Porosity and root dentine to material interface assessment of calcium silicate-based root-end filling materials

The aim of this study was to evaluate the porosity and assess the root dentine to material interface of four root-end filling materials based on tricalcium silicate cement using two microscopy techniques. The porosity of Bioaggregate, Biodentine, a prototype radiopacified tricalcium silicate cement (TCS-20-Zr) and intermediate restorative material (IRM) was evaluated after immersion for 28 days in Hank's balanced salt solution (HBSS) using mercury intrusion porosimetry. The root dentine to material interface of the cements when used as root-end filling materials in extracted human teeth was assessed after 28 days of dry storage and immersion in HBSS using a confocal microscope together with fluorescent tracers and also a field emission gun scanning electron microscope. Biodentine and IRM exhibited the lowest level or degree of porosity. The confocal microscopy used in conjunction to fluorescent tracers demonstrated that dry storage resulted in gaps at the root dentine to material interface and also cracks in the material with Biodentine being the most affected. Zinc was shown to be present in root dentine adjacent to the IRM restorations. Dry storage of Biodentine resulted in changes in the material microstructure and cracks at the root dentine to Biodentine interface. Furthermore, the gaps resulting from material shrinkage allowed the passage of the fluorescent microspheres thus indicating that these gaps are significant and can potentially allow the passage of micro-organisms.