OBJECTIVE: Since passive fixed space maintainers do not restore the lost tooth or provide chewing function, this study seeks to assess the effectiveness of an innovative approach for maintaining space following the premature extraction of first primary molars, utilizing functional space maintainers designed with CAD/CAM. METHODS: This randomized controlled trial included 28 patients allocated into two groups (15 in 3D Printing group and 13 in Milling group). The inclusion criteria required extraction or loss of the first primary molar due to complications of caries, with a prolonged period until eruption of the successor. Space maintainers were fabricated using 3D printing metal (Co 69 %, Cr 25 %, W 9.5 %, Mo 3.5 %, Si 1 %, Scheftner, Germany) and milling composite (breCAM.HIPC, Bredent, Germany). This study evaluated the efficiency of space maintainers through clinical check-ups at one, three, and six months, maximum occlusal bite force, and masticatory performance assessments. RESULTS: A positive clinical trend was noted over time, with the "type of space maintainer" factor (Milling vs. 3D Printing) influencing the degree of clinical assessment (p <
0.001). There were no significant differences in maximum occlusal bite force between sides for both types of space maintainers (p = 0.270 for 3D Printing and p = 0.765 for Milling). Significant improvements were observed in masticatory performance after the placement of both types of space maintainers. CONCLUSION: A six-month follow-up showed that 3D-printed metal outperformed milled composite ones, with no significant differences in bite force or masticatory performance, indicating that CAD/CAM technology could set new standards in producing functional space maintainers. CLINICAL SIGNIFICANCE: This study underscores the potential of the manufacturing technologies to set new standards in pediatric dentistry, particularly for maintaining space following premature tooth loss, while ensuring improved functional outcomes for young patients.