# A Novel Digitized Method for the Design and Additive Manufacturing of Orthodontic Space Maintainers
## 4 Discussion  
This study presents a digital framework for designing customized pediatric unilateral space maintainers using intraoral scanning, generative algorithms, and additive manufacturing. The digital approach offers several advantages over traditional methods of space maintainer design and fabrication. Conventional appliances, produced manually in dental  
Figure 8: The plastic region in red (i.e., equivalent plastic strain > 0.1 mm/mm) after bending test: (**a**) top view, (**b**) bottom view. Figure 9: Space maintainer fitted to the model of the teeth on which it was created: (**a**) buccal side and (**b**) lingual side. This case refers to the replacement of a primary first molar. laboratories, often exhibit imperfect fitting and prolonged chair time for band selection due to the wide anatomical variability of primary teeth. Moreover, the use of materials like nickel in these devices can lead to allergies, and their larger size and geometry pose a risk of bacterial growth and hinder oral hygiene. Normally, space maintainers increase the plaque retention rate in the area of their positioning, and patients must be especially careful in the oral hygiene of this area [27; 28]. Furthermore, fitting issues and pinching can arise, presenting challenges for pediatric dentits in their management, and can also be uncomfortable for the child. Therefore, the development of a fully digital workflow is aimed at addressing these concerns and improving patient acceptance, health, and comfort. The use of intraoral scanning ensures an accurate representation of the patient's teeth, reducing the risk of improper fit and interference with mastication. Because of the accurate reconstruction of the patient's teeth, the selection of the 3D model of the patient's dentition of specific surfaces is possible. This allows us to maintain a certain distance from the teeth-gum border (as highlighted in Figure 3b). The high customization level helps to optimize cleaning, prevent gum irritation and plaque formation, also ensuring mechanical locking of the space maintainer, and reduces the risk of interference with mastication. The generative design was demonstrated to be effective in the exploration of different solutions and the creation of customized geometries, leading to a small overall size, better adaptation to the patient's dentition, and enhanced effectiveness of the space maintainer. The finite element analysis was demonstrated to be valuable in assessing the effect of a bending loading condition on the planar stiffness of the appliance. This scenario could occur when an external element, such as food, applies pressure on the device during occlusion movement, potentially resulting in significant plastic deformation of the material. The simulations indicated that despite experiencing unusual loading conditions, the planar stiffness of the device remains relatively unchanged, ensuring its functionality is maintained. The implementation of the DLP 3D printing process facilitated the use of a biocompatible resin with a tooth-like color. This, along with the small size of the device, could be useful in enhancing patient acceptance of orthodontic therapy. The dimensional accuracy and surface finish of the printed space maintainer proved adequate to allow its proper fit on the corresponding dental structures (as evidenced in Figure 9). At the same time, the designed distance from the teeth-gum border was maintained, which is supposed to improve dental hygiene. Moreover, the 3D printed space maintainer can be bonded through adhesive cementation by treating the tooth substrate with an etch and rinse adhesive system and applying a 10 methacryloyloxydely dihydrogen phosphate (MDP) primer on the appliance substrate. The space maintainer can be securely cemented using dual-cure cement. Due to its precise fit and adherence to tooth anatomy, the space for cement application is minimal, making it ideal for adhesive cementation. Undoubtedly, all space maintainers carry a risk of debonding.