Dynamic Bioactive Interface with the Dental Tissues

Objectives: To investigate the morphological and chemical characteristics of the interface between human dentine and a new calcium silicate based dental cement (BiodentineTM-Septodont, Saint Maur des Fosses- France). Methods: Occlusal cavities were prepared in extracted human teeth. Cavities were filled with Biodentine (n=26), and Fuji IX Glass ionomer cement (GIC)(n=11). Samples were divided into three groups; Micro-permeability group, where Rhodamine-B dye solution was applied into exposed pulp chambers of Biodentine (n=14) and GIC (n=5) samples. In the second “double labelling” group, Biodentine (n=6) and GIC (n=3) cements were mixed with a fluorescent dye then applied into the cavities just before conducting micropermeability test. These samples were examined using confocal microscopes after sectioning and polishing. In the third group; Biodentine (n =6) and GIC (n=3) samples were kept in distilled water for two days after mixing, then sectioned and polished before they were examined using a micro-Raman spectroscope to obtain chemical maps for the interfaces. Furthermore, fractured surfaces of these interfaces were examined using the SEM. Results: A highly reflective band was detected just beneath the dentine-Biodentine interface in reflection mode confocal images. Double labelled samples revealed a highly permeable zone beneath the interface which was richly infiltrated by the fluorescent dye leaching out of both cements but with two different patterns, indicating an inversed effect of these cements on the peritubular and intertubular dentine. Structural changes were confirmed by the SEM images that showed a band of structurally altered dentine beneath the interface, and tag-like structures forming within the dentinal tubules. Raman maps indicated an increase in the carbonate content of interfacial dentine, which suggested intertubular diffusion of Biodentine hydration products. Conclusions: The dentine Biodentine interface is dynamic and interactive; that is manifested by water movement between the two substrates, and hydrated cement diffusion into the dentine, accompanied by microstructural changes.