Biocompatibility of printed, milled, and conventionally fabricated indirect resin-based restorative materials: an in vitro comparative study

The increasing use of digitally fabricated resin-based materials for definitive dental restorations has raised concerns regarding their biological performance and biocompatibility. This in vitro study evaluated the biocompatibility and surface characteristics of different indirect resin-based restorative materials used in definitive dental restorations. A total of 144 disc-shaped specimens (diameter 15 mm, height 2 mm) were fabricated using printed, milled, and conventional resins (48 specimens per material), with 12 specimens allocated to each analysis (n=12). Specimens were sterilized using ultraviolet irradiation. Culture medium extracts were obtained on days 1, 3, and 7 and evaluated using L929 mouse fibroblast cells. Cell viability was assessed using the XTT assay, apoptosis by Annexin V-FITC/PI staining, and interleukin-6 (IL-6) release using a Mouse IL-6 ELISA kit. Cell viability, apoptosis, and IL-6 levels were analyzed using two-way ANOVA; surface roughness was analyzed using one-way ANOVA, followed by Tukey’s HSD post hoc tests (p<0.05). Significant differences were observed among the manufacturing groups across incubation periods in terms of cell viability, apoptosis rate, and IL-6 release (p<0.05). The milled-resin group showed the highest cell viability on day 7, whereas the conventional resin group showed the lowest (p<0.05). On days 3 and 7, the conventional resin group exhibited the highest rates of apoptosis and IL-6 release (p<0.05). Both printed and milled-resin groups showed no significant impact on fibroblast cell responses, whereas exposure to eluates from the conventional resin group resulted in altered cell viability, IL-6 levels, and apoptosis, suggesting potential cytotoxicity relevant to material selection for definitive prosthodontic restorations.