The main purpose of this study was to experimentally classify the histogenesis and malignant course of gingival carcinoma, showing its relationship to the clinical progress of chronic periodontitis.
The experiment was performed using an oral cancer model induced by the oral administration of 4 NQO solution. Seventy S-D rats were given administered with a 0.001% 4 NQO solution for 34 weeks. Ten rats were prepared as controls. Fifty-seven rats were killed with ether at intervals between 30 and 75 weeks after the beginning of administration of 4 NQO, and the gingiva was histologically examined at the first and second molars, and at the retromolar area in both maxilla and mandible.
The incidence of gingival carcinoma was relatively high; 80% between 60-64 weeks. All carcinomas induced were of the squamous cell type. Carcinogenesis in the gingiva was observed in the junctional and differentiation and gingival epithelium. Histogenesis in the junctional epithelium was also discernable parthy as a result of malignant processes in the inner epithelium; particularly by malignant changes localized in the junctional epithelium, slight dysplasia of the gingival oral epithelium, and the maintenance of on obvious border between junctional and gingival epithelium. Malignant changes in the junctional epithelium, combined with extension of epithelium in to the cementum, exfoliation of epithelium and retraction away from the enamel by dysplastic changes all resulted in the formation of a gingival pocket. Finally, invasion of the periodontium by cancer nests resulted in the so-called “floating tooth”
Carcinogenesis in the junctional epithelium may indicate the histogenesis of human gingival carcinoma, whilst appearing clinically to follow the course of chronic periodontitis. It is considered that formation of gingival pockets by malignant changes of junctional epithelium further indicate the clinical charactristics of gingival carcinoma of this type.
Malignant processes in junctional epithelium by replacement of epithelium by atypical cells indicates “epithelial dysplasia-carcinoma in situ-early invasive carcinoma”. In the gingival epithelium, the malignant processes showed “epithelial dysplasia-early invasive carcinoma” by atypical downward proliferation of epithelium.