Monomer elution and cytotoxicity of 3D-printed resin-based composites

To investigate cytotoxicity and monomer release of 3D-printed resin-based composites (RBCs) for both provisional and permanent intraoral use and the influence of post-processing on biocompatibility.

Cylindrical specimens (10 mm diameter and 1 mm thickness) were prepared from three 3D-printed RBCs and a direct restorative RBC (reference). The specimens were divided into two groups: post-processed (PP) and non-post-processed (NPP) and were immersed in a DMEM cell culture medium for 24 h. The cytotoxicity of the eluates was tested by LDH and XTT assays, and the effect on cell cycle distribution was analyzed by flow cytometry. The degree of conversion was assessed up to 7 days, and the elution of monomers (BisEMA3, BisEMA6, BisEMA10, BisGMA, TEGDMA, and UDMA) was measured up to 7 days in water and ethanol using UHPLC-MS/MS.

The eluates of 3D-printed RBCs did not cause cytotoxicity and no effect on cell cycle distribution was observed. Furthermore, the PP group exhibited a significantly higher DC than the NPP group and the direct composite. In ethanol, the PP group released lower quantities of monomers than the NPP group and the direct RBC.

Post-processed 3D-printed RBCs exhibited better biocompatibility than direct RBCs in terms of monomer release. Irrespective of post-processing, the amounts of monomers released from the tested RBCs was too low to elicit in-vitro cytotoxicity. However, thanks to the extra-oral post-processing steps, 3D-printed RBCs reached higher DC and released lower quantities of monomers than the direct RBC, which may be relevant for patients with allergic predisposition.