Actinomycosis of the periapical tissues.
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This case of periapical actinomycosis presented the clinical picture of chronic periapical inflammation. The diagnosis was based on the histological examination of the periapical lesions suggesting the necessity for routine histological examination. Although root canals provide a primary port of entry the Actinomyces organisms into the periapical tissue, periapical actinomycosis, is considered extremely rare. This may be due to the omission of routine histological examination of periapical lesions and the clinical behavior of the disease. The large number of cases reported during the last decade indicates that periapical actinomycosis is more frequent than what it is believed and this is important in the daily dental practice.
We studied the possibility of the clinical use of a calcium phosphate-type newly developed sealer composed of tetracalcium phosphate, dicalcium phosphate dihydrate, and a modified McIlvain's buffer solution (TDM). Another sealer using the buffer solution, to which 2.5% chondroitin sulfate was added to promote wound healing (TDM-S), was also studied. TDM and TDM-S were histopathologically compared with another type of calcium phosphate sealer (ARS), which is commercially available in Japan, in the dorsal subcutaneous tissue and in the periapical tissue of rats. TDM and TDM-S caused no inflammatory reactions in the subcutaneous tissue. The periapical tissue reacted mildly to them. ARS caused severe inflammatory reactions in both the subcutaneous and the periapical tissue. These results indicate that TDM-S has excellent histocompatibility and potential as a root canal sealer.
Bone defects caused by periapical inflammation can be treated and improved by endodontic therapy. However, the mechanism for osseous healing of periapical lesions after root canal treatment is unclear. In this study we examined whether fibroblastic cells from human periapical granulation tissue could produce calcified matrix in vitro. Periapical lesions from three patients were dissected in endodontic surgery, and fibroblastic cells (HFC) migrating from these lesions in vitro were used in this study. The HFC were cultured with or without beta-glycerophosphate (beta-GP) and ascorbic acid (AA), and the expression of human runt-related transcription factor-2 (Runx2), osterix (Osx), osteopontin (Opn), and osteocalcin (Ocn) mRNA, and alkaline phosphatase (ALPase) was examined by reverse transcriptase-polymerase chain reaction (RT-PCR) or by an enzyme-cytochemical technique. Furthermore, calcification in the cells was investigated by von Kossa staining. At the beginning of the culture, HFC expressed Runx2 mRNA faintly, but neither Opn mRNA nor ALPase activity. Immunocytochemical study also showed HFC expressed Runx2 more weakly, compared to SaOS2. However, the expression levels of ALPase, and Runx2, Osx, and Opn mRNA, were stimulated by 2 mM beta-GP and 50 microg/ml AA. After 4 weeks of culture with 2 mM beta-GP and 50 microg/ml AA, HFC formed von Kossa staining-positive calcified deposits on culture dishes, and also expressed Ocn mRNA. These results suggest that inflamed periapical granulation tissue contains osteogenic cells that have the potential to differentiate into mature osteoblastic or cementoblastic cells, and that such cells might contribute to osseous healing after root canal treatment.