## 4 CAD-CAM Devices Production
### Customized Orthodontic Appliances  
Another CAD/CAM application in orthodontics is the laser-melting process, which allows for the production of metallic orthodontic appliances directly from the digital project. Following the intra-oral digital scan, the framework can be designed using the CAD/CAM  
Figure 20: Aligner construction. (**A–C**), Aligner definition; (**D**), aligner refinement.  
software, and then the stereolithographic (STL) file can be exported to the digital platform for 3D metal printing. The printer then builds the metal framework layer by layer using a laser-melting (sintering) process. The print medium is generally a powdered cobalt-chromium metal alloy. In the production of a maxillary expander, the only non-digitally designed part is the jackscrew, which is soldered to the digitally designed framework. Lastly, the inner surfaces of the appliance that lie against the dental surfaces are generally sandblasted to enhance their bond strength. Another advantage of digital platform is the possibility of generating digital templates to better communicate to the lab-technician where the exact position of the appliance is located. Figure 21 shows an example of a maxillary expander with the framework obtained from laser-melting process while active components (expansion screw) were assembled analogically. A digital template for screw placement has been design and included in the 3D printed model.  
The greatest advantage of direct metal printing is customization. This technology allows us to tailor the appliances that match specifically to the patient's teeth. One example is customizable bands or pads that are essentially bondable pads that cover the occlusal, buccal, or lingual surfaces of the anchoring teeth, but do not extend interproximally. In fact, they are designed to fit the lingual or vestibular tooth surface, avoiding interference with gingival sulcus and pressure in the interproximal era and avoiding the usage of separators. They are designed to be as large as possible and with close adaptation to the tooth's surface (0.05 mm gap). Additionally, with CAD-CAM and laser-melting technology, it is possible to design specific configurations of the bands and pads without affecting neither bonding strength nor resistance (Figure 21D-F).  
Recently, the possibility to design customized orthodontic brackets that adapt perfectly to the vestibular surface of a tooth for a real expression of torque and to produce differential resin pads to gain better retention have been introduced. In general, customized 3D printed appliances, both resin-based (prototyped) and metallic (laser melted), present as a great  
Figure 21: CAD-CAM maxillary expander. (**A**), Positioning of the template matched with digital screw; (**B**), template in place according anatomical and biomechanical characteristics, (**C**), 3D printed maxillary model with screw template; (**D**), maxillary expander with laser-melted framework and screw placed onto the template; (**E**), intra-oral view; (**F**), the band of the upper-left deciduous second molar was designed with an open shape to allow for temporary restorations.  
advantage for enhanced accuracy, better standardization, improved patient comfort, and reduced orthodontic appointments [55; 56].