Application of α-TCP/Te-CP Cement to Pulp Capping Materials

Abstract

Purpose: Preparation of a large amount of calcium hydroxide forms a dentin bridge in the early phase. However, problems due to its strong alkalinity have been pointed out, such as wide-ranging dental pulp necrosis, cleft in the dentin bridge, and porosity. On the other hand, α-TCP/Te-CP cement composed of calcium phosphate compounds is highly biocompatible and induces hard tissue. Focusing on this α-TCP/Te-CP cement, we initially analyzed the physical and engineering properties, and then investigated it histopathologically by applying this cement to the exposed surface of rat molar pulp. Methods: Using calcium carbonate and dicalcium phosphate dihydrate as bases, α-TCP/Te-CP cement powder was prepared and subjected to experiments under various conditions using orthophosphoric acid, sodium dihydrogenphosphate, and citric acid aqueous solutions as mixing solutions. Firstly, the hardening time, compressive strength, and pH behavior of the cement mixed under various conditions were measured. In addition, the solid phase involved in hardening was investigated using X-ray diffraction (XRD) and scanning electron microscopy (SEM). Furthermore, direct pulp capping was applied to the right upper first molar in Wistar rats. After 7 and 14 days, the test tooth was excised with the maxilla en bloc after perfusion fixation under general anesthesia, decalcified at a neutral pH, and stained with HE following the standard method. Results: The longest and shortest hardening times were about 52 and 2 minutes, respectively. The largest and smallest compressive strengths were about 14.7 and 0.3 MPa, respectively. The pH ranged from about 6.0 to 9.8. Transition to apatite with hardening was noted in cement mixed with orthophosphoric acid and sodium dihydrogenphosphate solutions. On histopathological examination, the formation of a dentin bridge was noted. Conclusion: α-TCP/Te-CP cement transitioned to apatite with hardening and formed a high-quality dentin bridge, compared to that formed by the calcium hydroxide preparation. The cement showed a superior ability to seal the exposed pulp surface, suggesting its usefulness as a direct pulp-capping agent.