Comparative Biocompatibility of Portland-Based Endodontic Cements Containing Niobium and/or Bismuth Oxides in Rat...

To evaluate the in vitro cytocompatibility and osteogenic potential and the in vivo biocompatibility of two experimental endodontic cements based on Portland cement combined with either Nb2O₅ (F6) and/or bismuth oxide (F7) in a rat subcutaneous implantation model.

For the in vitro study, MC3T3-E1 preosteoblastic cells were exposed to MTA Angelus, F6, or F7, and cell viability was assessed at 24 and 48 h using the Alamar Blue assay. Osteogenic differentiation was evaluated by alkaline phosphatase (ALP) activity after 14 days. For the in vivo analysis, polyethylene tubes containing the materials were implanted into the dorsal subcutaneous tissue of rats and evaluated at 7, 14, and 30 days, with empty tubes used as controls. Histological and histochemical analyses included hematoxylin and eosin (H&E), Picrosirius Red, Von Kossa staining, and TNF-α immunohistochemistry. Chemical characterization was performed using Raman spectroscopy and X-ray fluorescence (XRF). In vitro data were analyzed using one-way ANOVA followed by Tukey's post hoc test, while semiquantitative histological data were analyzed using the Kruskal-Wallis test followed by Dunn's test. A significance level of 5% (p < 0.05) was adopted.

In vitro, F6 showed cell viability comparable to MTA Angelus at both 24 h (36.22 ± 2.66% vs. 35.75 ± 1.18%) and 48 h (34.18 ± 3.09% vs. 35.20 ± 2.35%) (p > 0.05). In contrast, F7 significantly reduced cell viability at 24 h (25.61 ± 1.11%) compared with MTA Angelus (p = 0.002), although no difference was observed at 48 h (p > 0.05). ALP activity after 14 days did not differ significantly among MTA Angelus (1.90 ± 1.23 UI/L/g), F6 (1.71 ± 0.88 UI/L/g), and F7 (1.78 ± 1.34 UI/L/g) (p = 0.703). In vivo, F6 induced mild to moderate inflammatory responses at the early time period, with a significant reduction by Day 14 and minimal inflammation at Day 30, comparable to MTA Angelus. No multinucleated giant cells were observed, and TNF-α expression was moderate. Von Kossa staining and XRF confirmed calcium deposition, while Raman spectroscopy detected niobium species in peri-implant tissues, indicating bioactivity. Picrosirius Red staining demonstrated progressive collagen fiber organization. Conversely, F7 elicited a pronounced and persistent inflammatory response characterized by multinucleated giant cells, intense TNF-α expression, and bismuth retention in surrounding tissues, as confirmed by XRF, with no niobium-related signals detected by Raman analysis.

The niobium-containing cement (F6) demonstrated favorable in vitro cytocompatibility and in vivo biocompatibility.