A Biphasic Calcium Phosphate Cement Enhances Dentin Regeneration by Dental Pulp Stem Cells and Promotes Macrophages M2 Phenotype In Vitro

Calcium phosphate cement (CPC) is promising for bone and dentin repair and regeneration. However, there has been no report of biphasic CPC for inducing dentin regeneration. The aim of this study was to develop a novel biphasic CPC containing β-tricalcium phosphate (β-TCP), and investigate its effects on odontogenic differentiation of human dental pulp stem cells (hDPSCs) and macrophage polarization. New biphasic CPC was formulated with different ratios of β-TCP to an equimolar mixture of tetracalcium phosphate and dicalcium phosphate anhydrous. Mechanical properties, biocompatibility, and odontogenic differentiation induction ability of the cements and the inflammatory reaction to the cements were examined. A series of CPC containing β-TCP were developed. CPC with 20% β-TCP exhibited homogeneity and injectability, an acceptable setting time, and a twofold increase in compressive strength. Significant increases in hDPSCs' alkaline phosphatase activity, mineral deposit, DMP1 and DSPP gene, and protein expressions were obtained for 20% TCP-CPC, compared with traditional CPC (p < 0.01). The addition of β-TCP did not promote macrophage polarization to the proinflammation phenotype. The addition of 10% and 20% β-TCP promoted macrophage polarization to the anti-inflammatory phenotype. In conclusion, a biphasic β-TCP-modified CPC was developed for the first time, demonstrating substantially increased dentin regeneration capability, while promoting macrophages to an anti-inflammation phenotype. The novel biphasic CPC is promising for tooth tissue engineering and dentin regeneration applications. Impact statement Dental pulp exposure from dental caries, wounds, or deep cavity preparation can cause pain and infection, which may lead to root canal treatment or tooth extraction. Maintaining pulp vitality is a major challenge in stomatology. We developed a new injectable β-tricalcium phosphate (β-TCP)-calcium phosphate cement (CPC) for the regeneration of dentin. Compared with traditional CPC, the new CPC +20%TCP possessed good cytocompatibility, acceptable injection force, higher compressive strength (increased by 63%), and greater odontogenic expression and mineral deposits (increased by more than twofolds), while avoiding any proinflammatory drawback. This new biphasic CPC is promising for dental pulp-capping, base, and liner applications to promote dentin regeneration, as well as potentially for bone tissue engineering applications, which warrant further studies.