Mineral trioxide aggregate (MTA) is a calcium silicate-based endodontic biomaterial with well-established sealing ability, biocompatibility, and hard-tissue induction potential; however, the extent to which its biological performance can be modulated by nanostructured reinforcements remains insufficiently defined. Hexagonal boron nitride (hBN) is a layered two-dimensional nanomaterial with high chemical stability, mechanical robustness, and growing relevance in regenerative biomaterials. Because no directly comparable in vivo study had evaluated hBN incorporation into an MTA matrix in a standardized rat tibial defect model, the present work was designed as an exploratory physicochemical and histological study. Standardized cylindrical defects (2.5 mm diameter, 4 mm depth) were created in the right tibial metaphysis of 40 systemically healthy rats randomly allocated to four groups (n = 10/group): empty defect control, pure MTA, MTA + 5 wt% hBN, and MTA + 10 wt% hBN. The study was conducted as a single 8-week in vivo experiment following institutional ethics approval. Pure MTA and hBN-modified composites were prepared under standardized mixing conditions and characterized qualitatively by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX). After 8 weeks, tibiae were harvested, decalcified, paraffin-embedded, stained with hematoxylin-eosin, and scored semi-quantitatively for fibrous tissue, new bone formation, and osteoblastic cell presence. Non-parametric comparisons were performed using Kruskal-Wallis and Dunn-Bonferroni tests (α = 0.05). XRD and FT-IR analyses showed preservation of the principal calcium silicate phase architecture and hydration-related bonding environment of MTA after hBN incorporation, while SEM-EDX demonstrated a progressively denser and more hBN-rich surface organization in the modified groups, particularly at 10 wt% hBN. Histologically, both hBN-containing groups displayed significantly higher new bone formation and osteoblastic cell presence scores than the empty-defect control. Fibrous tissue scores were also higher in the hBN groups than in the control group, indicating that the tissue response should be interpreted as a modified fibro-osseous reparative profile rather than as simple suppression of fibrosis. Compared with pure MTA, the 10 wt% hBN formulation showed the most favorable overall trend within the tested range, although differences between 5 wt% and 10 wt% hBN were not statistically significant. Within the boundaries of this exploratory 8-week rat tibial defect study, hBN could be incorporated into MTA without evidence of major physicochemical destabilization and with a more pronounced bone-related healing response than that observed in untreated control defects. The findings do not support an overextended claim of direct osteoblast activation or definitive concentration optimization; rather, they indicate that hBN-reinforced MTA is a promising proof-of-concept composite whose long-term remodeling behavior, mechanical performance, ion release, systemic safety, and true optimum hBN window require further quantitative investigation. First in vivo investigation of MTA reinforced with hexagonal boron nitride (hBN) in a rat tibial bone defect model. hBN addition preserved the crystalline and chemical stability of MTA while improving microstructural organization. MTA–hBN composites showed enhanced new bone formation and osteoblast activity compared with pure MTA and control defects. SEM–EDX analysis revealed homogeneous B/N distribution and improved surface compactness at higher hBN concentrations. Findings support the potential of hBN-modified MTA as an advanced biomaterial for endodontic surgery and bone regenerative therapies.
Öztekin et al. (Wed,) studied this question.