## 4 Discussion
They concluded that even though the 3D-printed SM was not the most cost-effective option, the benefits outweighed the disadvantages [55]. It is important to consider that reduced plaque accumulation or gingival inflammation may also be influenced by the oral hygiene practices of the patient. In a study conducted in 2022, the fitting of conventional and 3D-printed metallic band-loop space maintainers was examined. The conventional group consisted of a 0.9 mm loop piece made from thick stainless-steel wire, which was soldered to a prefabricated stainless steel molar band. For the digital group, space maintainers were designed digitally and fabricated using an HBD-100 metal 3D printer with titanium powder metallurgy. To assess the fit, the space maintainers from both groups were digitally evaluated by superimposing the standard tessellation language (STL) files obtained from scans. After performing a best-fit alignment, the abutment teeth were selected, and a 3D deviation analysis was conducted. The results indicated no significant differences in the fit of the conventional and 3D-printed metallic band-loop space maintainers (_p_-value = 0.56) [39]. _Milling_  
In comparison to the additive manufacturing process, subtractive processes, such as CAD/CAM milling, are slower and result in more material waste. Another characteristic of the milling process is that it does not allow for adjustments in mechanical and aesthetic properties during 3D printing since the properties are predetermined by the manufacturer of the prefabricated blocks [65; 68]. A study in 2022 introduced a fully digital workflow for manufacturing fixed esthetic space maintainers in growing patients [2]. In this study, a scan taken prior to tooth extraction enabled the restoration of the pontic in the space maintainer using a digital wax pattern. In cases where only an intraoral scan was available after extraction, the CAD software's \"copy/mirror\" tool was used to replicate the pontic from the contralateral tooth. The position of the pontic was adjusted within the dental arch, and two digitally designed clasp retainers were placed on adjacent teeth. Subsequently, the STL file of the designed space maintainer was imported into a milling machine, and the space maintainer was milled from PMMA material. After extraction, the 3D-printed space maintainer was cemented in place and its fit was assessed [2]. The authors concluded that the fully digital workflow and CAD/CAM fabrication technique led to favorable clinical outcomes and could be used not only on pediatric patients but also on any patients who were waiting for prostheses or dental implants [2]. The results of this study align with the findings of [PERSON] et al. (2020), who conducted a comparative analysis of the fit accuracy of space maintainers manufactured using two different methods: milling PMMA and conventional techniques. The space between the tissue surface and the space maintainer was measured using 3D variation analysis. The quantitative assessments revealed statistically significant differences between the conventional space maintainersand the PMMA digital space maintainers. This study examined the feasibility of employing CAD/CAM technology in the fabrication of space maintainers and lays the groundwork for future clinical applications in this field [42]. In the studies conducted by [PERSON] et al. [33] and [PERSON] et al. [16], PEEK material was utilized in the fabrication of removable space maintainers (RSMs) using a CAD/CAM system [16; 33]. PEEK, a semi-crystalline polymer, exhibits favorable characteristics, including biocompatibility, mechanical strength, durability, lightweight, dimensional stability, and low affinity for plaque accumulation. These properties make PEEK a promising alternative material for manufacturing space maintainers [33; 69; 70; 71; 72]. Furthermore, a study conducted in 2020 demonstrated the high suitability of removable PEEK space maintainers for clinical applications.