A cyst is an epithelium-lined sac containing fluid or semisolid material. In the formation of a cyst, the epithelial cells first proliferate and later undergo degeneration and liquefaction. The liquefied material exerts equal pressure on the walls of the cyst from within. Cysts grow by expansion and thus displace the adjacent teeth by pressure. May can produce expansion of the cortical bone. On a radiograph, the radiolucency of a cyst is usually bordered by a radiopaque periphery of dense sclerotic bone. The radiolucency may be unilocular or multilocular. Odontogenic cysts are those which arise from the epithelium associated with the development of teeth. The source of epithelium is from the enamel organ, the reduced enamel epithelium, the cell rests of Malassez or the remnants of the dental lamina.