Accuracy and clinical fit of milled versus rapid prototyped orthognathic surgical splints

Three-dimensional (3D) printing has become an integral part of orthognathic surgery. However, there is a lack of studies evaluating accuracy of orthognathic surgical splints fabricated from subtractive milling versus additive 3D printing. The primary aim of this in-vitro study was to compare the differences in trueness between milled and 3D-printed splints, while the secondary aim was to compare the differences in clinical fit of these splints. A sample of eight patients was selected, and STL files of the final orthognathic surgical splint were used to fabricate three splints for each of the eight cases. The first splint was fabricated by subtractive milling (SM), whereas the second and third splints were 3D printed with Digital Light Processing (DLP) and Laser Stereolithography (SLA), respectively. Paired superimposition of scans was performed using a reference model. The clinical fit of the splints to the printed models was also assessed. The mean root mean square (RMS) deviations for the SM, SLA, and DLP were 0.11 ± 0.02, 0.16 ± 0.02 and 0.14 ± 0.02 respectively. The post-hoc analysis showed that the SM splints had the highest accuracy (p < 0.01). However, DLP splints showed the best clinical fit, followed by SM and SLA. In conclusion, splints fabricated by SM were more accurate than those fabricated by 3D printing, although this difference may not be clinically significant. The site, rather than the magnitude of the errors, may have a greater effect on the clinical usability of splints. In general, SM and DLP splints demonstrated a good clinical fit and were suitable for the fabrication of surgical splints.