# A Novel Digitized Method for the Design and Additive Manufacturing of Orthodontic Space Maintainers
## 1 Introduction and Background
Digital space maintainers, instead, leverage intraoral scanners as a foundational element. Although an intraoral scan or impression sent to the technician to create a patient-specific space maintainer is an extra step in the workflow, it yields highly personalized results and substantially reduces the need for post-treatment interventions and modifications. Consequently, treatment times are shortened, also enabling clinicians to adopt a more child-friendly and child-oriented approach [16]. Personalization improves the adaptability of the space maintainer while also providing better hygiene for the area and reducing the bulkiness of the appliance, thus increasing patient comfort. Figure 1: Conventional unilateral (band-and-loop) metal space maintainer. In recent years, scientific research has oriented towards the digitalization of the design process of space maintainers with the aim of improving the patients' acceptance of the treatments. There are a few examples of solutions adopting computer-aided design/computer-aided manufacturing (CAD/CAM) technologies in pediatric dentistry [17; 18]. These works usually adopt a 3D intraoral scanner to acquire the anatomy of the child's dentition and dedicated software to model a band-and-loop space maintainer. An example of this approach can be found in studies by [PERSON] [19] and [PERSON] et al. [20]. In [PERSON] [19], the space maintainer has been designed by the Dental System (3 Shape) software, adapting the pre-defined \"crown\" function and bridging the teeth using connectors. Then, the space maintainer was manufactured by a 5-axis milling machine starting from a zirconia block. [PERSON] and colleagues [20] designed the appliance with the DentalCAD 2.2 Valletta (Exocad) software and used a micro laser sintering technology with a titanium-based powdered material for its manufacturing. The integration of digital design with additive manufacturing allows to produce space maintainers in virtually any shape or form. Personalized design through digital scans and three-dimensional modelling software enables us to create space maintainers that precisely fit patient's teeth, optimizing adaptability and effectiveness. This customization reduces the risk of displacement or discomfort compared to non-customized devices. Additionally, personalized design enhances patient compliance by creating more comfortable and less intrusive space maintainers, leading to better patient acceptance. Moreover, additive manufacturing offers greater design freedom and flexibility since it allows for the creation of complex geometries without the same limitations imposed by traditional manufacturing techniques. This freedom from constraints allows for greater innovation, improved adaptability, and enhanced performance of orthodontic devices [18]. In addition, the digital design process can be assisted by finite element analyses, which are perfectly suited to simulate both conventional and unusual loading conditions. It is crucial to ensure that the designed appliance is structurally capable of withstanding the forces and stresses encountered in the oral environment. However, it is worth noting that digital approaches also entail certain limitations. A first shortcoming, for example, is given by the reliance on design software, which may have pre-defined functions or limitations that restrict the creation of free-form geometries. Many design software tools used in the orthodontic field are proprietary and may have specific constraints that limit the design possibilities. These software tools often provide a range of pre-defined shapes that guide the design process. While these functions can be useful for commonly used designs, they may not offer the same level of flexibility when it comes to creating complex, free-form geometries. This can restrict the exploration of innovative designs, characterized by unconventional shapes, that could potentially improve the adaptability or functionality of the space maintainer.