Cytotoxicity of 3D‐printed, milled, and conventional oral splint resins to L929 cells and human gingival fibroblasts

Objectives
Evidence on the biocompatibility of three-dimensional (3D)-printed and milled resins for oral splints is limited. This in vitro study assessed the influence of the manufacturing method on the cytotoxicity of oral splint resins on L929 cells and human gingival fibroblasts (GF1).

Materials and Methods
Standardized specimens of four 3D-printed, two-milled, one-thermoformed, and one-pressed splint resin were incubated with L929 and GF1 cells for 24 h. Immunofluorescence and WST-8 assay were performed to evaluate cytotoxic effects. One-way analysis of variance and Tukey's multiple comparison test were applied with the variables “splint resin” and “manufacturing method” (p < .05).

Results
Immunofluorescence showed attachment of L929 and GF1 cells to the splint resins. Irrespective of the manufacturing method, the WST-8 assay revealed significant differences between splint resins for the viability of L929 and GF1 cells. L929 cells generally showed lower viability rates than GF1 cells. The evaluation of cell viability by the manufacturing method showed no significant differences between 3D printing, milling, and conventional methods.

Conclusions
The cytotoxic effects of 3D-printed, milled, and conventional oral splint resins were similar, indicating minor influence of the manufacturing method on biocompatibility. Cytotoxicity of the resins was below a critical threshold in GF1 cells. The chemical composition might be more crucial than the manufacturing method for the biocompatibility of splint resins.