virtual model of dental arches and a Cone Beam Computed Tomography (CBCT) image of maxillary bone. Then, the appliance is designed in a computer-aided design (CAD) environment, manufactured by additive manufacturing (AM), laser-welded to prefabricated molar bands, disinfected and finally positioned in the oral cavity. Compared to the conventional approach, in the proposed workflow the appliance presents bushings where miniscrews are  
Figure 1: Three-dimensional (3D) design of DIVA (Divergent Anchors) appliance. (**A**) Occlusal view, showing the parts of the appliance: (a) pushing for the miniscrew (b) connecting bar (c) T-shaped rest on incisors (d) occlusal rest on first premolar (e) rod for guiding mesial movement of molars (f) molar tube attached to molar band (g) hook on molar tube (h) hook on rod (i) conventional prefabricated molar band (in orange). (**B**) Lateral view, showing that bushings (green) and miniscrews (light blue) are not parallel among them, and slightly diverge in an apical direction. Not parallel miniscrews prevent any vertical movement of the appliance during the clinical use. inserted after the appliance cementation in the oral cavity, to simplify the clinical procedure of appliance delivery. The impression of patient dental arches was taken with alginate material, stone models were poured and then scanned with Aton scanner (88 Dent, Pero, Italy) to obtain a virtual model. Alternatively, the 3D digital model of dental arches can be directly generated with the use of an intra-oral scanner [10]. Then a Cone Beam Computed Tomography (CBCT) exam of the patient maxilla with a Field of View (FOV) of 5 \(\times\) 8 cm\({}^{2}\) was obtained with a Carestream CS 8100 3D machine (Carestream Dental LLC., Atlanta, GA, USA). The Real Guide software ([PERSON], Figino Serenza, Italy) was used to align the virtual model of the dental arches with the CBCT image through a best-fit automatic algorithm in order to create an integrated model (Figure 3) on which the DIVA appliance was subsequently virtually designed. The appliance was designed in a CAD environment (Rhinoceros 6.0, by Robert McNeel & Associates, Seattle, WA, USA). A virtual model of a bushing with a cylinder inside, representing the bushing and the miniscrew of the Diva appliance, was generated (Figure 4A,B). The bushing, serving as a guide for the miniscrew, presents height of 4.5 mm, an inner diameter of 1.9 mm, while the external diameter is of 4.9 mm in the region close to the miniscrew head and of 2.8 mm towards the opposite end to prevent interference with the palatal mucosa (Figure 4C). Figure 3: Alignment between virtual model of maxillary dental arch (**A**) and virtual model of the maxilla cone beam computed tomography (CBCT) (**B**) to create the integrated model (**C**). Figure 2: Conventional (**a**) vs. DIVA (**b**) workflow. The * symbol indicates a step performed with digital technology. The cylinder representing the miniscrew is 13 mm long and has a diameter of 1.8 mm. Since there are two common lengths for the palatal miniscrews (i.e., 11 mm and 13 mm), to facilitate distinguishing them during virtual planning a shoulder is present at the 11 mm, 2 mm from the most apical end.