The incidence of epithelium in periapical granulomas and the mechanism of cavitation in apical dental cysts in man

In two series of periapical granulomas, approximately one third contained proliferating epithelium, the highest incidence being in the third and fourth decades. Histological observations on the walls of radicular cysts suggest that the cyst wall may result from a three-dimensional proliferation of epithelium. The hypotheses of the mechanism whereby apical cysts undergo central cavitation were investigated histochemically. Proteolytic enzyme activity was detected (a) in the connective tissue within and around the loops of epithelium, suggesting that cavitation may occur owing to connective tissue breakdown, followed by epithelial proliferation and (b) within the epithelium, suggesting that cavitation may be caused by intra-epithelial breakdown.