| Objective: Odontogenic keratocyst (OKC) is a kind of odontogenic cystic lesion of jaws. It approximately accounts for between 3% and 12% of odontogenic cysts. OKC derives from dental lamina epithelial rests, which attracts researchers' attentions because of its special histologic features, postoperative recurrence and developmental characteristics. It always grows aggressively through the marrow spaces. Some of OKCs may attain a considerable size without symptoms. High recurrence rate is the primary clinical problem. A number of studies were focused on the relationship between clinical and histologic feature and postoperative recurrence. However, the reason of the recurrence doesn't reach a common conclusion. Radicular cyst is a kind of infective odontogenic cyst originated from Malassez epithelial rest proliferation, which stimulated by chronic periapical inflammation. It expands slowly, and the conjoint teeth have necrosis of pulp. A large radicular cyst promotes bone expansion and induces root resorption, movement and displacement of corresponding teeth. Compared with odontogenic keratocyst, radicular cyst growth pattern is less aggressive and the recurrence rate is lower. The historical research of OKC and radicular cyst elucidated the original and developing mechanism of them. A number of historical morphologic researches on OKC and radicular cyst under the light microscopy have been published, but the ultrastructural feature researches are rare. In this study, ultrastructural features of the OKC and radicular cyst were investigated under the transmission electron microscopy. Through comparison, the mechanism of OKC's aggressive behavior, high recurrence rate, and some evidences for the molecular biological research were shown.Material and Method: Two groups were divided: OKC group, radiculai cyst group. There were 4 patients in OKC group: 2 male, 2 female; aged between 24 and 50, and the average age was 38. There were 6 patients in radicular cyst group, 4 male and 2 female, aged between 22 and 48, and the average age was 34.2. All the histologic and ultrastructural specimens wereresected from OKCs and radicular cysts enucleated from the above cases. The specimens were immediately immersed and fixed in glutaraldehyde-formamint, preserved in 4C, rinsed sequentially in 0.1M dimethyl arsinic acid buffer, and postfixed in osmium tetroxide. Then the specimens were dehydrated through a graded series of ethanol and embedded in epoxy resin. They were made into semithin section, stained in 1% toluidine blue and accurately localized. At last, the specimens were made into serial ultrathin section, stained in uranyl acetate and lead citrate, and the specific ultrastructure features were observed under transmission electron microscope. Results:l.The ultrastructure of OKC: Basal cell layers of the epithelial lining of the cyst wall were proliferated significantly (about 5-6 layers), even presented para-basal cell. The amount of prickle cells were oppositely reduced, and the number of layers of stratum spinosum were decreased. Stratum corneum presented parakeratosis. The interface between the epithelial lining and connective tissue displayed collagen proliferation and edema. A part of microvessel endothelial cell proliferated, with stasis and focal inflammation cell response.2.The ultrastructure of radicular cyst: No marked proliferation in basal cell layer (about 1 -2 layers), with large intercellular spaces forming. In prickle cells layer (about 3-4 layers), neutrophilic granulocyte and activated lymphocyte infiltration were observed. The integrity of keratinocyte was diminished, because of shedding from surface layer. Connective tissue presented granulomatosis and cellular nodules, formed by inflammatory cell aggregation. Microvessel endothelial cell and mesenchymal collagen fibers were proliferated. Conclusion:1 .The ultrastructure feature of OKC and radicular cyst are manifestly different: (1) Basal cell layers of the epithelial lining of the keratocyst proliferate s... |
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