An Experimental Study on the Genesis of Periapical Cyst in Monkeys
Grant-in-Aid for General Scientific Research (C)
|Allocation Type||Single-year Grants|
|Research Institution||The Nippon Dental University|
KAWASAKI Kohichi The Nippon Dental University, School of Dentistry at Niigata, Professor, 新潟歯学部, 教授 (90013961)
MIYOSHI Toshiro The Nippon Dental University, School of Dentistry at Niigata, Assistant, 新潟歯学部, 助手 (70229904)
MIYASATO Tsuyoshi The Nippon Dental University, School of Dentistry at Niigara, Assistant, 新潟歯学部, 助手 (00239378)
足達 美弥 日本歯科大学, 新潟歯学部, 助手 (90212521)
水沼 秀樹 日本歯科大学, 新潟歯学部, 助手 (70219640)
|Project Period (FY)
1990 – 1991
Completed(Fiscal Year 1993)
|Budget Amount *help
¥2,200,000 (Direct Cost : ¥2,200,000)
Fiscal Year 1991 : ¥400,000 (Direct Cost : ¥400,000)
Fiscal Year 1990 : ¥1,800,000 (Direct Cost : ¥1,800,000)
|Keywords||genesis of periapical cysts / experimental study / light microscopic observations / Malassez epithelial proliferation / cyst lumen formation / overinstrumentation / chemical irritants / saliva contamination / 歯根嚢胞 / 発生機序 / マラッセ上皮遺残 / 病理組織学的研究 / 機械的・化学的・細菌学的刺激|
The exact etiology of the periapical crystogenesis is unknown, although there are several theories of how cysts form. The purpose of this study was to examine histopathologically the epithelial proliferation in the vicinity of root apex induced by endodontic procedures. Fifty-six root canals of 46 healthy permanent teeth obtained from 2 adult crab-eating monkeys (Macaca irus) were examined. Pulpectomy were performed under general and local anesthesia, with tooth isolated by a rubber dam. The root canals were prepared on the apical foramen. Furthermore overinstrumentation was performed about 1mm beyond the root apices. The root canals were irrigated with 6% sodium hypochlorite and 3% hydrogen peroxide alternately, and eventually with normal saline solution. The immediate root canal filling was carried out. The used filling materials were as follows.
Group 1 : filled with zinc oxide eugenol cement sealer (CANALS) and gutta percha point by the lateral condensation method
Group 2 : filled wi
th 1% carrageenin solution and gutta percha point
Group 3 : filled with eugenol and gutta percha point
Group 4 : filled with gutta percha point contaminated by saliva
Group 5 : filled with apical dentin filings contaminated by saliva and gutta percha point
The endodontic cavities were carefully filled with composite resin. After the experimental period from 7 to 87 days, the animals were sacrificed and fixed with 10% formalin. Longitudinal serial paraffin sections about 6mum thick were stained with hematoxylin-eosin and for detecting bacteria. The following findings were obtained.
1.In the groups 2 and 3, proliferating epitherium and cyst formation were not observed in the periapical tissues of the overfilled teeth. In both groups of 46 days later, the teeth with overfilled root canal exhibited persistent chronic inflammatory responses in the periodontal tissues around the apices.
2.In group 1 of the filling with CANALS, there was frequently small abscess formation in the surrounding of sealers forced beyond the apices. 28 days after treatment, proliferating epithelium had lined the abscess lumen consisting of the degenerate and necrotic cells. The epitherial cells did not grow with eventual cyst formation. The abscess was gradually surrounded by collagen fibers and superseded by cicatrization of granulomatous tissues.
3.In group 5 of contaminated dentin filings by saliva, granulomatous lesion with infiltration of polymorphonuclear leukocytes often appeared around the filings pushed into periapical tissues in later period.
4.13 days after treatment in group 4 of the overfilling with contaminated gutta percha point by saliva, a small intial cyst formation was seen in the vicinity of the root apex. The epithelium surrounding the cyst lumen was thinly stratified by a few cells. Less
Research Output (2results)