Characterization of Dentin Bridge Induced by New Calcium Cement

Objective: The nature of the hard tissue formed under pulp capping materials is not completely characterized and depends on the properties of the material. A calcium silicate cement has been shown to induce the formation of a homogenous dentin bridge in a pulp injury rat model when compared with MTA and Ca(OH)₂. The purpose of this study was to characterize the dentin bridge formed after direct pulp capping with this new calcium silicate cement. Methods: Cavities with a mechanical pulp exposure were prepared on the maxillary first molars of nine 6-week-old male rats (protocol CEEA34.CC.016.11). Their damaged pulps were capped and restored with Biodentine™ (Septodont, St Maur des Fossés, France). The nature of the reparative dentin bridge formed under material after 30 days was analyzed by histology and immunohistochemistry for DSP expression, SEM for microstructural and morphological characterization, EDX for chemical composition, and micro-Raman spectroscopic analysis for chemical mapping of organic and inorganic phase, in comparison with primary dentin. Results: A histological analysis showed that the dentin bridge induced by Biodentine™ was homogenous, regular and immunolabeled for DSP. SEM analysis showed the presence of dentinal tubules through the newly formed hard tissue but their density appeared lower than in the primary dentin. EDX analysis revealed that the dentin bridge contained oxygen, phosphorus and calcium. No statistical difference of the Ca/P ratio was found between the dentin bridge and the primary dentin. Raman spectroscopic analysis showed that the dentin bridge and the primary dentin had the same mineral phase and organic phase. However, the mineral phase intensity of the primary dentin was higher than those of the dentin bridge. Conclusion: These results indicate that the reparative dentin bridge induced by Biodentine™ is continuous and is similar to the primary dentin in terms of morphology and chemical composition.