The connective tissue wall of the cyst is usually composed of an inner and an outer layer. The inner zone, made up of inflammatory connective tissue. underlies the epithelium in all its ramifications. The outer peripheral layer is the true "capsule" of the cyst. Collagenous fibers here are often densely arranged. Their connections with the alveolar bone are comparatively loose, however. For this reason, it is often possible to enucleate an apical cyst intact. Occasionally, tooth and cyst are removed as one.

The outermost perimeter, of course, is the alveotar bone. Always responsive, the bone tells its own story of growth or status quo in the life of the cyst. Evidences of new peripheral bone are often seen. These may reflect a narrowing of the width of the connective tissue zone as the inflammatory process diminishes. The majority of jaw sections available to us show trabeculae of compact bone on the margins of the apical cysts. In fact, the bone which forms the cystic enclosure and the bone of the alveolar tooth socket (alveolar bone proper) present a similar appearance.

The apical cyst shares many of the clinical and roentgenographic features of chronic apicai periodontitis. This is to be expected. After all, the cyst arises as a rule within an existing apical "granuloma" and often remains a minor feature of that inflammatory tissue mass. Both grow slowly. Both are asymptomatic. Seldom does either expand to a size greater than that of a large pea. On a roentgenographic basis alone, distinction between the two is usually impossible.

The roentgenogram can reveal neither the epithelial tining nor the fluid content of a cyst. The observation of a fine radiopaque line on the circumference of the area cannot be considered diagnostic. Several studies heve made clear thạt this "condensation" of peripheral bone is not llmited tơ the apical cyst, but occurs in the case of chronic apical periodontitis as well. It is interesting to note that both "granuloma" and cyst may be invisible in the roentgenogram. Should either lesion grow entirely within cancellous bone, the intact outer cortical plate of the alveolar process can impart a normal image despite the presence of the lesion inside.

Direct observation of apical lesions at the time of surgery reveals much to the dentist. But many a small cyst, we may be sure, passes unnoticed during the clinical inspection. Only serial microscopic sections, carefully studied, will reveal the epitheliumline cavity of the early cyst.

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