Clinical transfer accuracy of pressure-moulded versus 3D-printed drilling guides for orthodontic mini-implants in the anterior palate: a randomized prospective clinical study

Abstract Precise placement of orthodontic mini-implants (OMIs) in the anterior palate, particularly in the median and paramedian regions, is essential for reliable skeletal anchorage. Digitally planned insertion guides may improve transfer accuracy, but clinical data comparing different fabrication workflows remain limited. This randomised clinical trial evaluated the transfer accuracy of pressure-moulded (PM) and three-dimensionally printed (3DP) insertion guides for palatal mini-implant placement in these regions. Thirty patients requiring palatal skeletal anchorage were randomly allocated (1:1) to receive either PM or 3DP insertion guides. Two OMIs were placed per patient, either in the median or paramedian region of the anterior palate. Planned and achieved implant positions were compared after insertion using three-dimensional superimposition. The primary outcome was three-dimensional angular deviation of the implant axis. Secondary outcomes included linear deviations at the implant shoulder and tip and angular deviations. Between-group comparisons were performed using independent-samples t-tests on patient-level averages. No intraoperative complications or missing data occurred. Overall, mean three-dimensional angular deviation was significantly lower for PM than for 3DP guides (3.61 ± 1.29° vs. 5.77 ± 2.45°, p = 0.006). Linear deviations were comparable between groups at the implant shoulder and higher at the implant tip, with no statistically significant differences (shoulder: PM 0.81 ± 0.27 mm vs. 3DP 0.84 ± 0.34 mm, p = 0.778; tip: PM 1.25 ± 0.40 mm vs. 3DP 1.49 ± 0.58 mm, p = 0.199). Both guide types achieved high clinical transfer accuracy; however, PM guides showed lower angular deviations, particularly for paramedian placement. Overall, differences between fabrication workflows were statistically significant but mainly affected angular precision and remained within clinically acceptable ranges. Trial Registration: German Clinical Trials Register (File Number DRKS 00028967, registered on May 04, 2022).