Development of Calcium Phosphate Cement as a Dual Cure Type Pulp Capping Agent

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In the application of the calcium phosphate cement (CPC) as a direct-pulp-capping agent to the dentin-pulp complex, it is necessary to use a CPC that is dentin-adhesive, which completes the setting as soon as possible without spoiling the biocompatibility and the mechanical properties of CPC.We first attempted to develop a CPC as a dual cure-type direct-pulp-capping agent that possesses a light cure system in addition to the setting reaction. The AQ Bond Plus【○!R】 bonding agent (AQP), a commercial one-step bonding system, was used as the liquid phase. AQP provided CPC with a light setting mechanism, resulting in a marked reduction in the setting time. However, its mechanical strength in the initial stage of setting and its conversion to hydroxyapatite (HA) were lower than those of the usual CPCs. These results suggest that further investigation is necessary regarding the monomer type, and water content of the polymerization initiator, to prevent interference with the HA conversion.We then investigated the adhesive strength of the CPC with various composite resin adhesive systems. The results show that the phosphate ester adhesive monomers produce significantly higher adhesive strengths than the carboxylic adhesive monomers. This may be because the -phosphate ester monomers, whose ability of dissolution against inorganic components is stronger than that of carboxylic monomers, reached the deep part by dissolving the CPCs. Based on these results, therefore, it is necessary to conduct further investigation regarding the mechanical properties of CPC, the composition of the set CPC, the difference from adhesive agents in the chemical reaction, etc.Thus, these experiments with a dual cure-type direct-pulp-capping agent that was produced using CPC and an AQP as a liquid phase promote the understanding of the adhesiveness of CPC with resins and its basic properties. It also suggests the possibility of the clinical application of this CPC.