Application of α-TCP/Te-CP Cement to Root Canal Sealer

Abstract

 Purpose: Gutta-percha points for root canal filling do not adhere to the root canal wall, and so root canal filling cement (sealer) is used to thoroughly coat the walls. However, some sealers used in clinical settings have tissue-destructive effects. Once the sealer has leaked from the apical foramen, it not only causes apical periodontal diseases but also prevents healing after root canal filling. The present study focused on α-TCP/Te-CP cement, which causes no irritation and shows marked bioaffinity. This cement does not show up radiographically, as is required for a sealer. Therefore, bismuth oxide is added to α-TCP/Te-CP cement as a radiographic contrast medium. Mechanical and physical properties and curing behavior of the cement were investigated, and the dye permeability and tissue-destructive effect were investigated histopathologically to evaluate the effectiveness of the cement as a sealer.
 Materials and Methods: α-TCP/Te-CP cement was produced using calcium carbonate and dicalcium phosphate dehydrate as base materials. The cement with 30 wt% bismuth oxide allowed similar radiographic visualization to Canals. The particle diameter of bismuth oxide was adjusted to under 25 µm and then it was added to the cement. Sodium dihydrogen phosphate solution (P) and sodium chondroitin sulfate solution (C) were used as mixing solutions. The consistency, film thickness, and setting time of cement were measured as mechanical and physical properties, and the solid phase of curing was investigated based on the pH of mixed paste, X-ray diffraction analysis, and electron scanning microscopy. Apical sealing was confirmed by a dye penetration test using an extracted human tooth, and histopathological evaluation was performed by filling a rat skull with cement.
 Results: The consistency of the cement met the JIS standard. A portion of C met the JIS standard for the film thickness of cement. The setting time ranged from 55 to 423 minutes. The pH behavior depended on the pH of the mixing solution. Apatite migration was observed with curing in a part of P. The dye penetration test showed a similar sealing property to CaN in all cements. Histopathological evaluation showed no tissue damage in any subject compared with CaN.
 Conclusion: When α-TCP/Te-CP cement with bismuth oxide added as a contrast medium is mixed with sodium chondroitin sulfate solution, it does not show apatite formation with curing. However, it fulfills the required mechanical and physical properties, has an apical sealing property similar to CaN, and shows bone-like hard tissue formation 14 days after filling, suggesting that it can be used as a sealer.