Comparison of additive and subtractive digital workflow for the accuracy of removable occlusal stabilization-splints – an in-vitro study

Abstract Objectives Patients with stage IV periodontitis often require additional rehabilitation of the compromised dentition due to anatomical and functional consequences of tooth loss. Removable occlusal splints can be helpful in these advanced cases. This in-vitro study compared the accuracy and internal fit of removable occlusal splints fabricated by 3D-printing and milling from a standardized STL-file. Materials and methods A standard-tessellation-language (STL)-file was created from a scanned master-model of the upper jaw and used for production of forty identical splints. Twenty splints were 3D-printed and twenty were milled. Subsequently all splints were rescanned, new STL-files resulted, which were compared with the original STL-file. Accuracy of both methods were assessed at 42 predefined points. Distances from vestibular to vestibular (v-v) respectively palatinal to palatinal (p-p) between molars were compared. Mann-Whitney-test was used for comparison ( p < 0.05). Results Mean values were 43.9 ± 31.29 μm (3D) and 22.0 ± 18.46 μm (milled), with a significant difference between groups ( p < 0.001, Mann-Whitney). The 3D technique resulted generally in a contraction (mean (SD) v-v: mean − 13.0 μm (± 92.16); p-p: -9.3 μm (± 123.03)). With the milled technique, a contraction vestibular-to-vestibular (-4.0 μm (± 53.63)), but palatinal-to-palatinal an expansion was measured (38.5 μm (± 33.86)). Vestibular, differences between groups were not significant ( p = 0.862, Mann-Whitney), but palatinal at the second molar ( p < 0.001, Mann-Whitney). Conclusion Both techniques showed deviations comparable to previous in-vitro studies of digitally manufactured occlusal splints. Less deviations were found in posterior areas of the dental arch with milled manufacturing. Clinical relevance Manufacturing of removable occlusal splints with CAD/CAM appears to be a precise and comfortable option.