3 <i>In vitro</i> toxicity assessment of ceramic resins used in additive manufacturing: implications for occupational health

Abstract Additive manufacturing (AM) is the process of fabricating a three-dimensional object by depositing successive layers of feedstock material. The feedstock materials used depend on the type of AM process and application and include polymers, metals, concrete, or ceramic resins. Ceramic resins have desirable material properties, such as high strength, corrosion resistance, thermal conductivity, and biocompatibility. Since AM operators still perform many manual tasks during fabrication, there are concerns regarding potential occupational exposure to ceramic resins via dermal absorption, accidental ingestion, or inhalation. This study aimed to investigate the in vitro toxicity of three commercially used Lithoz® ceramic resins, namely LithaBone HA 480 (hydroxyapatite; LBONE), LithaCon 3Y 210 (zirconia, LCON), and LithaLox 350 (aluminium oxide, LLOX). Feedstock dispersions (1 mg/mL) were diluted in cell culture media to obtain exposure concentrations (1, 5, 10, 20, 50, 100, and 200 µg/mL). Cytotoxicity, oxidative stress, and DNA damage were assessed in human (RPMI-2650 nasal and A549 lung) cell cultures using the real-time xCELLigence cell proliferation, 2′,7′-dichlorodihydrofluorescein diacetate, and 8-hydroxydeoxyguanosine (8-OHdG) enzyme-linked immunosorbent assays, respectively. LBONE caused cytotoxicity in the nasal cells (200 µg/mL) while LLOX caused cytotoxicity towards the lung cells at 100 to 200 µg/mL. LCON was non-cytotoxic. Both LBONE (5 µg/mL) and LCON (1 to 5 µg/mL) induced oxidative stress (P &amp;lt; 0.05) in the nasal cells. The ceramic resins did not cause DNA damage. The findings of this study show that selected ceramic resins used in AM cause cellular toxicity and may pose occupational health risks to AM operators.