HYPERCEMENTOSIS is a dental condition characterized by an "abnormal thickening of the cementum. It may be diffuse or circumscribed, i. e., it may affect all the teeth or only certain parts of one tooth."1 The root of a tooth (Fig. 1) consists of a root canal (A) surrounded by dentine (B). Immediately around the root, and entirely surrounding it, is a thin even black line, the peridental membrane (C). Immediately surrounding the peridental membrane is a thin even white line, the lamina dura (D), which represents the dense plate of bone lining the socket of the tooth. Just beneath the peridental membrane is the thin layer of cementum. Hypercementosis (Fig. 2) is diagnosed roentgenographically by the increased deposition of cementum immediately beneath the peridental membrane (A) and the bulging of the peridental membrane and lifting of the lamina dura from the surface of the root at the point of