The mechanism of pocket formation. A light microscopic study on undecalcified human material.

Two hundred eighteen human teeth with surrounding periodontal tissues in different stages of pathogenesis were studied under light microscopy using the "sawing and grinding" technique. This was done without decalcification and with special emphasis on the dentogingival junction area so as to study the mechanism of pocket formation. Thirty early, 133 established, and 214 advanced lesions were included. No initial lesion was seen. Pocket formation, provoked by microbacterial plaque, seemed to be initiated by the degenerative changes in the second or third cell layers from the innermost cells in the most coronal part of the junctional epithelium facing the microbial plaque. Consequently, an intraepithelial cleavage was formed followed by the degeneration and desquamation of the cells lining the split. This resulted in a deep crevice and gingival pocket formation in both early and established lesions. In advanced lesions, the deep pocket epithelium was exposed for such a long distance adjacent to the plaque and calculus, that the epithelium could be directly affected by toxic bacterial products and mechanical irritation of calculus. Finally, the epithelium became very thin and ulcerated, and a typical periodontal pocket was formed. The disruption of the epithelial barrier along with the concomitant penetration of bacteria and/or their toxic products were considered to be the most significant factors related to the conversion of an established lesion to an aggressive lesion.