<i>In Vivo</i> Inflammatory Effects and Surface Composition Changes in Implanted Root Canal Sealer Containing Bioactive Glass

<p> Purpose: Root canal sealers that directly contact the periodontal tissue after root canal filling require high biocompatibility. We aimed to evaluate the inflammatory response and surface elemental composition changes of a root canal sealer containing bioactive glass after implantation into the subcutaneous tissue of rats.</p><p> Methods: Bioactive glass (BG)-based, calcium silicate-based (ES), zinc oxide eugenol-based (NC), and non-eugenol-based zinc oxide (NCN) sealers were implanted into the dorsal subcutaneous tissues of rats. CD68 immunostaining analysis was performed 10 and 35 days post-surgery. Histological observations and scoring of the degree of inflammatory cell infiltration were also performed using hematoxylin-eosin-stained sections. Subsequently, the border between the sealer and the subcutaneous tissue was observed using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) on day 35.</p><p> Results: The CD68 immunostaining intensities (pixel×1,000) of the BG, ES, NC, and NCN groups were 2.8, 1.9, 6.4, and 6.6, respectively, at 10 days, and 0.3, 0.5, 3.5, and 1.8, respectively, at 35 days. The intensity was significantly lower in the BG and ES groups than that in the NC and NCN groups. No significant differences were observed between the BG and ES groups. The inflammatory cell infiltration scores of the BG, ES, NC, and NCN groups were 1.7, 1.5, 2.6, and 2.7, respectively, on day 10, and 1.4, 1.5, 2.2, and 2.3, respectively, on day 35. The scores in the BG and ES groups were significantly lower than those in the NC and NCN groups. On SEM and EDX analyses, Ca and P were detected approximately 200 μm deep from the BG sealer surface. The Ca and P intensities were strong at the sealer surface and gradually decreased away from it. In the ES group, Ca, P, and Si, the main components of ES, were detected overall, and the intensity of Ca was high approximately 40 μm from the sealer surface. Additionally, regions containing Ca- and P-like precipitation were observed in the subcutaneous connective tissue close to the sealer. In the NC and NCN groups, C and P, which may be related to biological tissue components, were found, in addition to Zn.</p><p> Conclusion: The BG and ES sealers showed less inflammatory cell infiltration than did the NC and NCN sealers and exhibited good biocompatibility in rat subcutaneous tissue. Ca and P were detected on the surfaces of BG and ES sealers, suggesting that calcium phosphate precipitated on the surface after in vivo implantation.</p>