Materials, washing and post-polymerization should be matched while printing splints to reduce cytotoxic effects during additive manufacturing, according to a recent study published in the Journal of Dentistry.

Printed splints may be an alternative as a treatment of functional disorders in addition to physical, manual and physiological therapeutics. The objective is to investigate whether different 3D printed splint materials, which are fabricated with different fabrication orientations and post-processing (washing and post polymerisation) exhibit different in vitro cytotoxicity.

600 discs (n = 25 per group, 5mmx1mm) were printed (P30+ DLP-printer, Straumann, CH; 100 µm layer) from splint materials (M1: Luxaprint OrthoPlus, DMG, G; M2: V-Print Splint, Voco, G). Printing was performed under 90° (A1), 45° (A2) or 0° (A3) alignment to the building platform. Specimens were either automatically washed (W1) (Straumann P Wash, Straumann, CH) or manually cleaned (W2) (Voco Pre-/Main-Clean protocol, Voco, G), and post-polymerization was performed (P1: Cure, Straumann, CH; P2: Otoflash N171, Ernst Hinrichs Dental, G). RAW264.7 mouse macrophages were exposed to extracts of the specimens and cytotoxicity was determined as cell survival using a crystal violet assay. Optical density values obtained from exposed cell cultures were normalized to untreated controls (100%), summarized as means and statistically analyzed (ANOVA, α=0.05).
Results:
Cell survival varied between 9.1+/-1.3% (alignment A2/post-cure P2/material M2/wash system W2) and 58.5+/-5.9% (alignment A1/post-cure P1/material M1/wash system W1). Univariate analysis of variance revealed significant differences between mean values for post-cure (p = 0.000), wash system (p = 0.002) and materials (p = 0.000), but not for the alignment (p = 0.406). With standardised washing and adapted post-cure, both tested materials provided the lowest cytotoxicity even in all three printing alignments.
Thus, the selection of the material, as well as the post-processing (post-polymerization, washing procedure), show an influence on the in vitro cytotoxicity. Alignment during manufacturing does not affect toxicity.
Reference:
Cytotoxicity of printed resin-based splint materials by Johann Wulff et al. published in the Journal of Dentistry.
https://www.sciencedirect.com/science/article/abs/pii/S0300571222001543

Keywords:
Cytotoxicity, printed splints, resin-based, resin-based splint materials, Journal of Dentistry, Johann Wulff, Helmut Schweikl, Martin Rosentritt, Splint materials, Printing conditions, Additive manufacturing, Cell survival