Study of Tetracalcium Phosphate-Citric Acid Complex Cement : a New Direct Pulp-Capping Agent

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Tetracalcium phosphate-citric acid complex cement (4CPC) has been shown to convert to hydroxyapatite in phosphate buffered saline and possess some excellent physical and chemical properties as a biocompatible cement. The purpose of this study was to evaluate the possibility of the application of 4CPC as a direct pulp capping agent.The cytotoxicity of 4CPC was assessed by the chromium-51 release cytotoxicity test. The histopathological and crystallographic examinations of 4CPC were made in permanent dog teeth. Thirty eight mongrel dogs were used. A class V cavity was prepared on the buccal surface of canines, premolars and molars. After a pin spot of pulp exposure was affected by sterile explorer, 4CPC was carefully placed on the exposure site. The contralateral tooth was used as a control and calcium hydroxide (Dycal^<(R)>, L.D.Caulk) was applied. After 3 days, 1,2,4,8 weeks, 6 months and 1 year, the dogs were perfused with 10% or 4% neutral formalin. The response of dental pulp to 4CPC,the process of reparative dentin formation and the relation between 4CPC and reparative dentin formation were investigated when the cement was placed directly on the dental pulp of dogs. The results were as follows ;1.4CPC was a non-cytotoxic material.2. No necrotic layr was found beneath 4CPC3. Reparative dentin was formed in the teeth capped with 4CPC earlier and more frequently than in those capped with Dycal^<(R)>.4. Reparative dentin was formed within 50% of the 4CPC mass, while no reparative dentin was formed within the Dycal^<(R)> mass.5. In the teeth capped with 4CPC,reparative dentin was formed after the increase of alkaline phosphatase activities in pulp cells, and the synthesis of primary dentin-like collagen and proteoglycans. All of these findings seemed to be in connection with 4CPC.6.4CPC intrinsically converts to hydroxyapatite.These findings suggest that 4CPC is biodegradable and a favorable material as a direct pulplining cement.